Enhancement of LTE random access procedure

1. A method of performing a random access procedure in a wireless communication system, the method comprising:

receiving random access information through a broadcast channel, the random access information comprising at least random access signature information, a power ramping parameter or an access slot configuration parameter;

initiating a random access procedure according to a cause parameter, the cause parameter corresponding to a condition requiring a new random access before each preamble transmission;

selecting a first signature for use in the preamble, the first signature based on the random access signature information;

determining a first access slot for transmission of the first signature on a random access channel, the first access slot based on the access slot configuration parameter;

determining transmission power for transmission of the first signature;

transmitting the preamble comprising the first signature using the determined first access slot;

selecting a second signature which is different from the first signature for re-transmission of the preamble based on a system frame number (SFN) when the transmission of the preamble comprising the first signature is not successful; and

determining a second access slot for the re-transmission of the second signature by applying a cyclic shift to the first access slot based on the SFN when the transmission of the preamble comprising the first signature is not successful, the second access slot not overlapping with the first access slot.

2. The method of claim 1 , further comprising performing delay control prior to transmitting the preamble in order to reduce conflicts by multiple mobile terminals using the random access channel.

3. The method of claim 2 , wherein the delay control is based on at least a number of preamble re-transmission, a random access channel load or a priority scheme of a mobile terminal.

4. The method of claim 2 , wherein the delay control is performed only when re-transmitting the preamble.

5. The method of claim 1 , further comprising:

attempting re-transmission of the preamble for a predetermine time or until a receipt acknowledgement is received.

6. The method of claim 5 , wherein the predetermined time comprises a maximum number of retransmissions based on a priority connection level of a mobile terminal.

7. The method of claim 5 , further comprising no longer attempting re-transmission if access is no longer necessary or upon interruption of the random access procedure.

8. The method of claim 1 , wherein determining the first access slot comprises selecting a random access slot offset in frequency or time in each successive transmission of the preamble.

9. The method of claim 1 , wherein the condition to which the cause parameter corresponds is at least initial access of a base station, handover or losing synchronization.

10. The method of claim 1 , wherein the transmission power is determined based on at least open loop power control, number of preamble retransmission or frequency of the determined access slot.

11. The method of claim 1 , further comprising increasing the transmission power according to the power ramping parameter in each hopping cycle if it is determined that power ramping is necessary.

12. A mobile terminal for performing a random access procedure in a wireless communication system, the mobile terminal comprising:

a transmitting unit transmitting signals;

a receiving unit receiving random access information through a broadcast channel, the random access information comprising at least random access signature information, a power ramping parameter or an access slot configuration parameter;

a display unit displaying information;

an input unit receiving inputs from a user; and

a processing unit initiating a random access procedure according to a cause parameter, selecting a first signature for use in the preamble, determining a first access slot for transmission of the first signature on a random access channel, determining transmission power for transmission of the first signature, controlling the transmitting unit to transmit the preamble comprising the first signature using the first access slot, selecting a second signature which is different from the first signature for re-transmission of the preamble based on a system frame number (SFN) when the transmission of the preamble comprising the first signature is not successful, and determining a second access slot for the re-transmission of the second signature by applying a cyclic shift to the first access slot based on the SFN when the transmission of the preamble comprising the first signature is not successful, the second access slot not overlapping with the first access slot,

wherein the cause parameter corresponds to a condition requiring a new random access before each preamble transmission, the first signature is based on the random access signature information, and the first access slot is based on the access slot configuration parameter.

13. The mobile terminal of claim 12 , wherein the processing unit further performs delay control prior to transmitting the preamble in order to reduce conflicts by multiple mobile terminals using the random access channel.

14. The mobile terminal of claim 13 , wherein the processing unit performs the delay control based on at least a number of preamble re-transmission, a random access channel load or a priority scheme of the mobile terminal.

15. The mobile terminal of claim 13 , wherein the processing unit performs the delay control only when re-transmitting the preamble.

16. The mobile terminal of claim 12 , wherein the processing unit further attempts re-transmission of the preamble for a predetermined time or until a receipt acknowledgement is received.

17. The mobile terminal of claim 16 , wherein the predetermined time comprises a maximum number of retransmissions based on a priority connection level of the mobile terminal.

18. The mobile terminal of claim 17 , wherein the processing unit no longer attempts re-transmission if access is no longer necessary or upon interruption of the random access procedure.

19. The mobile terminal of claim 12 , wherein the processing unit determines the first access slot by selecting a random access slot offset in frequency or time in each successive transmission of the preamble.

20. The mobile terminal of claim 12 , wherein the condition to which the cause parameter corresponds is at least initial access of a base station, handover or losing synchronization.

21. The mobile terminal of claim 12 , wherein the processing unit determines transmission power based on at least open loop power control, number of preamble retransmission or frequency of the determined access slot.

22. The mobile terminal of claim 12 , wherein the processing unit increases the transmission power according to the power ramping parameter in each hopping cycle if it is determined that power ramping is necessary.