Traditionally, a packet with errors, either due to channel noise or collisions, is discarded and needs to be retrans- mitted, leading to performance losses. Network Diversity Multiple Access (NDMA) handles collisions by combining a multipacket detection scheme with time diversity. In NDMA, the Base Station (BS) forces Mobile Terminals (MTs) to transmit J copies of each packet when J MTs collide. Diversity combining is limited to J copies of the packets, not allowing it to adapt to severe errors due to channel noise. This paper considers a multipacket detection scheme recently proposed, which reduces the packet error rate (PER) when more than J copies of the packets are available.
In this paper, an Hybrid-ARQ NDMA access mechanism is proposed. The access mechanism forces contending MTs during a collision resolution epoch to transmit more than J times when errors are detected. Analytical models are proposed for the goodput and delay, considering Poisson traffic. The proposed system performance is evaluated for a Single-Carrier with Frequency Domain Equalization (SC-FDE) scheme, and compared to classical NDMA.