COOPERATIVE TRANSMISSION SCHEMES FOR DECODE-AND-FORWARD RELAYING

We consider a low mobility cellular relaying system downlink where two mobile users are served by two neighboring decode-and-forward relays concurrently using the same frequency channel. We propose two cooperative relaying transmission schemes where each relay can choose proper preceding vectors based on its local channel knowledge to transmit data in the second hop. Each user can receive its own data without interference, which simplifies the user receiver design. We show that the diversity of each user's received data signal can be improved by receiving data from multiple relays. In addition, higher array gain can be achieved by the first scheme at the cost of higher synchronization accuracy requirements. Furthermore, we show that the two transmission schemes achieve higher transmission rate than serving different users in separate channels.