BER performance of M-QAM using OFDM with RF carrier phase noise

Orthogonal frequency division multiplexing (OFDM) requires strict attention to synchronization to maintain the orthogonality of subchannels. Pollet et al. (1995) pointed out the severe nature of a frequency offset impairment in the OFDM receiver. However, even if zero frequency error is achieved, frequency conversion for RF or microwave channels unavoidably imposes phase noise, a portion of which is untracked and contributes to BER performance degradation. The situation can be magnified by low cost RF synthesis techniques used in commercial communications, and the increasing sensitivity of M-QAM to phase jitter as M increases. The paper considers the bit-error rate (BER) performance of OFDM systems, taking into account the important relationship between the rate of the jitter process, and the OFDM subchannel baud rate. For OFDM, in order to properly characterize the degradation, four important items must be understood: nature of the untracked phase jitter; single carrier M-QAM phase noise performance; multicarrier interference effect (interbin interference); and relationship of phase jitter rate to subchannel baud rate. Each of these is discussed, and the results used to generate BER performance expressions.