FMT系统中的子信道Turbo迭代均衡

Sub-channel Turbo Iterative Equalization in FMT Systems

在滤波多音调制(FMT)系统中,子信道频谱不重叠通过不满足理想重构条件的原型滤波器来实现,这不可避免地引入符号间干扰(ISI),尤其当FMT应用于无线多径环境时,ISI将进一步增大。而Turbo均衡将信道均衡和译码联合处理,能够有效地消除ISI。本文提出了一种FMT系统子信道Turbo迭代均衡算法,信道衰落采用单抽头均衡器来补偿,而FMT系统自身所产生的ISI则通过基于线性滤波器结构的Turbo迭代均衡来消除。仿真结果表明,不论采用QPSK还是16QAM调制方式,经过2次以上的迭代后,新算法的误码率性均优于传统的判决反馈均衡算法。

The non-overlapping sub-channel characteristics are realized in the FMT systems by the imperfect reconstruction prototype filter.It inevitably introduces ISI（Inter-symbol interference）.ISI is increased when FMT is applied in wireless multipath environment.And Turbo equalization can effectively eliminate ISI because it uses the redundant information from channel coding in the iterative process.According to the above-mentioned analyses,this paper proposes a Turbo sub-channel iterative equalization algorithm for FMT systems.The wireless channel can be equalized by a one tap subchannel equalizer,while the imperfect reconstruction prototype filers are equalized by the Turbo sub-channel iterative equalizer adopting linear filers.Simulation results indicate that the bit error ratio（BER） performance for both QPSK and 16QAM modulation of the proposed algorithm is superior to the decision feedback equalization（DFE） algorithm by more than two iterations.