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Noise‐based spreading in code division multiple access systems for secure communications
Author(s) -
Berber Stevan M.
Publication year - 2014
Publication title -
international journal of communication systems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.344
H-Index - 49
eISSN - 1099-1131
pISSN - 1074-5351
DOI - 10.1002/dac.2840
Subject(s) - computer science , pseudorandom noise , synchronization (alternating current) , chaotic , algorithm , communications system , sequence (biology) , fading , transmission (telecommunications) , code (set theory) , signal (programming language) , additive white gaussian noise , theoretical computer science , white noise , code division multiple access , channel (broadcasting) , telecommunications , decoding methods , spread spectrum , artificial intelligence , set (abstract data type) , biology , genetics , programming language
SUMMARY Binary spreading sequences or chaotic nonbinary sequences are used in code division multiple access systems. In contrast to those sequences, this paper presents the theory, simulation, and implementation in digital signal processor technology of a code division multiple access system that uses random spreading sequences. The expressions for probability of bit error are derived for the cases when the additive white Gaussian noise and fading are present in the channel. Because the overall transmitted signal is a sum of random signals, the security of signal transmission in this communication system can be enormously increased and will depend on the goodness of the random sequence generator. The developed theory was confirmed by a prototype of the system that was designed in digital signal processor technology. The prototype used spreading sequences that had statistical characteristics very close to the characteristics of theoretical random sequences. The main problem in the system is how to synchronize the received spread sequence with the locally generated sequence. Hence, a mathematical model of the synchronization block for the system has been separately designed and developed. The synchronization procedure has been demonstrated on the basis of application of a periodically repeated pilot sequence. Copyright © 2014 John Wiley & Sons, Ltd.