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					                  Enhanced Data
                  GSM Environment
                                    Justin Champion
                               Room C208 - Tel: 3273
Enhanced Data GSM Environment

n   Contents
    ¨ Why    do we need it?
       n   Increased Data Rate
            ¨   Video-on-Demand
    ¨ EDGE
            over GPRS
    ¨ Benefits
    ¨ Movement towards 3G
       n   Quality of Service
       n   Packet Switched Voice
    Enhanced Data GSM Environment
n   Increased Data Use                                      3G UMTS
    ¨ As  discussed last lecture the
      introduction of increased data rates
      technology will take place over time.
                                                           2.5 G
    ¨ Each of these introductions will then                EDGE
      allow development towards 3G.                        GPRS
       n   Each of these technologies will be built
           upon to allow 3G
             ¨   Last lecture we introduced GPRS
             ¨   This time we are looking at EDGE
             ¨   Both are referred to as 2.5G technology   2G
    Enhanced Data GSM Environment
n   Edge
    ¨   Will allow another step towards the use of 3G
    ¨   This will allow the infrastructure to grow and improve
         n   Consider what would happen if a network went from 9.6 Kbps data access
             to 2Mbps in a short time
               ¨   It would not be able to cope as the companies would not be available to update
                   the entire network infrastructure that quickly
         n   The network infrastructure would not cope and upgrades will be required.
               ¨   This is already a consideration with EDGE level access
               ¨   20 devices receiving a football stream at 200 (reasonable quality) Kbps in a
                   town centre
                     § Base station needs 20 * 200 = 4 Mbps
               ¨   Now consider how many other base stations are also requesting the same
Enhanced Data GSM Environment
n   Edge
    ¨ Isnow being considered as a replacement for 3G
    ¨ Vodafone are intending to allow EDGE services this
       n   Vodafone are pushing Edge now as a 3G technology
            ¨   It will be available later this year via a data card attached to your
                   § Intended for business data users only initially
                   § Manchester, Liverpool and London are the cities it will operate
                   § (www.computerweekly.com/Article127287.htm, 2004)
Enhanced Data GSM Environment
n   The amount of value added services is predicted
    to increase
    ¨ To allow a greater choice of these services a higher
      throughput will be required for the devices
    ¨ Device will always have limited storage in comparison
      to what is available for them
       n   A solution to this is to provide those services on-demand and
           download them.
       n   After use these can be deleted with no impact on the actual
             ¨   Video on Demand is an example of this
             ¨   Location based services i.e. show me a web cam of the inside
                 of the “Peking Temple” restaurant now!
Enhanced Data GSM Environment

n   Video-on-Demand (VOD)
    ¨ Two    choices for VOD
       n   Stream the entire film across the network in real-time
             ¨   Sensitive to any delays in the network
             ¨   A powerful enough server would be needed to supply the demand
             ¨   Does not need a large amount of storage on the actual device
       n   Download parts of the film in the background to the device and
           play it when the film is in the storage of the device
             ¨   Device will need sufficient storage
             ¨   Some method would be needed to know what a person might be
                 interested in
                    § A pre-registration scheme for example with a football match
       n   A scheme somewhere between the two would be ideal
             ¨   Part of the video would be downloaded to get the viewer watching
                 whilst the rest would be downloaded in real-time
    Enhanced Data GSM Environment
n   EDGE
    ¨   Developed by Erricson for the benefit of the loser in the 3G spectrum bidding
    ¨   Operates at a theoretical 384 Kbps within the current GSM transmission bands
         n   This means that a company who has not paid for out 3G can still provide fast data
         n   Companies that have bought 3G spectrum, will benefit from the infrastructure put in
             place for EDGE, as this will be used for UMTS
    ¨   Current infrastructure
         n   The current Base stations will require a new transceiver and a software upgrade to
             allow EDGE transmission
               ¨   This can take place as and when the normal BS are being serviced
         n   This allows for a wider coverage than will be available at least initially with the
             UMTS network.
         n   Obviously there are still the same issues as GPRS in respect that a channel that is
             used for EDGE takes one away from a voice call
Enhanced Data GSM Environment
 n   EDGE continued
     ¨ The   data transferred is transferred using 8 Phase
       shifting Key (8 PSK)
        n   This can change and will be discussed further in a further
        n   This allows the transfer of 3 bits in each modulation
        n   Three times GPRS and one of the reason why EDGE is 3x
              ¨   EDGE is more sensitive to errors and as such needs to be
                  close to the transmitter to allow maximum throughput of data
    Enhanced Data GSM Environment
n   EDGE continued
    ¨ Works   the same as GPRS as in a single GSM frame
      is divided between the transmission
                                             Data Users
              Channel   Use of the Channel       A = User 1
                 1      Voice                    B = User 2
                                                 F = User 3
                 2      AAAABBABBAAAAFA
                                             In this instance we
                 3      Voice                have 3 voice calls and
                                             5 users receiving data
                 4      AAABAABAAAFAAAA
                 5      AAAFAFAFFFAFFFFB
                 6      BBBBABABAFFFFFFF
                 7      Voice
                 8      FFAFFAFFABABBBBB
Enhanced Data GSM Environment

