Method and apparatus for initiating communications on a shared channel in a mobile communication system

A user equipment (UE) for performing random access, the UE comprising:

• a transceiver configured to transmit, to a base station, an uplink signal corresponding to a first identifier;
• and
• a controller configured to:
• determine whether a downlink signal responding to the uplink signal is received on a downlink channel from the base station during a time period, a start of the time period being determined based on information signaled by the base station, the downlink signal comprising a second identifier corresponding to the first identifier and an UE ID of the UE, and
• communicate data with the base station, in response to the downlink signal being received during the time period.

A method for initiating communications in a base station, the method comprising:

• receiving an uplink signal corresponding to a first identifier from a user equipment (UE);
• transmitting a downlink signal responding to the uplink signal on a downlink channel within a time period, a start of the time period being determined based on information signaled by the base station, the downlink signal comprising a second identifier corresponding to the first identifier and an UE ID of the UE;
• and
• communicating data with the UE, in response to the downlink signal being transmitted to the UE within the time period.

A base station for initiating communications, the base station comprising:

• a transceiver configured to:
• receive an uplink signal corresponding to a first identifier from a user equipment (UE),
• transmit a downlink signal responding to the uplink signal on a downlink channel within a time period, a start of the time period being determined based on information signaled by the base station, the downlink signal comprising a second identifier corresponding to the first identifier and an UE ID of the UE, and
• communicate data with the UE, in response to the downlink signal being transmitted to the UE during the time period;
• and
• a controller configured to control the transceiver to transmit the downlink signal in the time period.