# US 7,613,156 B2 · Method for energy efficient prospective peer discovery in an ad hoc network > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,613,156 B2 - Document ID: US7613156B2 - Status: Granted - Kind: B2 - Application number: 11/422,954 - Filed: 2006-06-08 - Published: 2007-12-13 - Granted: 2009-11-03 - Earliest claimed: 2006-06-08 - Assignees: Motorola, Inc. - Inventors: Loren J. Rittle; Tzvetan T. Horozov; Nitya Narasimhan; Venugopal Vasudevan - Web page: https://patentgrep.com/patent/US7613156B2 ## CPC - H04W 8/005: {Discovery of network devices, e.g. terminals} - H04W 52/0216: {using a pre-established activity schedule, e.g. traffic indication frame} - H04W 48/08: Access restriction or access information delivery, e.g. discovery data delivery (signalling during connection H04W76/00) - H04W 48/16: Discovering, processing access restriction or access information - H04W 76/10: Connection setup - H04W 84/18: Self-organising networks, e.g. ad-hoc networks or sensor networks - Y02D 30/70: in wireless communication networks - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - Y02D: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE ## Abstract Energy-efficient discovery techniques are provided for a client node to discover at least one peer provider node in an ad hoc network. For example, the client node can be configured to turn on its first ad hoc interface while in a discovery mode to establish a channel for a first time period. The client node can then transmit a first beacon to advertise its presence to other nodes within the transmission range of the client node to acquire service information from at least one of a plurality of prospective peer provider nodes within the transmission range of the client node. At least one of the prospective peer provider nodes is configured to turn on its second ad hoc interface for a second period of time to listen for beacons from other nodes. The second period of time is less than or equal to the first period of time. ## Claims ### Claim 1 A method for a client node to discover a peer provider node in an ad hoc network, comprising: activating a first ad hoc interface in the client node while in a discovery mode to establish a channel for a first time period; transmitting a first beacon to advertise presence of the client node including a request to acquire service information from at least one prospective peer provider node within the transmission range of the client node; receiving, during the first time period at the client node, a second beacon from the at least one prospective peer provider node; analyzing information in the second beacon to determine if the at least one prospective peer provider node offers the service the client node is requesting; and transmitting a response message from the client node to the at least one prospective peer provider node when the at least one prospective peer provider node offers the service requested by the client node, wherein the response message indicates that the at least one prospective peer provider node is to keep a second ad hoc interface active for a period of time. ### Claim 2 (depends on 1) A method according to claim 1, further comprising: activating the second ad hoc interface in the at least one prospective peer provider node for a second period of time to listen for beacons from other nodes, wherein the second period of time is less than or equal to the first period of time; and transmitting the second beacon from the at least one prospective peer provider node at the beginning of the second period of time to advertise services which the at least one of the plurality of prospective peer provider node can provide to other nodes, wherein the second beacon comprises a service extension field comprising a list of services that are currently running on the at least one prospective peer provider node or that the at least one prospective peer provider node is capable of running. ### Claim 3 (depends on 2) A method according to claim 2, wherein the second ad hoc interface is activated in response to either: receiving another beacon, or at regular predetermined time intervals. ### Claim 4 (depends on 1) A method according to claim 1, wherein the first beacon comprises: a first field indicating the first period of time the client node will keep the channel on for, and a second field indicating a service the client node is requesting, wherein the first time period is of sufficient duration to ensure that a prospective peer provider node within the transmission range of the client node can detect and respond to the first beacon, and wherein the first time period is of sufficient duration to ensure that, if a response beacon is transmitted by a prospective peer provider node, the client node will detect a response beacon within the first time period. ### Claim 5 (depends on 1) A method according to claim 1, wherein the second beacon further comprises: a first field specifying a duration of the second time period (α) during which the second ad hoc interface will be on and a duration of the third time period (β) during which the second ad hoc interface will be off; a MAC beacon field which specifies the IEEE 802.11 MAC beacon; an IP extension field which specifies the IP address of the particular node that is transmitting the second beacon; and a second field comprising a number of neighbor nodes a particular prospective peer provider node has seen recently within a particular time period. ### Claim 6 (depends on 5) A method according to claim 5, further comprising: receiving a second beacon from a first prospective peer provider node; receiving a second beacon from a second prospective peer provider node; evaluating each of the second beacons; and choosing either the first prospective peer provider node or the second prospective peer provider node based on the fields specified in each of the second beacons. ### Claim 7 (depends on 5) A method according to claim 5, wherein a duration of the second time period (α) and a duration of the third time period (β) define a duty cycle for the particular node. ### Claim 8 (depends on 5) A method according to claim 5, further comprising: determining, at each prospective peer provider node, a duration of the second time period (α) and a duration of the third time period (β) based on the particular service(s) being offered by the particular prospective peer provider node. ### Claim 9 (depends on 8) A method according to claim 8, wherein the duration of the second time period (α) can be adjusted based on the particular radio protocol being used, and wherein the duration of the third time period (β) can be adjusted based on the real time requirements of the particular service(s) being offered by the particular node. ### Claim 10 (depends on 5) A method according to claim 5, wherein a sum of the second time period (α) and the third time period (β) is less than or equal to the value of the first time period (Ymax) on all nodes. ### Claim 11 (depends on 1) A method according to claim 1, wherein the first beacon comprises a first application service beacon and the second beacon comprises a second application service beacon. ### Claim 12 (depends on 1) A method according to claim 1, wherein the beginning of the first time period is synchronized with the beginning of the second time period based on a time constant provided from a cellular network or service. ### Claim 13 (depends on 12) A method according to claim 12, wherein the end of the first time period is synchronized with the end of the second time period based on a time constant