n   EDGE
    ¨ As  with GSM and GPRS will have separate downlink
      and uplink channels
    ¨ A discussion is currently taking place regarding the use
      of 8-PSK
    ¨ As the internet is a download intensive environment
       n   8-psk may only be used in the downlink
       n   Uplink may well remain as the GSM GMSK
    ¨ This   will reduce the overhead of the 8-PSK
Enhanced Data GSM Environment

n   Quality
    ¨   EDGE uses packets which are physically closer together than the
        GPRS system
         n   This increases the likelihood of error taking place
    ¨   Coding Scheme
         n   As with GPRS, EDGE has a number of coding schemes to allow for
             these errors
               ¨   They range from
                     § MSC1 to MCS4 (using GMSK modulation)
                     § MSC5 to MSC9 (using the 8PSK modulation)
         n   As with other wireless technologies
               ¨   The best transmission rate is used to start and then a lower one will be
                   selected until successful communications can take place
Enhanced Data GSM Environment
n   Quality
    ¨   The code rate indicates how much of the packet is data
        (including headers) and how much is error checking code
         n   MCS3 indicates that 15% of the packet is error checking code
         Modulation       Data Rate    Modulation Technique     Code Rate
             MSC1          8.8 Kbps            GMSK                0.53
             MSC2         11.2 Kbps            GMSK                0.66
             MSC3         14.8 Kbps            GMSK                0.85
             MSC4         17.6 Kbps            GMSK                  1
             MSC5         22.4 Kbps             8PSK               0.37
             MSC6         29.6 Kbps             8PSK               0.49
             MSC7         44.8 Kbps             8PSK               0.76
             MSC8         54.4 Kbps             8PSK               0.92
             MSC9         59.2 Kbps             8PSK                 1
    Enhanced Data GSM Environment

n   Packet Handling improvements over GPRS
    ¨ If   a packet is sent which arrives corrupted
           n   GPRS will send the packet again using the same modulation
           n   EDGE will lower the modulation technique used and send the
               packet again.
                ¨   The lowering of the modulation is a problem
                      § The available data in a new packet is reduced
                ¨   EDGE allows for resegmentation and the packet being sent again
                ¨   This allows EDGE to send packets at a rate which would normally
                    corrupted and then resend them again when a error takes place
    Enhanced Data GSM Environment

n   Error checking continued
    ¨   Receipts for frames
         n   In GPRS a maximum addressing number is 128
              ¨   The window for receipts is a maximum of 64
              ¨   This means that after a sequence of packets are sent an acknowledgement
                  for the last (at most) 64 packets is sent
              ¨   If one of these packets were in error that packet must be resent based on the
                  addressing number
              ¨   This can be an issue with large amounts of data being sent in error as the
                  addressing window will restart again at 0
                      § Indicating that an incorrect packet maybe resent
                      § In this event the entire frame sequence would need sending again to the
         n   EDGE
              ¨   Has increased the addressing number to 2048 and the window is now 1024
                    § Thereby reducing the chance of lost packets
    Enhanced Data GSM Environment

