| 摘要 |
A packet relay system in which each node calculates a link cost of each adjacent node based on an arrival rate of a packet from each adjacent node, acquires an accumulated value of a link cost calculated by each node in a range of nodes from a sink node for each adjacent node, calculates, for each adjacent node, a path cost of the one adjacent node by adding the link cost calculated to the accumulated value, and relays a data packet to one adjacent node selected from among nodes adjacent to the node based on a path cost of each adjacent node. This enables establishment of an upstream path to a sink node without increasing the amount of communication in a network. |
| 主权项 |
1. A packet relay system including a plurality of nodes which relay a data packet to each other, one of the plurality of nodes being a sink node, each one of the nodes including:
a packet transmitting unit which transmits a hello packet to its own adjacent nodes at predetermined time intervals; an arrival rate calculation unit which calculates, for each of said adjacent nodes, an arrival rate of a packet from said sink node, wherein the arrival rate is calculated based upon a sequence number included in a header of the packet and a total number of hello packets received from the sink node; a link cost calculation unit which calculates a link cost based on the arrival rate for each of said adjacent nodes; an accumulated link cost value acquisition unit which receives the hello packet transmitted from each of said adjacent nodes and acquires, for each of said adjacent nodes, an accumulated value of a link cost calculated by each node in a range of nodes from said sink node to each of said adjacent nodes, said accumulated value being included in the received hello packet; a path cost calculation unit which calculates, for each of said adjacent nodes, a path cost by adding the link cost calculated to the accumulated value; and a packet relay unit which relays the data packet to one adjacent node on a path having a lowest path cost of the path costs calculated for the adjacent nodes, wherein the arrival rate calculation unit, the link cost calculation unit, the accumulated link cost value acquisition unit, the path cost calculation unit, and the packet relay unit are implemented using an electric arithmetic circuit, wherein the packet relay unit determines whether a relay of the data packet is successful or not, wherein, if it is determined that relay of the data packet to the adjacent node is unsuccessful, the packet relay unit selects another adjacent node of the remaining adjacent nodes other than the one adjacent node in ascending order of the path cost to relay the data packet, wherein, if it is determined that relay of the data packet to each of the remaining adjacent nodes is unsuccessful, the packet relay unit re-selects the one adjacent node to relay the data packet, and wherein, each time it is determined that the relay of the data packet has been unsuccessful, the packet relay unit counts a number of retransmissions of the data packet and, if the number of retransmissions reaches a predetermined limit value, the packet relay unit terminates the relay process for the data packet. |
