Usually OFDMA is used as a multiple access technique of a multi-user system, where the channel is divided into U subcarriers and each user assigned N=U/M subcarriers where M is the number of users. In this system, all user transmit at the same time to the base station, and each user is separable from others, thanks to the orthogonality of the subcarriers. Note that here the base station just receiving.
I am thinking if we can use the same concept on a relaying system consists of one source, one relay, and one destination the way I described it earlier. It is the same as multi-user OFDMA except that the relay will have to transmit and receive at the same time slot. My concern is here: Is this practically implementable efficiently and without extra complexity requirements than the TDMA counterpart?
Thanks