Impact of Local-Oscillator Imperfections on Nonregenerative TDD and FDD Relaying

In this work we investigate the impact of imperfect local oscillators (LOs) at the relays in nonregenerative two-hop networks. Due to the specific traffic pattern of multihop networks, hardware imperfections at the relays have a different impact on the system than hardware imperfections at the sources and destinations. Based on the assumption that one LO generates all oscillations in each node, we consider baseband sampling time as well as sampling frequency offsets, RF frequency and phase offsets, timing errors, and phase noise. In the presence of these imperfections, time division duplex (TDD) and frequency division duplex (FDD) relays introduce errors to their forwarded signals. We identify these errors for both types of relays and use Monte-Carlo simulations to compare the performance of a multiuser network employing either TDD or FDD relays with imperfect LOs.