all u want to know about 4 g communication

1. 4G MAGIC COMMUNICATIONS
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2. ABSTRACT Service Evolution
The approaching 4G (fourth
generation) mobile communication systems The evolution from 3G to 4G will be driven
are projected to solve still-remaining by services that offer better quality (e.g.
problems of 3G (third generation) systems video and sound) thanks to greater
and to provide a wide variety of new services, bandwidth, more sophistication in the
from high-quality voice to high-definition association of a large quantity of information,
video to high-data-rate wireless channels. The and improved personalization. Convergence
term 4G is used broadly to include several with other network (enterprise, fixed) services
types of broadband wireless access will come about through the high session data
communication systems, not only cellular rate. Machine-to-machine transmission will
telephone systems. One of the terms used to involve two basic equipment types: sensors
describe 4G is MAGIC—Mobile multimedia, (which measure arameters) and tags (which
anytime anywhere, Global mobility support, are generally read/write equipment). It is
integrated wireless solution, and customized expected that users will require high data
personal service. As a promise for the future, rates, similar to those on fixed networks, for
4G systems, that is, cellular broadband data and streaming applications. Mobile
wireless access systems have been attracting terminal usage (laptops, Personal digital
much interest in the mobile communication assistants, handhelds) is expected to
arena. The 4G systems not only will support
the next generation of mobile service, but also
will support the fixed wireless networks. This
paper presents an overall vision of the 4G
features, framework, and integration of
mobile communication. The features of 4G
systems might be summarized with one word
—integration. The 4G systems are about
seamlessly integrating terminals, networks,
and applications to satisfy increasing user
Figure 1:Service evolution vision
demands. The continuous expansion of
Grow rapidly as they become more users
mobile communication and wireless networks
friendly. Fluid high quality video and
shows evidence of exceptional growth in the
network creativity are important user
areas of mobile subscriber, wireless network
requirements. Key infrastructure design
access, mobile services, and applications.

3. requirements include: fast response, high in which Code Division Multiple Access
session rate, high capacity, low user charges, (CDMA) will be progressively pushed to the
rapid return on investment for operators, point at which terminal manufacturers will
investment that is in line with the growth in give up. When this point is reached, another
demand, and simple autonomous terminals. technology will be needed to realize the
required increases in capacity and data
Figure 3: Multiple overlay architecture
Dimensioning targets rates. The second path is the radio LAN one. Widespread
Figure 2: Dimensioning examples
A simple calculation illustrates the order of
magnitude. The design target in terms of
radio performance is to achieve a scalable
capacity from 50 to 500 bit/s/Hz/km2
deployment of WiFi is expected to start in 2005 for PCs,
(including capacity for indoor use), as shown laptops and PDAs. In enterprises, voice may start to be
carried
in Figure 2.Gebit/s/km2)0000 by Voice over Wireless LAN (VoWLAN).
As a comparison, the expected best However, it is not clear what the next
performance of 3G is around 10 bit/s/Hz/km2 successful technology will be. Reaching a
using High Speed Downlink Packet Access consensus on a 200 Mbit/s (and more)
(HSDPA), Multiple-Input Multiple-Output technology will be a lengthy task, with too
(MIMO), etc. No current technology is many proprietary solutions on offer. A third
capable of such performance. path is IEEE 802.16e and 802.20, which are
simpler than 3G for the equivalent
Multi-technology Approach
performance. A core network evolution
Many technologies are competing on the road towards a broadband Next Generation
to 4G, as can be seen in Figure 3. Three paths Network (NGN) will facilitate the
are possible, even if they are more or less introduction of new access network
specialized. The first is the 3G-centric path, technologies through standard access

