On the use of basis functions in blind equalization based on deterministic least squares
On the use of basis functions in blind equalization based on deterministic least squares
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论基函数在确定性最小二乘盲均衡中的应用
DOI：
10.1109/acssc.1997.680557
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
T. Thomas
中科院分区：
文献类型：
--
作者：
M. Zoltowski;Der;T. Thomas
提出了一种用于线性调制窄带数字通信的盲信道识别方案，该方案仅依赖于至少两个空间分离的天线的相应输出。所提出的方法是基于由Xu，Liu，Tong和Kailath观察到的相同输入信号馈送的两个FIR滤波器的相应输出之间的确定性关系（参见IEEE Trans. on Signal Processing，p.2982-93，1995）。它还依赖于使用从奈奎斯特符号波形导出的基函数来表征每个信道各自的脉冲响应，如Schell和Smith首先提出的（参见IEEE Milcom-94，p.128-32，1994）。对于城市蜂窝的情况下，延迟扩展的顺序为T/子0/，其中1/T/子0/是符号率，我们表明，对于一个给定的天线的连续时间信道可以很好地近似由一个线性组合的少量的时移版本的奈奎斯特符号波形。相应的时间偏移可以在延迟扩展上等间隔，而不管实际多径的数量及其相应的到达时间。这导致了一个关键的观察，即对于给定的天线，相同的基本系数值表征了由在t=0开始的符号间隔采样实现的“真实的”离散时间信道和由在t=（T/sub 0/）/2开始的符号间隔采样实现的虚拟离散时间信道。这又导致在中等SNR情况下需要在每个天线处每个符号两个样本的信道识别方案，其用相对少量的符号盲识别每个信道。进一步的结果是，可以直接从每个天线的基函数系数值计算大致跨越延迟扩展的一组低阶FIR均衡滤波器。
A blind channel identification scheme for narrowband digital communications with linear modulation is proposed that relies solely on the respective outputs of at least two spatially separated antennas. The proposed method is based on a deterministic relationship between the respective outputs of two FIR filters fed by the same input signal observed by Xu, Liu, Tong, and Kailath (see IEEE Trans. on Signal Processing, p.2982-93, 1995). It also relies on the use of basis functions derived from the Nyquist symbol waveform to characterize each channel's respective impulse response as first proposed by Schell and Smith (see IEEE Milcom-94, p.128-32, 1994). For urban cellular scenarios where the delay spread is on the order of T/sub 0/, where 1/T/sub 0/ is the symbol rate, we show that the continuous-time channel for a given antenna may be well approximated by a linear combination of a small number of time-shifted versions of the Nyquist symbol waveform. The corresponding time shifts may be equi-spaced across the delay spread regardless of the number of actual multipaths and their respective times of arrival. This leads to a critical observation that for a given antenna the same basis coefficient values characterize both the "real" discrete-time channel realized by symbol-spaced sampling starting at t=0 and the virtual discrete-time channel realized by symbol-spaced sampling starting at t=(T/sub 0/)/2. This, in turn, leads to a channel identification scheme requiring two samples per symbol at each antenna that blindly identifies each channel with a relatively small number of symbols in a moderate SNR scenario. A further result is that a bank of small order FIR equalizing filters spanning roughly the delay spread may be computed directly from the basis function coefficient values for each antenna.