On the Use of Correlative Coding for OFDM

Recent published work suggests that correlative coding can improve OFDM performance by several dB. This work, however, does not consider fully a symbol error rate performance measure for the OFDM systems. Exploiting an equivalence between correlative coding and partial-response signaling, a bit error rate performance measure is employed to assess the performance of OFDM systems using correlative coding. It is shown that although partial-response pulse-shaping or correlative coding can reduce intercarrier interference due to carrier frequency offset, they do not necessarily improve the system bit error rate performance because of the introduction of multilevel signaling with associated reduced receiver decision distance. It is observed that bit error rate performance improvement for symbol-by-symbol detection can be achieved only in some cases of large frequency offset. In the case of smaller, practical, values of frequency offset the bit error rate is increased by correlative coding or partial-response pulse-shaping.