CP不足情况下OFDM系统信道估计与均衡

Channel Estimation and Equalization of OFDM Systems with Insufficient Cyclic Prefix

正交频分复用(OFDM)系统中的循环前缀具有一定的抗码间干扰(ISI)和子载波间干扰(ICI)的能力,但是当多径衰落信道的最大信道脉冲响应(CIR)长度超过了循环前缀(CP)长度时,OFDM系统的性能将会严重下降。传统的信道估计和均衡方案面对循环前缀长度不够的情况无法避免性能的严重衰落。由此提出了一种可以估计出大于CP长度CIR的信道估计方法,并且给出了一种基于逼零(ZF)准则的低复杂度均衡器,以抵消ISI和ICI的影响。仿真结果表明所提方案与传统方案相比在复杂度上和性能上有明显的优势。

Inherent inter-symbol and inter-carrier interference elimination ability of orthogonal frequency division multiplexing （OFDM） system attribute to its cyclic prefix. But the case of multipath fading channels whose the channel impulse response （CIR） length exceeds the duration of cyclic prefix （CP） causes intersymbol interference （ISI） and intercarrier interference （ICI）, which may degrade system performance severely. Conventional channel estimation and equalization schemes, if applied to this case of insufficient CP, suffer significant performance degradation. This paper presents a channel estimation scheme that enables the estimation of a complete CIR even beyond the CP length. A Zero-forcing （ZF） based low complexity equalizer for the suppression of insufficient CP generated interference is also derived. Simulation results for the proposed schemes show the advantage of significantly lower computational complexity, compared with earlier schemes, without any loss in performance and transmission efficiency.