4G Networks: A Case for Bypassing 3G

A quantum jump in data rates will be possible with appearance of 3G networks,
which offer wideband air interfaces. ETSI and ARIB of Japan have arrived at
WCDMA-based air interfaces, which can support speeds of 2 Mbps for pedestrians
inside the buildings, making it possible for multimedia type of information to
appear on handheld terminals. Billions of dollars have been expended by major
telecom operators in buying the needed spectral bandwidths in open auctions held
by the respective governments. Many of the telecom companies have in the process
gone in the red, posing a question mark on their ability to create a 3G-based
network infrastructure in the projected time frame.

Meanwhile, a new wireless access technology called wireless LAN (WLAN) is
making headway. In fact, standards have already been laid by IEEE and these
networks are coming up in major parts of the developed countries. Sooner or
later, these networks will start overlapping and a continuous wireless broadband
network will evolve. It will deliver everything that 3G claims but is still a
data network. The WLAN-based access technology can offer data speeds of 11 Mbps.

4G Mobile Networks

3G networks will prove inadequate to accommodate WLANs as access networks,
which offer data rates of 11 Mbps.

A quantum leap has been conceived in the form of 4G networks, which will
offer air interface data rates at 10 times the speeds offered by the 3G
networks. The broad objectives of 4G networks and the new technologies that will
enable implementation of such networks are as follows:

lHigh-speed:
Pedestrian/indoor 20 Mbps, vehicle 2 Mbps

lHigh
capacity: 10 times higher than 3G

l
Higher frequencies: Microwave: 3—10 GHz

l
Next-generation Internet support: IPV6, QoS, MO-IP

l
Seamless services with fixed NW and private NW

l
Lower system costs: 1/10 of IMT-2000

To achieve these objectives the roadmap of enabling technologies is as
follows:

n Advanced
adaptive modem

The higher data rates expected in 4G will necessitate the use of new
modulation scheme and codes. OFDM and related modulations are emerging as a
preferred set of technologies. In OFDM, multiple coherent sub-carriers are
modulated and codes are used to insure that encoded bits can be decoded even if
some of the sub-carriers arrive at very low Eb/(No+1). OFDM is inherently more
resistant to inter-symbol interference.

THE LURE OF 4G
	4G networks are designed to accommodate WLANs based on Bluetooth technologies
	The core 4G networks will be all-IP networks incorporating IPv6
	India, where investments have not been made for 3G, can leapfrog to the 4G network era

n Software
defined radios (SDR)

Solutions to a multiplicity of radio link standards are needed if users are
to roam from one station to another. A software BS that can use a common
hardware platform to support multiple technologies (multi-mode BS) can offer
service to any roamer that enters the system. The BS transmits the pilot signal
for each type of air interface that is supported by the BS. Recently, a greater
degree of programmability is made available on devices that are nearly as
inexpensive as fixed function devices, and software infrastructure to control
these is emerging. A number of companies are making baseband processors
available, which include greater flexibility than ever before. Baseband chipsets
able to carry out WCDMA and GSM or CDMA 2000, CDMA 1 and AMPS, or 802.11b are
emerging. SDR technologies continue to evolve, hardware architectures for both
baseband and RF sides continue to improve, and although there is churning,
standard technologies may not be too far in the future.

n All
IP-based core networks

4G will more resemble a conglomerate of the existing technologies rather
than an entirely new standard. An all IP-based core network has been conceived,
which will be accessed by different access systems through the use of gateways.

An all IP-based 4G wireless network has inherent advantages
over its predecessors. It is compatible with, and independent of the actual
radio access technology. With IP, you basically get rid of the lock-in between
core networking protocol and the link layer, the radio protocol.

IP tolerates a variety of radio protocols. It lets you design
a core network that gives you complete flexibility in the access network type.

You could be a core network provider that supports many
different access technologies, 802.11, WCDMA, Bluetooth, hyper LAN, and some
that have not been invented as yet, such as some new CDMA protocols. An all-IP
network technology tolerance means unimpeded innovation all around. The core IP
network can evolve independently from the access network. That is the key for
using all-IP.

A 4G IP wireless network enjoys the financial advantage over
3G as well. 4G equipment costs are four to ten times less than the equivalent
circuit-switched equipment for 2G and 3G wireless infrastructure. An open system
IP wireless environment would probably reduce cost for services provided by
ushering in an era of real equipment interoperability. Wireless service
providers would no longer be bound by single vendors of proprietary equipment.

An IP wireless network would replace the old SS7 signaling
system, telecommunications protocols, a task that many believe to be long
overdue. The SS7 network is massively redundant. That is because SS7 signal
transmission consumes a larger part of network bandwidth even when there is no
signaling traffic. IP networks use other less bandwidth expensive mechanisms to
achieve reliability.

n Fully
adaptive multi-layer protocol architecture

From a technological reference point, there are four major factors in achieving
the degree of integration, flexibility and efficiency envisioned in 4G. These
are:

• Seamless integration

• A high performance physical layer

• Flexible and adaptive multiple access

• Service and application adaptation

Standardization Moves

In ITU-R, the international wireless standardization organization, WP-8F was
organized in November 1999. The role of WP-8F is to investigate and standardize
the systems that include 4G.

NTT DoCoMo of Japan has proposed a draft for the concept of 4G, and is now
researching the technologies that solve the technical problems.

Migration Path

A big question has arisen regarding the migration path to next-generation
networks from the existing GSM/GPRS environments. 4G technology is still in the
R&D stage and international standards do not exist yet. On the other hand,
proper standards exist for 3G technologies, and big MNCs have already invested
huge sums to acquire the needed spectrum space. As a result, many of these
telecom companies have gone in the red, leaving little resources with them to
set up 3G network infrastructures in the foreseeable future. It is expected that
meanwhile 4G technologies will arrive, which offer an order of magnitude, higher
bandwidth with lower cost per bit of transmission, and better spectral
efficiency, as compared to a 3G network. 4G standards are also likely to emerge
in this time frame. Should companies bypass 3G and leapfrog straight to 4G is a
matter of intense debate. It is also being argued that 3G and 4G technologies
are not mutually-exclusive but are complimentary to each other. But that is more
true for countries that have already made huge investments in 3G. Migration to
4G in such countries is expected to follow an evolutionary path, i.e. via 3G.

On the other hand, countries like India where investments have not been made
for 3G, need not follow the 3G migration route. They can leapfrog to 4G networks
bypassing 3G.

4G networks have been particularly designed to accommodate WLANs and PANs
based on Bluetooth technologies. 3G suffers bandwidth limitations to accommodate
these networks. 4G core networks are all-IP networks. In fact, IP has been
extended to radio access nodes as well. So the disadvantages of circuit
switching are totally absent. These networks will be incorporating advanced
IPv6. Even the signaling will be done through IP. The setting up costs of
network infrastructure will be lower. Since they can be built up atop existing
networks and won’t require operators to completely retool. Even better, they
won’t require carriers to purchase the costly extra spectrum, since much of
what is needed is public and does not require a license. So, leapfrogging to 4G
technologies will be eminently suitable in the Indian context.

Wg Cdr SC Sharma

is dean, Amity School of Telecom Technologies