Data Directed Estimation Techniques for Single-Tone HF Modems
Data Directed Estimation Techniques for Single-Tone HF Modems
复制标题
单音高频调制解调器的数据导向估计技术
DOI：
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发表时间：
1985
期刊：
影响因子：
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通讯作者：
F. Hsu
中科院分区：
文献类型：
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作者：
F. Hsu
本文研究了用于单音高频调制解调器的数据定向估计（DDE）技术。该方案采用最小二乘自适应技术来处理衰落和多径高频信道。DDE是基于信道参数和数据块的直接估计。训练数据以训练位块的形式嵌入到传输中，在传输的固定（尽管是可选择的）部分与源数据块交替。本文讨论了两种DDE技术，即线性和非线性。在线性DDE中，源数据块由Levinson递归算法估计。在非线性DDE中，只有数据块的结束符号被保留、量化和从联立方程中减去。块中剩下的符号再次由Levinson算法估计，以此类推。这里描述的过程递归地使用，直到获得所有已知的符号。在线性和非线性DDE技术中，信道估计都采用最陡下降算法。与线性均衡器一样，线性DDE缺乏应对衰落色散高频无线电信道的能力。然而，非线性DDE在相同信道条件下工作良好。分析表明，在已知信道条件下，非线性DDE可以达到与决策反馈均衡（DFE）技术相似的性能。如果使用类似的自适应算法，DDE技术中使用的信道估计器将比DFE收敛得更快（参见第七节）。
This paper is concerned with data directed estimation (DDE) techniques for use in single-tone HF modems. The proposed scheme uses least-squares adaptive techniques for dealing with fading and multipath radio HF channels. The DDE is based on direct estimation of channel parameters and data blocks. Training data is imbedded into the transmission in the form of blocks of training bits alternated with blocks of source data at a fixed (though selectable) fraction of the transmission. Two DDE techniques, i.e., linear and nonlinear, are discussed in this paper. In the linear DDE, the source data block is estimated by a Levinson recursive algorithm. In the nonlinear DDE, only the end symbols of the data block are kept, quantized, and subtracted from the simultaneous equations. The symbols left in the block are estimated by a Levinson algorithm again, and so forth. The procedure described here is used recursively until all the known symbols are obtained. In both linear and nonlinear DDE techniques, the channel is estimated by a steepest-descent algorithm. As with a linear equalizer, the linear DDE lacks the ability to cope with the fading dispersive HF radio channels. However, the nonlinear DDE works well under the same channel conditions. The analysis shows that the nonlinear DDE can achieve performance similar to the decision-feedback equalization (DFE) technique with known channel conditions. The channel estimator used in the DDE techniques will converge faster than the DFE (see Section VII) if a similar adaptive algorithm is utilized.