Yang T C, Yang Wen-Bin
Naval Research Laboratory, Washington, DC 20375, USA.
J Acoust Soc Am. 2008 Feb;123(2):842-55. doi: 10.1121/1.2828053.
Direct-sequence spread-spectrum signals collected from the TREX04 experiment are analyzed to determine the bit-error-rate (BER) as a function of the input signal-to-noise ratio (SNR) for a single receiver. A total of 1160 packets of data are generated by adding ambient noise data collected at sea to the signal data (in postprocessing) to create signals with different input-SNR, some as low as -15 dB. Two methods are analyzed in detail, both using a time-updated channel impulse-response estimate as a (matched) filter to mitigate the multipath-induced interferences. The first method requires an independent estimate of the time-varying channel impulse-response function; the second method uses the channel impulse-response estimated from the previous symbol as the matched filter. The first method yields an average BER <10(-2) for input-SNR as low as -12 dB and the second method yields a similar performance for input-SNR as low as -8 dB. The measured BERs are modeled using the measured signal amplitude fluctuation statistics and processing gain obtained by de-spreading the received signal with the transmitted code sequence. Performance losses caused by imprecise symbol synchronization at low input-SNR, uncertainty in channel estimation, and signal fading are quantitatively modeled and compared with data.
对从TREX04实验中收集的直接序列扩频信号进行分析，以确定单个接收器的误码率（BER）作为输入信噪比（SNR）的函数。通过将在海上收集的环境噪声数据添加到信号数据中（在后期处理中），总共生成了1160个数据包，以创建具有不同输入SNR的信号，有些低至-15 dB。详细分析了两种方法，这两种方法都使用时间更新的信道脉冲响应估计作为（匹配）滤波器来减轻多径引起的干扰。第一种方法需要对时变信道脉冲响应函数进行独立估计；第二种方法使用从前一个符号估计的信道脉冲响应作为匹配滤波器。第一种方法对于低至-12 dB的输入SNR产生平均BER<10（-2），第二种方法对于低至-8 dB的输入SNR产生类似的性能。使用测量的信号幅度波动统计和通过用发射码序列解扩接收信号获得的处理增益对测量的BER进行建模。对低输入SNR下不精确符号同步、信道估计中的不确定性和信号衰落引起的性能损失进行了定量建模，并与数据进行了比较。
