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					Motorola Canopy



Voice over IP over Canopy



September 27, 2004
                                                                                                                                     Motorola
                                                                                                                    Voice over IP over Canopy




                                        ......................................................................................................................... 2
                                          ....................................................................................................................... 4
                                              ................................................................................................................... 6
CIRCUIT SWITCHED VS. PACKET SWITCHED TELEPHONY ........................................................................... 6
  Circuit Switched: .................................................................................................................................... 6
  Packet-Switched Telephony:................................................................................................................... 6
CODER/DECODER (CODEC) ........................................................................................................................ 6
INTEGRATION OF VOIP WITH THE PUBLIC SWITCHED TELEPHONE NETWORK ............................................ 7
THE ANATOMY OF A VOIP CALL ................................................................................................................ 7
  Encoding and Packetization ................................................................................................................... 7
  Transport ................................................................................................................................................ 8
  Dejittering and Decoding ....................................................................................................................... 8
  Mouth-to-ear delay and overall distortion ............................................................................................. 8
STANDARDS FOR MEASURING CALL QUALITY ........................................................................................... 9
CONSIDERATIONS FOR NETWORK CAPACITY PLANNING ............................................................................ 9
ERLANG TABLES ...................................................................................................................................... 10
  Erlang to VoIP Bandwidth Calculation................................................................................................ 11
                                                                                         ..................................................................... 12
CANOPY FRAME PACKETS ........................................................................................................................ 12
 Control slots ......................................................................................................................................... 12
 Downlink and Uplink Acknowledgement slots...................................................................................... 12
HIGH PRIORITY / QUALITY OF SERVICE (QOS) ......................................................................................... 12
                                                                        ...................................................................................... 13
ADVANCED CALL QUALITY MEASUREMENTS ............................................................................................ 13
TESTS VOIP-ENABLED NETWORK EQUIPMENT .......................................................................................... 13
EMULATES COMPLEX NETWORKS IN TEST LAB .......................................................................................... 13
OPTIMIZES NETWORK DESIGN ................................................................................................................... 13
                                                     !                                                                                      .................. 14
CANOPY CONFIGURATION ........................................................................................................................ 14
VONAGE CONFIGURATION ........................................................................................................................ 14
TEST SCENARIOS ...................................................................................................................................... 14
TEST RESULTS .......................................................................................................................................... 15
FINDINGS .................................................................................................................................................. 15
RECOMMENDATIONS ................................................................................................................................ 15
                                                                                                                     ......................................... 16
CANOPY CONFIGURATION ........................................................................................................................ 16
IXIA CHARIOT CONFIGURATION .............................................................................................................. 16
TEST SCENARIOS ...................................................................................................................................... 17
TEST RESULTS .......................................................................................................................................... 17
FINDINGS .................................................................................................................................................. 17
  Summary of Results .............................................................................................................................. 17
  Quality of Service ................................................................................................................................. 18
  Theoretical Modeling based on Actual Results .................................................................................... 19
RECOMMENDATIONS ................................................................................................................................ 21
                                                                                                                                    Motorola
                                                                                                                   Voice over IP over Canopy


         !           .......................................................................................................................................... 23
PHASE II TEST RESULTS ........................................................................................................................... 23
 Canopy set at 50% downlink / 50% uplink – G.711a ........................................................................... 23
 Canopy set at 50% downlink / 50% uplink – G.711u ........................................................................... 23
 Canopy set at 50% downlink / 50% uplink – G.726 ............................................................................. 24
 Canopy set at 50% downlink / 50% uplink – G.729 ............................................................................. 24
 Canopy set at 50% downlink / 50% uplink – G.723.1-ACELP............................................................. 24
 Canopy set at 50% downlink / 50% uplink – G.723.1-MPMLQ........................................................... 25
 Canopy set at 75% downlink / 25% uplink – G.711a ........................................................................... 25
 Canopy set at 75% downlink / 25% uplink – G.711u ........................................................................... 26
 Canopy set at 75% downlink / 25% uplink – G.726 ............................................................................. 26
 Canopy set at 75% downlink / 25% uplink – G.729 ............................................................................. 27
 Canopy set at 75% downlink / 25% uplink – G.723.1-ACELP and G.723.1-MPMLQ......................... 27
TEST RESULTS WITH CANOPY QOS .......................................................................................................... 28
 High Priority = 1 Slot........................................................................................................................... 28
 High Priority = 2 Slots ......................................................................................................................... 28
 High Priority = 3 Slots ......................................................................................................................... 29
                                                  ............................................................................................................ 31
                     ......................................................................................................................................... 32
                                                                                           Motorola
                                                                          Voice over IP over Canopy




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The Motorola Canopy solution is an excellent wireless broadband data transporter between a
central site access point (AP) and many end-point subscriber modules (SM). The solution is
being well received world-wide by telecom providers, wireless internet service providers (WISPs),
and enterprises where site-to-site wireless data connectivity is preferred over traditional wired
solutions. It has also been observed that the Canopy product can be an effective transport
medium for real-time Voice over Internet Protocol (VoIP) technology. VoIP over Canopy is a
reality for early adopters because of the low latency, high bandwidth, reliability, and scalability of
Canopy. Based on this information, Motorola has been receiving an increased interest in using
Canopy as more than a general data mover for such applications as real-time VoIP solutions.
Therefore, Motorola has retained an external third party consulting and testing organization, West
Monroe Partners, to validate the potential for VoIP over Canopy as well as to conduct testing to
benchmark performance and scalability.

To begin, the team focused on modeling and testing VoIP calls to confirm and benchmark the
usability and performance over Canopy. A lab was built to simulate a test environment where a
number of elements were varied to determine optimal configuration and performance limitations
for potential Motorola customers of the Canopy product.

The testing was conducted in two phases. The goal of the initial phase of VoIP testing over
Canopy was to develop a theoretical model using the Vonage broadband product to simulate an
actual VoIP phone call and document the results and performance. Vonage broadband phone
service was used to test an actual VoIP call going through Canopy out through the Internet. The
call was monitored to gather statistics on bandwidth usage so a theoretical model could be
created to determine how many VoIP calls a Canopy AP can support. The Canopy modules were
setup in a point to multipoint network configuration with one Access Point (AP) and two
Subscriber Modules (SM).

During the second phase the objective was to test scalability with more than just one VoIP call
and determine where the theoretical breaking points of the Canopy network exist. To enable
multiple VoIP call testing without needing the interaction of actual people to test calls and judge
call quality, IXIA’s Chariot product was used to perform traffic pattern analysis and load testing of
multiple calls across a Canopy network. Canopy modules were setup in a point to multipoint
network configuration with one Access Point (AP) and two Subscriber Modules (SM) in Phase II.
Several settings and configurations were adjusted during the second phase to determine optimal
design for performance and scalability. The types of settings that were adjusted during the
second phase of testing to determine the Canopy network limitations and optimal configuration
were:
            Bandwidth percent allocation between downlink and uplink connections
            Number of calls per SM
            Number of SMs per AP
            Compression Algorithm (Codec)
            Quality of Service – High Priority (on or off)
            Voice Traffic with and without data traffic

For the purposes of this paper Canopy 5.2 GHz radios were used and all SMs were set at a
distance of within 2 miles of the AP. This testing was based on typical RF configurations without
interference.


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                                                                          Voice over IP over Canopy




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Taking into consideration the anticipated traffic patterns of the end users (predominately data or
voice or an equal mixture of both) the customer can configure the network optimally to maximize
their return on investment of equipment and capital expense, while still providing a high quality of
service and cost effective alternative solution to toll dialing to the end user.

Based on our findings, it has been calculated that in an all voice traffic network using the G.711
codec (common VoIP codec), Canopy can support 28 - 33 simultaneous voice calls per AP (see
Phase 2 Findings). The call volume can be distributed over a number of SMs, not to exceed 5
calls per individual SM. If a wireless ISP is looking to support both voice and data traffic on the
same connection to the end user, and half of the bandwidth was allocated to data and half to
voice, then it is expected that approximately 14 to 16 simultaneous calls could be transmitted per
AP. This would allow the voice calls to be transmitted at a high quality level while still allocating
sufficient bandwidth for data transmission.

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Depending on a Canopy customer’s business plan for rate of oversubscription and acceptable
level of blocks calls, the number of calls stated above will be adjusted up or down depending on
the expected traffic volume. To properly plan a Canopy network configuration with VoIP, Canopy
customers are strongly advised to use Erlang tables in creating a business plan to estimate the
load on their network to be able to determine a specific oversubscription rate (acceptable amount
of blocked calls). Please see the “Voice Over IP Basics” section of this paper for more
information on Erlang tables.




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                                                                                           Motorola
                                                                          Voice over IP over Canopy




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Voice over IP (VoIP) permits the movement of voice traffic over Internet Protocol (IP)-based
network. IP is a standard for data transmission based on packet-switching technology. Voice is
broken into a series of packets at the transmitting end. The components are then reassembled
and decoded at the receiving device.

Voice communications is both real time and mission-critical. Any delay can make a call prohibitive
and lead to an undesired poor quality of service. Packet loss can be caused by router congestion
that may lead to a loss of portions of words or sentences. Traffic can multiply as the number of
routers is increased in the network leading to longer delays. Network jitter, where packets don't
arrive in sequence, can lead to unavoidable delays and poor quality of service.

