15 April 2010
Telecom Regulatory Authority of India
Mahanagar Door Sanchar Bhavan
Jawahar Lal Nehru Marg
New Delhi - 110002
Sub: Response to TRAI pre-consultation paper on “IMT-Advanced (4G) Mobile wireless
broadband services” dated 10th Feb 2010
The Broadband Wireless Consortium of India (BWCI) is pleased to respond to the call for
comments on the pre-consultation paper on the IMT-Advanced (4G) Mobile Wireless
Broadband services. As you may be aware, BWCI has been actively working on the 4G
technologies – WiMAX2.x and LTE-Advanced, from Analysis, Research to Technology
demonstration. The Center of Excellence in Wireless Technology (CEWiT), an autonomous
R&D organisation funded by DIT and industry through BWCI, is very deeply involved in the
ongoing evaluation of IMT-Advanced (4G) technologies along with TCoE India, which is one
of the Independent Evaluation Groups identified by ITU for the task. BWCI has also prepared
and released a report on “India Broadband Wireless Technology Requirements” in Nov
2007. We thank you for giving us an opportunity to pool in this experience and provide our
views on 4G services for India.
Hon. Director CEWiT and Professor, IIT madras
#152, CSD Building, ESB, IIT Madras Campus
Chennai - 600 036
Response from BWCI to TRAI pre-consultation paper on
“IMT-Advanced (4G) Mobile wireless broadband services”
dated 10th Feb 2010
IMT-A requirements for 4G
ITU defines ´IMT-Advanced´ systems as those which go beyond IMT-2000 to provide a global
platform on which to build the next generations of mobile services - fast data access, unified
messaging and broadband multimedia - in the form of exciting new interactive services. IMT-
Advanced (4G) status will be conferred upon wireless technologies that achieve super high-speed
mobile broadband with data rates of the order of 1Gbps for slow moving, nomadic & stationary
users, and 100 Mbps for highly mobile users, both with low latency of 10ms. More importantly, the
IMT-A requirements call for a spectral efficiency of at least 7 bps/Hz/site, which is very important for
a country like India. We are seeking to use wireless broadband technologies to provide primary
broadband access to all, in view of the limited wire-line access infrastructure in our country. High
spectral efficiency, which in turn yields high system capacity for a given amount of spectrum, is
critical for meeting the needs of a vast population with high densities such as ours. The document
titled “India Broadband Wireless Technology Requirements” published by BWCI in 2007  provides
a summary of the Indian broadband wireless requirements. Currently there are two candidate
technologies, namely 3GPP LTE-Advanced and IEEE 802.16m being evaluated by ITU-R and generally
expected to achieve the 4G status. The ITU evaluation process is scheduled to complete by Feb 2011.
To achieve the kinds of high speeds specified in IMT-Advanced requirements and to get good
spectral efficiencies, the quantum of spectrum required to deploy 4G technologies (LTE-Advanced
and 802.16m) will be a minimum of 2x10MHz or 1x20MHz. While this is the minimum for an
operator, assignments in most countries are typically 30 MHz or more per operator. The availability
of such amounts of spectrum is very important for the best use of this technology. Moreover, it is
best if the spectrum is made available in bands that are common with the other big markets of the
world, in order to ensure both competitive pricing of equipment, as well as international roaming. It
is expected to take several years for the deployments to get the scale and cost-effectiveness for the
4G technologies. The progress towards 4G would thus be evolutionary with the initial deployments
basing on LTE (or enhanced HSPA) or IEEE 802.16e. We submit to TRAI that the considerations
towards 4G that we discuss here are not just relevant for 4G but also to be addressed in the journey
towards it, some of which are relevant for the pre-4G technologies too.
The ITU report ‘Trends in Telecommunication Reform 2008’ highlighted the different forms of
sharing that can be used to reduce the cost of deploying broadband networks, particularly in
developing countries. Infrastructure share was identified as one of the enablers for providing
affordable and widespread access to ICT.
