Performance of Relay-Assisted DS-CDMA Conflicting Multiuser/Inter-Relay Interference in Nakagami-m Fading Channels

In relay-assisted cellular wireless communications the mobile terminals (MTs) near the base-station (BS) are usually preferred to being chosen as the relays for assisting the uplink transmission, for the sake of achieving the relay diversity while maintaining the system power-efficient. However, this strategy may result in the so-called ´bottleneck´ problem, when each user chooses different relays. In this case a huge number of relays might be required, but the available relays around the BS are limited. In this contribution we propose a relay strategy for direct-sequence code-division multiple-access (DS-CDMA) systems, where a set of MTs in the vicinity of the BS are chosen to act as the relays for all the uplink users. Explicitly, this relay strategy can significantly mitigate the ´bottleneck´ problem. In this contribution the performance of the DS-CDMA using our proposed relay strategy is investigated, when considering that there exist both multiuser and inter-relay interference. The bit error rate (BER) performance is investigated, when communicating over Nakagami-m fading channels, where signals from the MT transmitters to the relays and that from the relays to the BS receiver may experience different fading.