A Circular Postamble Structure Enabling Low Complexity Equalization in Frequency Domain for Noncausal Channels: Cyclic Suffix

Realizable root-raised cosine (RRC) filters have finite length. When these filters are used in transmitter and receiver side, frequency response of the effective filter does not have flat fading characteristic and it results two-sided intersymbol interference (ISI). In addition, relatively low up sampling factors result in synchronization errors and thus, two-sided ISI. Consequently, impulse response of the effective filter becomes noncausal. Moreover, nonlinearities in transmitter and receiver chains strengthen ISI. Such a channel-like behaviour of the noncausal effective filter can be overcome by conventional Half-Duplex systems where it should be avoided by In-Band Full-Duplex and higher order constellation systems due to being vulnerable to even low powered effects. In this article, we are providing a new cyclic postamble structure, namely Cyclic Suffix (CS), for constructing circularly symmetric convolution matrices for noncausal channels. CS provides the utilization of frequency domain equalization (FDE) in a low complex manner for cancelling the effects of such noncausal channels.