   Circuit Switched vs. Packet Switched Telephony
Circuit Switched:
Nearly all voice traffic is circuit switched and transmitted over a Public Switched Telephone
Network (PSTN). The speed with which voice is transmitted is an aggregate rate of 64 kbps. A
direct connection between two connection points provides a permanent 64 kbps link for the
duration of the call. This link cannot be used for any other purpose during this time. PSTN
provides low latency (delay) and is bidirectional, allowing for a two-way or full-duplex
conversation to take place. The main shortfalls of circuit switching are provided by the inflexibility
and inefficiency inherited in the network by requiring a dedicated connection each time.

Packet-Switched Telephony:
In a packet-switched network, data is broken down into packets, each with a destination address.
When the packets are transmitted through the network, the addresses are read at each router, or
network switch, for forward routing. At the destination, the packets are reassembled and re-
sequenced. Depending on congestion levels in the network, packets may take different routes on
their way to the destination. Packet switching provides a virtual circuit connection and is generally
half-duplex. The main difference from the circuit-switched network is that there is no dedicated
connection. This is a connectionless network, which allows network resources to be used very
efficiently as bandwidth can be shared between applications.

   Coder/Decoder (Codec)
A voice coder is the device that converts an analog voice signal into a digital signal. The digital
signal is also compressed to reduce bandwidth requirements. Using a hybrid coding technique
with complex algorithms, the voice waveform is sampled and the speech parameters are
extracted. Thus, in any predefined time period, the waveform is assembled by a synthesis
technique to closely assemble the original waveform. The best way to reduce latency is to change
the voice coding method; however, the trade-off is voice quality vs. bandwidth required. While
there is a delay in the voice compression methods used, there is little further delay with
decompression regardless of the algorithm used.




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                                                                          Voice over IP over Canopy


Table 1

                                       Compression Algorithms

 Algorithm                                      Description and Rates

               Pulse code modulation (PCM) specifies the initial analog-to-digital conversion of
   G.711u      speech. Speech is transmitted at 64 kbps – which is considered to be toll quality.
               ITU standard for H.323-compliant codecs and most frequently used in the USA.
               Same as above, however it uses the A-law for companding, which is the most
   G.711a
               frequently used standard in Europe.
               A waveform coder that uses Adaptive Differential Pulse Code Modulation (ADPCM)
    G.726      at 32 kbps. ADPCM is a variation of PCM, which only sends the difference between
               two adjacent samples, producing a lower bit rate.
               High-performing codec; offers compression with high quality. Algorithm runs at 8.4
    G.729
               kbps with 10-ms delay and a compression ratio of 8-to-1.
               ITU algorithm that offers voice transmission with quality at a rate of 6.3 kbps with 30-
  G.723.1-
               ms delay. Uses the multi-pulse maximum likelihood quantization (MPMLQ)
  MPMLQ
               impression algorithm.
               ITU algorithm that offers voice transmission with quality at a rate of 5.3
  G.723.1-
               kbps with 30-ms delay. Uses the conjugate structure algebraic code excited linear
  ACELP
               predictive compression (ACELP) algorithm.
Source: Gartner & IXIA

   Integration of VoIP with the Public Switched Telephone Network
Despite some similarities, there are fundamental differences in the way signaling takes place in a
PSTN and in packet networks based on IP. Signaling is essential to ensure call-related control
information necessary to establish, bill and terminate connections. To allow full convergence and
seamless integration of functionality between PSTN and IP networks, signaling has to be
developed to avoid degradation of services. The signaling used in a PSTN is carried over a
different physical network known as Signaling System 7 (SS7). SS7 messages are exchanged in
the form of data packets similar to the way IP networks transmit data, on a dedicated overlay
network used exclusively for signaling. By using this separate network for "out-of-band" signaling,
this ensures that lines are clear and are free prior to setting up calls.

IP networks do not use the same type of “out-of-band” signaling. Instead, they use the protocols
such as H.323 or SIPs that are not compatible with the PSTN. A new signaling architecture has
been required to integrate both networks seamlessly; however, this does not yet exist. A variety
of protocols have been proposed to meet PSTN-IP integration, and these include H.323, SIP
IPS7 and Megaco to migrate interoperability and signaling issues. Nevertheless, these standards
are being improved to protect against packet loss and to allow for the transmission of toll-quality
voice services. Until these are resolved, it is likely that Internet telephony traffic will be carried
over dedicated IP networks.

   The Anatomy of a VoIP Call
Encoding and Packetization
In the first stage, the digitized voice signal (for example, in G.711 format) is encoded and
packetized. This operation can be performed either in the user terminal or in a gateway (for
example, between a PSTN and a packet-based network). In the latter case, it is assumed that the
circuit-switched transport of the voice signal from the user terminal to the gateway introduces only

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                                                                            Voice over IP over Canopy


a negligible amount of delay and distortion. The packetization delay is defined as the time
needed to collect all voice samples that end up in one packet. A new voice packet is produced at
the end of every interval of duration equal to the packetization delay. The choice of the
packetization delay involves a trade-off between effective bit rate and delay, because the payload
size also scales linearly with the packetization delay

Transport
In the second stage, packet transport, the resulting flow of voice packets is transported over a
packet-based network consisting of several (access and/or core) nodes. The network delay, i.e.,
the delay incurred by transporting a voice packet over the network, can be split into two parts: a
deterministic part referred to as the minimal network delay; and a stochastic part referred to as
the total queuing delay. The minimal network delay consists mainly of the propagation delay (5
µs/km), the sum of all serialization delays, and the route look-up delay. It is assumed that route
updates are so infrequent that the probability of one occurring during a phone call is negligible.
Hence, the minimal network delay is constant. The total queuing delay is the sum of the queuing
delays in all the nodes that are crossed. The queuing delay in one network node is due to the
competition of several flows for the available resources in the queue of that node. The total
queuing delay is responsible for the jitter introduced in the voice flow. That is, a flow of voice
packets that entered the network with constant inter-arrival times does not leave the network in
the same way, because some voice packets are delayed more than others. The jitter (also
referred to as packet delay variation) is defined as the delay difference between the fastest
packet and the slowest packet (though one still considered as on time). Note that during
transport over the network, a fraction of the packets may get lost, either due to overflowing
queues or due to the erroneous transport over unreliable links.

Dejittering and Decoding
Dejittering is absolutely necessary. Since the decoder needs the packets at a constant rate, the
jittered packet flow is dejittered and decoded in the third stage. Dejittering a voice flow consists
of retaining the fast packets in the dejittering buffer to allow the slow ones to catch up. The fast
packets are the ones that do not have to queue in any of the nodes. As voice can tolerate some
packet loss, it is not mandatory that the dejittering mechanism wait for the slowest packet. A
(small) fraction of the packets may be considered as arriving too late. This fraction of overdue
packets results in what is called a dejittering loss. If the dejittering buffer were to know if the first
packet that arrived was a slow or a fast one, it could compensate precisely for its queuing delay.
Since this knowledge is generally not available, the dejittering mechanism can either assume the
worst case (i.e., assume that the first packet to arrive was the fastest possible) or try to gradually
learn how the delay of the first packets relates to the delay of consecutive packets.

Mouth-to-ear delay and overall distortion
The individual contributions of the above stages (Encoding and Packetization, Transport,
Dejittering and Decoding) combine to give the one-way mouth-to-ear delay and the overall packet
loss. The mouth-to-ear delay of a packetized phone call (in one direction) is made up of four
components:
    1. The packetization delay.
    2. The DSP delay, which includes the delay due to encoding, decoding, look-ahead, and
         echo control. The lower limit of this delay is the sum of all look-aheads: even if
         technology continues to evolve to culminate in DSPs with dazzling processing power, the
         look-aheads remain unaffected.
    3. The total minimal network delay, which is the delay of the fastest possible packet. The
         total propagation delay is the lower limit of the minimal network delay.




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                                                                                          Motorola
                                                                         Voice over IP over Canopy


    4. The dejittering delay, which is the delay introduced by the adaptive dejittering mechanism
       on the fastest possible packet to compensate for the total queuing delay encountered by
       the slowest packet.

Overall distortion stems from encoding the voice signal and packet loss in the network or in the
dejittering buffer.

   Standards for Measuring Call Quality
Call quality measurement has traditionally been subjective: picking up a telephone and listening
to the quality of the voice. The leading subjective measurement of voice quality is the MOS (mean
opinion score) as described in the ITU (International Telecommunications Union)
recommendation.

In voice communications, particularly Internet telephony, the mean opinion score (MOS) provides
a numerical measure of the quality of human speech at the destination end of the circuit. The
scheme uses subjective tests (opinionated scores) that are mathematically averaged to obtain a
quantitative indicator of the system performance.

Compressor/decompressor (codec) systems and digital signal processing (DSP) are commonly
used in voice communications because they conserve bandwidth. But they also degrade voice
fidelity. The best codecs provide the most bandwidth conservation while producing the least
degradation of the signal. Bandwidth can be measured using laboratory instruments, but voice
quality requires human interpretation.