RAN Sharing –This maximizes radio capacity and enables multiple service providers to
effectively share the RAN with the other RNC(s) routing calls to up to four different service
providers’ Core Networks.
Infrastructure sharing/Site sharing – Passive infrastructure sharing, which has been in use for
quite some time, primarily targets sharing of non-electrical components such as cables,
ducts, trenches, masts, pylons, towers, physical space, power supplies, air conditioning etc.
Infrastructure that forms part of active sharing includes active network elements such as
antennas, transmission systems, gateways etc.
Common Shared Networks – In this scenario, operators build and operate a common
network comprising of the Core (Both Circuit and Packet). However the HLR, Gateway, Billing
systems and subscriber databases, etc., are kept separate.
DoT has allowed infrastructure sharing between service providers. As per its guidelines:
Sharing of active infrastructure amongst Service Providers based on the mutual agreements entered
amongst them is permitted. Active infrastructure sharing will be limited to antenna, feeder cable,
Node B, Radio Access Network (RAN) and transmission system only. Sharing of the allocated
spectrum will not be permitted. The licensing conditions of UASL/CMSP will be suitably amended
wherever necessary to permit such sharing.
In practice, operators have found it difficult to realize active infrastructure sharing. To some extent,
it is because legacy networks were not designed in such a way and hence active sharing was
considered too complex and costly. Given the large number of operators in India, it is important to
encourage active infrastructure sharing and enable it at least in future technologies. It is worth
considering whether interface specifications for 4G equipment that enable such sharing should be
drawn up and policy guidelines implemented that strongly encourage deployment by operators of
equipment that meet these specifications. Such an initiative can benefit in reducing the overall
Capex and Opex costs which could finally help in giving a more cost-effective service to the
customers. Since the migration from existing systems to 4G networks will be gradual, the initial
deployments will be of limited capacity. It may be thus worth looking at facilitating the sharing of
Core Network elements as well in addition to RAN, while keeping the billing, charging and other
subscriber related systems separate for each operator.
Femto Base Stations and Personal Relays
Femto Base stations and Personal Relays are low-power access points, providing wireless voice and
broadband services to customers primarily at home. They help improve spectral efficiency indoors
and thus provide high quality, high speed signal at home. They also improve the spectral efficiency,
either by offloading traffic to the wireline connection, or due to the improved link via the relay. They
are a very important element of 4G networks.
Femto base stations need to have a DSL or cable connectivity to hook up to the network which is not
however widely available in Indian homes. Personal Relays overcome this shortcoming by providing
communication with Radio base stations using the same channel frequencies employed for
communication with mobiles devices at home. The concept of Personal Relay, which is of great
importance to India, is not yet widely known internationally since most advanced markets have good
wireline (DSL or cable) infrastructure and Femto base stations are the natural choice there. BWCI
and CEWiT are active in evangelizing the concept of indoor personal relay in the 4G standards
bodies, and in enabling the standards to support such a user self-installed low-cost product as an
effective alternative to Femto base stations.
Some of the aspects to look into for Femto base stations and Personal Relays are
Spectrum usage and license
The Femto base stations and Personal relays will be a part of the operator’s network and will
use the same frequencies allocated to the operators. The devices will be under the control of
Power levels and Public health concerns
The power levels used would be comparable to or less than that of the Wireless LAN devices.
These also help in mobiles operating at lower power levels.
Location of Femto base stations and Personal Relays
When Femto base stations are connected to the DSL or similar broadband connection, it is
possible to identify the Femto base stations by associating it with the location of the fixed
broadband connection. In case of Personal Relays, the location can be associated with the
Base Station it communicates with.
TRAI could look at the various aspects of Femto base stations and Personal Relays, and issue
appropriate regulatory guidelines for the operators to encourage their use and provide the service
to consumers. In particular, TRAI could encourage the development and deployment of indoor
personal relays for enhancing indoor broadband performance and spectrum efficiency.
