Timing and Iterative IBI and ICI Cancellation

Cyclic prefix or guard interval is usually used in OFDM to mitigate interblock interference (IBI). It must be longer than the delay span of wireless channels to completely cancel IBI. In some environments, the delay span of wireless channels is very large; therefore, the efficiency of OFDM is significantly reduced if it is still designed with long enough cyclic prefix. An alternative way is to use certain cyclic prefix to deal with those channels with reasonable length of delay span and to apply signal processing techniques at the receiver to deal with IBI caused by the channels with extremely long delay spans. In this chapter, we first analyze IBI and inter-carrier interference (ICI) for OFDM systems with insufficient cyclic prefix or zero-padding guard interval and propose a dynamic and static timing approach to mitigate ICI and IBI. We then develop iterative signal detection approaches for OFDM systems with insufficient cyclic prefix and zero-padding guard interval, respectively.

Keywords: inter-block interference, inter-carrier interference, interference cancellation, OFDM, maximum likelihood sequence estimation