Performance of optimum and suboptimum combining at the antennaarray of a W-CDMA system

摘要

The performance of an array of antennas combined with a RAKEnreceiver at the base station of a wideband code division multiple accessnsystem with quaternary phase shift keying modulation is investigated fornsingle-user reception. This receiver structure is also known as anmultidimensional RAKE receiver. Expressions for the interferencencorrelation matrix are derived, and subsequently, an analysis of thenerror probability is provided. With regard to antenna weights, thenoptimum combining linear receiver, which takes into account the spatialndistribution of all the users in the system, is compared with thensuboptimum combining receiver (SOC), which exploits knowledge of thendesired user array vector only. It is shown how the two receivers, idealnin the sense that perfect channel estimation is assumed, achieve verynsimilar performances under realistic conditions. Consequently, theninvestigated pilot assisted combining receiver, which estimates thenchannel based on limited overhead, calculates weights according to thenSOC strategy by a very simple algorithm