Data-Collecting Protocol Based on a Rooted Tree for Wireless Ad Hoc Networks Constructed Using Data Transmission Modems

摘要

This paper presents a simple communication protocol that effectively enables a base station to collect data from nodes in wireless ad hoc networks. The proposed protocol assumes that the network is constructed using a data transmission modem that uses a lower frequency radio wave than that employed by the frequently used systems such as wireless LANs or ZigBee. Since a lower frequency radio wave is advantageous because of less signal attenuation, the modem can provide a more reliable wireless link. Unfortunately, the modem does not support network functions. To construct a network with the modem and collect data from nodes, an appropriate communication protocol is required. The protocol must avoid packet collision because radio waves transmitted from nodes may generate interference. In addition, since the network is multihop and has mesh topology, a routing mechanism is necessary. To satisfy these requirements, the proposed method employs a token-passing approach that utilizes a rooted tree structure, which is extracted from a given network. By utilizing the tree structure, the routing mechanism is significantly simplified. Furthermore, packet collisions are eliminated by the token circulated in a tree. The algorithm that extracts a rooted tree from a given network is also shown. The feasibility and performance of the proposed protocol was examined on a prototype network.