Channel Access Using Opportunistic Reservations in Ad Hoc Networks

We introduce a medium access control protocol for ad hoc networks. The new protocol, which we call ORMA (opportunistic reservation multiple access) is aimed at providing both high throughput and bounded channel access delays, which are critical for supporting integrated voice and data services over ad hoc networks. In ORMA, the channel is divided into a random access section and a scheduled access section. The first is used to exchange neighborhood information, the latter is used for data transmissions over time slots organized in frames, with each time slot being accessed through reservations or probabilistic elections. To attain high throughput, nodes access data slots based on a fair election in which they win with a certain probability. To attain bounded channel access delays, nodes reserve time slots by using a novel opportunistic reservation. The performance of ORMA is studied by both analysis and simulations. It is also compared against the performance of schemes based entirely on probabilistic or fixed conflict-free slot assignment