To determine MOS, a number of listeners rate the quality of test sentences read aloud over the
communications circuit by male and female speakers. A listener gives each sentence a rating as
follows: (1) bad; (2) poor; (3) fair; (4) good; (5) excellent. The MOS is the arithmetic mean of all
the individual scores, and can range from 1 (worst) to 5 (best).

                                              Table 2
                    Mean Opinion Score
                                                          User Satisfaction
                       (lower limit)
                           4.34                             Very satisfied
                           4.03                                Satisfied
                           3.60                        Some users dissatisfied
                           3.10                        Many users dissatisfied
                           2.58                       Nearly all users dissatisfied

The E-model is a complex formula; the output of an E-model calculation is a single score, called
an “R factor,” derived from delays and equipment impairment factors. Once an R factor is
obtained, it can be mapped to an estimated MOS. R factor values range from 100 (excellent)
down to 0 (poor). An estimated MOS can be directly calculated from the E model’s R factor.

   Considerations for Network Capacity Planning
When a Canopy provider (WISP) is building a business plan they must take into account,
oversubscription rate, number of acceptable blocked calls, and quality of service to customers.
All of these factors are important and must be considered before providing or advertising VoIP
service. The WISP will have to make a choice on whether or not they will provide VoIP service
through call manager equipment (i.e. Cisco, Nortel, etc.) or if customers will acquire service on

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                                                                                            Motorola
                                                                           Voice over IP over Canopy


their own (i.e. Vonage, AT&T CallVantage, etc.) and leverage Canopy for broadband access
where the third-party CPE (customer premise equipment) device does the VoIP encapsulation.

As in any other bandwidth based network there is going to come a point when the network is at
capacity. When this happens, there are a few options on how to handle it depending on the
choice of service. In the case of VoIP service being provided through a call manager, the WISP
has a couple of options. The WISP can either continue to allow calls to be added to the network
and allocate less and less bandwidth per call or block the last call that pushes the network over
its capacity. If the number of calls on the network is allowed to increase without limit, this will
degrade the call quality of all calls on the network because less bandwidth will be available per
call. This is not the recommended approach because this will cause an overall low quality of
service resulting in jittering phone connections to many customers. However, if the last call is just
blocked and given a “network is busy” signal, then this user can just try redialing in a few seconds
when some capacity will most likely have become available and all other calls will not be affected.
Managing the bandwidth in this fashion will allow a higher level of service to be provided and
managed across the network.

If the WISP is going to allow its customers to purchase a Vonage type service on their own and
utilize Canopy for broadband bandwidth, this is a little more difficult to manage. In this scenario,
the WISP will not be able to differentiate between regular data packets and voice packets that are
encapsulated as data. They will only have the option to manage overall bandwidth consumption.
A WISP should take this into consideration when forming their business plan in this scenario.
Since the WISP will have less control over voice call quality on an individual call level, they may
want to be more conservative in the service guarantees that they state for their customers around
voice quality.

To assist WISPs in this type of capacity planning it is recommended that they take into
consideration Erlang tables which are discussed in the next section.

   Erlang Tables

An Erlang is a unit of telecommunications traffic measurement. Strictly speaking, an Erlang
represents the continuous use of one voice path. In practice, it is used to describe the total traffic
volume of one hour. For example, if a group of users made 30 calls in one hour, and each call
had an average call duration of 5 minutes, then the number of Erlangs this represents is worked
out as follows:

             Minutes of traffic in the hour =   number of calls x duration = 30 x 5 = 150
             Hours of traffic in the hour =     150 / 60
             Hours of traffic in the hour =     2.5
             Traffic figure                 =   2.5 Erlangs

Erlang traffic measurements are made in order to help telecommunications network designers
understand traffic patterns within their voice networks. This is essential if they are to successfully
design their network topology. Erlang traffic measurements or estimates can be used to work out
how many lines are required between a telephone system and a central office, or in the case of
Canopy, given a level of available bandwidth, determine the acceptable amount of blocked calls
between a SM and an AP. Several traffic models exist which share their name with the Erlang
unit of traffic. They are formulas which can be used to estimate the number of lines required in a
network.



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                                                                          Voice over IP over Canopy


The main Erlang traffic models are listed below:

              Erlang B
              This is the most commonly used traffic model and is used to work out how many lines
              are required if the traffic figure (in Erlangs) during the busiest hour is known. The
              model assumes that all blocked calls are immediately cleared.

              Extended Erlang B
              This model is similar to Erlang B, but takes into account that a percentage of calls are
              immediately represented to the system if they encounter blocking (a busy signal).
              The retry percentage can be specified.

              Erlang C
              This model assumes that all blocked calls stay in the system until they can be
              handled. This model can be applied to the design of call center staffing
              arrangements where, if calls cannot be immediately answered, they enter a queue.

Erlang to VoIP Bandwidth Calculation

As explained above, the concepts of Erlang tables can be applied in a number of different ways to
a voice telecommunications network. In the context of a Canopy network, the users will be
applying these concepts to VoIP applications. There are a number of calculators that are
available to assist Canopy users in developing an appropriate business plan for their network.
Below is an example calculation of Erlangs capacity for a VoIP network using a Erlang to VoIP
                      7
Bandwidth Calculator :

Given That:

              G.711 Codec (64 kbps) is being used with a 20 ms packet duration
              The Acceptable amount of blocked calls is 1 out of 100 (.01)
              Available bandwidth is 3.1 Mbps (3250.59 kbps)

Then the network can handle a level of 28.1 Erlangs. This means that in its busiest hour the
network can handle 28.1 hours worth of total traffic volume. This volume can be distributed
among a number of different users, which should be taken into consideration in developing an
appropriate business plan.




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                                                                                             Motorola
                                                                            Voice over IP over Canopy




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   Canopy Frame Packets
There are 33 data slots in a basic canopy frame and each slot has a 64 byte payload. However,
this number will vary based on the number of control slots selected. Each frame has three control
slots by default and can be increased at the cost of data slots. Every two control slots allocated
decreases available data slots by one. There are also three downlink and three uplink
acknowledgement slots.

Control slots
The control slots are contention slots for the SMs to request to transmit data to the AP. Frame
duration is 2.5ms (400 frames/second). The SMs can only transmit data when they have been
granted a control slot by the AP.

Downlink and Uplink Acknowledgement slots
There are three downlink and three uplink acknowledgement slots in a canopy frame. The
purpose of the acknowledgement slots is to confirm a successful receipt of an upload or
download to the AP. The amount of acknowledgement slots can be altered in the AP
configuration, but is not suggested unless turning on QoS.

   High Priority / Quality of Service (QoS)
The purpose of the high priority channel is to handle traffic with a small tolerance for latency, such
as voice. If the Type of Service (TOS) bit is set for high priority the AP will prioritize this traffic in
the queue and hold back any data that is not designated as such. The high priority designation is
a static allocation, meaning that when a number of slots are reserved for high priority they can
only be used for this purpose. If no high priority traffic is being passed the designated high
priority bandwidth will remain idle and unavailable for other traffic.




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                                                                        Voice over IP over Canopy




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To determine values such as MOS and R-factor, it is not feasible to have human listeners to
make these subjective judgments at all times. For the purposes of these tests and this paper,
IXIA’s Chariot software product was used to determine these values and compile the data
necessary. Chariot has the capability to provide a tremendous amount of data in a testing
environment. The following is an example of the types of information that can be gathered. For
the purposes of this whitepaper, the focus was to use the advanced call quality measurements to
determine how VoIP traffic performs on the Canopy network.

   Advanced call quality measurements
Predicts call quality by calculating a MOS based on the industry standard E-model specified in
the ITU recommendation G.107. Improving on the base standard, the VoIP Test Module takes
into account additional network factors, such as jitter and consecutive lost datagrams, which can
severely impact overall call quality

   Tests VoIP-enabled network equipment
Examines the effectiveness and performance of VoIP-enabled network equipment. The VoIP Test
Module enables the user to verify that prioritization techniques work as planned with a mixture of
traffic and measure the performance impact of other network elements, such as VPNs, on delay-
sensitive VoIP traffic. Enables the user to test the limits of the network by generating up to
10,000 VoIP sessions. By identifying the point where call quality begins to suffer, the VoIP Test
Module empowers the user to make informed decisions about the implementation and expansion
of VoIP in the network.

   Emulates complex networks in test lab
Allows the user to emulate complex networks with a mixture of both VoIP and non-VoIP traffic by
using Chariot and its VoIP Test Module. By using Chariot in the lab environment, the user can
stress test network equipment, test network changes before deployment or replicate end-user
environments and reported problems. Chariot evaluates the effectiveness of QoS. The user can
ensure that voice traffic is receiving necessary resources at the proper time without starving other
business-critical applications.

   Optimizes network design
Supplies on-demand testing for tuning network to minimize delay, jitter and lost data.




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                                                                           Voice over IP over Canopy




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In the initial phase of VoIP testing over Canopy, a Vonage broadband phone was used to test an
actual VoIP call going through Canopy out through the Internet. The call was monitored to gather
statistics on bandwidth usage so a theoretical model could be created to determine how many
VoIP calls a Canopy AP can support.

