A method for connection admission control, CAC, in a broadband wireless access, BWA, system, the method comprising: detecting a QoS class of a call requesting connection admission; determining an application layer required bandwidth for the detected QoS class by using QoS parameters of a service flow, SF, of the detected QoS class; determining a required bandwidth weight of the QoS class in consideration of a packet header overhead by determining a ratio of a size of a protocol data unit, PDU, with various packet header overheads to a size of a pure application layer payload without various packet header overheads; determining per-slot available bandwidths of a reference QoS class and the QoS class by using the determined application layer required bandwidth; determining a required bandwidth conversion ratio of the QoS class by using the determined per-slot available bandwidths; determining an equivalent media access control, MAC, layer required bandwidth by using the determined application layer required bandwidth, the required bandwidth weight, and the required bandwidth conversion ratio; determining a signal overhead of the QoS class: determining an available bandwidth by excluding, from the entire slots, a slot allocated to the determined signal overhead and a slot allocated to a data burst of all the QoS SFs except best effort, BE; determining an equivalent available bandwidth by using the determined available bandwidth and the per-slot available bandwidth of the reference QoS class; and performing a CAC operation by comparing the determined equivalent MAC layer required bandwidth and the equivalent available bandwidth. detecting a QoS class of a call requesting connection admission; determining an application layer required bandwidth for the detected QoS class by using QoS parameters of a service flow, SF, of the detected QoS class; determining a required bandwidth weight of the QoS class in consideration of a packet header overhead by determining a ratio of a size of a protocol data unit, PDU, with various packet header overheads to a size of a pure application layer payload without various packet header overheads; determining per-slot available bandwidths of a reference QoS class and the QoS class by using the determined application layer required bandwidth; determining a required bandwidth conversion ratio of the QoS class by using the determined per-slot available bandwidths; determining an equivalent media access control, MAC, layer required bandwidth by using the determined application layer required bandwidth, the required bandwidth weight, and the required bandwidth conversion ratio; determining a signal overhead of the QoS class: determining an available bandwidth by excluding, from the entire slots, a slot allocated to the determined signal overhead and a slot allocated to a data burst of all the QoS SFs except best effort, BE; determining an equivalent available bandwidth by using the determined available bandwidth and the per-slot available bandwidth of the reference QoS class; and performing a CAC operation by comparing the determined equivalent MAC layer required bandwidth and the equivalent available bandwidth. determining an available bandwidth by excluding, from the entire slots, a slot allocated to the determined signal overhead and a slot allocated to a data burst of all the QoS SFs except best effort, BE; determining an equivalent available bandwidth by using the determined available bandwidth and the per-slot available bandwidth of the reference QoS class; and performing a CAC operation by comparing the determined equivalent MAC layer required bandwidth and the equivalent available bandwidth.