Two-stage random-access for multihop systems

Higher transmission rates are major characteristics of fourth-generation (4G) of mobile communications. Furthermore, operating at higher frequency bands means larger distance decay. These result in larger required transmission power. This causes problems particularly for uplink communications as a typical mobile station (MS) has a limited transmission power. Multihop systems have been proposed to address this problem. In this paper, we consider the issue of random-access (RA) in the multihop systems. A two-hop mobile communication system requires a two-stage RA. In this paper, we investigate a hybrid of code division multiple access (CDMA) and slotted-ALOHA for RA. We evaluate the basic performance in multihop systems, and propose interval slots allocation (ISsA) technique. This proposed technique means that dedicated slots are only used for the hop station (HS)-base station (BS) communications at intervals. Simulations demonstrate superior throughput-delay performance of a two-stage RA multihop system, including our proposed ISsA technique