provided from a cellular network or service. ### Claim 14 (depends on 1) A method according to claim 1, wherein the client node turns off the first ad hoc interface and enters sleep mode when it does not receive a response from a prospective peer provider node within the first time period. ### Claim 15 (depends on 1) A method according to claim 1, further comprising: communicating, between the client node and the at least one prospective peer provider node, information associated with the service requested by the client node; and turning off the second ad hoc interface once the at least one prospective peer provider node has communicated the information associated with the service requested by the client node. ### Claim 16 (depends on 1) A method according to claim 1, wherein the prospective peer provider nodes not receiving a response message from the client node turn off their second ad hoc interfaces at the end of the second time period. ### Claim 17 An ad hoc network, comprising: at least one prospective peer provider node; and a client node configured to: turn on a first ad hoc interface in the client node while in a discovery mode to establish a channel for a first time period; transmit a first beacon to advertise presence of the client node including a request to acquire service information from at least one prospective peer provider node within the transmission range of the client node; receive, during the first time period at the client node, a second beacon from the at least one prospective peer provider node; analyze information in the second beacon to determine if the at least one prospective peer provider node offers the service the client node is requesting; and transmit a response message from the client node to the at least one prospective peer provider node when the at least one prospective peer provider node offers the service requested by the client node, wherein the response message indicates that the at least one prospective peer provider node is to keep a second ad hoc interface active for a period of time. ### Claim 18 (depends on 17) An ad hoc network according to claim 17, wherein the at least one of the prospective peer provider nodes is configured to: activate the second ad hoc interface in the at least one of the prospective peer provider nodes for a second period of time to listen for beacons from other nodes, wherein the second period of time is less than or equal to the first period of time; and transmit the second beacon during the second period of time to advertise services the prospective peer provider node can provide to other nodes wherein the second beacon comprises a service extension field comprising a list of services that are currently running on the prospective peer provider node or that the prospective peer provider node is capable of running. ### Claim 19 (depends on 17) An ad hoc network according to claim 17, wherein the first beacon comprises: a first field indicating the first period of time the client node will keep the channel on for, and a second field indicating a service the client node is requesting, wherein the first time period is of sufficient duration to ensure that a prospective peer provider node within the transmission range of the client node can detect and respond to the first beacon, and wherein the first time period is of sufficient duration to ensure that, if a response beacon is transmitted by a prospective peer provider node, the client node will detect a response beacon within the first time period. ### Claim 20 (depends on 17) An ad hoc network according to claim 17, wherein the second beacon further comprises: a first field specifying a duration of the second time period (α) during which the second ad hoc interface will be on and a duration of the third time period (β) during which the second ad hoc interface will be off; a MAC beacon field which specifies the IEEE 802.11 MAC beacon; an IP extension field which specifies the IP address of the particular node that is transmitting the second beacon; and a second field comprising a number of neighbor nodes a particular prospective peer provider node has seen recently within a particular time period. ### Claim 21 (depends on 20) An ad hoc network according to claim 20, wherein the client node is further configured to: receive a second beacon from a first prospective peer provider node; receive a second beacon from a second prospective peer provider node; evaluate each of the second beacons, and choose either the first prospective peer provider node or the second prospective peer provider node based on the fields specified in each of the second beacons. ### Claim 22 (depends on 20) An ad hoc network according to claim 20, wherein a duration of the second time period (α) and a duration of the third time period (β) define a duty cycle for the particular node. ### Claim 23 (depends on 20) An ad hoc network according to claim 20, wherein each of the prospective peer provider nodes is configured to determine a duration of the second time period (α) and a duration of the third time period (β) based on the particular service(s) being offered by the particular prospective peer provider node. ### Claim 24 (depends on 23) An ad hoc network according to claim 23, wherein the duration of the second time period (α) can be adjusted based on the particular radio protocol being used, and wherein the duration of the third time period (β) can be adjusted based on the real time requirements of the particular service(s) being offered by the particular node. ### Claim 25 (depends on 20) An ad hoc network according to claim 20, wherein a sum of the second time period (α) and the third time period (β) is less than or equal to the value of the first time period (Ymax) on all nodes. ### Claim 26 (depends on 17) An ad hoc network according to claim 17, wherein the first beacon comprises a first application service beacon and the second beacon comprises a second application service beacon. ### Claim 27 (depends on 17) An ad hoc network according to claim 17, wherein the beginning of the first time period is synchronized with the beginning of the second time period based on a time constant provided from a cellular network or service. ### Claim 28 (depends on 27) An ad hoc network according to claim 27, wherein the end of the first time period is synchronized with the end of the second time period based on a time constant provided from a cellular network or service. ### Claim 29 (depends on 17) An ad hoc network according to claim 17, wherein the second ad hoc interface is activated in response to either: receiving another beacon, or at regular predetermined time intervals. ### Claim 30 (depends on 17) An ad hoc network according to claim 17, wherein the client node turns off the first ad hoc interface and enters sleep mode when it does not receive a response beacon from a prospective peer provider node within the first time period. ### Claim 31 (depends on 17) An ad hoc network according to claim 17, wherein the at least one prospective peer provider node is configured to communicate information associated with the service requested by the client node, and to turn off the second ad hoc interface once the at least one prospective peer provider node has communicated the information associated with the service requested by the client node. ### Claim 32 (depends on 17) An ad hoc network according to claim 17, wherein the prospective peer provider nodes not receiving a response message from the client node turn off their second ad hoc interfaces at the end of the second time period.