Node Selection

For a bundle carrier, it may always wish that there is a low price to buy a relay node’s service. As there are many social ties among nodes, a node is usually willing to help its friends even if it can only get a low benefit. Therefore, bundle owners always wait for friend nodes to forward the bundle. However, when the remaining buffer or energy of a carrier or the remaining TTL of the bundle is little, the gain will be outweighed by the loss for the carrier if it still keeps waiting for its friend nodes. Therefore, bundle owners may select their relay nodes according to their current statuses.

A selection threshold oi is defined to determine whether it is appropriate for node i to wait for friends. When node i encounters a relay candidate, it will check its current status. If SMJDm > oi, which denotes the status of node i is loose, it tends to purchase relay service from its friend nodes, where the agreement price is usually low. If SMID < oi, which denotes the status of node i is tense, it will forward the bundle to a relay candidate, regardless of whether the candidate is a friend or not.

In fact, when the status is loose, it is unreasonable that a carrier waits for its friend nodes for a long time, as it has few friends or it takes a long time to encounter a friend. Therefore, LD denotes how many candidates node i encounters at most for bundle IDm when the status is loose, i.e.,

Here, |*J represents the floor function, and k reflects the change of status, including the attenuation of energy and buffer.

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