Equalization of Co-Channel Interferens in Future
Mobile Communication Systems
Anders Nilsson- Stig and Henrik Perbeck
Centre for Mathematical Sciences
Lund Institute of Technology
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.