Multi-user Detectio

Multi-user detection is for CDMA in parallel efficient testing program transmitted signal in td-scdma, it has been widely used in. Multi-user detection technology can make CDMA system spectrum efficiency is greatly increased.

In CDMA mobile communication system, must resist two types of interference. The first kind is due to different users to share the same frequency band between the bandwidth (each user because of its corresponding address correlativity exists between) resulting from the Multiple Access devices, MAI (Multiple Access Interference), and the second is due to the characteristics of the channels is not ideal and cause ISI (Inter - Symbol Interference between devices, symbols. If each user relative to other users of interference can be eliminated, then system capacity will be greatly improved and theoretically possible to eliminate near-far effect. Multi-access interference is restricted CDMA system capacity of an important factor. When the user number a little while, multi-access interference generally are small. But as subscribers purpose increased, multi-access interference will be more and more big. In order to more effective resist near-far effect and decline in order to improve the system capacity in the early 1980s, proposed multi-user Detection technology (Multiuser Detection) to eliminate multi-access interference, also can use victor Viterbi) algorithm than (such as equilibrium method to fight among symbols interference.

In reverse link adopts the concept of multi-user detection was first proposed by Baiser Klein and analyzed, they forced Zero Block Equalizer (Zero Forcing - which Equalizer) performance. Linear, Then, Jung and Klein and puts forward such other multi-user detection algorithm, such as ZF - BDFE, MMSE - BDFE BLE, MMSE - such algorithm. The basic idea is to receive each signal linear matrix operations done together. These multi-user detection receiver can also and coherent receiver antenna diversity technology and combining Turbo yards.

Multi-user detection techniques of main shortcoming is its high computational complexity, especially in descending on the link. In fact, because multi-user detection the amount of calculation is only part of the whole mobile station need a small part of the amount of calculation, so it was necessary to control the algorithm complexity.