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OFDMA Systems, Pilot Signals
and Doppler Effect
-- Miriam Bank, Michael Bank, Boris Hill and Uri Mahlab
This article examines the use of Orthogonal Frequency Division Multiple Access (OFDMA) method with pilot signals
in cellular systems. The main goal of the investigation and simulation is to examine the Doppler effect influence
on orthogonality disturbance in critical but real situations. The simulation results enable us to conclude that the
influence of Doppler effect on pilot signals leads to an adverse effect instead of a beneficial one, and may perhaps be the
main reason for mobile OFDMA system failure.
© 2010 IUP. All Rights Reserved.
Optimization of Soft Handover Margin in WCDMA Cellular System
-- S Tamilselvan and K Manivannan
The focus of the paper is to analyze the downlink performance of a Wideband Code Division Multiple Access
(WCDMA) system with Site Selection Diversity Transmission (SSDT) power control during Soft Handover (SHO) mode and to
find the optimum SHO margin (MSH) in terms of maximum system capacity under energy-per-bit to noise spectral
density ratio
(Eb/N0) quality requirements. Besides analyzing the dependency of the connection probabilities, percentage
of users connected to one, two, or three Base Stations (BSs) simultaneously as a function of the MSH, it also studies the system capacity and required resources dependency on MSH for voice service and combined multimedia
mobile services. System capacity dependency on MSH is analyzed by considering two types of user distributions: (1)
uniform user distribution; and (2) a concentration of all the users in the location that requires maximum transmitted power
(the worst case). The result of this analysis shows an increase in the user capacity by about 16-20% for the optimum MSH of
5-5.5 dB. Nevertheless, the resources required (number of scrambling codes) by the base station increase faster
than the number of active users in terms of MSH.
© 2010 IUP. All Rights Reserved.
Implementation and Analysis of OFDM and CDMA-Based MIMO V-BLAST
for MUD Using ZF and MMSE
-- Kishor G Maradia, Patil Ajay Kumar V and S M Joshi
The goal of future wireless communication is to provide high quality wireless multimedia services so that data
with high rate can be transmitted reliably. Recent information on theoretic research has shown that Multiple Input
Multiple Output (MIMO) systems can achieve enormous spectral efficiency. The use of multiple antennas allows an
independent channel to be created in the space and is the most interesting and promising wireless research area. The use of
multiple antennas at both ends of a wireless link holds the potential to drastically improve the spectral efficiency and
link reliability in future wireless communications systems. It seems to be a promising candidate for the next generation.
In this paper, two techniques for the next 4G system—OFDM and CDMA—are compared with respect to their
error performance in multiuser environment. The studies of both transmission techniques are performed for MIMO
architecture. This paper provides a comparison of OFDM and CDMA-based MIMO technique.
© 2010 IUP. All Rights Reserved.
Banyan-Based Switching Fabrics
for Next Generation Networks
-- V S Tripathi and S Tiwari
Communication networks are facing new challenges, and as a response, the Next Generation Networks (NGNs)
are being developed under pressure from new services and enabled by technology innovation. The switching fabrics
play a very important role in the evolution of communication networks and services. A new and efficient switching
fabric can control and manage the resources in the NGNs. The purpose of this paper is to review a popular category
of switching fabrics NGNs—Banyan architecture-based switching fabrics suitable for NGNs, in terms of their
architecture and performance evaluation under various traffic conditions.
© 2010 IUP. All Rights Reserved.
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