Two of the major problems associated with implementing a mobile, distributed, packet radio network using a TDMA (time division multiple access) communications scheme are the tendency of the network conditions to change at any time and the lack of global network information which would enable a member node to instantaneously adapt to these changes. Instead, a node must rely on its own view of the network (consisting of its own neighbors and its neighbor’s neighbors) and information passed along from neighbors to enable it to communicate without contention and adapt to network changes. In order to create algorithms that will be used by all nodes to adapt to network changes, the types of changes which can occur must be considered beforehand. The three types identified so far are a deleted connection, which would correspond to a node moving out of communications range of another node, an added connection, which would correspond to a node moving into the communications range of another node, and an added node, which would correspond to a node “powering up” in the middle of a functioning network. Algorithms for the deleted connection and the added connection have already been created and tested. Therefore, this research explores the feasibility adding a node to a functioning network.
The proposed scheme for adding a node is as follows. When a node R powers up, it must first spend some time listening to network communications in order to find out who its neighbors are and when they transmit. Then it spends a short amount of time “shouting” over its neighbors telling them who was heard and to stop transmitting. When R is done shouting, its neighbors wait until their assigned transmission slot to relay information to their respective neighbors telling them to quiet down also. Now that the immediate area around R is quiet, R’s neighbors can help it build a complete list of neighbors and provide other network information that will help R determine which time slots it can transmit in. During this time, R and its neighbors will also try to coordinate their transmission schedules for near optimal network performance. Finally, R sends a message to its neighbors saying they can resume normal transmissions, and R’s neighbors relay that information to their neighbors.
Created on ... June 12, 2002
by Brian Wolf