# US 9,439,105 B2 · Frame synchronization with acknowledgment timeout in wireless networks > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,439,105 B2 - Document ID: US9439105B2 - Status: Granted - Kind: B2 - Application number: 10/547,727 - Filed: 2004-03-02 - Published: 2006-08-17 - Granted: 2016-09-06 - Earliest claimed: 2003-03-05 - Assignees: Koninklijke Philips N.V. - Applicants: Amjad Soomro - Inventors: Amjad Soomro - Web page: https://patentgrep.com/patent/US9439105B2 ## CPC - H04W 28/24: Negotiating SLA [Service Level Agreement]; Negotiating QoS [Quality of Service] - H04L 1/188: {Time-out mechanisms} - H04W 52/0248: {dependent on the time of the day, e.g. according to expected transmission activity} - H04W 56/00: Synchronisation arrangements - 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) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - 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 A wireless local area network (WLAN) includes a first device and a second device. The first device sends a first frame including a first transmission indicator, which indicates that a service interval is to begin at a certain time. The second device sends an acknowledgement from the second device to the first device indicating receipt of the first transmission indicator. The first device sends a second frame including another first transmission indicator if, after a prescribed time period, the acknowledgement is not received by the first device. The first device also sends a last transmission indicator, which indicates that the service period will end at a certain time. The WLAN and its method of use provide synchronicity between the first and second devices as to the beginning and the end of a service period. ## Claims ### Claim 1 A method of transmitting frames from a first device of a wireless local area network (WLAN) to a second device of the WLAN, the method comprising: sending, by the first device, a first frame to the second device, the first frame including a first transmission indicator using a frame bit set in a Quality of Service (QoS) control field frame indicating that a service period is to begin at a first certain time; sending, by the first device, a second frame to the second device, the second frame including another first transmission indicator using a frame bit set in the QoS control field frame indicating that the service period is to begin at a second certain time when, after a prescribed time period, an acknowledgement of receipt of the first frame is not received by the first device, the second certain time being later than the first certain time; sending, by the first device, a last frame to the second device, the last frame including a last transmission indicator using another frame bit in the QoS control field; terminating, by the first device, the service period, when an acknowledgment of receipt of the last frame is received; and when an acknowledgement of receipt of the last frame is not received after a prescribed time period, terminating, by the first device, the service period, when a maximum service duration time has expired. ### Claim 2 (depends on 1) The method as recited in claim 1, wherein the method further comprises repeating, by the first device, the sending of the second frame until an acknowledgement of receipt of the second frame is received. ### Claim 3 (depends on 1) The method as recited in claim 1, wherein the method further comprises setting, by the first device, the service period to begin at the first certain time when an acknowledgment is received for the first frame, and setting, by the first device, the service period to begin at the second certain time when an acknowledgment is received in response to the second frame. ### Claim 4 (depends on 1) The method as recited in claim 1, wherein the method further comprises, after the sending of the first transmission indicator and before the sending of the last transmission indicator, sending a plurality of transmissions between the first device and the second device. ### Claim 5 (depends on 1) The method as recited in claim 1, wherein the first device is a Quality of Service (QoS) access point (QAP), and the second device is a Quality of Service Station (QSTA). ### Claim 6 (depends on 5) The method as recited in claim 5, further comprising: sending, by the QAP, the first transmission indicator when a current time is equal to a scheduled service period start time; setting, by the QAP, a service period start time to begin at the first certain time when an acknowledgment is received for the first frame including the first transmission indicator; and when, after a prescribed time period, the acknowledgement of receipt of the first frame is not received by the QAP, sending, by the QAP, the second frame including another first transmission indicator and setting, by the QAP, the service period start time to begin at the second certain time, when an acknowledgment is received in response to the second frame. ### Claim 7 (depends on 6) The method as recited in claim 6, further comprising sending, by the QSTA, an acknowledgement of