   Canopy Configuration
In this phase, the Canopy modules were setup in a point to multipoint network configuration with
one Access Point (AP) and two Subscriber Modules (SM). All Canopy modules were 5.2 GHz
with uplink and downlink percentages at 50%. During this test, Quality of Service (QoS) was not
set as it would not have any affect on one VoIP call with no data traffic in the throughput of the
call.

The AP was connected to the Internet via a DMZ and router. We used a Vonage VT1000 (made
by Motorola) to conduct actual VoIP calls via the Internet. While conducting the VoIP calls,
Compuware’s Application Vantage tool was used to monitor the calls and gather call statistics
(throughput, frames, etc.).



                                                                                          Internet
                 Compuware
                    Tool



                                 Hub         SM          AP          DMZ        Router




               Vonage/Motorola

Analog Phone
                                             SM


   Vonage Configuration
The Vonage VT1000 can be used with three different codecs:
             G.711 (listed at 90 kbps by Vonage)
             G.726 (listed at 50 kbps by Vonage)
             G.729 (listed at 30 kbps by Vonage)
All three codecs were used during the tests to determine theoretical call capacity results for the
AP depending on the codec being tested.

   Test Scenarios
Three calls were completed from the Vonage VT1000 for each codec. Each call was recorded
and monitored with the Compuware’s Application Vantage tool.




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                                                                                          Motorola
                                                                         Voice over IP over Canopy


   Test Results
The results below were gathered using Compuware’s Application Vantage tool. The “Theoretical
maximum VoIP calls per AP” is based on Motorola’s Canopy documentation that the maximum
uplink throughput using more than one SM is 3.1 Mbps (3250.59 kbps). Since a VoIP call is full-
duplex and approximately the same amount of throughput will go upstream as well as
downstream, the amount of VoIP calls Canopy can support is limited by the lower throughput
limitation of the AP. When the AP is configured with two or more SMs on the network, the
Canopy AP is documented as having up to 3.1 Mbps (3250.59 kbps) upstream, so 3.1 Mbps
(3250.59 kbps) was used as the theoretical maximum.
Table 3
                               Ave.                                              Frame      Frames
 Vonage call      Duration               AP Max*     Theoretical max
                            Bandwidth                                             Size        per
   (kbps)        (seconds)                (kbps)     VoIP calls per AP
                              (kbps)                                             (bytes)    second
  G.711 (90)       94.63           162    3250.59                  20.1              214         96
  G.726 (50)      105.04             99   3250.59                  32.8              134         93
  G.729 (30)       76.96             58   3250.59                    56               74         99
* Upstream maximum of AP is approximately 3.1 Mbps (3250.59 kbps)

   Findings
The Access Point should be able to handle anywhere from 20 to 56 calls depending on the codec
used and if all the traffic is VoIP (no data). The Access Point can handle more VoIP calls when
using a codec that uses lower compression.
The Canopy system was fairly easy to setup and assemble and integrates well with the Vonage
product. There were no special configurations needed to setup the Vonage VoIP product to work
successfully on the Canopy network.

   Recommendations
The following recommendations are based on the output and statistics determined during the
above testing:
            When configuring a Canopy network that is primarily for VoIP traffic, the AP should
            be set at 50% for the ratio of uplink to downlink traffic. Since the uplink throughput is
            the constraint for VoIP traffic on a Canopy network, the user needs to have the uplink
            throughput as close to the 3.1 Mbps (3250.59 kbps) maximum.
            In a primarily data network, it is likely that the downlink to uplink percentage will be
            set at approximately 75% to accommodate for most subscribers doing more
            download-type traffic. If VoIP is added to a saturated data network, customers could
            experience choppy and jittery VoIP calls. A WISP will need to carefully plan and test
            before adding VoIP as the throughput to an SM has many variables (distance
            between AP and SM, uplink/downlink percentage, number of SMs on the network,
            etc.).




                                                 15
                                                                                           Motorola
                                                                          Voice over IP over Canopy




  ,                    #         %
                                % )          %+$ %+                          %
                                                                            ,(
In the second phase, the objective was to test scalability with more than just one VoIP call. To
enable multiple VoIP call testing without needing the interaction of actual people to test calls and
judge the call quality, IXIA’s Chariot product was used to perform traffic pattern analysis and load
testing of multiple calls across a Canopy network.

   Canopy Configuration
In this phase, Canopy modules were setup in a point to multipoint network configuration with one
Access Point (AP) and two Subscriber Modules (SM). Tests were performed using both one and
two SMs, but two SMs were always registered with the AP. All Canopy modules were 5.2 GHz
with the following variables:
              Uplink / Downlink percentage
                  o 50% / 50%
                  o 75% / 25%
              Quality of Service (QoS)
                  o Tests were run with QoS on and off
                  o High priority percentage was set at 25%.
                  o Acknowledgement and Control slots:
                               High priority uplink acknowledgement slots, high priority downlink
                               acknowledgement slots, and high priority control slots were set at 3.
                               Total uplink acknowledgement slots, total downlink
                               acknowledgement slots, and total control slots were set at 6.




   IXIA EndPoint

                        Hub        SM



IXIA Chariot Monitor
                                              AP         Switch
                                                                  IXIA Endpoint


                       Switch      SM
  IXIA EndPoint


   IXIA Chariot Configuration
The Chariot tool consists of two programs: the IXIA Chariot Console and the IXIA Endpoints.
The console station is used to setup and initiate all tests. The tests can consist of VoIP traffic,
multiple types of data traffic, or both VoIP and data traffic. The Endpoints are used to accept and
receive the data defined in the test scenario. The tool allows VoIP or data traffic to be generated
and sent to different Endpoints to simulate real-world traffic over a network. In this scenario, an
Endpoint was put on the end of each SM and the AP with the Chariot console connected via a
hub at an SM to be able to initiate and monitor all tests.



                                                   16
                                                                                             Motorola
                                                                            Voice over IP over Canopy


   Test Scenarios
The testing environment was a combination of one or two SMs and one AP. Additionally, there
are a number of variables that can influence the overall performance of the voice/data network.
The variables that were adjusted during testing included:

             Bandwidth percent allocation between downlink and uplink connections
                 o The downlink and uplink percentage allocation was adjusted to determine
                     optimal performance and limitations of the equipment. The two scenarios
                     that were tested were 50% downlink and 50% uplink as well as 75%
                     downlink and 25% Uplink.
             Number of calls per SM
                 o The call volume was adjusted from one call up to as many as 25 calls per
                     SM. The purpose of adjusting this variable was to determine the theoretical
                     maximum capacity of each SM and AP.
             Number of SMs per AP
                 o This was adjusted to test the limitations and performance of the AP under
                     different conditions.
             Compression Algorithm (Codec)
                 o As a result of altering the compression, the codec affects the possible call
                     volume and call quality.
             Quality of Service – High Priority (on or off)
                 o The high priority bit in the Canopy product is simply a Type of Service (TOS)
                     bit that the user can select to either have on or off. In an all data world the
                     high priority bit designation is not as critical given that a slight delay on the
                     transmission of data traffic is not nearly as meaningful to network
                     performance as a delay on a voice packet. A delay to a voice packet can
                     result in an audible flaw in quality as jitter and lost information. The high
                     priority bit was applied in different test scenarios to demonstrate the impact it
                     would have on transmitting voice traffic more cleanly and managing data
                     traffic accordingly.
             Voice traffic with and without data traffic
                 o To properly test the impact of having a high priority bit designated this
                     scenario was tested in conjunction with data traffic passing at the same time.

   Test Results
For a summary of the test results from Phase II, please see the “Findings” section below. For
detailed test results broken down codec and variable scenario please see Appendix A.


   Findings
Summary of Results
After collectively looking at the testing results for the different codecs with different variables it is
more apparent which performed the best with the most robust call quality. The summary below is
looking at the tests with two SMs. The detailed information on the testing results with one SM is
included in Appendix A., however, for the purposes of analysis and theoretical modeling the
results from two SMs were used as they gave more real world results. One of the other main
distinctions to note in the data is the difference in performance of 50/50 downlink/uplink
percentage versus 75/25. The uplink connection is the limiting factor in the call quality and
bandwidth throughput because the SMs have less bandwidth capacity on the uplink. Taking this
into consideration along with the amount of percentage that is allocated for downlink/uplink traffic,


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                                                                                           Motorola
                                                                          Voice over IP over Canopy


some conclusions can be drawn about which scenarios would work best for each network
configuration. For the most robust codecs five calls per SM appeared to be the “breaking point”
after which point the call quality dropped off considerably.

Given that the Canopy product is currently used primarily as a “data mover,” one would want to
take into consideration the performance of the Canopy under these different configurations.
Noting that the downlink/uplink allocation is a static setting, the user wants to make sure that they
are not leaving more bandwidth than necessary in an idle position. When determining how to
allocate the data it is worth while to take a look at the differences in performance below.

In a 50/50 configuration one can clearly push more calls through with a higher rate of quality
(higher MOS). If the anticipation is that the network will have predominately voice traffic, the user
will want to get as close to the 50/50 configuration as possible to raise the amount of possible
VoIP calls that Canopy can support. In a 75/25 configuration where users will still be doing some
download of “data” traffic, the user can still expect acceptable call quality with a significant volume
of calls being pushed through the Canopy network.