The 4G technologies based on LTE and WiMAX add tremendous capacity and speeds to the existing
networks based on 2G and 3G. The capacity requirements of Cell site backhaul and aggregation to
carry this traffic will increase manifold, from few megabytes/sec to gigabytes/second. The current
backhaul networks have to migrate to the higher capacities over time in phases.
There are several technologies which could be deployed for this. We are mentioning a few which
would need attention from the Regulation aspects.
One of the key aspects with 4G networks would be the need to have a standardized
transport/backhaul mechanism from the eNodeB/BS to S-GW/ASN. The core network envisaged for
both WiMaX and LTE is an all IP network. Current architecture has fiber connectivity to all the hub-
nodes supporting Ethernet over SDH. The cell-site nodes are mostly connected over Microwave.
Operators are considering hybrid and Ethernet radio in addition to PDH radios. This makes a case for
using Ethernet unlike other countries. For example, the LTE based access networks require backhaul
of S1 from multiple eNodeB locations to one or two Serving GateWays. The LTE networks can also
use the backhaul for X2 from any eNodeB to any eNodeB defined for mobility purposes. The former
from a transmission perspective is point to multipoint (P2MP) and the latter is multipoint to
multipoint (MP2MP) Ethernet. MEF has defined this construct as E-Tree and E-LAN respectively. The
typical requirement as specified by NGMN standard is around 150/50 Mbps DL/UL for a 20MHz
carrier. The networks could evolve from the speeds as required today to the peak ones supported by
these technologies. To provide multiple path redundancy for link between eNB and S-GW additional
point-to-point (P2P) E-Line bandwidth from third party service provider also may be needed.
The authority could consider pricing guidelines for such Ethernet services (E-line, E-Tree, E-LAN)
which could be based on distance between the nodes and the number of nodes. This would allow
multiple operators to share the transmission cost at standardized pricing. Pricing guidelines can be
based on the NGMN  Reference rate of 2 Mbps between 2-30Mbps, and increments of 10Mbps
up to 100Mbps, and increments of 100Mbps beyond 100Mbps consisting of both peak information
rate (PIR) and committed information rates (CIR) with maximum burst size. For example, pricing can
be provided for 50Mbps CIR, 100 Mbps PIR as rate x1, 50Mbps CIR, 200 Mbps PIR as rate x2,
50Mbps CIR, 100 Mbps PIR as rate y1 and so on. Extending this E-line price modeling to E-TREE and
E-LAN would mean pricing for CIR, PIR for 1 x N, N x 1 and N x N respectively, where N = number of
end-points from 1, 2, 3, ..16 (Max of 16 is specified by NGMN).
The transmission network for 4G has to take care of the synchronization requirement of the BS so
that the handoff is seamless without any packet drop . For FDD, frequency synchronization is
required while for TDD both frequency and timing synchronization are required. In case the
transmission is a shared pipe, then stringent QoS should be met to ensure that
control/synchronization gets higher priority over other traffic. The QoS of transmission layer should
also ensure that voice and video traffic are prioritized over best effort internet traffic. In addition to
having a good customer experience the transmission should have no single point of failure. Any
failure in transmission layer can affect the services to large number of customers.
In case TDD option is selected by the regulator, there is a need to time synchronize BSs of collocated
networks, using multiple sources like GPS, transport network etc. The mechanisms selected for time
synchronization need to ensure that it is not dependant on only one source. Currently GPS is
provided only by American GPS constellation. India is slated to have its own GPS constellation in a
few years. It may be necessary from a national perspective to mandate cutover to this source for
synchronization. Other aspects to look into for GPS based systems are call drop (sudden jitter during
the shift of synchronization from one GPS satellite to another) and timing quality (due to the effect
of climate changes on access to GPS). NGMN also mandates the need to support multiple sources for
synchronization. Hence, the time synchronization needs for base station can be provided in the
guidelines from the Authority by mandating the support of standards such as IEEE (IEEE 1588v2) or
3GPP based standards by all the 4G base station operators with a minimum accuracy of, say, at least
The backhaul capacity requirements become manifold for 4G networks. When wireless backhaul is
to be provided, there is a need to have much higher bandwidth than that is allocated now for the
same purpose. Currently the cell sites are connected over few E1/T1 circuits. The cell site backhaul
has to evolve from this to initially several tens of Mbps and ultimately to the speeds supported in 4G
technologies. We recommend that the authority gives a holistic look at this for smooth
implementation of the 4G technologies.
