A novel optimization approach for packet-wise Selective Relaying in CDMA uplink communications

In this paper, we propose a novel approach for cooperative systems performance optimization. We are interested on the uplink CDMA communications, known to be both intra-cell and inter-cell interference limited. More precisely, we define a multi-access interference (MAI) cost that reliably quantifies the additional interference generated by a relayed communication to the whole cellular system. For CDMA uplink communications, this MAI cost hides an implicit and smart power control that takes into account not only the reception quality required at the serving base station but also the interference generated to the whole network. Here, the optimization process aims to improve the system performance, in terms of Packet-Error-Rate (PER) for a certain required quality of service (QoS). The optimization process is carried for both Selective Relaying (SR) and Incremental Selective Relaying (ISR) schemes, on packet-by-packet basis. A variety of simulation results are carried using analytical expressions of Packet-Error-Probability that are derived for SR and ISR schemes. We show that, for a target PER of 10^-2, our optimized ISR scheme could provide up to 14 dB gain, in terms of MAI cost reduction, over the direct transmission scheme. Additionally, results highlight that our optimized ISR relaying is always more powerful than the optimized SR scheme and provides as much as 4 dB gain in the most favorable cases.