Actual Results with two SMs

Table 4
                         Downlink/Uplink      Number of Calls        Total # of
          Codec                                                                          MOS
                           Percentage          from Each SM            Calls
       G.711a                 50/50                  5                  10               4.36
       G.711a                 75/25                  4                   8               4.13
       G.711u                 50/50                  5                  10               4.37
       G.711u                 75/25                  4                   8               4.32
       G.726                  50/50                  5                  10               4.16
       G.726                  75/25                  5                  10               4.02
       G.729                  50/50                  5                  10               3.93
       G.729                  75/25                  5                  10               4.01
   G.723.1 ACELP              50/50                  8                  16               3.60
   G.723.1 MPMLQ              50/50                  8                  16               3.80

Quality of Service
The high priority setting on the Canopy product is strictly a bit designation indicating that the
traffic with that bit set has high priority and goes before any other data. Several different
configurations were tested to determine the robustness of the QoS setting. One, two and three
high priority slots were allocated during testing. The results showed that with the 75/25
downlink/uplink configuration, the best performance was with two high priority slots set with two
SMs. The high priority slots are set in the Canopy configuration table by indicating which
percentage of available slots the user would like to set as high priority. To achieve two slots, the
high priority percentage was set to 25% (to achieve two slots, a customer may need to try
multiple percentage configurations as the slots allocated will be dependent on the specific
Canopy setup). Tests in this configuration yielded a very good MOS value of 4.33.

As part of the QoS testing, different size data packets were sent with the voice traffic to determine
if there would be any negative impact on the quality of the voice call. These tests were
successful with varying data size files being passed. Starting with a file size of 128 kb and
gradually moving up to a file size of 1.2 Mb added to the network during voice testing, calls were
still transmitted with a MOS value of approximately 4.3. This demonstrates that the Canopy QoS



                                                  18
                                                                                           Motorola
                                                                          Voice over IP over Canopy


performs as desired as the latency and delay sensitive voice traffic is given priority and is able to
perform with acceptable quality no matter how much data is being passed at the same time.

Theoretical Modeling based on Actual Results
After looking at the actual results from testing and knowing the maximum throughput of the AP, it
is possible to extrapolate what the system performance would be like under expanded conditions.

The capacity of the AP for an uplink connection with multiple SMs is 3.1 Mbps (3250.59 kbps) of
data. The theoretical bandwidth compression of each codec is also known and listed in the table
below. The actual bandwidth compression can be calculated by taking the rate at which the data
was sent for a particular call and multiplying that by the frame size.. The rate is calculated by
taking the total amount of data sent over one call test and dividing that by the call duration. For
example, the G.711 codec sent 7,500 packets of data during a 150 second call. The rate is 50
packets/sec. The rate for G.726 and G.729 was identical to G.711, 50 packets/sec. G.723.1
MPMLQ and ACELP had a rate of 33 packets/sec.

It is also known that a Canopy frame is 64 bytes. From the testing done with the Ixia Chariot
software, the frame size used for all of the codecs is also known. The frame size for each codec,
including overhead, is listed in the table below. By knowing the total frame size and the rate of
transmission, the actual compression rate can be calculated. By continuing the example of the
G.711 codec, 50 packets/sec (rate of transmission) times 238 bytes (frame size) equals 11,900
Bps. This now should be converted from Bytes/sec to Bits/sec by multiplying the value by 8,
which equals 95 kbps.

When the size of the frame packet of the codec is larger than 64 bytes, 4 bytes for overhead must
be added for routing purposes to each packet before the packet is fragmented into 64 byte
packets. Using this information as a benchmark for a typical VoIP application, the efficiency of
data transfer on the network can be calculated. By taking into account all of this information a
more accurate theoretical model can be constructed. Given all of this information, the theoretical
total number of simultaneous calls that the AP can support can be calculated and is listed in the
below table.

Looking at the G.711 codec as an example, the flow of the calculation would be as follows:

            Given that there is approximately 3.1 Mbps (3250.59 kbps) of total bandwidth
            available and the actual data compression rate is 95 kbps, the theoretical calculation
            would simply be 3250.59 Kbps / 95kbps = 34 simultaneous calls.
            Since the total frame size is 238 bytes and the Canopy equipment transmits in 64
            byte packets, 4 Canopy frames (256 bytes) would be required to handle the total
            bandwidth from the G.711 codec. To account for overhead, 4 bytes must be added
            to each fragmented frame. In this case 4 frames are required, so 16 bytes total must
            be added to the 238 byte frame. This produces an average transmission efficiency
            rate of 99% overall (254 bytes/256 bytes). In a transmission where each 64 byte
            Canopy packet was being completely utilized (the application produced packets in 64
            bytes frames), the network would be operating under perfect conditions.
            The theoretical 34 calls can now be used in conjunction with the efficiency rate to
            calculate the adjusted theoretical number of calls the network can handle. This
            results in 34 calls times 99% efficiency, which is equal to 33 calls total.
            This same calculation can be made for each codec using the corresponding numbers
            with each different compression algorithm.




                                                  19
                                                                                          Motorola
                                                                         Voice over IP over Canopy




  Table 5
                                                                                          Theoretical
                                                                                         Simultaneous
                                             Total        Theoretical
                              Actual                                    Transmission      Calls an AP
           Listed                           Frame        Simultaneous
Codec                      Compression                                    Efficiency     Can Support
         Compression                         Size         Calls an AP
                            Throughput                                       Rate          Factoring
                                            (bytes)      Can Support
                                                                                           Efficiency
                                                                                              Rate
G.711a
  &          64 kbps          95 kbps         238            34              99%               33
G.711u
G.726        32 kbps          55 kbps         138            59              78%               46
G.729       8.4 kbps          39 kbps         98             83              83%               68
G.723.1
   -        6.3 kbps      26 kbps        98           125             83%                     103
MPMLQ
G.723.1
   -        5.3 kbps      27 kbps        102          120             86%                     103
ACELP
      *Upstream maximum of AP is approximately 3.1 Mbps (3250.59 kbps)

  The test scenarios that were conducted with one and two SMs demonstrated a clear
  understanding of the capabilities of individual SMs and the call volume limitations. These results
  are documented by codec in Appendix A. These tests demonstrated that by utilizing different
  codecs the SM will have a varying breaking point of when call quality becomes unacceptable.
  For one SM, this point was approximately five calls depending on the codec.

  The AP also has a breaking point at the number of simultaneous calls it can support with
  acceptable call quality with the uplink being the limitation. The initial thought would be that the
  AP has a total bandwidth limitation and the theoretical maximum should be approximately the
  same no matter whether the calls are coming from one SM or multiple SMs. However, it is known
  that the performance of the AP does scale with an increased number of SMs. An example of this
  is shown by looking at the performance of the G.711 codec when comparing one SM to two SMs.
  With the G.711 codec and one SM, the total number of calls that the AP could handle at an
  acceptable quality level was five calls. Similarly looking at the performance with two SMs it is
  shown that the AP can now handle a total of ten calls between the two SMs. These results show
  that the AP does scale as SMs are added and suggests that as more SMs are added, the AP will
  be able to support the theoretical numbers listed in the table above.

  It is important to note that these results are in a voice only environment. As the amount of data
  transferred on the upstream increases, the amount of bandwidth allocated to voice traffic will
  decrease. The way to guarantee that the same bandwidth is consistently allocated to voice traffic
  is through the high priority classification under the quality of service option.

  Taking the actual data from the test results and comparing it against the theoretical calculations
  of what an AP can handle, the maximum number of calls to AP can be estimated and evaluated
  per codec. Knowing that the G.711a, G.711u, G.726 and G.729 codecs have produced the most
  reliable results during testing, those codecs are evaluated below. The test results (low MOS
  scores) from the G.723.1-ACELP and G.723.1-MPMLQ codecs suggest that these codecs do not


                                                    20
                                                                                         Motorola
                                                                        Voice over IP over Canopy


transfer well over a VoIP network due to the low data compression (kbps). It is recommended to
not use these codecs for any VoIP applications independent of the network being used.


G.711a & G.711u
By looking at the column “Theoretical Simultaneous Calls an AP Can Support Factoring Efficiency
Rate” from the above table one can see that when using the G.711a and G.711u codecs the AP
can theoretically handle approximately 33 calls at 95 kbps per call. This call volume can be
generated using as few as 7 SMs or as many as 33 SMs depending on the call volume per SM.

Since it has been shown that the AP’s robustness scales with increased traffic it is expected that
it should be able to actually handle the theoretical value of 33 calls. Given the high MOS score
value with five calls from each SM (4.37), it is expected that the AP will still be able maintain a
quality level that is considered satisfactory as it scales to 33 calls.

G.726
By looking at the column “Theoretical Simultaneous Calls an AP Can Support Factoring Efficiency
Rate” from the above table one can see that when using the G.726 codec the AP can
theoretically handle approximately 46 calls at 55 kbps per call. This call volume can be
generated using as few as 10 SMs or as many as 46 SMs, depending on the call volume per SM.

Although theoretically the G.726 codec appears like it can handle a large volume of simultaneous
calls, by looking at the MOS score at a low call volume it is the expectation that as the network
scales any additional degradation in the MOS score would make the call quality unacceptable.
Using two SMs and five calls from each SM, the MOS score was 4.16, which is considered a
good value. However, when the network scales to as many as 46 simultaneous calls per AP it is
expected that the MOS score will continue to degrade to an unacceptable level and may not be
able to reach the theoretical maximum.

