Bit error rate performance of OFDM in narrowband interference with excision filtering

The effect of narrowband interference on OFDM systems is considered, with particular regard to the receiver post-detection bit error rate performance. It is shown both by analysis and by computer simulation that the ensemble average bit error rate is severely affected by narrowband interference and that particular values of interferer carrier frequency and phase can produce bit error rates significantly higher than the ensemble average. An interference suppression technique based on excision (notch) filtering is proposed and is shown by computer simulation to improve ensemble average bit error rates to about 0.001 for BPSK modulated OFDM with signal-to-interference ratios as low as -30 dB

I. INTRODUCTION

Orthogonal frequency division multiplexing (OFDM) [1], [2] has become the physical layer of choice for many wireless communications systems [3]–[8]. An attractive feature of current wireless local area network (WLAN) [3], [4] and wireless metropolitan area network (WMAN) [5], [6] standards based on OFDM is the designed ability to operate in unlicensed spectrum. However, these systems must share spectrum with other unlicensed systems; such as cordless telephones, garage door openers and baby monitors; which produce narrowband interference in WLAN and WMAN systems. Further, radio non-idealities such as transmitter carrier feedthrough (also known as carrier leakage) also introduce narrowband interference in the form of single-frequency carrier residues [9].