4. gateways, based on ETSI-TISPAN, ITU-T, Key 4G Technologies
3GPP, China Communication Standards
Some of the key technologies required for 4G
Association (CCSA) and other standards.
are briefly described below:
How can an operator provide a large number
of users with high session data rates using its OFDMA
existing infrastructure? At least two Orthogonal Frequency Division Multiplexing
technologies are needed. The first (called (OFDM) not only provides clear advantages
“parent coverage”) is dedicated to large for physical layer performance, but also a
coverage and real-time services. Legacy framework for improving layer 2
technologies, such as 2G/3G and their performance by proposing an additional
evolutions will be complemented by Wi-Fi degree of free-dom. Using ODFM, it is
and WiMAX. A second set of technologies is possible to exploit the time domain, the space
needed to increase capacity, and can be domain, the frequency domain and even the
designed without any constraints on coverage code domain to optimize radio channel usage.
continuity. This is known as Pico-cell It ensures very robust transmission in multi-
coverage. Only the use of both technologies path environments with reduced receiver
can achieve both targets (Figure 4). complexity. As shown in Figure 5, the signal
Handover between parent coverage and Pico is split into orthogonal subcarriers, on each of
cell coverage is different from a classical which the signal is “narrowband” (a few kHz)
roaming process, but similar to classical and therefore immune to multi-path effects,
handover. Parent coverage can also be used as provided a guard interval is inserted between
a back-up when service delivery in the Pico each OFDM symbol.
cell becomes too difficult.
Figure 5: OFDM principles
OFDM also provides a frequency diversity
gain, improving the physical layer
Fig 4: Coverage performance trends performance.It is also compatible with other

5. enhancement technologies, such as smart multi-band equipment with reduced
antennas and MIMO. OFDM modulation can development effort and costs through
also be employed as a multiple access simultaneous multi-channel processing.
technology (Orthogonal Frequency Division
Multiple Access; OFDMA). In this case, each Multiple-input multiple-output
OFDM symbol can transmit information MIMO uses signal multiplexing between
to/from several users using a different set of multiple transmitting antennas (space
subcarriers (subchannels). This not only multiplex) and time or frequency. It is well
provides additional flexibility for resource suited to OFDM, as it is possible to process
allocation (increasing the capacity), but also independent time symbols as soon as the
enables cross-layer optimization of radio link OFDM waveform is correctly designed for
usage. the channel. This aspect of OFDM greatly
simplifies processing. The signal transmitted
by m antennas is received by n antennas.
Software defined radio
Processing of the received signals may
deliver several performance improvements:
Software Defined Radio (SDR) benefits from
range, quality of received signal and spectrum
today’s high processing power to develop
efficiency. In principle, MIMO is more
multi-band, multi-standard base stations and
efficient when many multiple path signals are
terminals. Although in future the terminals
received. The performance in cellular
will adapt the air interface to the available
deployments is still subject to research and
radio access technology, at present this is
simulations (see Figure 6). However, it is
done by the infrastructure. Several
generally admitted that the gain in spectrum
infrastructure gains are expected from SDR.
efficiency is directly related to the minimum
For example, to increase network capacity at
number of antennas in the link.
a specific time (e.g. during a sports event), an
operator will reconfigure its network adding
several modems at a given Base Transceiver
Station (BTS). SDR makes this
reconfiguration easy. In the context of 4G
systems, SDR will become an enabler for the
aggregation of multi-standard pico/micro
cells. For a manufacturer, this can be a
powerful aid to providing multi-standard,

6. Handover technologies based on mobile IP
technology have been considered for data and
voice. Mobile IP techniques are slow but can
be accelerated with classical methods
(hierarchical, fast mobile IP). These methods
are applicable to data and probably also
voice. In single-frequency networks, it is
necessary to reconsider the handover
methods. Several techniques can be used
when the carrier to interference ratio is
negative (e.g. VSFOFDM, bit repetition), but
Figure 6: Alcatel test-bed performance roadmap
the drawback of these techniques is capacity.
Interlayer optimization In OFDM, the same alternative exists as in
CDMA, which is to use macro-diversity. In
The most obvious interaction is the one the case of OFDM, MIMO allows macro-
between MIMO and the MAC layer. Other diversity processing with performance gains.
interactions have been identified (see However, the implementation of macro-
Figure7). diversity implies that MIMO processing is
centralized and transmissions are
synchronous. This is not as complex as in
CDMA, but such a technique should only be
used in situations where spectrum is very
scarce.
Caching and Pico Cells
Memory in the network and terminals
facilitates service delivery. In cellular
systems, this extends the capabilities of the
MAC scheduler, as it facilitates the delivery
of real-time services. Resources can be
assigned to data only when the radio
conditions are favorable. This method can
Figure 7: Layer interaction and associated optimization
double the capacity of a classical cellular
Handover and mobility system. In pico cellular coverage, high data

