Method and system for transitioning between radio access technologies (RATS)

1. A method in a wireless communications device having a first protocol stack for use with a first radio access technology and a second protocol stack for use with a second, different, radio access technology, the first protocol stack comprising a reordering component associated with a first layer of the first protocol stack and arranged to implement a data reordering queue, the method for performing a handover from the first radio access technology to the second radio access technology, the method comprising:

determining that the device should perform a handover from the first radio access technology to the second radio access technology;

in response to determining that the device should perform a handover and before handover commences:

determining that data is present in a reordering queue implemented by the reordering component; and

sending the data present in the reordering queue to a second layer of the first protocol stack which is higher than the first layer of the first protocol stack; and

thereafter attempting a handover from the first radio access technology to the second radio access technology.

2. A method according to claim 1 , wherein the first protocol stack comprises a timer associated with the reordering component and the method further comprises:

in response to determining that the device should perform a handover, determining that the timer is running; and

stopping the timer.

3. A method according to claim 1 , wherein the first radio access technology is a 3G access technology.

4. A method according to claim 3 , wherein the first radio access technology is UMTS.

5. A method according to claim 4 , wherein the first radio access technology is HSPA.

6. A method according to claim 5 , wherein the first radio access technology is HSDPA.

7. A method according to claim 1 , wherein the first layer is a Medium Access Control (MAC) layer.

8. A method according to claim 7 , wherein the reordering component is a reordering entity comprised by a MAC-hs entity.

9. A method according to claim 1 , wherein the second layer is a Radio Link Control layer.

10. A method according to claim 1 , wherein the second radio access technology is a 2G access technology.

11. A method according to claim 10 , wherein the first radio access technology is one of GSM and GPRS.

12. A wireless communications device having a first protocol stack for use with a first radio access technology, a second protocol stack for use with a second, different, radio access technology, the first protocol stack comprising a reordering component associated with a first layer of the first protocol stack and arranged to implement a data reordering queue, and a processor operable according to a computer program to cause the wireless communications device to:

determine that the device should perform a handover from the first radio access technology to the second radio access technology;

in response to determining that the device should perform a handover and before handover commences:

determine that data is present in a reordering queue implemented by the reordering component; and

send the data present in the reordering queue to a second layer of the first protocol stack which is higher than the first layer of the first protocol stack; and

thereafter attempt a handover from the first radio access technology to the second radio access technology.

13. A computer program product comprising program code stored on a non-transitory computer readable medium for use in a wireless communications device, the wireless communications device having a first protocol stack for use with a first radio access technology and a second protocol stack for use with a second, different, radio access technology, the first protocol stack comprising a reordering component associated with a first layer of the first protocol stack and arranged to implement a data reordering queue, the computer program arranged, in use, to cause the wireless communications apparatus to:

determine that the device should perform a handover from the first radio access technology to the second radio access technology;

in response to determining that the device should perform a handover and before handover commences:

determine that data is present in a reordering queue implemented by the reordering component; and

send the data present in the reordering queue to a second layer of the first protocol stack which is higher than the first layer of the first protocol stack; and

thereafter attempt a handover from the first radio access technology to the second radio access technology.

14. A method according to claim 1 , further comprising: before handover commences processing in the first protocol stack the data sent to the second layer; and thereafter attempting a handover from the first radio access technology to the second radio access technology.

15. The device according to claim 12 , wherein the first protocol stack comprises a timer associated with the reordering component and in which the processor is further operable according to a computer program to cause the wireless communications device to:

in response to determining that the device should perform a handover, determine that the timer is running; and

stop the timer.

16. The device according to claim 12 , wherein the first radio access technology is a 3G access technology.

17. The device according to claim 12 , wherein the first radio access technology is UMTS.

18. The device according to claim 12 , wherein the first radio access technology is HSPA.

19. The device according to claim 12 , wherein the first radio access technology is HSDPA.

20. A product according to claim 13 , wherein the first layer is a Medium Access Control layer.