Communication between MAC and PHY for parallel random access procedures of dual connectivity

1. A method of communicating with a network at a user equipment (UE) in a wireless communication system, the method comprising:

receiving, by a medium access control entity (MAC) of the UE instructions to transmit a first access preamble to a first base station to start a first random access procedure and a second random access preamble to a second base station to start a second random access procedure;

dropping, by a Physical layer (PHY) entity of the UE, the transmission of the second random access preamble of the second random access procedure, when the transmission of the first random access preamble overlaps with the transmission of the second random access preamble;

informing, by the PHY entity to the MAC entity, an indication associated with the dropped second random access preamble; and

continuing, at the MAC entity of the UE, the second random access procedure for a case of unsuccessful reception of a random access response without incrementing a number of random access preamble transmissions, if the indication has been received from the PHY entity of the UE.

2. The method of claim 1 , wherein the indication is different from an indication for a random access procedure failure.

3. The method of claim 1 , wherein the second random access procedure for the case of unsuccessful reception of the random access response includes:

determining whether the number of random access preamble transmissions reaches to a maximum allowable number of transmissions;

reporting the reach to the maximum allowable number of transmissions to higher layer entity or concluding the random access procedure is unsuccessfully completed, if the number of random access preamble transmissions reaches to the maximum allowable number of transmissions; and

reselecting a random access resource, if the number of random access preamble transmissions does not reach to the maximum allowable number of transmissions.

4. The method of claim 1 , wherein the MAC entity comprises a first MAC entity responsible for transferring data to the first base station and a second MAC entity responsible for transferring data to the second base station, and

wherein a first service area of the first base station is larger than a second service area of the second base station.

5. A user equipment (UE) communicating with a network in a wireless communication system, the UE comprising:

a transceiver configured to transmit and receive signals from a first base station and a second base station;

a processor connected to the transceiver and comprising a physical layer (PHY) entity and a MAC medium access control (MAC) entity;

wherein the processor is configured to:

control the PHY entity to receive instructions to transmit a first random access preamble to the first base station to start a first random access procedure and a second random access preamble to the second base station to start a second random access procedure:

drop the transmission of the second random access preamble of the second random access procedure, when the transmission of the first random access preamble overlaps with the transmission of the second random access preamble;

inform the MAC entity an indication association with the dropped second random access preamble of the second random access procedure; and

control the MAC entity to continue a random access procedure for a case of unsuccessful reception of a random access response without incrementing a number of random access preamble transmissions, if the indication has been received from the PHY entity.

6. The UE of claim 5 , wherein the processor is further configured to:

control the MAC entity to reselect a random access resource without increasing the number of random access preamble transmissions; and

instruct the PHY entity to transmit another second random access preamble after a predetermined time, if the MAC entity received the indication from the PHY entity.

7. The UE of claim 5 , wherein the MAC entity comprises a first MAC entity responsible for transferring data to the first base station and a second MAC entity responsible for transferring data to the second base station, and

wherein a first service area of the first base station is larger than a second service area of the second base station.