... signals to the relays, forming aninterference channel; and in the second phase, the relaysforward the signals to the base stations, which cooperateto perform joint processing to form a multiple-antennamultiple ... signal to the relay while the MS is silent, that is, the DL, (ii) the MStransmits its signal to the relay while the BS is silent, thatis, the UL and (iii) the relay jointly processes the DL and ... relaychannel. In other words the relays cannot preform zero-forcing between themselves as was done in the previous phaseby the base stations. Thus, the rate in the second hop of the downlink (and,...