Al-Rafidain Engineering Journal (AREJ)

Abstract

Abstract:
Multiuser detection is the demodulation of signals of different users interfering
with each other. This phenomena known as multiple access interference occurs mostly
in code division multiple access (CDMA) systems. In this paper the study and
analysis of the blind adaptive multiuser detection algorithm is achieved for directsequence
code division multiple access (DS-CDMA) communication systems. The
goal is to obtain multiuser detectors that require only knowledge of the signature
waveform and timing of the desired user. Comparison is performed of the blind
adaptive technique with the conventional detector (matched filter detector) or (M.F.D)
in perfect power control and in the presence of the near-far effect. In the present
simulation, the blind adaptive multiuser detection showed an excellent bit error rate as
compared to the conventional detection with the same requirements. Also the blind
detector showed an immunity towards the near-far problem. In this simulation the use
of adaptive variable step size is used in contrast to the constant step size shows
improvement in speed convergence and stability of the algorithm adapte