Patent ID: 8897170

Claim:
A communication method for a mobile terminal in a sensor network, the method comprising: continuously broadcasting an agent request message specifying request information at predetermined time intervals during a first period, receiving an agent reply message containing a reply value corresponding to the request information from at least one of a plurality of sensor nodes that has received the agent request message; and selecting, as an upstream agent, a sensor node that has transmitted a best value among the reply values of the agent reply messages received during the first period, wherein the agent request message includes a first field specifying the request information and a second field specifying a current best value among the reply values of the agent reply messages received during the first period, and wherein the broadcasting comprises specifying the best value among the reply values of the agent reply messages in the second field of the agent request message to be broadcast in a second period immediately after the first period, and broadcasting the agent request message; selecting the upstream agent to transmit an upstream packet received from the plurality of sensor nodes of the sensor network; piggybacking information of the neighboring sensor nodes on the upstream packet and transmitting the upstream packet to the upstream agent; and receiving a downstream packet responsive to the upstream packet through a downstream agent selected by a gateway that has received the upstream packet through the upstream agent.