A Blind Single Antenna Interference Cancellation Algorithm for Asynchronous OFDM Communication Systems

摘要

In orthogonal frequency division multiplexing (OFDM) based cellular systems, co-channel interference (CCI) from adjacent interfering base stations (BSs) operating and co-existing with the desired BS in the same frequency channel would greatly degrade the bit error rate (BER) performance of mobile receivers which are near to cell borders. GCI cancellation algorithms by using only one receiving antenna named single antenna interference cancellation (SAIC) have been under intense research. However, most of these algorithms require additional information from interfering signals. Furthermore, the orthogonality of a asynchronous interfering signal is destroyed and therefore, conventional SAIC algorithms cannot be applied. In this paper, we propose a blind SAIC algorithm named least mean square-blind joint maximum likelihood sequence estimation (LMS-BJMLSE) for asynchronous interference cancellation. The proposed LMS-BJMLSE algorithm is blind with respect to interfering signals and neither the training sequence (TS) nor pilot signal from interfering signals is needed. Its complexity is independent of channel length compared to the conventional time domain JMLSE algorithm. Simulation results show that the proposed LMS-BJMLSE algorithm could greatly improve the BER performance in both synchronous and asynchronous interference conditions. In the second part, both the upper and lower bounds for JMLSE based MQAM-OFDM systems are derived. A tighter lower bound is given by replacing the smart genie with a less generous one. This lower bound is valid for any MQAM and an arbitrary number of interferers.