Employing simulated acknowledgment signals for efficient handoffs in cellular packet networks
An improved arrangement is described for maintaining throughput of date packets over a cellular packet network from an Internet server to an end user machine during handoff of a mobile subscriber unit from a first base station to a second base station. The end user machine conventionally generates, in response to successive bytes from the server, acknowledgment signals including here applicable a “zero” acknowledgment signal that advertises a closed receive window at the end user machine and that is effective to pause transmission of data from the server. In response to a handoff start signal from the subscriber unit, a gateway unit associated with the first base station sends to the server a simulated zero acknowledgment signal to pause such transmission. Upon completion of handoff, an actual non-zero acknowledgment signal stored at the gateway unit at the start of handoff is applied to the server to resume transmission from the server to the end user machine.
1. A method for data packet delivery to a subscriber unit during handoff from a first base station to a second base station, the method comprising:
receiving subscriber unit acknowledgements of transmitted data packets;
buffering the received subscriber unit acknowledgements;
pausing data packet delivery on a condition that detecting a handoff has commenced;
forwarding the buffered subscriber unit acknowledgements on a condition that handover is completed.
2. The method of claim 1 , wherein pausing data packet delivery further comprises:
detecting a zero acknowledgement signal instead of the buffered acknowledgement of received data packets;
wherein upon detection of the zero acknowledgement signal, data packet transmission is paused.
3. The method of claim 1 , wherein the data packets are delivered to the subscriber unit sequentially.
4. The method of claim 1 , wherein the data packets are delivered to the subscriber unit in accordance with transport control protocol (TCP).
5. The method of claim 4 , wherein the subscriber unit acknowledgement forwarded after completion of handoff is not the subscriber unit acknowledgement most currently buffered.
6. The method of claim 1 , wherein pausing data packet delivery on a condition that handoff commences further comprises detecting a handoff required signal.
7. A serving base station for data packet delivery to a subscriber unit during handover to a target base station, the serving base station comprising:
a sensor device for monitoring received subscriber unit acknowledgements of transmitted data packets;
a detector for detecting a condition that handover to the target base station has commenced and completed;
a session database for storing received subscriber unit acknowledgements until detection of an optimizer for pausing data packet delay using a simulated zero acknowledgement on a condition that handoff has been detected; and
delivering the data packets on a condition that detection of the completion of handover using the stored subscriber unit acknowledgement has occurred.