G.729
By looking at the column “Theoretical Simultaneous Calls an AP Can Support Factoring Efficiency
Rate” from the above table one can see that when using the G.729 codec the AP can
theoretically handle approximately 68 calls at 39 kbps per call. This call volume can be
generated using as few as 13 SMs or as many as 68 SMs depending on the call volume per SM.

Similarly to the G.726 codec, theoretically the G.729 codec appears like it can handle a large call
volume of simultaneous calls. However, looking at the MOS score at a low call volume it is the
expectation that as the network scales any additional degradation in the MOS score would make
the call quality unacceptable. Using two SMs and five calls from each SM, the MOS score was
3.93, which is already on the borderline of when call quality begins to falter. In conclusion, even
though 68 calls is the theoretical maximum, the call quality will lower to an unacceptable level and
will most likely not get very close to 68 calls with an acceptable call quality.


   Recommendations
Based on the testing done in Phase II the following Conclusions & Recommendations are being
made:
           The G.711a & G.711u codecs performed the best in terms of highest MOS value with
           a high number of successful simultaneous calls completed. It is recommended to
           use these codecs for all VoIP applications. Although other codecs may allow more


                                                 21
                                                                                Motorola
                                                               Voice over IP over Canopy


calls to pass through, it is at the cost of degraded call quality.

As the number of SMs is increased the performance of the AP also scales, which will
aid in the Canopy network reaching the theoretical call maximum.

The number of calls an AP can handle will vary based on the codec. The codecs
with higher bandwidth compression, such as G.729, will allow more calls to be
completed per AP as they take up less bandwidth per call. However, with these
codecs the call quality is considerably less and as the call volume increases the MOS
value will degrade and lead to unacceptable call quality as the theoretical maximum
is approached.

The codecs with the lower bandwidth compression, such as G.711, allowed fewer
calls to pass through at a much higher quality level. It would be expected that
degradation in MOS value here would not have as much of an impact because it is
starting at a much higher value.

Bandwidth allocation through Canopy is static and should be taken into consideration
when determining how much bandwidth is needed for a customer’s network.

o   For a network that will be running primarily voice traffic, a WISP would want to
    consider setting the downlink/uplink percentage at 50/50. This will give sufficient
    bandwidth to the uplink on the AP and will allow the SM to support more calls at
    a higher call quality rate.
o   In a customer environment where “non-voice data” is still the primary type of data
    being transferred, it may be that the WISP will require a significant amount of
    bandwidth for downstream data transfer. The downstream bandwidth allocation
    requirement could force the WISP to put the downlink/uplink closer to a 75%/25%
    configuration. If the expectation is that a customer will not be doing more than 1
    - 2 calls simultaneously from one SM, the 75%/25% configuration can transmit
    the calls with very good quality (MOS value greater than 4 and low packet loss).

A high performance setting for Canopy QoS with the downlink/uplink set at 75%/25%
is two high priority slots active. This will allow sufficient bandwidth for 1 or 2 calls to
be completed with good call quality, which will be typical in most Canopy applications
in a residential setting.

QoS was shown to successfully filter data traffic independent of the size of the data
file. While increasing the data file size incrementally up to 1.2 Mb the voice call
quality still passed at a MOS value well above the acceptable level of 4.




                                      22
                                                                                           Motorola
                                                                          Voice over IP over Canopy




  **        %
           ."

   Phase II Test Results
The following tables depict the statistical results for each test using the IXIA Chariot software.
Within each of the results below, the test setup, explanation and all variables are defined.

Canopy set at 50% downlink / 50% uplink – G.711a
Multiple tests were conducted with VoIP traffic only for the G.711a (64 kbps) codec over one and
two SMs. From the test results below, five VoIP calls were run successfully over one SM, but the
addition of a sixth call begins to show call degradation. As the upstream VoIP traffic begins to get
a large one-way delay and amount of lost packets, the MOS score lowers which indicates call
quality would become jittery and would not be acceptable.

Tests were then conducted using traffic from two SMs. As SMs are added, the AP is able to
scale better as 5 calls from each SM were successfully completed (10 total). As a sixth call was
added to each SM, a sharp increase in lost bytes and one-way delay resulted which contributed
to unacceptable MOS scores. In a two SM environment, 10 – 11 calls can be supported
successfully, but any additional calls will cause degradation in performance.
Table 6
           Downlink /              Number of     One way                            R-
                         Number                                           MOS
  Codec      Uplink                calls from     delay     Bytes Sent             Value   Lost Bytes
                         of SMs                                           avg.
           Percentage               each SM      avg (ms)                          Avg.

 G.711a       50/50         1           5          20       12,000,000    4.37    91.32        0

 G.711a       50/50         1           6          56       13,942,400    3.62    71.21     221,594

 G.711a       50/50         2           5          32       11,999,840    4.36    90.85       160
 G.711a       50/50         2           6          93       13,932,160    2.87    51.10     467,680

Canopy set at 50% downlink / 50% uplink – G.711u
The tests below were conducted for the G.711u codec (64 kbps). This codec is very similar to
G.711a and received similar results. From the data below, five VoIP calls were run successfully
over one SM, but the addition of a sixth call begins to show call degradation. When the tests are
run over two SMs, very similar results to the G.711a codec are produced. Five calls from each
                                                    th      th
SM were successful, but the addition of a sixth (11 and 12 calls) increased lost bytes and one-
way delay which contributed to unacceptable MOS scores.
Table 7
            Downlink /              Number of    One way                            R-
                          Number                                           MOS
  Codec       Uplink                calls from    delay      Bytes Sent            Value    Lost Bytes
                          of SMs                                           avg.
            Percentage               each SM     avg (ms)                          Avg.
 G.711u        50/50         1          5           19      11,979,040     4.34    90.42     20,960
 G.711u        50/50         1          10          66      18,892,320     2.69    45.82    4,843,840
 G.711u        50/50         2          5           13      11,999,840     4.37    91.35       160

 G.711u        50/50         2          6          100      13,928,960     2.86    51.24     456,160




                                                  23
                                                                                          Motorola
                                                                         Voice over IP over Canopy


Canopy set at 50% downlink / 50% uplink – G.726
Multiple tests were conducted with VoIP traffic only for the G.726 codec (32 kbps) over one and
two SMs. From the test results below, six VoIP calls were run successfully over one SM, but the
addition of a seventh call begins to show call degradation. As the upstream VoIP traffic begins to
get a large one-way delay and amount of lost packets, the MOS score lowers which indicates call
quality would become jittery and choppy and would not be acceptable.

Tests were then conducted using traffic from two SMs. As SMs are added, the AP is able to
scale better and is able to successfully complete 5 calls from each SM (10 total). As additional
calls were added to each SM a sharp increase in lost bytes and one-way delay resulted which
contributed to unacceptable MOS scores. In a two SM environment, 12 – 14 calls can be
supported successfully, but any additional calls will cause degradation in performance.
Table 8
                                     Number
             Downlink /                          One way                         R-
                           Number     of calls                           MOS
  Codec        Uplink                             delay     Bytes Sent          Value     Lost Bytes
                           of SMs      from                              avg.
             Percentage                          avg (ms)                       Avg.
                                     each SM
  G.726        50/50            1       6          23        7,199,920   4.18   84.44         80
  G.726        50/50            1       7          68        8,397,120   2.60   45.75     1,390,320
  G.726        50/50            2       5          22       11,998,320   4.16   83.96       1,680
  G.726        50/50            2       8          66       16,963,960   2.52   40.57     2,236,000

Canopy set at 50% downlink / 50% uplink – G.729
Multiple tests were conducted with VoIP traffic only for the G.729 (8 kbps) codec over one and
two SMs. From the test results below, six VoIP calls were run successfully over one SM, but the
addition of a seventh call begins to show call degradation. As the upstream VoIP traffic begins to
get a large one-way delay and a large amount of lost packets, the MOS score lowers which
indicates call quality would become jittery and would not be acceptable.

Tests were then conducted using traffic from two SMs. As SMs are added, the AP is able to
scale better as five calls from each SM (10 total) were completed at the acceptable limit. As
additional calls were added to each SM, a sharp increase in lost bytes and one-way delay
resulted in unacceptable MOS scores. In a two SM environment, 10 calls can be supported
successfully, but any additional calls will cause degradation in performance.
Table 9
           Downlink /               Number of    One way
                          Number                                         MOS    R-Value      Lost
  Codec      Uplink                 calls from    delay     Bytes Sent
                          of SMs                                         avg.    Avg.        Bytes
           Percentage                each SM     avg (ms)
  G.729      50/50          1           6           21      1,800,000    4.02    79.87        20
  G.729      50/50          1           7           57      2,096,860    3.41    67.18      98,260
  G.729      50/50          2           5           21      2,991,500    3.93    77.72       8,500
  G.729      50/50          2           8           54      4,799,760    2.90    56.66      486,640

Canopy set at 50% downlink / 50% uplink – G.723.1-ACELP
Multiple tests were conducted with VoIP traffic only for the G.723.1-ACELP (5.3 kbps) codec over
one and two SMs. From the test results below, this codec received a low MOS score even
though there was no lost data and a low one-way delay. Test results showed that anywhere from
one to five calls had approximately the same results. Also, performing a test with a low amount of
calls between two SMs resulted in a low MOS score.