TDD and FDD spectrum
The spectrum bands will be released as TDD or FDD, both of which are supported in the LTE and
WiMAX technologies. The issue of TDD or FDD will need to be looked at for each band considering
the band available, technology available, global adoption of the same and interference issues.
In the case of FDD, the downlink and uplink bands respectively must be the same for both LTE and
WiMAX when deployed in the same geography.
In the case of TDD operation in contiguous (or near contiguous) bands, the UL and DL sub-frames of
co-located WiMAX and LTE deployments must be time aligned at all times, and the two systems
must be frame-synchronized to a common source as discussed above. The issue of time-aligned UL
and DL sub-frames has been addressed to an extent by the standards bodies. However, there is
scope for increasing the number of time-alignment options available. The Authority may consider
taking a view on this matter and urging the standards bodies to increase the options available in
order to give flexibility in configuring the UL/DL ratio to match the traffic patterns. This ratio has to
be the same across co-located TDD operators. Emerging standards need to be suitably amended to
enable co-existence with older TDD standards. Appropriate mechanisms for synchronization
between TDD operators such as GPS, Indian national positioning system, Synchronous Ethernet
based on G.8261, SDH, Packet synchronization methods like PTP or NTP etc. need to be specified.
Spectrum is the lifeline of the cellular and wireless world. IMT-Advanced (4G) Mobile wireless
broadband services bring in high speed high capacity connectivity to the end users and devices. This
is facilitated by availability of an adequate amount of spectrum to operate these services.
The major requirements of spectrum are
Very good coverage across the service areas from thickly populated cities to the sparsely
populated rural areas.
Sufficient capacity to provide the multi-media and data services required for multitude of
existing and new services
Choice of the spectrum should be such that the devices and networks are cost effective. This
aspect is very important to make the overall cost of the service attractive and affordable to
As per WRC-07, following are the spectrum which can be considered for the Broadband Wireless:
450 – 470 MHz
790 – 960 MHz (698 – 806 MHz has been identified for India)
1710 – 2025 MHz
2110 – 2200 MHz
2300 – 2400 MHz
2500 – 2690 MHz
3400 – 3600 MHz (Identified for India)
As mentioned in the “Consultation paper on Overall Spectrum Management and review of license
terms and conditions”, the use of digital dividend in the band 698-806 MHz (700 MHz band) gives an
opportunity to the governments for reaping economic benefits. The use of this spectrum will help
bridge the digital divide by giving good coverage in rural areas. It also helps to give better coverage
for vast majority of Indian urban users who are mostly indoor and nomadic. Use of these lower
frequency bands can reduce the cost of providing service by increasing the coverage per base station
resulting in a corresponding increase in the economically viable coverage area. As mentioned earlier,
the bandwidth available to each operator has to be of sufficient bandwidth to deliver the 4G
services. In keeping with the recommended norms, at least 2x10MHz block for each operator for
FDD, or 20 MHz for TDD operation may be considered.
When frequency bands used are common globally, it has a significant impact on lowering the cost of
terminals. WiMAX Forum has published three licensed spectrum profiles: 2.3 GHz, 2.5 GHz and
3.5 GHz, in order to get higher economies of scale. Similarly the LTE deployments across Europe and
Americas are primarily in the 700 MHz and 2.6 GHz bands.
