الفهرس 
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Abstract
Multiple access interference (MAI) is a factor, which limits the capacity and performance of direct-sequence CDMA (DS-CDMA) systems. MAI refers to the interference between DS-CDMA users. This interference appears in both synchronous and asynchronous systems because of the multipath nature of the cellular channels, which causes different time offsets between signals from different users. The existence of these random time offsets between the received signals from all users makes it impossible to design spreading codes that are orthogonal to each other for all time shifts. Although, the MAI caused by any one user is usually small, as the number of users increases, the factor of MAI becomes of great importance. Another factor which may make the MAI problem more severe, is the near-far (NF) problem, which results from the existence of different users at different distances from the base-station. This causes the users near the base-station to have higher power than the users far from the base-station, which results in increasing the MAI affecting the users with low powers.
Conventional DS-CDMA receivers do not take into account MAI, it follows the single user matched filter detection strategy. Taking the MAI under consideration in the detection process greatly improves the performance of the receiver and increases the capacity of the system. Receivers which take the MAI into account are called multi-user detectors (MUD).
The focus of the thesis is on blind adaptive algorithms that are used in MUD in both single path and multipath channels. The word ”blind” means that the receiver has no information about the interference structure and doesn’t need any training sequence. The word ’”adaptive” means that it adapts itself with time to mitigate the interference. For the interference to adaptively learn about the interference structure, the interference must have a cyclostationary nature. For DS-CDMA to have a cyclostationary nature, it must apply short spreading codes which repeat every symbol.