                                                   24
                                                                                                Motorola
                                                                               Voice over IP over Canopy



The test results suggest that this codec does not transfer well over a VoIP network due to the low
kbps. It is recommended to not use this codec for any VoIP applications independent of the
network being used.
Table 10
             Downlink /               Number of      One way
                           Number                                              MOS     R-Value       Lost
  Codec        Uplink                 calls from      delay      Bytes Sent
                           of SMs                                              avg.     Avg.         Bytes
             Percentage                each SM       avg (ms)
 G.7231 -
               50/50         1          1-5            18         990,000      3.63     70.65            0
 ACELP
 G.7231 -
               50/50         1           10            45        1,977,540     3.24     62.61       38,000
 ACELP
 G.7231 -
               50/50         2            8            30        3,168,000     3.60     70.09         320
 ACELP
 G.7231 -
               50/50         2           10            56        3,959,780     3.19     61.56       76,180
 ACELP

Canopy set at 50% downlink / 50% uplink – G.723.1-MPMLQ
Multiple tests were conducted with VoIP traffic only for the G.723.1-ACELP (6.3 kbps) codec over
one and two SMs. From the test results below, this codec received very similar scores as the
ACELP codec as it displayed a low MOS score even though there was no lost data and a low
one-way delay. Test results showed that anywhere from one to five calls had approximately the
same results. Adding a low amount of calls between two SMs resulted in a similarly low MOS
score.

The test results suggest that this codec does not transfer well over a VoIP network due to the low
kbps. It is recommended to not use this codec for any VoIP applications independent of the
network being used.
Table 11
                                         Number
              Downlink /                              One way                          R-
                             Number       of calls                             MOS
   Codec        Uplink                                 delay      Bytes Sent          Value      Lost Bytes
                             of SMs        from                                avg.
              Percentage                              avg (ms)                        Avg.
                                         each SM
  G.7231 -
                50/50            1        1-5             19      1,176,000    3.80   74.63          0
  MPMLQ
  G.7231 -
                50/50            1            10          58      2,346,672    3.44   67.06       35,184
  MPMLQ
  G.7231 -
                50/50            2            8           24      3,763,200    3.80   74.39         312
  MPMLQ
  G.7231 -
                50/50            2            10          91      4,646,688    2.46   42.11      1,198,272
  MPMLQ

Canopy set at 75% downlink / 25% uplink – G.711a
Multiple tests were conducted with VoIP traffic only for the G.711a (64 kbps) codec over one and
two SMs. From the test results below, four VoIP calls were run successfully over one SM, but the
addition of a fifth call begins to show call degradation. As the upstream VoIP traffic begins to get
a large one-way delay and a large amount of lost packets, the MOS score lowers which indicates
call quality would become jittery and would not be acceptable.

Tests were then conducted using traffic from two SMs. As SMs are added, the AP is able to
scale better as four calls from each SM (8 total) were completed successfully. As a fifth call was
added to each SM, a sharp increase in lost bytes and one-way delay contributed to unacceptable


                                                     25
                                                                                           Motorola
                                                                          Voice over IP over Canopy


MOS scores. In a two SM environment, 8 – 9 calls can be supported successfully, but any
additional calls will cause degradation in performance.
Table 12
                                   Number
           Downlink /                            One way                           R-
                         Number     of calls                              MOS
Codec        Uplink                              delay avg   Bytes Sent           Value     Lost Bytes
                         of SMs      from                                 avg.
           Percentage                              (ms)                           Avg.
                                   each SM

G.711a       75/25         1          4             22       9,512,000    4.22    87.07      16,960

G.711a       75/25         1          5             68       11,906,720   3.54    69.87     218,880
G.711a       75/25         2          4             24       19,047,040   4.13    85.02      52,320

G.711a       75/25         2          5             71       16,842,240   3.41    67.24     349,280


Canopy set at 75% downlink / 25% uplink – G.711u
Multiple tests were conducted with VoIP traffic only for the G.711u (64 kbps) codec over one and
two SMs. From the test results below, four VoIP calls were run successfully over one SM, but the
addition of a fifth call begins to show call degradation. As the upstream VoIP traffic begins to get
a large one-way delay and a large amount of lost packets, the MOS score lowers which indicates
call quality would become jittery and choppy and would not be acceptable.

Tests were then conducted using traffic from two SMs. As SMs are added, the AP is able to
scale better as four calls from each SM (8 total) we completed successfully. As a fifth call to each
SM was added, a sharp increase in lost bytes and one-way delay contributed to unacceptable
MOS scores. In a two SM environment, 8 – 9 calls can be supported successfully, but any
additional calls will cause degradation in performance.
Table 13
            Downlink /              Number of     One way
                          Number                                          MOS     R-Value      Lost
 Codec        Uplink                calls from     delay     Bytes Sent
                          of SMs                                          avg.     Avg.        Bytes
            Percentage               each SM      avg (ms)
G.711u        75/25            1          4          23      9,600,000    4.33     90.13      4,960
G.711u        75/25            1          5          69      12,000,000   3.78     76.11     121,600
G.711u        75/25            2          4          28      19,200,000   4.32     89.67      11,840
G.711u        75/25            2          5          70      23,999,360   3.78     76.29     240,960


Canopy set at 75% downlink / 25% uplink – G.726
Multiple tests were conducted with VoIP traffic only for the G.726 (32 kbps) codec over two SMs.
From the test results below, 5 calls from each SM (10 total) were completed successfully. As a
sixth call was added to each SM, a sharp increase in lost bytes and one-way delay contributed to
unacceptable MOS scores. In a two SM environment, 10 – 11 calls can be supported
successfully, but any additional calls will cause degradation in performance.
Table 14
            Downlink /              Number of     One way
                          Number                                          MOS     R-Value      Lost
 Codec        Uplink                calls from     delay     Bytes Sent
                          of SMs                                          avg.     Avg.        Bytes
            Percentage               each SM      avg (ms)
 G.726        75/25            2          5          40      11,875,520   4.02     80.70      22,720

 G.726        75/25            2          6          75      14,399,360   2.83     50.64     948,720



                                                     26
                                                                                                  Motorola
                                                                                 Voice over IP over Canopy


Canopy set at 75% downlink / 25% uplink – G.729
Multiple tests were conducted with VoIP traffic only for the G.729 (8 kbps) codec over two SMs.
From the test results below, 5 calls from each SM (10 total) were completed successfully. As a
sixth call to each SM was added, a sharp increase in lost bytes and one-way delay contributed to
unacceptable MOS scores. In a two SM environment, 10 – 11 calls can be supported
successfully, but any additional calls will cause degradation in performance.
Table 15
            Downlink /                Number of     One way
                          Number                                                 MOS           R-Value      Lost
  Codec       Uplink                  calls from     delay      Bytes Sent
                          of SMs                                                 avg.           Avg.        Bytes
            Percentage                 each SM      avg (ms)
  G.729       75/25          2            5           24        2,961,440        4.01          79.73        1,040

  G.729       75/25          2            6           61        3,546,880        3.57          70.44        96,880


Canopy set at 75% downlink / 25% uplink – G.723.1-ACELP and G.723.1-MPMLQ
Due to the poor performance of these codecs during the tests where Canopy was set at 50%
downlink and 50% uplink, no tests were run in the 75% / 25% configuration. Since the uplink is
the known constraint, lowering it would only lower the performance of the codec. The test results
suggest that this codec does not transfer well over a VoIP network due to the low kbps. It is
recommended to not use these codecs for any VoIP applications independent of the network
being used.


   Test Scenarios with Canopy Quality of Service (QoS)
To test the robustness of the quality of service functionality a data file was passed through at the
same time as the VoIP. The purpose was to see how effectively the AP could regulate the traffic
and if it was at all affected by the amount of data that was being simultaneously passed with the
VoIP traffic. The size of the data files were incrementally increased starting at 128 Kb up to 1.2
Mb. As shown in the table below, the quality of the call did not fluctuate noticeably with increased
amount of data being passed. This is shown by noting the MOS values being at 4.36 when 128
kbps file was passed and 4.29 when a 1.2 Mbps file was passed. These results demonstrate that
regardless of the amount of data, the AP will provide a level of guaranteed bandwidth for VoIP
traffic.
Table 16
           Downlink/       Testing     Number of      Data File
                                                                                        MOS       R-Value     Lost
 Codec       Uplink        Config.     Calls from    Bandwidth      Bytes Sent
                                                                                        Avg.       Avg.       Bytes
           Percentage    (# of SMs)       SM            Size

G.711u       75/25           1             1         128 Kbps       8,800,000           4.36       90.95       480

G.711u       75/25           1             1         1.2 Mbps      62,400,000           4.29       88.89      2,400


Now that it has been shown that the high priority bit will serve the function of regulating the data
traffic while voice traffic is present, the limitations needed to be tested. In the following test
scenarios the number of high priority slots allocated for voice traffic was adjusted from 1 slot up to
3 slots. This was done to demonstrate whether there is a positive, negative or indifferent impact
on overall performance and throughput as a result of adding more slots for high priority.

