Performance of capture-division packetized access (CDPA) with partial frequency reuse and power control

Previously, a new method for achieving spectrum reuse in cellular systems, called capture-division packetized access (CDPA), has been introduced. The method uses a single frequency in all cells but, unlike CDMA, allows each transmitter to access the full bandwidth. Practically, the CDPA's way of operation can be seen as an S-ALOHA scheme among different cells in which the mobile terminals belonging to the same cell transmit using a collision-free mechanism, which is easily obtained due to the very short intra-cell propagation delay. Parallel transmission in different cells is achieved through the "capture" capability. Packets that are not captured are almost immediately retransmitted, thus assuring that packets are eventually correctly received. In this paper we analyze an extension of the CDPA that uses partial frequency reuse. In fact, in this case, a trade-off exists between the bandwidth wasted by retransmissions and the bandwidth wasted by subdividing spectrum usage in K parts. It is shown that, depending on the capture threshold ratio b at receivers, an optimal choice exists. In all cases, the spectrum efficiency obtained almost doubles the efficiency of systems, like GSM, with K=7. The gain offered by power-control techniques is also investigated.