>>>> Poster
Existing MAC protocols can be divided into allocation-based and random access schemes. In allocation-based schemes such as Time-Division
Multiple Access (TDMA), a central authority shares the channel resources among the multiple users in a fixed manner. In random access schemes such as Carrier-Sense Multiple Access (CSMA), the network nodes contend for the medium in a decentralized manner. Allocation-based MAC protocols perform well in environments where the traffic is predictable and the network topology is static. Random access schemes are more flexible but lack efficiency, especially when demand for bandwidth is high.
We propose a MAC scheme that combines the advantages of allocation-based and random access schemes to provide an efficient
scheduling of the transmissions in ad hoc networks with high traffic load and contention. Like allocation-based schemes, it creates dense, collision-free transmission patterns. However, the transmission patterns are obtained dynamically in a distributed manner, like in random access schemes.
Our MAC scheme is based on the so-called reaction-diffusion mechanism. Reaction-diffusion was proposed by Turing in 1952
to explain the formation of patterns in biological systems. Typical examples are mammalian coat patterns such as
zebra stripes or felines' spots. In Reaction-Diffusion MAC (RDMAC), we use the reaction-diffusion mechanism to create transmission patterns. Our scheme is decentralized and relies exclusively on local interactions between the network nodes to create global transmission patterns.
A transmission inhibits other transmissions in its immediate surrounding and encourages nodes located further away to transmit. The right most figure below illustrates the creation of a transmission pattern by RDMAC on a two-dimensional network where the nodes are placed on a grid. As in biological systems, the pattern formation is spontaneous and can adapt to changes in the environment.
 |  |  |
| Transmission pattern created by a centralized TDMA strategy | Mammalian coat pattern | Transmission pattern created by the decentralized RDMAC scheme |
| Illustration of different types of patterns: a crystalline pattern obtained by a centralized
TDMA scheme (a), and a less regular pattern obtained by the decentralized RDMAC scheme (c), which is inspired by the mechanism governing pattern formation in biological systems such as mammalian coat patterns (b). In (a) and (c) we consider a two-dimensional grid network. Active
transmissions are highlighted by black disks and the gray area around an active transmission corresponds to its exclusion domain (i.e., the
area where other nodes must remain silent to avoid a collision with the active transmission). |
People
Publications
[1] M. Durvy and P. Thiran, `Reaction-Diffusion Based Transmission Patterns for Ad Hoc Networks' in Proc.
INFOCOM, Miami, March 2005.
