Multichannel ALLIANCES: A cooperative cross-layer scheme for wireless networks

A random access protocol named ALLow Improved Access in the Network via Cooperation and Energy Savings (ALLIANCES) was recently proposed, that achieves high throughput by resolving collisions in wireless networks. ALLIANCES exploits diversity provided by user cooperation. In this paper we propose a multichannel extension of ALLIANCES that in addition to cooperation diversity can exploit multipath diversity. The total bandwidth is divided into noninterfering subchannels and each packet occupies one subchannel for its transmission. First, two schemes are proposed for rate-limited traffic. Users transmit packets on all subchannels. Collisions on a subchannel. are resolved via cooperative transmissions, involving either the subchannel on which they occurred only, or all subchannels in a shared fashion. Second, for the case of bursty traffic, a random subchannel selection scheme is proposed to adaptively control the number of transmitted packets for each active user and, thus, keep collision orders small. Third, to accommodate heterogeneous traffic with diverse quality of service requirements, a fixed subchannel selection scheme is presented, where packets with the same traffic type are allocated to the same cluster of subchannels and predefined traffic priorities are taken into account. Analytical performance characterization of the proposed schemes at the physical layer is provided. The analysis provides insight on the relationship between achievable diversity and parameters such as collision order, number of relays, channel length, and number of carriers per subchannel.