Uplink performance evaluation of multicode DS/CDMA systems in thepresence of nonlinear distortions

摘要

This paper investigates the behavior of multicode direct sequencencode division multiple access (DS/CDMA) systems in the presence ofnnonlinear distortions caused by high power amplifiers. The performancenof the multicode system can be degraded due to a large variation in thenenvelope of the multicode signal. A technique that uses a small numbernof parallel transmitted sequences is proposed for combating thennonlinearity. This technique ran be modified to have a constant envelopenfor achieving further performance improvement. Comprehensive comparisonsnare made for different systems, based on both theoretical analysis andncomputer simulation. Our study shows that the technique employing a fewnparallel transmitted sequences, in conjunction with quasi-ML (maximumnlikelihood) detection, and the use of the modified scheme, are veryneffective for combating the nonlinearity