一种用于TD-SCDMA系统下行链路单用户检测的快速算法

A Low Complexity and Fast Joint Detection Algorithm for Downlink TD-SCDMA System

对于TD-SCDMA系统中的下行单用户检测技术,通过改变信道矩阵的形式,得到了一种低复杂度的实现方法。这种方法利用离散傅立叶变换而大大降低了矩阵求逆的运算量,可以应用于迫零数据块线性均衡单用户检测(ZF-BLE-SD)和最小均方误差数据块线性均衡单用户检测(MM SE-BLE-SD)等联合检测算法中。仿真结果也证明了这种算法的有效性。

Joint Detection （JD）, as one of the key technologies of TD-SCDMA （Time Division Synchronization Code Division Multiple Access） system, can resist the inter-symbol interference and the multiple access interference in wireless communication. The obvious drawback of JD algorithms is the high computational complexity. In this paper, a low complexity algorithm for the joint detection in downlink TD-SCDMA is proposed. The computational complexity of traditional JD algorithms, such as the two most popular downlink JD algorithms——ZF-BLE-SD （Zero Forcing Block Linear Equalizer Single user Detection）, and MMSE-BLE-SD （Minimum Mean Square Error Block Linear Equalizer Single user Detection） , is O（M^3）, where M is associated with a N×M matrix and M≤N. We make two wellknown assumptions： the noise is Gaussian white and the data transmitted to the single user are unrelated. These two assumptions are generally satisfied. With these two assumptions, we can easily transform the N × M matrix, whose inversion causes high computational complexity, into a matrix which is simple to deal with. By expanding the channel matrix into a circular matrix, the computations can be carried out very efficiently through extensive use of Discrete Fourier Transform （DFT）. In this way, the computational complexity of ZF-BLE-SD or MMSE-BLE-SD algorithm can be reduced from O（M^3） to O （Mlog2M）. Although the proposed method reduces the computational complexity, the results from simulation based on standard Rayleigh fading environment show that the method can achieve comparative performance as the traditional methods.