Component carrier selection method and apparatus for random access attempts in a communications network
View Patent ↗Methods and apparatus for selecting component carriers for random access attempts. A user equipment arranged to communicate with the base station over multiple component carriers, selects a component carrier from the multiple component carriers, based on a likelihood, and transmits a random access attempt to the base station over the selected component carrier. After maintaining statistics of component carriers selected for random access attempts per component carrier of the multiple component carriers, the user equipment adjusts the likelihood of selecting a specific component carrier for a subsequent transmission of a random access attempt based on the maintained statistics.
1. A method in a user equipment for selecting component carriers for random access attempts, wherein the user equipment is arranged to communicate with a base station over multiple component carriers, the method comprising:
selecting a component carrier from the multiple component carriers, based on a selection likelihood for the selected component carrier;
transmitting a random access attempt to the base station over the selected component carrier;
maintaining statistics of component carriers selected for random access attempts per component carrier of the multiple component carriers; and
adjusting a likelihood of selecting a specific component carrier for a subsequent transmission of a random access attempt based on the maintained statistics;
wherein said adjusting is performed by adjusting the likelihood of selecting the specific component carrier for subsequent transmissions of random access attempts by reducing the likelihood of selecting the specific component carrier when a number of unsuccessful transmitted random access attempts for the specific component carrier comprised in the maintained statistics exceeds a predetermined number N, and wherein said adjusting further comprises readjusting the likelihood of selecting the specific component carrier for subsequent transmissions of random access attempts by increasing the likelihood of selecting specific component carrier when a number of unsuccessful transmitted random access attempts for other component carriers than the specific component carrier comprised in the maintained statistics exceeds a predetermined number P, performed after the adjustment.
2. The method of claim 1 , wherein subsequent random access opportunities in time are shifted on different multiple component carriers.
3. The method of claim 1 , wherein the likelihood of selecting the specific component carrier for subsequent transmissions of random access attempts is reduced to zero.
4. A method in a user equipment for selecting component carriers for random access attempts, wherein the user equipment is arranged to communicate with a base station over multiple component carriers, the method comprising:
selecting a component carrier from the multiple component carriers, based on a selection likelihood for the selected component carrier;
transmitting a random access attempt to the base station over the selected component carrier;
maintaining statistics of component carriers selected for random access attempts per component carrier of the multiple component carriers; and
adjusting a likelihood of selecting a specific component carrier for a subsequent transmission of a random access attempt based on the maintained statistics;
wherein a total number of random access attempts to be performed before declaring a random access problem is predetermined, wherein the total number of random access attempts is evenly spread across the multiple component carriers, and wherein said adjusting is performed by: adjusting the likelihood of selecting the specific component carrier for subsequent transmissions of random access attempts such that the likelihood of selecting the specific component carrier is defined as a number of random access attempts left on the specific component carrier divided by a total number of remaining random access attempts.
5. The method of claim 4 , wherein declaring the random access problem triggers a declaration of a radio link failure.
6. A user equipment for selecting component carriers for random access attempts, which user equipment is arranged to communicate with a base station over multiple component carriers, the user equipment comprising a processor coupled to a memory configured to:
select a component carrier from the multiple component carriers, based on a selection likelihood for the selected component carrier;
transmit a random access attempt to the base station over the selected component carrier;
maintain statistics of component carriers selected for random access attempts per component carrier of the multiple component carriers; and
adjust a likelihood of selecting a specific component carrier for a subsequent transmission of a random access attempt based on the maintained statistics, wherein the processor is configured to adjust the likelihood of selecting the specific component carrier for subsequent transmissions of random access attempts by reducing the likelihood of selecting the specific component carrier when a number of unsuccessful transmitted random access attempts for the specific component carrier comprised in the maintained statistics exceeds a predetermined number N, and wherein the processor is further configured to readjust the likelihood of selecting the specific component carrier for subsequent transmissions of random access attempts by increasing the likelihood of selecting the specific component carrier when a number of unsuccessful transmitted random access attempts for other component carriers than the specific component carrier comprised in the maintained statistics exceeds a predetermined number P, performed after the adjustment.
7. The user equipment of claim 6 , wherein the processor is configured to reduce the likelihood of selecting the specific component carrier for subsequent transmissions of random access attempts to zero.
8. The user equipment of claim 6 , wherein subsequent random access opportunities in time are shifted on different multiple component carriers.
9. A user equipment for selecting component carriers for random access attempts, which user equipment is arranged to communicate with a base station over multiple component carriers, the user equipment comprising a processor coupled to a memory configured to:
select a component carrier from the multiple component carriers, based on a selection likelihood for the selected component carrier;
transmit a random access attempt to the base station over the selected component carrier;
maintain statistics of component carriers selected for random access attempts per component carrier of the multiple component carriers; and
adjust a likelihood of selecting a specific component carrier for a subsequent transmission of a random access attempt based on the maintained statistics;
wherein a total number of random access attempts to be performed before declaring a random access problem is predetermined, wherein the total number of random access attempts is evenly spread across the multiple component carriers, and wherein the processor is further configured to adjust the likelihood of selecting the specific component carrier for subsequent transmissions of random access attempts, such that the likelihood of selecting the specific component carrier is defined as a number of random access attempts left on the specific component carrier divided by a total number of remaining random access attempts.
10. The user equipment of claim 9 , wherein declaring random access problem triggers a declaration of a radio link failure.