Method and apparatus for idle user equipment redistribution in a HetNet for load balance

1. A user equipment comprising:

a processor configured to,

receive a message,

determine whether to perform a carrier frequency selection process based on the received message, the carrier frequency selection process being performed for determining a carrier frequency for the user equipment to operate on, and

determine the carrier frequency by performing the carrier frequency selection process if the processor determines to perform the carrier frequency selection process, the processor configured to

perform the carrier frequency selection process based on matching a random number to a probability value from among one or more probability values included in the received message, the one or more probability values corresponding to any two or more carrier frequencies each of the one or more probability values representing a probability of a corresponding one of the two or more carrier frequencies being selected for the user equipment to operate on,

wherein the random number is within a first range that corresponds in a lower value and an upper value to a second range of the one or more probability values.

2. The user equipment of claim 1 , wherein the processor determines to perform the carrier frequency selection process if,

the received message includes a first list and the user equipment detects a new cell identification for a cell currently serving the user equipment, the first list including the one or more probability values corresponding to at least one of a small cell carrier frequency selection probability value and a list of neighboring macro cell carrier frequency selection probability values corresponding to the one or more carrier frequencies, or

the received message includes the first list and a randomization bit indicates that the carrier frequency selection process is to be performed.

3. The user equipment of claim 1 , wherein the processor is further configured to perform the carrier frequency selection process by,

determining a target carrier frequency,

determining a priority of the target carrier frequency,

determining an availability of the target carrier frequency, and

determining whether to change a current carrier frequency of the user equipment to the target carrier frequency based on the priority and the availability of the target carrier frequency.

4. The user equipment of claim 3 , wherein the processor is further configured to determine the target carrier frequency by,

generating the random number,

matching the random number to one of the one or more probability values, the one or more probability values including a small cell carrier frequency selection probability value, at least one neighboring macro cell carrier frequency selection probability value and a probability of remaining on the current carrier frequency of the user equipment, and

selecting a carrier frequency associated with the matched one of the one or more probability values, to be the target carrier frequency.

5. The user equipment of claim 4 , wherein the received message further includes

a second list, the second list including carrier frequencies of small cells known to a serving macro cell from which the message is received, and

the processor is further configured to

assign a highest priority value to the target carrier frequency if the target carrier frequency is the carrier frequency associated with one of the at least one neighboring macro cell carrier frequency selection probability values, and

assign a highest priority value to all the carrier frequencies of the small cells if the target carrier frequency is the carrier frequency associated with the small cell carrier frequency selection probability value.

6. The user equipment of claim 5 , wherein the processor is further configured to

select, with equal priority, any one of the carrier frequencies of the small cells to be the target carrier frequency when the processor assigns the highest priority value to all of the carrier frequencies of the small cells.

7. The user equipment of claim 4 , wherein the processor is further configured to,

assign a lowest priority value to a cell if the cell was previously associated with the user equipment, and

determine whether the target carrier frequency is associated with the cell.

8. The user equipment of claim 7 , wherein the processor is further configured to

determine, if the processor determines that the target carrier frequency is available and the target carrier frequency is associated with the cell, the carrier frequency by,

determining whether a timer has expired, and

determining, based on the expiration of the timer, whether to remain on the current carrier frequency of the user equipment or change the current carrier frequency of the user equipment to the target carrier frequency.

9. The user equipment of claim 7 , wherein the processor is further configured to

determine, if the processor determines that the target carrier frequency is not available, the carrier frequency, by

remaining on the current carrier frequency of the user equipment.

10. The user equipment of claim 7 , wherein, the processor is further configured to

determine, if the processor determines that the target frequency is available and the target carrier frequency is not associated with the cell the carrier frequency, by

changing the current carrier frequency of the user equipment to the target carrier frequency.

11. The user equipment of claim 1 , wherein the processor determines to perform the carrier frequency selection process if,

the processor detects a new cell identification for a cell currently serving the user equipment,

the user equipment detects at least one small cell, or

the message includes a randomization bit indicating that the carrier frequency selection process is to be performed.

12. The user equipment of claim 11 , wherein the processor is further configured to

perform the carrier frequency selection process, if the processor determines to perform the carrier frequency selection process, by,

determining a target carrier frequency,

determining a priority of the target carrier frequency,

determining an availability of the target carrier frequency, and

determining whether to change a current carrier frequency of the user equipment to the target carrier frequency based on the priority and the availability of the target carrier frequency.

13. The user equipment of claim 12 , wherein the processor is further configured to determine the target carrier frequency by,

generating the random number,

matching the random number to the one or more probability values corresponding to the one or more carrier frequencies, the one or more probability values including probability values of selecting neighboring macro cell carrier frequencies, probability values of selecting neighboring small cell carrier frequencies and a probability of remaining on the current carrier frequency of the user equipment, and

determining a carrier frequency associated with the matched one of the one or more probability values, to be the target carrier frequency.

14. The user equipment of claim 13 , wherein the processor is further configured to

assign a highest priority value to the carrier frequency of the small cell if the target carrier frequency is a carrier frequency of a small cell, and

assign a highest priority value to the carrier frequency of the macro cell if the target carrier frequency is a carrier frequency of a macro cell.

15. A user equipment comprising:

a processor configured to,

receive a message, the message including a list identifying at least one cell, a carrier frequency associated with the at least one cell and a probability of selecting the carrier frequency associated with the at least one cell, and

determine a carrier frequency, for the user equipment to operate on, based on the list and a status of the user equipment, the processing configured to determine the carrier frequency based on a random number, matching a probability value from among one or more probability values included in the received message, the one or more probability values corresponding to any two more carrier frequencies each of the one or more probability values representing a probability of a corresponding one of the two or more frequencies being selected for the user equipment to operate on,

wherein the random number is within a first range that corresponds in a lower value and an upper value to a second range of the one or more probability values.

16. The user equipment of claim 15 , wherein the at least one cell is an overloaded cell or a cell anticipated to be overloaded.

17. The user equipment of claim 15 , wherein the processor is further configured to,

determine whether the status of the user equipment indicates that the user equipment is in an idle mode,

update a priority list of the user equipment based on the received message, the priority list including a plurality of target carrier frequencies, and

select one of the plurality of target carrier frequencies with a highest priority value, if the processor determines that the status of the user equipment indicates that the user equipment is in an idle mode.

18. The user equipment of claim 17 , wherein the processor is further configured to

update the priority list by assigning a lowest priority value to the carrier frequency of the at least one cell.

19. The user equipment of claim 17 , wherein the processor is further configured to

determine the carrier frequency by,

determining an availability of the selected one of the plurality of target carrier frequencies, and

changing a current carrier frequency of the use equipment to the target carrier frequency by based on the availability of the selected one of the plurality of target carrier frequencies.

20. The user equipment of claim 19 , wherein the processor is further configured to

change the current carrier frequency of the user equipment to another one of the plurality of target carrier frequencies having a next highest priority value if the processor determines that the selected one of the plurality of target carrier frequencies is not available.