一种基于分组截短PN码的SOFDM信道估计方法

Grouped Truncate PN Code Based Channel Estimation Method for SOFDM Symbols in Satellite Communication

基于PN序列的信道估计方法的特点是计算过程简明,已被广泛应用在地面无线局域网系统中。在卫星正交频分多路复用传输体制(SOFDM)系统中引入传统PN序列信道估计方法的主要问题在于卫星信道的多径延时远大于SOFDM数据符号的持续时间,信道特性比较复杂,使得传统方法的估计精度严重下降。提出了一种改进的方法,根据信道的近似周期特性对数据帧进行合理的等长度分组,并把长PN序列改为短PN码来跟踪信道局部特性的变化,再对分组后的数据子帧分别进行信道估计。对该方法的设计思想进行了理论分析,并通过仿真验证了该方法的估计精度比传统方法至少提高了10倍。

The channel estimation method that based on the PN sequence is generally characterized by a concise computational process and a lower computational complexity, which has been already applied in the terrestrial WLAN system. While adopting such means for estimating SOFDM symbols in satellite communication, there comes a problem that the muhipath delay is much longer than the period of SOFDM symbol, which makes the traditional measure failed and the estimate precision lost. Therefore, an improved method was proposed, which divided the data frame into several fixed groups by considering that the channel characteristics was approximately cycled with a periodicity which was related to the RMS value of multipath delay. Afterwards, the long PN sequence was designed to be truncated to many short PN codes in order to track the partial changes of the channel, thus their channel response value （CRV） could be estimated respectively＇ The experimental results prove that it is able to estimate data symbols＇ CRVs with a higher accuracy and improve the estimate precision by at least 10 times paralleling to that of other ordinary methods.