1. A method implemented in a node of a multiple radio access technology (multi-RAT) system, comprising: acquiring resource status information associated with each RAT of the multi-RAT system; and maintaining an N-bit global flag representing an overall resource availability of the multi-RAT system based on the acquired resource status information, for use in admission control; wherein the N-bit global flag is encoded such that each of its N bits describes each of the multiple RATs; wherein the N-bit global flag is associated with a pre-defined set of overall resource availability states of the multi-RAT system; wherein the availability states are defined in terms of admission control decisions, and comprise at least one of the following admission control decisions: unconditional acceptance of all services; conditional acceptance of broadband guaranteed bit rate (GBR) services and unconditional acceptance of all other services; conditional acceptance of broadband GBR services, conditional acceptance of narrowband GBR services, and unconditional acceptance of other services; and unconditional rejection of all services; wherein conditional acceptance involves performance of admission control; and wherein unconditional acceptance and unconditional rejection do not involve performance of admission control.