Performance of M-ary/spread spectrum communication system in the presence of continuous wave interference

This paper describes an evaluation method and performance improvement for an M-ary/spread spectrum (SS) communication system in the presence of continuous wave interference. First, we introduce a theoretical equation for the average bit error rate of M-ary/SS receiver in transmission line with AWGN and single CW interference. Second, we define the required jamming margin for M-ary/SS receiver to satisfy a certain level of average of bit error rate. Then we analyze the theoretical value of the required jamming margin and evaluate the performance of receiver by a simulation. From this study, we found that the jamming margin relates to the spectrum spreading factor of the total system and does not relate to code length of pseudo-random noise sequence. To improve performance against CW interference, we first examine the effect of improvement when we use error correcting code as a spreading code. However, we cannot find any effect of the improvement, even if the jamming margin relates to spectrum spreading factor and even if there is a coding gain by the error correcting code. Second, we studied the performance improvement when whitening filter based on LMS algorithm is added to the receiver to reduce CW jamming. For a spreading factor between 7 and 25 dB, the jamming margin can be improved by 15 dB to 25 dB. (C) 1998 Scripta Technica.