OFDM系统中低复杂度的时变信道迭代均衡算法

针对正交频分复用系统在时变信道中的均衡问题，提出了一种低复杂度的时变信道均衡算法。该算法首先运用一阶多项式基扩展模型对时变信道进行建模，利用频域信道矩阵能量主要集中在对角线附近的特点，将频域信道矩阵按梳状导频的位置沿对角线分块，然后运用高斯置信传播算法分别进行线性迫零均衡。算法避免了矩阵求逆运算，降低了计算复杂度，同时有效补偿了多普勒频移引起的载波间干扰，提高了系统性能。计算机仿真结果和算法复杂度分析表明，提出的分块迭代均衡算法有效降低了时变信道中系统的误码率，并且具有复杂度低，可分布式计算的特点，因此适用于专用集成电路等硬件实现。 

Low-Complexity Iterative Equalization for Time-Variant Channels in OFDM Systems

Abstract:In order to tackle the inter-carrier interference (ICI) problem caused by time-variant channels in orthogonal frequency division multiplexing (OFDM) systems, a low-complexity iterative equalization technique was proposed in this paper. The impulse response of a time-variant channel was represented by the first-order polynomial basis expansion model to reduce channel parameters. Since the frequency-domain channel matrix was nearly banded, it was divided by the positions of pilot clusters into blocks along the diagonal for equalization. Then the linear zero-forcing equalization was applied to each block. In order to simplify the computational complexity, the Gaussian belief propagation (GaBP) algorithm was used to solve the linear equations in the equalization. Thus the proposed algorithm avoided the matrix inverse operation, and canceled the effects of inter-carrier interference efficiently. Computational complexity analysis and simulation results showed that the proposed equalization technique reduced the bit error rate significantly with low computational cost. In summary, the proposed block-GaBP equalizer has the superiority of low computational complexity and distributed approach for equalization, and therefore, is suitable for hardware implementation such as application-specific integrated circuit.