Patent ID: 8693366

Claim:
A communication system, comprising: a core node that connects to a backbone network; and a plurality of slave nodes that connect to the core node with wireless communication directly or via another slave node, wherein the core node transmits, to one of the slave nodes, a reset routing packet for instructing the slave node to initialize a communication route from the core node to the slave node itself, and afterwards, a plurality of normal routing packets for instructing the slave node to construct a communication route from the core node to the slave node itself; the slave node includes: an own route evaluation value storing unit that stores an own route evaluation value which is an evaluation value of a communication route from the core node to the slave node itself; an uplink forwarding target storing unit that stores an uplink forwarding target information which shows an uplink forwarding target node which is a first node on a communication route from the slave node itself to the core node; and a route making processing unit that decides a communication route from the core node to the slave node itself, when receiving the reset routing packet and n (n is a counting number) of the normal routing packets from a single transmission source node, after judging whether to replace the uplink forwarding target node by the transmission source node; the route making processing unit includes: a reception power evaluation value calculating unit that calculates a reception power evaluation value which is an evaluation value of reception power between the slave node itself and the transmission source node, based on reception power of an n-th normal routing packet received; a new accumulated route evaluation value calculating unit that calculates a new accumulated route evaluation value which is an evaluation value of a communication route that the n-th normal routing packet received has gone through, based on an evaluation value of a relay route from the core node to the transmission source node and on the reception power evaluation value; and a route making processing unit that, if the new accumulated route evaluation value is smaller than the own route evaluation value, makes the uplink forwarding target storing unit store a transmission source node of the normal routing packet as a new uplink forwarding target node, and makes the own route evaluation value storing unit store the accumulated route evaluation value as a new own route evaluation value for a route making processing; and the reception power evaluation unit, if n equals to or is larger than two, calculates a reception power evaluation value which is an evaluation value of a reception power between the slave node itself and the transmission source node, based not only on a reception power of the n-th normal routing packet received but also on a part of or all of reception power of the reset routing packet and/or the normal routing packet separately received.