Enhanced polling method for preventing deadlock in a wireless communications system
A method of polling in a wireless communications system includes prohibiting polling within a first predetermined period and triggering a poll function while polling is prohibited. After the first predetermined period has expired the method determines that there are no protocol data units (PDUs) scheduled for transmission or re-transmission and that there is at least a transmitted PDU that is not acknowledged yet, and selects a PDU to schedule for re-transmission to fulfill the poll function.
1. A method of polling in a wireless communications system that employs protocol data units (PDUs) and service data units (SDUs), the method comprising:
prohibiting polling before Timer_Poll_Prohibit expires;
triggering a poll function while polling is prohibited;
after Timer_Poll_Prohibit expires, if there is no PDU scheduled for transmission or re-transmission and if there is at least a transmitted PDU that is not acknowledged yet, selecting a PDU to schedule for re-transmission to fulfill the poll function; and
after Timer_Poll_Prohibit expires, if there is no PDU scheduled for transmission or re-transmission and if there is no transmitted PDU that is not acknowledged yet, no PDU is selected to fulfill the poll function.
2. The method of claim 1 , wherein the selected PDU is a PDU that is sequentially last PDU that has been transmitted at least once.
3. The method of claim 1 , wherein the selected PDU is a PDU that has been transmitted but not yet acknowledged when a transmission window size is less than half the value of a space of sequence numbers of PDUs in the communications system.
4. A communication device for polling a wireless communication system that employs protocol data units (PDUs) and service data units (SDUs), the communication device comprising:
a control circuit;
a processor installed in the control circuit;
a memory installed in the control circuit and operatively coupled to the processor;
wherein the processor is configured to execute a program code stored in the memory for polling by:
prohibiting polling before Timer_Poll_Prohibit expires;
triggering a poll function while polling is prohibited;
after Timer_Poll_Prohibit expires, if there is no PDU scheduled for transmission or re-transmission and if there is at least a transmitted PDU that is not acknowledged yet, selecting a PDU to schedule for re-transmission to fulfill the poll function; and
after Timer_Poll_Prohibit expires, if there is no PDU scheduled for transmission or re-transmission and if there is no transmitted PDU that is not acknowledged yet, no PDU is selected to fulfill the poll function.
5. The communication device of claim 4 , wherein the selected PDU is a PDU that is sequentially last PDU that has been transmitted at least once.
6. The communication device of claim 4 , wherein the selected PDU is a PDU that has been transmitted but not yet acknowledged when a transmission window size is less than half the value of a space of sequence numbers of PDUs in the communications system.