Desynchronization with an artificial force field for wireless networks

Supasate Choochaisri, Kittipat Apicharttrisorn, Kittiporn Korprasertthaworn, Pongpakdi Taechalertpaisarn, Chalermek Intanagonwiwat
Appears in: 
CCR April 2012

Desynchronization is useful for scheduling nodes to perform tasks at different time. This property is desirable for resource sharing, TDMA scheduling, and collision avoiding. Inspired by robotic circular formation, we propose DWARF (Desynchronization With an ARtificial Force field), a novel technique for desynchronization in wireless networks. Each neighboring node has artificial forces to repel other nodes to perform tasks at different time phases. Nodes with closer time phases have stronger forces to repel each other in the time domain. Each node adjusts its time phase proportionally to its received forces. Once the received forces are balanced, nodes are desynchronized. We evaluate our implementation of DWARF on TOSSIM, a simulator for wireless sensor networks. The simulation results indicate that DWARF incurs significantly lower desynchronization error and scales much better than existing approaches.

Public Review By: 
Bhaskaran Raman

In many situations in distributed networks, “synchronization” of nodescan be bad, and “desynchronization” is desired. For instance, in a time division multiple access (TDMA) system, nodes should not transmit concurrently, to avoid wireless collision. A body of literature has grown in the recent past, on mechanisms to achieve this desynchronization. The main contribution of this paper is the application of a novel and interesting abstraction, that of repulsive electromagnetic forces, to desynchronize network nodes in the vicinity of one another. Nodes communicate with each other, their positions on an imaginary circle, and “electromagnetic forces” are computed to act in a manner as to “push” nodes away from one another to a state of perfect desynchronization. The paper presents the details of how this abstraction may be achieved in a distributed manner. The mechanism has minimal computational and communication overhead, and is thussuitable for implementation on low-end embedded sensing platforms. Simulation studies are presented using TOSSIM, to show that theproposed mechanism (DWARF: Desynchronization With an ARtificial Forcefield) performs more effectively than existing approaches. While this paper represents an initial exploration of an interesting idea, which the reviewers liked, questions on the practical usefulness of the proposed scheme need further study. This will require real implementation in the context of specific example applications. The extension of the scheme to multi-hop topologies is also a necessary part of future work in this context.