7. rate (non-real-time) services can be delivered shown in Figure 8. At the entrance of the
even when reception/transmission is access network, lines of cache at the
interrupted for a few seconds. Consequently, destination of a terminal are built and stored.
the coverage zone within which data can be When a terminal enters an area in which a
received/transmitted can be designed with no transfer is possible, it simply asks for the line
constraints other than limiting interference. of cache following the last received. between
Data delivery is preferred in places where the the terminal and the cache. A simple, robust
bitrate is a maximum. Between these areas, and reliable protocol is used between the
the coverage is not used most of the time, terminal and the cache for every service
creating an apparent discontinuity. In these delivered in this type of coverage
areas, content is sent to the terminal cache at .Multimedia service delivery, service
the high data rate and read at the service rate. adaptation and robust transmission
Coverages are “discontinuous”. The
Audio and video coding are scalable. For
instance, a video flow can be split into three
Flows which can be transported
independently: one base layer (30 kbit/s),
which is a robust flow but of limited quality
(e.g. 5 images/s), and two enhancement flows
(50 kbit/s and 200 kbit/s). The first flow
provides availability, the other two quality
and definition. In a streaming situation, the
terminal will have three caches. In Pico
cellular coverage, the parent coverage
establishes the service dialog and service
start-up (with the base layer). As soon as the
terminal enters Pico cell coverage, the
terminal caches are filled, starting with the
Figure 8: Pico cell network design
base cache. Video (and audio) transmissions
advantage of coverage, especially when
are currently transmitted without error and
designed with caching technology, is high
without packet loss. However, it is possible to
spectrum efficiency, high scalability (from 50
allow error rates of about 10-5 /10-6 and a
to 500 bit/s/Hz), high capacity and lower cost.
packet loss around 10-2 /10-3. Coded images
A specific architecture is needed to introduce
still contain enough redundancy for error
cache memory in the network. An example is

8. correction. It is possible to gain about 10 dB coverage have yet been resolved. However,
in transmission with a reasonable increase in indoor coverage can be obtained by:
complexity. Using the described technologies, • Direct penetration; this is only possible in
multimedia transmission can provide a good low frequency bands (significantly Below 1
quality user experience. GHz) and requires an excess of power, which
may raise significant Interference issues.
Coverage • Indoor short range radio connected to the
Coverage is achieved by adding new fixed network.
technologies (possibly in overlay mode) and • Connection via a relay to a Pico cellular
progressively enhancing density. Take a access point.
WiMAX deployment, for example: first the
parent coverage is deployed; it is then made Integration in a Broadband NGN
denser by adding discontinuous Pico cells, The focus is now on deploying an
after which the Pico cell is made denser but architecture realizing convergence between
still discontinuously. Finally the Pico cell the fixed and mobile networks (ITU-T
coverage is made continuous either by using Broadband NGN and ETSI- TISPAN). This
MIMO or by deploying another Pico cell generic architecture integrates all service
Coverage in a different frequency band (see enablers (e.g. IMS, network selection,
Figure 9). The ultimate performances of the middleware for applications providers), and
various technologies are shown in Figure 10. offers a unique interface to application
Parent coverage performance may vary service providers.
From 1 to 20 bit/s/Hz/km, while Pico cell
Conclusion
technology can achieve from 100 to 500
As the history of mobile communications
shows, attempts have been made to reduce a
number of technologies to a single global
standard. Projected 4G systems offer this
promise of a standard that can be embraced
worldwide through its key concept of
Figure 9: example of deployment in dense traffic areas
integration. Future wireless networks will
Bit/s/Hz/km?, depending on the complexity
need to support diverse IP multimedia
of the terminal hardware and software. These
applications to allow sharing of resources
performances only refer to outdoor coverage;
among multiple users. There must be a low
not all the issues associated with indoor

9. complexity of implementation and an which can reach between 100 and 500
efficient means of negotiation between the bit/s/Hz/km2. The distributed, full IP
end users and the wireless infrastructure. The architecture can deployed using two main
fourth generation promises to fulfill the goal products: base stations and the associated
of PCC (personal computing and controllers. Terminal complexity depends on
communication)—a vision that affordably the number of technologies they can work
provides high data rates everywhere over a with. The minimum number of technologies
wireless network. is two: one for the radio coverage and one for
The provision of megabit/s data rates to short range use (e.g. PANs). However, the
thousands of radio and mobile terminals per presence of legacy networks will increase this
square kilometer presents several challenges. to six or seven.
Some key technologies permit the progressive REFERENCES
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• Sufficient spectrum, with associated
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• Caching technology in the network and
terminals.
• OFDM and MIMO.
• IP mobility.
• Multi-technology distributed architecture.
• Fixed-mobile convergence (for indoor
service).
• Network selection mechanisms.
Many other features, such as robust
transmission and cross-layer optimization,
will contribute to optimizing the performance,