A multiple branch fractionally-spaced decision feedback equalizer (MB FS DFE) for CDMA wireless systems

Summary form only given. CDMA is the most promising method of wireless communications and is mainly proposed for third generation mobile systems. One of the most difficult and demanding aspects is the design of a receiver combining high efficiency and small complexity. In this work an FS DFE receiver with minimum MMSE and the smallest complexity comparing to others, named MB FS DFE, is implemented. It is found that delay and sampling phase at the input of the equalizer are crucial parameters for the efficiency. A multiple-branch version of the receiver proposed by Abdulrahman and Falconer (1992) and by Abdulrahman, Sheikh and Falconer, (1994) is presented. In the proposed receiver each branch relates to a different sampling phase. A number of design cases characterized of variant number of forward filter taps and branches lead us to the optimization of the receiver. That happens for certain values of MMSE and outage probability under different propagation environments and system capacity and load. An important conclusion is that there is a relation between all the above for succeeding certain efficiency and smallest possible complexity. Pointing to the simplicity of the receiver in the case of high traffic a large number of forward filter taps is needed whereas the number of branches can be smaller. In the case of low traffic the least complexity is succeeded by using small number of forward filter taps and a larger number of branches than in the previous case. It seems that the presented receiver can be regarded as a good choice for mobile units. Its main characteristics is the performance and simplicity relatively to other existent structures.