11-02-2013, 03:59 PM
WIRELESS NETWORK (3G & 4G)
WIRELESS .pdf (Size: 375.92 KB / Downloads: 43)
Abstract
Due to the increase in demand for speed,
multimedia support and other resources, the wireless
world is looking forward for a new generation
technology to replace the third generation. This is
where the fourth generation wireless communication
comes into play. 4G wireless communication is
expected to provide better speed, high capacity, lower cost
and IP based services. The main aim of 4G wireless is
to replace the current core technology with a single
universal technology based on IP. Yet there are several
challenges that inhibhit the progress of 4G and
reasearchers throughout the world are contributing
their ideas to solve these challenges. This project
deals with understanding the features and challenges,
the proposed architectural frameworks, multimedia
support and multiple access schemes for 4G.
INTRODUCTION
The wireless communication filed is a very fast growing
area with the number of users and their demand for
better resources increasing day by day. The R&D
departments of many companies are working on a future
technology that can meet these demands at a lower cost.
3G is necessary but not sufficient for the demands today. So
the world is taking its leap towards the fourth generation
wireless communication that promises to bring an end to
most of the problems faced. 4G wireless is expected to
be launched by 2010, but there are numerous challenges
faced by researchers in achieving the desired features. Most
of the ongoing researches are in the area of distributed
computing, mobile agents, multimedia support etc. Some
other research area is to improve the Quality of Service
from the viewpoint of both the user and service
providers. 4G wireless infrastructures are expected to be
deployed in an environment where many other types of
wireless and wired communication systems already exist.
This paper is organized as follows. Section II provides a
brief review of the previous generations, desired features and
research challenges faced by 4G. Section III describes the core
architectural framework and some architectural models
proposed for 4G. Section IV provides some proposed solution
for hand off mechanism for 4G.
Main Challenges
To achieve the desired features listed above researches have
to solve some of the main challenges that 4G is facing. The
main challenges are described below
Multimode user terminals: In order to access different kinds
of services and technologies, the user terminals should be able
to configure themselves in different modes. This eliminates the
need of multiple terminals. Adaptive techniques like smart
antennas and software radio have been proposed for achieving
terminal mobility.
Wireless system discovery and selection: The main idea
behind this is the user terminal should be able to select the
desired wireless system. The system could be LAN, GPS, GSM
etc. One proposed solution for this is to use software radio
approach where the terminal scans for the best available
network and then it downloads the required software and
configure themselves o access the particular network.
MULTIPLE ACCESS TECHNIQUES
3G wireless multiple access techniques were widely
based on CDMA and WCDMA. But 4G demands a better
multiple access technique for reducing the MAI (Multiple
Access Interference) and ISI (Inter Symbol Interference) and
thus improve the bit error rate performance. MC-CDMA is the
best candidate that would satisfy the demands of 4G wireless
systems. Moreover adaptive modulation techniques have been
proposed for 4G, where the modulation scheme is changed
dynamically based on the current channel estimates. MCCDMA
is the hybrid combination of OFDM (Orthogonal
Frequency Division Multiplexing) and CDMA. MC-CDMA
with adaptive modulation promises to meet the demands of 4G
regarding high data rate with a lower BER (Bit Error Rate).
CONCLUSION
4G seems to be a very promising generation of wireless
communication that will change the people’s life in the
wireless world. There are many striking attractive features
proposed for 4G which ensures a very high data rate, global
roaming etc. Table 1 shows the features and comparison
between the different generations. New ideas are being
introduced by researchers throughout the world, but new ideas
introduce new challenges. There are several issues yet to be
solved like incorporating the mobile world to the IP based core
network, efficient billing system, smooth hand off
mechanisms etc. 4G is expected to be launched by 2010 and
the world is looking forward for the most intelligent
technology that would connect the entire globe.