Method and apparatus for managing random access preamble set in a wireless communication system with multiple random-access priority classes

A method of determining a random access preamble in a wireless communication system, the method performed by a base station (BS) and comprising:

• transmitting a first UE information request message to a first type user equipment (UE);
• receiving, in response to the first UE information request message, a first UE information response message from the first type UE, the first UE information response message indicating a number of preambles sent by the first type UE during a last successfully completed random access procedure;
• transmitting a second UE information request message to a second type user equipment (UE) different from the first type UE;
• receiving, in response to the second UE information request message, a second UE information response message from the second type UE, the second UE information response message indicating a number of preambles sent by the second type UE during a last successfully completed random access procedure;
• estimating a first arrival rate for the first type UE and a second arrival rate for the second type UE;
• determining a random access preamble allocation mode based on the first and second arrival rates, wherein available random access preamble allocation modes include a first allocation mode in which the random access preambles are allocated to the first type UE and the second type UE without overlap and a second allocation mode in which the random access preambles are allocated to the first type UE and the second type UE with partial overlap, wherein a number of random access preambles allocated to the first type UE and a number of random access preambles allocated to the second type UE are determined based on the first and second arrival rates;
• and
• broadcasting a radio resource control (RRC) message including a first information element and a second information element, wherein the first information element indicates the determined random access preamble allocation mode, and the second information element indicates the number of random access preambles allocated to the first type UE and the number of random access preambles allocated to the second type UE.