The nth-order cyclostationarity of OFDM signals in time dispersive channels

Previous studies on the cyclostationarity aspect of orthogonal frequency division multiplexing (OFDM) signals considered only second-order cyclostationarity or assumed additive white Gaussian noise (AWGN) channel for propagation. This paper presents new results for the nth-order cyclostationarity of OFDM signals transmitted through time dispersive channels. An analytical closed-form expression is derived for the nth-order cyclic cumulant polyspectum of OFDM signals propagating through such channels, and affected by additive Gaussian noise, carrier phase, and frequency and symbol timing offsets at the receiver end. Furthermore, a necessary and sufficient condition on the oversampling factor per subcarrier is derived for such signals to avoid aliasing. Numerical results are presented.