The Role of Phase Compensation in Preventing Channel Dispersion in Variable-Gain Relay OFDM Systems

We show that the length of a composite channel is regarded up to the whole symbol duration for variable-gain relay (VGR), which generates the received power constant instantaneously. The enlarged channel length causes system burden, which is due to long-channel estimation, i.e., an increase in pilot overhead, a decrease in bandwidth efficiency, and a degradation of system performance. To prevent this effect and minimize the length of the composite channel, phase compensation of the source-relay (S-R) link channel should be added to the VGR, although this addition increases complexity. A system that adopts VGR with phase compensation performs better and has higher bandwidth efficiency.