Equalization of Co-Channel Interferens in Future Mobile Communication Systems

Anders Nilsson- Stig and Henrik Perbeck


Centre for Mathematical Sciences
Mathematical Statistics
Lund Institute of Technology
Lund University
1999:E1


Abstract:

This study shows that Joint Detection is a powerful method of eliminating co-channel interference in 8-PSK modulation, provided a carrier SNR greater than 15 dB. Joint Detection refers to decoding information from two parallel data sources receiving one single input signal.
A full-state Joint MLSE algorithm was implemented, showing good performance but great numerical complexity. For multipath fading channels, a BER less than 5% is achieved for any strength of the interferer, provided a carrier SNR of 25 dB or more.

To reduce complexity, a Conventional MLSE for the carrier including a built-in Decision Feedback algorithm for the interferer was implemented and evaluated. For multipath fading channels, in most cases this MLSE/DF algorithm provides about 95% of the performance gain produced by Joint MLSE. Thus, for practical implementation, MLSE/DF may be an interesting solution.
The results are based on the assumption that carrier and interferer bursts are synchronized, and that the training sequences of both carrier  and interferer are known to the channel estimator. The need for further studies on Blind Detection of the interferer is pointed out, and a moment estimator for detection of a possible interferer is also discussed.