Abstmet-We consider the problem of link scheduling in a sensor network employing a TDMA MAC protocol. Our link scheduling algorithm involves two phases. In the first phase, we assign a color to each edge in the network such that no two edges incident on the same node are assigned the same color. We propose a distributed edge coloring algorithm that needs at most (d+l) The main challenge in adopting a TDMA MAC protocol for sensor networks is in allocating timeslots for each pair of neighboring nodes, This problem is referred to as link scheduling [6], [21]. To avoid collisions. a feasible timeslot allocation should be such that exactly one of the neighbors of a receiving node should transmit in a timeslot; the other neighbors might receive during the timeslot. A naive approach for a feasible timeslot allocation is to assign a unique timeslot to each pair of neighbors in the network. Although this eliminates the possibility of collisions, the large number of timeslots required increases the latency of communication. We therefore require a feasible fimeslor allocation tAat 14ses a minitrial number of titneslots. The timeslot assignment problem is closely relaled to the edge coloring problem for a graph. In a valid edge coloring, no two edges incident on tile same node are assigned the same colas. Vizing's theorem [7] states that a valid edge coloring for a graph can be obrained by using at most ( a -t l ) colors, where 6 is the maximum degree of a node in the graph. Given a valid edge coloring of the graph that represents the sensor network, a timeslot assignment for the sensor nodes can be obtained by mapping each timeslot to a color. However, such a TDMA schedule suffers from the hidden tenninal probIetn [24]. To illustrate this, consider the topology shown in Figure l(a) . Here, edges (1, 4) and (2, 3 ) are assigned color 1 and edges (1, 2) and ( 3 , 4) are assigned color 2. Let the directions of 2492 0-7803-
In REF , Gandham et al. propose a link scheduling algorithm involving two phases.
Link scheduling in sensor networks: distributed edge coloring revisited
Proceedings IEEE 24th Annual Joint Conference of the IEEE Computer and Communications Societies.
Proceedings IEEE 24th Annual Joint Conference of the IEEE Computer and Communications Societies.
Computer Science