Two-Way Amplify–Forward Relaying Using Frequency-Domain Oversampling on Frequency-Selective Fading Channels

Frequency-domain oversampling (FDO) is studied for two-way amplified-and-forward relaying (TWAR) on the frequency-selective fading channel. In the FDO-based scheme, a zero postfix (ZP) is inserted in the transmitted data block, and a fractionally spaced frequency-domain (FSFD) minimum mean-square-error (MMSE) estimate is performed on the received data block. Compared with the conventional MMSE receiver using a cyclic prefix (CP) without FDO, the FSFD-MMSE receiver can extract the frequency diversity on the frequency-selective fading channel. Moreover, a semi-analytical result on the error performance of the FSFD-MMSE receiver is also provided, which matches the simulation result closely. Finally, the robustness of the FDO-based scheme to the time-varying fading and the frequency offset is also studied through simulations.