Frame synchronization with acknowledgment timeout in wireless networks

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.

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.