Application of Blind Adaptive LMS Algorithm for Detection of CDMA Signals in Frequency Selective Fading Channels

Document Type : Original Article

Authors

1 Egyptian Armed Forces.

2 Libyan Armed Forces.

Abstract

Abstract:
The conventional matched filter (MF) receiver is considered the optimum filter to
recover the CDMA signals. One of its problems is that its performance is significantly
degraded due to the channel impairments and the increase of the multiple access
interference (MAI). Parallel interference cancellation (PIC) is considered a simple yet
effective multi-user detector for direct-sequence code-division multiple-access (DSCDMA)
systems. However, its performance may deteriorate due to unreliable
interference cancellation in the early stages. Thus, a partial PIC detector, in which partial
cancellation factors (PCFs) are introduced to control the interference cancellation level,
it has been developed as a remedy. Recently, an interesting adaptive multistage PIC
algorithm was proposed. In this paper, an application of the least mean square (LMS)
adaptive algorithm is presented by training the adaptive coefficients blindly to optimize
the values of the PCFs. The performance of the presented receiver is measured in terms
of bit error rate (BER) and compared with other receivers over frequency selective
fading channel. It is found that the performance of the adaptive PPIC receiver is better
than the performance of the other receivers in the frequency selective fading channel
especially in the last stages.

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