Quality-of-service analysis for linear multiuser detectors in the uplink of a wireless network

In any wireless network is important to measure the Quality-of-Service (QoS) at the mobile units. Based on this information, the network will relocate their resources in order to achieve the performance specifications. Hence this objective motivates this paper, where analytical evaluations of the signal-to-noise plus interference ratio (SNIR) are carried out for each active user in a wireless communication system. In particular, this work studies the performance of linear detectors for Direct-Sequence Code Division Multiple Access (DS-CDMA) systems at different loading levels using singular value decomposition (SVD) techniques in the uplink channel. The QoS in terms of the SNIR are compared for the matched filter (MF), decorrelator, projector and minimum-mean-squared error (MMSE) detectors. In the analytical evaluations, two techniques are proposed to quantify the SNIR according to the multiple-access interference (MAI) and noise representation. The first one is based on an average of the MAI and noise information of all mobile users at the base station. The second approach relies on computing explicitly the interference for each active user. Simulation results show a performance comparison between both approaches, and a Monte-Carlo numerical evaluation in terms of the SNIR and the number of active users.