Another variable that was adjusted was the bandwidth allocation on the downlink and uplink from
75/25 to 50/50. The number of “Acknowledgement” slots for downlink and uplink were not varied.



                                                     27
                                                                                                           Motorola
                                                                                          Voice over IP over Canopy


The different codecs were tested with one or two SMs as well as different call volumes to
determine the breaking point in quality.

   Test Results with Canopy QoS
Testing on QoS was done using both the 75/25 and 50/50 downlink/uplink settings. In regards to
QoS, the most important setting is how many high priority slots are allocated. This is a function of
the downlink/uplink percentage and the high priority percentage that is set in the configuration of
the AP. Different percentage configurations will yield a varied number of high priority slots
depending on your Canopy environment and configurations. When applying these settings it is
encouraged to adjust them accordingly such that the desired number of high priority slots is
produced. Some example scenarios and their results from the testing are shown below.

High Priority = 1 Slot
This test was done with 1 high priority slot set. To achieve one high priority slot, the
downlink/uplink percentage was set to 75/25, the high priority percentage was set to 25%, and
the G.711u codec was tested. The tests were run with one and two SMs. With one SM two calls
were successfully completed, which is shown in the table below with a MOS score of 4.34. With
two SMs, one call from each SM failed to complete at an acceptable quality level, which is shown
in the table below with a MOS score of 2.69.

         Downlink Data Percentage                   75%         UpLink Data Percentage            25%
         Downlink Slots                                 21      Uplink Slots                       7

         High Priority Slots                            1

         Total Num UAck Slots                           6       UAcks Reserved High                3

         Num DAck Slots                                 6       DAcks Reserved High                3

         Num Ctl Slots                                  6       Num Ctl Slots Reserved High        3



Table 17
           Downlink/             Testing    Number            Data File
                                                                                         MOS    R-Value
Codec        Uplink              Config.     of Calls        Bandwidth     Bytes Sent                     Lost Bytes
                                                                                         Avg.    Avg.
           Percentage          (# of SMs)   from SM             Size

G.711u        75/25                1           2                22         4,800,000     4.34   90.43       2,080

G.711u        75/25                1           3                231        7,195,680     2.69   45.81     1,766,880

G.711u        75/25                2           1                355        4,800,000     2.69   45.81      132,800


High Priority = 2 Slots
This test was done with two high priority slots set. To achieve two high priority slots, the
downlink/uplink percentage was set to 75/25, the high priority percentage was set to 25% and the
G.711u codec was tested. The tests were run with one and two SMs. With one SM two calls
were successfully completed, which is shown in the below table with a MOS score of 4.30. With
two SMs, two calls total (one from each SM) were completed at an acceptable quality level, which
is shown in the table below with a MOS score of 4.33. Once the call volume was increased to
two calls per SM, the high priority channel failed to handle it at an acceptable quality level.




                                                                28
                                                                                                           Motorola
                                                                                          Voice over IP over Canopy


         Downlink Data Percentage                   75%         UpLink Data Percentage            25%
         Downlink Slots                                 21      Uplink Slots                       7

         High Priority Slots                            2

         Total Num UAck Slots                           6       UAcks Reserved High                3

         Num DAck Slots                                 6       DAcks Reserved High                3

         Num Ctl Slots                                  6       Num Ctl Slots Reserved High        3



Table 18
           Downlink/             Testing    Number            One Way
                                                                                         MOS    R-Value
Codec        Uplink              Config.     of Calls        Delay Avg.    Bytes Sent                     Lost Bytes
                                                                                         Avg.    Avg.
           Percentage          (# of SMs)   from SM             (ms)

G.711u        75/25                1           2                30         4,800,000     4.30   89.32       2,880
G.711u        75/25                1           3                128        7,200,000     2.73   49.60      529,440

G.711u        75/25                2           1                21         4,800,000     4.33   90.14       2,400
G.711u        75/25                2           2                68         9,600,000     2.73   47.41      282,240

The G.711 codec has shown to be the most consistent and highest in quality in terms of overall
performance. The above tests showed that the 75/25 bandwidth allocation did not allow a large
amount of calls through the network while using the G.711 codec and some instances didn’t allow
even one call through. It was determined that further testing on the other codecs would not
produce more favorable results, so the testing was limited to just this codec.

High Priority = 3 Slots
This test was with 3 high priority slots set. To achieve three high priority slots, the downlink/uplink
percentage was set to 50/50, the high priority percentage was set to 25% and the G.711, G.726
and G.729 codecs were tested. The tests were run with one and two SMs. By allocating more
bandwidth by increasing the uplink percentage, an extra high priority slot was made available.
This allowed more calls to be successfully completed utilizing the high priority channels.
However, keep in mind that these slot allocations are static and one data slot needs to be traded
for every additional slot that is allocated for high priority VoIP traffic. To make sure that there is
not too much idle bandwidth in the network, it is in the best interest of the customer to closely
calculate how much bandwidth is necessary for high priority.

         Downlink Data Percentage                   50%         UpLink Data Percentage            50%
         Downlink Slots                                 14      Uplink Slots                       13

         High Priority Slots                            3

         Total Num UAck Slots                           6       UAcks Reserved High                3

         Num DAck Slots                                 6       DAcks Reserved High                3

         Num Ctl Slots                                  6       Num Ctl Slots Reserved High        3




                                                                29
                                                                                             Motorola
                                                                            Voice over IP over Canopy


G.711
G.711a and G.711u performed almost identically, so the results of just G.711u have been listed
below as a representation of both tests. With one SM, three calls were successfully completed
with an average MOS score of 4.29. When another SM was added the total number of
successful calls increased to four, (2 calls from each SM), with a MOS score of 4.29.

Table 19
           Downlink/      Testing    Number       One Way
                                                                           MOS    R-Value
Codec        Uplink       Config.     of Calls   Delay Avg.   Bytes Sent                    Lost Bytes
                                                                           Avg.    Avg.
           Percentage   (# of SMs)   from SM        (ms)
G.711        50/50          1           3           31        7,200,000    4.29   89.06       6,560
G.711        50/50          1           4           108       9,599,680    2.68   45.76      967,040
G.711        50/50          2           2           25        9,600,000    4.29   89.05       8,320

G.711        50/50          2           3           124       14,369,120   3.08   59.59      455,040


G.726
With one SM, three calls were successfully completed with an average MOS score of 4.12.
When an additional SM was added, the total number of successful calls increased to six (3 calls
from each SM) with a MOS score of 4.07.
Table 20
           Downlink/      Testing    Number       One Way
                                                                           MOS    R-Value
Codec        Uplink       Config.     of Calls   Delay Avg.   Bytes Sent                    Lost Bytes
                                                                           Avg.    Avg.
           Percentage   (# of SMs)   from SM        (ms)

G.726        50/50          1           3           25        3,600,000    4.12   82.82       2,640
G.726        50/50          1           4           91        4,800,000    2.84   55.82      142,560

G.726        50/50          2           3           25        7,200,000    4.07   81.77       8,880
G.726        50/50          2           4           93        9,600,000    2.87   56.44      290,640


G.729
With one SM, four calls were successfully completed with an average MOS score of 4.02. When
another SM was added the total number of successful calls increased to eight (4 calls from each
SM) with an average MOS score of 4.02.
Table 21
           Downlink/      Testing    Number       One Way
                                                                           MOS    R-Value
Codec        Uplink       Config.     of Calls   Delay Avg.   Bytes Sent                    Lost Bytes
                                                                           Avg.    Avg.
           Percentage   (# of SMs)   from SM        (ms)

G.729        50/50          1           4           22        1,200,000    4.02   79.90        80
G.729        50/50          1           5           77        1,500,000    3.39   66.52      63,900

G.729        50/50          2           4           22        2,400,000    4.02   79.82        640
G.729        50/50          2           5           78        2,999,920    3.38   66.21      128,460




                                                    30
                                                                                   Motorola
                                                                  Voice over IP over Canopy




          )
          (       (
                 # )'


Acronym          Meaning
AP               Access Point
Codec            Compressor/Decompressor
CPE              Customer Premise Equipment
DSP              Digital Signal Processing
ITU              International Telecommunications Union
kbps             1000 bits per second
Kbps             1024 bits per second
Mbps             1024 Kbps = 1,048,576 bits
MOS              Mean Opinion Score - To determine MOS, a number of listeners rate the
                 quality of test sentences read aloud over the communications circuit by
                 male and female speakers. A listener gives each sentence a rating as
                 follows: (1) bad; (2) poor; (3) fair; (4) good; (5) excellent. The MOS is the
                 arithmetic mean of all the individual scores, and can range from 1 (worst)
                 to 5 (best)
PSTN             Public Switched Telephone Network
QoS              Quality of Service
R-Value/Factor   The E-model is a complex formula; the output of an E-model calculation is
                 a single score, called an “R factor,” derived from delays and equipment
                 impairment factors. R factor values range from 100 (excellent) down to 0
                 (poor).
SM               Subscriber Module
TOS              Type of Service
VoIP             Voice Over IP
VPN              Virtual Private Network
WISP             Wireless Internet Service Provider




                                          31

				
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