海面FH-OFDM系统联合同步和信道估计算法

在跳频正交频分复用(FH-OFDM)系统的海面军事应用中,为了提高接收机在航空移动通信中不同海况下的误码性能,提出了基于递归最小二乘法的联合同步和信道估计算法。在同步跳中使用并行搜索实现跳频同步,对基带时域信号的子载波间干扰(ICI)进行了预先补偿。借助于慢时变信道下新的跳频帧结构,构建了统一的代价函数通过线性误差函数对信道冲激响应(CIR),载波频率偏差(CFO)和采样率偏差(SFO)进行估计。使用了新的极大似然代价函数来估计各参数的初始值。给出了系统中带宽效率,跳频速率及子载波总数的权衡条件。仿真结果表明,该算法在平静海面和粗糙海面下的参数估计均方差和系统误码率优于传统算法。

Joint Synchronization and Channel Estimation Algorithm of FH-OFDM Systems Above Sea Surface

In military frequency hopping orthogonal frequency division multiplexing(FH-OFDM) application above sea surface,a joint synchronization and channel estimation algorithm based on recursive least square was proposed to improve bit error rate(BER) performance of aircraft communication receiver under different sea conditions.Frequency hopping synchronization was completed by parallel detection.Inter-carrier interference(ICI) of baseband signal was compensated in time domain.With the help of proposed frequency hopping frame structure in slow time-varying channel,a cost function with linear error was formulated to estimate channel’s impulse response(CIR),carrier frequency offset(CFO) and sampling frequency offset(SFO).Estimation of parameters’ initial values was improved by new maximum likehood cost function.Balance expression among bandwidth efficiency,frequency hopping rate and subcarrier numbers was presented.Simulation results showed that the proposed algorithm has better estimation mean square error and BER performance than conventional algorithm under calm sea condition and rough sea condition.