The integration of different layered network is one of the most feature in the next telecommunication systems, for this reason the paper explains the potential role of an integrated satellite-HAP-terrestrial system. A simple and suitable architecture is presented, it consists of three layers: terrestrial layer, HAP Layer and GEO layer. The terrestrial layer's terminals within the same HAP coverage area have to use HAP transponder and HAP master control station (H-MCS) to send data amongst themselves. Satellite layer is used to interconnect terrestrial terminals belonging to distinct HAP coverage areas. Since high quality multimedia application support is a key objective for upcoming communication systems, this paper investigates the issues related to the optimal admission control strategy in order to guarantee an adequate quality of service to the multimedia traffic connections.