Method and system for efficient DRX operation during handover in LTE

1. A method for efficient discontinuous reception (‘DRX’) operation during handover in Long Term Evolution (‘LTE’) in which a user equipment expects handover to occur between a source enhanced Node B (‘eNB’) and a target eNB, the method comprising the steps of:

checking, at the user equipment, whether a no handover initiation decision by the source eNB is received from the source eNB within a predetermined time period; if the no handover initiation decision by the source eNB is not received from the source eNB within a predetermined time period, performing the steps of:

ensuring the user equipment is not in a DRX sleep period during reception of a handover grant;

checking whether a handover grant is received,

if the handover grant is received, performing a handover procedure; and

if the handover grant is not received, resuming a DRX sleep interval; and

if the no handover initiation decision by the source eNB is received from the source eNB within the predetermined time period, resuming a DRX sleep interval; and wherein

the step of ensuring the user equipment is not in the DRX sleep period utilizes a short DRX period;

the short DRX period has a length set based on a value that is one of received from the source eNB or pre-configured; and

the value is dependent on whether the handover is inter radio access technology or intra radio access technology.

2. The method of claim 1 , wherein the step of ensuring the user equipment is not in the DRX sleep period utilizes continuous reception on the user equipment.

3. The method of claim 1 , wherein the step of ensuring the user equipment is not in the DRX sleep period utilizes an extended DRX awake period.

4. The method of claim 1 , wherein the value is predetermined and stored on the source eNB.

5. The method of claim 1 , further comprising the steps of:

making, at the source eNB, the handover initiation decision; and

signaling the handover initiation decision to the user equipment.

6. The method of claim 1 further comprising, after said resuming step, receiving updated measurement control information for handover procedures.

7. The method of claim 1 , wherein the user equipment is expecting handover to occur based on the sending of a measurement report.

8. The method of claim 1 , wherein the user equipment is expecting handover to occur based on a parameter in the measurement report being above or below a predetermined threshold.

9. A system for efficient discontinuous reception (‘DRX’) operation during handover in Long Term Evolution (‘LTE’) comprising user equipment and an enhanced node B, the system configured to:

check, by the user equipment, whether a no handover initiation decision by the enhanced Node B is received from the enhanced Node B within a predetermined time period;

if the no handover initiation decision by the enhanced Node B is not received from the enhanced Node B within the predetermined time period,

ensure the user equipment is not in a DRX sleep period during reception of a handover grant;

check whether a handover grant is received,

if the handover grant is received, perform a handover procedure; and

if the handover grant is not received, resume a DRX sleep interval;

if the no handover initiation decision by the enhanced Node B is received from the enhanced Node B within the predetermined time period, resume a DRX sleep interval at the user equipment; and wherein

ensuring the user equipment is not in the DRX sleep period comprises utilizing a short DRX period;

the short DRX period has a length set based on a value that is one of received from the enhanced node B or preconfigured; and

the value is dependent on whether the handover is inter radio access technology or intra radio access technology.

10. The system of claim 9 , wherein ensuring the user equipment is not in the DRX sleep period comprises utilizing continuous reception on the user equipment.

11. The system of claim 9 , wherein ensuring the user equipment is not in the DRX sleep period utilizes an extended DRX awake period.

12. The system of claim 9 , wherein the value is predetermined and stored on the enhanced node B.

13. The system of claim 9 further configured to receive, at the user equipment, updated measurement control information for handover procedure.

14. The system of claim 9 , wherein the user equipment is adapted to expect handover to occur based on the sending of a measurement report.

15. The system of claim 9 , wherein the user equipment is adapted to expect handover to occur based on a parameter in the measurement report being above or below a predetermined threshold.