We summarize that the spectrum which could be considered for allocation to Broadband Wireless
698 – 806 MHz (700 MHz band)
2300-2400 MHz (already planned in BWA auction in 2010)
2500 – 2690 MHz
3400 – 3600 MHz over a long term to be decided based on the availability of the
The channeling within the allocated bands must be done so as to be in alignment with the WiMAX
and LTE standards. In case of 700 MHz channels, it also has to be appropriately done so as to have
sufficient guard-band and minimum interference with the digital broadcast channels.
Both the candidate 4G technologies, LTE and WiMAX will be capable of supporting a bandwidth up
to 100 MHz. Based on the existing spectrum allocations across the world, identifying such
contiguous frequency allocation will be challenging. In order to mitigate this scarcity, both standards
will support spectrum aggregation. This will be useful for Indian deployments, where operators are
likely to get distributed chunks of smaller bandwidths. The Authority may consider specifying the
granularity of aggregation that will be best suited for the Indian scenario given the availability of
Re-farming current spectrum
Government of India has already allotted spectrum in the frequency bands of 800, 900, and 1800
MHz for the GSM and CDMA networks. The spectrum in the 2.1 GHz band is planned to be allotted
through the 3G auction now.
The IMT-Advanced technologies based on LTE and WiMAX support multiple carrier bandwidths as
well as the carrier aggregation option. Globally, 3G equipment is already becoming available in 2G
bands, and it will not be long before 4G equipment becomes available in 3G and even 2G bands.
Given the carrier aggregation options available in 4G technologies, operators should be permitted to
leverage economies of scale by migrating the networks in existing bands to newer generation
technologies at the appropriate time and in a manner that protects legacy subscribers. The Authority
may consider a study to project a roadmap for enabling flexibility in use of licensed spectrum across
multiple generations of technologies. Such flexibility will need addressing of issues related to
interference, licensing conditions, etc.
The new technologies are most optimum at higher spectrum blocks than allocated in 2G and 3G. For
example, the LTE-advanced and 802.16m based WiMAX provide the best efficiency and highest
speed for users when the block is 2x20MHz or 1x40MHz. Considering the number of players that we
have in the Indian market and also noting that spectrum efficiency increases with channel
bandwidth, it is worth looking at sharing the spectrum across providers. This topic has already been
discussed in the “TRAI Consultation paper on Overall Spectrum Management and review of license
terms and conditions”, and the Authority could provide the necessary guidelines on the same.
When 4G networks are established in India, it has to co-exist with previous generations of GSM,
CDMA and WiMAX networks. These networks will be operated by the Mobile Network Operators
who own the spectrum. Many subscribers would need to connect to networks from multiple
technologies and generations to get the services they need. This would entail that the operator a
subscriber obtains service from should be able to provide services in some manner on those
networks they don’t directly operate. MVNO route is one of the established approaches for such a
need. The Authority may consider the relevance of MVNOs in the Indian context, particularly when
multiple generations of technology co-exist, and recommend appropriate policies.
Voice Solution in 4G
Voice and SMS are the most popular services for the Indian mobile subscribers. These will continue
to be the most important services for a long time to come. Thus it is very important to look at the
Voice and SMS services on 4G technologies.
Today’s mobile voice network is based on circuit technology. LTE-Advanced (and LTE) and WiMAX
networks are end-to-end packet-based networks optimized for data transmission. For voice calls, in
a pure LTE-Advanced or WiMAX network, use of Voice over IP (VoIP) supports lower call setup
latency and high data rates during simultaneous voice and data transmission. IMS services such as
presence and instant messaging would also be supported. However, realistically, these networks will
coexist and interwork with circuit switched networks such as CDMA2000 1X and GSM, as well as
IMT-2000 networks such as EVDO, WCDMA and HSPA. With this background, several operators
considering deployment of LTE or WiMAX around the world are considering a variety of options to
provide voice services along with LTE/WiMAX. Among these, the Circuit Switched Fallback and IMS
based Voice Call Continuity are two specific approaches.
