Sidelobe suppression using differential coding in OFDM cognitive radios

Orthogonal frequency division multiplexing (OFDM) is a recognized transmission technique for Cognitive radio (CR) systems but one of the major drawback of OFDM scheme is its out-of-band (OOB) leakage due to high spectral sidelobes. In this paper we propose a sidelobe suppression technique using a differential coding. The concept working behind the scheme is polynomial-cancellation-coding (PCC) in which one data symbol is transmitted on group of subcarriers. The proposed scheme have advantageous results when information source produces symbols with unequal probabilities which may be the case in practical transmission. Unlike to the basic PCC scheme, the proposed technique does not affect the throughput of the system. The technique is very simple to implement. Simulation results show reduction in in-band and out-of-band spectrum leakage.