Tracking of a Frequency-Hopping Interferer in an OFDM System

Abstract

We consider an OFDM system in the presence of a frequency-hopping interferer. We derive the Shannon channel capacity of the system with perfect and partial channel state information at the receiver (CSIR), where partial CSIR corresponds to knowledge of which sub-carrier the interferer affects. We also estimate the mutual information of the system with no CSIR, from which we compute the SNR gains that CSIR obtains. The results show that partial CSIR achieves the majority of the potential SNR gain for a given performance level. We consequently design a peak energy detector to estimate the interfered sub- carrier for a practical system and test the performance of the estimator both as a function of the interference dwell time and as a function of the interference power. The results indicate that longer dwell times enable the estimator to approach the performance of a genie-aided system and that a trade-off for increasing interference power exists between ease of detection and harm caused by missed detections.