LTE/WiMAX terminal drops back to 2G/3G networks for voice connections
IMS based VCC
Uses IMS for the session continuity
Voice over LTE via Generic Access (VoLGA)
Using Generic Access Network principles which were defined for WiFi access
This is being supported by many operators and is based on a kind of IMS implementation
Among these, CSFB takes advantage of the time-tested 2G technologies for voice calls, while using
LTE/WiMAX for data services. CSFB with idle terminals kept on CS networks, with a few
enhancements will make best use of the existing and the new networks from an overall perspective,
while being economical as well, especially supporting economical handsets. The drawbacks are
however increased call setup latency and the inability to support simultaneous voice and data
services. IMS was standardized several years ago, but has not been deployed despite hundreds of
EVDO and HSPA networks being operational around the world. In other words, IMS architecture and
services are as yet untested. As with any new and comprehensive technology, IMS deployment
would be a costly affair on the network side, and on part of the consumers too with higher device
TRAI may consider instituting a study jointly with the Telecom industry, government and academic
experts for voice and data services requirements in LTE devices and networks. The study group will
need to find the best solutions which meets the subscribers requirements and at the same time
keeps the costs low so as to deliver the services at the same price levels that we have now for 2G
The 4G networks will be all-IP networks where all services are finally delivered over IP. The Voice
services will also be using IP based mechanisms like IMS, SIP for the service delivery as given in some
of the options above. There will also be over-the-top voice services like Skype which will have users
in 4G networks. The existing internet telephony policy guidelines may need to be revisited and
explicitly clarified as to which connections are allowed or not allowed in the 4G all-IP network
Wiretapping requirements need to be considered and specified for the VoIP services as well as data
services in 4G networks. These may be common to 3G networks as well, but the all-IP nature of 4G
networks may necessitate some changes in the methodology. The requirements must be mandated
and specified well in advance so that all infrastructure deployed in the country are compliant, and
national security is enhanced.
Given the importance of public telecommunication networks for emergency mitigation in a country
like India, the Authority may consider how mandatory provisions can be made in a cost-effective
manner to enable emergency communications over the 4G networks.
4G networks will bring in a dramatic change in the way Quality of Service can be ensured in the
mobile networks. The QoS Management Functions in these technologies allow differentiation
between the subscribers and among the services of subscriber.
Quality of Experience is of paramount importance in the delivery of Multi-media services in 4G
networks. QoE as an integrated user experience is a difficult measure to determine, however it is
possible to publish the parameters that the network has guaranteed for a specific priority service.
Given that the Indian 4G networks will be used to provide primary broadband connectivity to large
numbers of nomadic users, it will be important to ensure that the QoS and QoE are clear to
subscribers as part of the tariff plan. The Authority may consider specifying QoS/QoE parameters
such as short-term average speed, probability of connect, etc., which are simple yardsticks that users
can understand or assess (based on standard parameters displayed ubiquitously on PCs/terminals).
Recent work done on end-user QoS assessment can be leveraged in this respect.
The growth of data networks, specifically 4G, will bring in a new category of use of the broadband
wireless services, M2M services. In Machine to machine (M2M) scenario, the cellular connectivity is
embedded into "machines" which can communicate with each other over the cellular or broadband
wireless networks. M2M will grow as companies respond to the need to operate more efficiently
and productively, to the regulatory mandates in specific industries and to the desire to introduce
new service and product capabilities. In some cases the spectrum used will be industry specific,
whereas in others it will be the services based on the licensed cellular/BWA spectrum which will be
used for this kind of communication.
 India Broadband Wireless Technology Requirements, www.bwci.org.in
 NGMN Optimized Backhaul requirements, Version 3.0, www.ngmn.org
 Metro Ethernet Forum, Ethernet World Congress 2010