receipt (ACK) to the QAP, after receiving the first transmission indicator. ### Claim 8 (depends on 6) The method as recited in claim 6, further comprising retransmitting, by the QAP, another first transmission indicator, when the QAP does not receive an acknowledgement of receipt (ACK) by the QSTA after waiting a prescribed time. ### Claim 9 (depends on 8) The method as recited in claim 8, further comprising repeating, by the QAP, the waiting and retransmitting until an acknowledgement from the QSTA is received. ### Claim 10 (depends on 5) The method as recited in claim 5, further comprising waiting, by the QAP, for an acknowledgement of receipt (ACK) of the last transmission indicator from the QSTA, after the QAP sends the last transmission indicator. ### Claim 11 (depends on 10) The method as recited in claim 10, further comprising retransmitting, by the QAP, the last transmission indicator, when the QAP does not receive the acknowledgement of receipt (ACK) of the last transmission indicator from the QSTA within a prescribed time. ### Claim 12 (depends on 11) The method as recited in claim 11, further comprising repeating, by the QAP, the waiting and retransmitting until one of the following occurs: receiving of the ACK of the last transmission indicator occurs, a maximum number of retries is exceeded, or a current service period is greater than a maximum service period. ### Claim 13 (depends on 10) The method as recited in claim 10, further comprising conducting, by the QSTA, internal queue management and/or entering, by the QSTA, a power save mode, after the QSTA completes sending the ACK of the last transmission indicator. ### Claim 14 (depends on 1) The method as recited in claim 1, wherein the second device enters an on-state when an elapsed waiting time for a start of the service period is equal to or greater than a minimum service period. ### Claim 15 A first device in a wireless local area network (WLAN), the first device comprising: a transmitter; a receiver; and a controller configured to: send a first frame to a second device, the first frame including a first transmission indicator, wherein the first transmission indicator is a frame bit set in a Quality of Service (QoS) control field frame indicating that a service period is to begin at a first certain time; send a second frame including another first transmission indicator, wherein the another first transmission indicator is a frame bit set in the QoS control field frame indicating that the service period is to begin at a second certain time that is later than the first certain time when, after a prescribed time period, an acknowledgement of the first frame is not received by the first device send, by the first device, a last frame to the second device, the last frame including a last transmission indicator using another frame bit in the QoS control field; terminate, by the first device, the service period, when an acknowledgment of receipt of the last frame is received; and when an acknowledgement of receipt of the last frame is not received after a prescribed time period, terminate, by the first device, the service period, when a maximum service duration time has expired. ### Claim 16 (depends on 15) The WLAN as recited in claim 15, wherein the first device is a Quality of Service Access Point (QAP) and the second device is a Quality of Service Station (QSTA). ### Claim 17 A wireless local area network (WLAN), comprising: a first device and a second device, wherein the first device is configured to send a first frame to the second device, the first frame including a last transmission indicator using a frame bit set in a Quality of Service (QoS) control field frame indicating that a service period is to end at a first certain time; the second device being configured to set the service period to end at the first certain time based on the last transmission indicator and send an acknowledgement to the first device indicating receipt of the first frame; and the first device being further configured to send a second frame including another last transmission indicator to the second device, wherein the another last transmission indicator is a frame bit set in the QoS control field frame indicating that the service period is to end at a second certain time that is later than the first certain time when, after a prescribed time period, the acknowledgement is not received by the first device, wherein when the second frame is received, the second device is configured to set the service period to end at the second certain time instead of the first certain time, and send an acknowledgement to the first device indicating receipt of the second frame, and, if the acknowledgement indicating receipt of the second frame is not received by the first device after a prescribed time, the first device is configured to end the service period, when the service period has not exceeded a maximum service period time. ### Claim 18 (depends on 17) The WLAN as recited in claim 17, wherein the first device is a Quality of Service Access Point (QAP) and the second device is a Quality of Service Station (QSTA).