PERFORMANCE EVALUATION OF A FREQUENCY MODULATED SPREAD-SPECTRUM SYSTEM
Analog frequency modulated (FM) systems offer advantages of reliable speech
quality and simplicity, whereas code division multiple access (CDMA) systems
promise high capacity, resistance to multipath fading, and simplified frequency
planning. In this thesis, we investigate the performance of a wireless local loop
(WLL) system that uses the frequency modulation with the CDMA technique.
The performance of the FM CDMA system is affected by the choice of the
frequency demodulation method. Performance of different state-of-art DSP
based FM demodulators is evaluated. Design improvements with threshold
extension, pre-deemphasis, and voice companding techniques are explored, and
the limitations of the DSP based FM demodulation methods are identifed.
The transmitter, the channel, and the receiver of the FM CDMA system are
simulated for particular values of FM bandwidth and spread-spectrum processing
gain. The capacity supported by the FM CDMA sysem is estimated with different
levels of orthogonal as well as non-orthognal multiple access interference. The
performance of the FM CDMA system in AWGN, multipath fading, Doppler
spread, and nonlinear signal processing effects is predicted. A power control
algorithm for the FM CDMA system is proposed, and its effect on the system
performance is studied.
The capacity of the FM based wireless system may saturate as the system evolves.
An adaptive FM CDMA interference cancelation technique and a digital
modulation with CDMA are two approaches investigated as ways to improve
Advisor:Dr. Dennis G. Sweeney; Dr. Brian D. Woerner; Dr. Jeffrey H. Reed
School:Virginia Polytechnic Institute and State University
School Location:USA - Virginia
Source Type:Master's Thesis
Keywords:electrical and computer engineering
Date of Publication:05/01/1996