Detection of digital signals transmitted over a known time invariant channel

2010-10-26T15:21:34Z (GMT) by Wee Ser
This thesis investigates various detection processes that operate with known time invariant channels. The investigations are divided into two main areas, the first of which involves uncoded digital signals. Three different detection processes have been studied here and some promising systems have been developed from these. The first of the detection processes is an iterative detection process whereas the second detection process involves the linear filtering of the received signal. Binary signals are considered in the investigations here. The third detection process achieves the near-maximum likelihood detection of a 16-point QAM digital signal transmitted over a telephone circuit at 9600 bits/second. The detector here operates on the received sample values directly without using any complex prefiltering. The second area of investigation covered in this thesis involves coded digital signals. Binary and 16-point QCM signals have been considered here. Rate2 and 3 non-systematic convolutional codes with optimum free distance have been used in conjunction with the appropriate Gray codes for the encoding of the signals. At the receiving end, a joint near-maximum likelihood detection/decoding process is used. Computer simulation tests have shown that the system improves the tolerance to Gaussian noise over the corresponding uncoded system at low error rates.