Method for contention based random access on a secondary carrier

1. A method in a mobile station for performing random access, comprising:

receiving, from a first cell, a message identifying a random access preamble to transmit to a second cell, wherein the first and second cell operate on different frequencies;

determining, by the mobile station, whether the random access preamble is from a set of contention based random access preambles;

receiving, by the mobile station, a random access response message, wherein the random access response message is addressed to a unique identifier of the mobile station; and

transmitting, by the mobile station, if the identified random access preamble is from the set of contention based preambles, a timing verification message.

2. The method according to claim 1 wherein the timing verification message is transmitted to the second cell.

3. The method according to claim 1 wherein determining whether the random access preamble is from a set of contention based preambles comprises

receiving system information of the second cell; and

determining whether the random access preamble is from the set of contention based preambles of the second cell.

4. The method according to claim 1 wherein transmitting a timing verification message further comprises:

receiving, in the random access response message, timing advance information;

configuring a timing advance for the uplink frequency of the second cell, wherein the timing advance is derived from the timing advance information; and

transmitting the timing verification message on the uplink frequency of the second cell.

5. The method according to claim 4 further comprising:

receiving, subsequent to transmission of the timing verification message, a timing confirmation message; and

applying the timing advance to all transmissions on the uplink frequency of the second cell.

6. The method according to claim 4 further comprising:

failing to receive, subsequent to transmission of the timing verification message, a timing confirmation message; and

disabling the timing advance for all transmissions on the uplink frequency of the second cell.

7. The method according to claim 6 wherein failing to receive a timing confirmation message includes failing to receive a timing confirmation message for a specified duration.

8. A method in a base station for performing random access by a mobile station, comprising:

configuring the mobile station for operation on at least a first cell and a second cell;

transmitting, on the first cell, a message assigning to the mobile station a random access preamble for performing random access on the second cell, wherein the random access preamble is a contention based random access preamble of the second cell;

detecting a transmission of the random access preamble on the second cell; and

transmitting a message addressed to a unique identifier of the mobile station, indicating a timing advance and an uplink resource grant, wherein the timing advance is determined based on the detected transmission of the random access preamble.

9. The method according to claim 8 wherein the uplink resource grant grants resources for uplink transmission on the second cell.

10. The method according to claim 8 further comprising:

transmitting, on the second cell, a message addressed to a common identifier, indicating a timing advance and an uplink resource grant, wherein the uplink resource grant grants resources for uplink transmission on the second cell.

11. The method according to claim 8 further comprising:

detecting a transmission by the mobile station in the uplink resources indicated in the uplink resource grant;

determining whether the timing advance used for the transmission by the mobile station is correct; and

transmitting, if the timing advance used for the transmission by the mobile station is correct, a message indicating a confirmation of timing.

12. The method according to claim 11 further comprising:

transmitting, if the timing advance used for the transmission by the mobile station is incorrect, a message indicating a timing failure.

13. The method according to claim 11 wherein determining whether the timing advance used for the transmission by the mobile station is correct includes determining that the transmission does not cause significant interference to other uplink transmissions.

14. The method according to claim 11 wherein determining whether the timing advance used for the transmission by the mobile station is correct includes:

determining a first time at which the transmission by the mobile station in the uplink resources indicated in the uplink resource grant is expected; and

determining whether the time at which the transmission by the mobile station in the uplink resources indicated in the uplink resource grant is received is substantially same as the first time.