Chaos Based Multi-user TDM Communication System

Abstract

AbstractThis chapter proposes a chaos based multi-user time division multiplexing (TDM) communication system. Its performance is compared to the performance of chaos based direct sequence code division multiple access (DS-CDMA) system in the noisy and Rayleigh fading channels. Initially, the benchmark performance of the systems is investigated in terms of the bit error rate under the assumption of perfect synchronization. The chaotic spreading signals, used to encrypt the binary messages, are generated using the logistic map. The degradation in performance of the systems in the Rayleigh fading channel as compared to the noisy channel is demonstrated. Furthermore, it is shown that in both noisy and Rayleigh fading channels the chaos based multi-user TDM system outperforms the chaos based DS-CDMA system for a larger number of users in the system, while the chaos based DS-CDMA system yields better performance for low number of users in the system. The sequence synchronization unit of chapter 7 is then adapted for the use within the proposed chaos based multi-user TDM communication system and its performance investigated without assuming perfect sequence synchronization. Again, it is shown that the chaos based TDM system outperforms the chaos based DS-CDMA system in the AWGN channel for a larger number of users and viceversa for low number of users in the system. As for the chaos based DS-CDMA system, it is shown that the proposed chaos based TDM system fails in the Rayleigh fading channel when perfect sequence synchronization is not assumed. To obtain the full characterization of the system, the sequence synchronization is also assumed with the PRBS pilot signal present on top of each signal. The effect of the pilot signal on the performance of the system is thus demonstrated in AWGN and Rayleigh fading channels. Finally, a generalized TDM chaotic communication system, which does not assume perfect synchronization, is proposed and investigated when there is more than one DS-CDMA user per TDM branch in the AWGN channel. In this way, it is shown that allocating more than one DS-CDMA user per TDM branch yields a better BER performance while at the same time increasing the total number of users.KeywordsAdditive White Gaussian NoiseRayleigh Fading ChannelAdditive White Gaussian Noise ChannelPilot SignalTime Division MultiplexThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.