n   Error checking continued
    ¨ Forward       Error Checking (FEC)
       n   As discussed previously it is better to send some redundant bits
           with each packet, which in the event of error can be used to
           mathematically recreate the original packet
             ¨   Alternative is to send each packet again with an increased rate of
       n   EDGE
             ¨   Will send the packet again, but the new packet will be combined with
                 the original packet to recreate the corrupted part of the packet
                   § No increase in the amount of FEC bits are sent the same
                      number are sent again, but using different bits.
       n   Correctly received packets
             ¨   The FEC bits are a waste of available bandwidth!
    Enhanced Data GSM Environment

n   Working out the correct sending rate
    ¨ This is a particular issue for data communications, rather
      than voice
    ¨ To carry this out the radio environment needs measuring
       n   Measuring for Bit error rate, carrier strength, interference, etc.
    ¨ Once measurements are made the correct coding scheme
      can be selected
       n   Measurements can be taken on every burst of data sent
             ¨   These measurements are used to generate the Bit Error Probability
             ¨   Several of these taken can be used to give an accurate reading of
                 the quality of the signal and to calculate the velocity of the device
Enhanced Data GSM Environment

n   Rollout Stages
    ¨ Phase      1
       n   Introduce single and multi-slot packet switched services
       n   Introduce single and Multi-slot circuit switched services
    ¨ Phase      2
       n   Web Use
       n   Email
       n   Real-time services
             ¨   VOIP
             ¨   Video Conferencing
Enhanced Data GSM Environment
n   Interleaving of data
    ¨   The data is sent in bursts
         n   These bursts refer to the amount of information sent
         n   If one of the bursts arrives corrupted the entire burst sequence
             needs sending again
    ¨   A radio block
         n   The sequence of the packets being sent is referred to as a radio
         n   GRPS
               ¨   The radio block are interleaved into 4
         n   EDGE
               ¨   The radio block are interleaved into 2
    ¨   Increased throughput
         n   The potential for interference in the EDGE system has now been
             reduced by a half
               ¨   Assuming all other factors remain the same
Enhanced Data GSM Environment
n    Infrastructure
      ¨ will   not need adding to from the GPRS environment

    (www.ericsson.com/products/white_papers_pdf/edge_wp_technical.pdf, 2003)
Enhanced Data GSM Environment
n   Infrastructure
    ¨ Changes
       n   Base station System GRPS Protocol (BSSGP)
             ¨   Different quality of services are required require minor changes to
                 the GPRS standards
             ¨   The other changes are obviously taking place in the layers 0 and 1
                 of the device and the base station
    ¨A EDGE Based device will be able to communicate with
       n   If a EDGE based service is not available at the time
    Enhanced Data GSM Environment
n   QOS classes
    ¨ The classes which are supported by EDGE are the same
      as UMTS
       n   Conversational
             ¨   Real-Time communications highest priority
                  § Two way communications
       n   Streaming
             ¨   Video – audio files, time dependent
                   § One way communication
       n   Interactive
             ¨   WWW usage, telnet etc
                  § Reduced request response time
       n   Background
             ¨   SMS, email, MMS
                  § Best effort delivery
    ¨ Each of the communications will be issued with one of
      these classes.
       n   This will depend ion the technology being used for EDGE
Enhanced Data GSM Environment

n   Problem with the installation of EDGE
    ¨ No   Killer App YET !
       n   There is no reason at this stage for user to want a EDGE based
    ¨ Potential     killer app maybe the downloading of music
       n   Apples i-pod (http://www.apple.com/ipod/, 2003)
       n   Allows the downloading of music onto the device, with 20Gb of
            ¨   Consider if these songs were downloaded in the background of
                your phone and you pay for them.
            ¨   You specify and pay for the album a few days in advance
            ¨   Albums available to you the second they are released
            ¨   Massive potential, with records that shops usually sell out of
Enhanced Data GSM Environment

n   Key Points
           upon GSM and GPRS
    ¨ Builds
    ¨ EDGE allows a theoretical 384 Kbps
       n   8-PSK
    ¨ Improved     error handling over GPRS
       n   Will operate at GPRS, GSM data rates in EDGE is not available
Enhanced Data GSM Environment

n   Summary
    ¨ Why    do we need it?
       n   Video-on-Demand
    ¨ EDGE
    ¨ Benefits   over GPRS

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