Conventional and Unconventional Cellular Admission Control Mechanisms

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The wide range of services offered by third generation (3G) networks made them more popular around the world. Examples of these services are web browsing, video streaming, image transmission, downloads, videoconference, voice over IP (VoIP), voice calls and Short Message Service (SMS). When an user requests a particular service, a new call is requested. The greater the diversity of services required, the greater is the network resources management difficulty. Availability, reliability and performance are the major goals of its management. Quality of Service (QoS) is related to the users’ satisfaction (Steinmetz & Wolf, 1997). Quality is not measured only by the resources availability, but also by the performance. For example, when an user wants to start a videoconference, it is important, for him or her, low delay, low jitter and high throughput. If these requirements are not met, then the QoS may not be honored. As the number of calls in the network increases, higher will be the difficulty in deciding which requests should be accepted or not. The absence of an admission control mechanism does not guarantee that the network resources will be well distributed, leading to bad resources utilization and a consequent interference in the network availability and QoS assurance. A Call Admission Control (CAC) is a QoSmechanism. Thismechanism decideswitch requests should be accepted according to the resource availability, to maintain QoS guarantee. A research challenge is the development of a CAC that solves the following problem: how to decide which application to accept in accordance with the network status. For instance, if a call is requested and the network is free, or a little bit congested, or even very congested, this new call can be accepted or not. This decision influences the QoS of the new call and the QoS of the already established calls. If the network can be guarantee the QoS, the CAC can accept the new call. Otherwise, the call must be blocked. Another challenge is the CAC’s precise knowledge in accept or reject a new call in accordance to its priority. Blocked calls can cause poor network resources utilization, which is unacceptable to cellular operators. Therefore, CAC needs to know which call should be accepted while it faces multiple calls requests in congestion times. Besides, CAC’s decision should be taken in the shortest time with the lowest complexity. In summary, CAC’s three main requirements are: (1) decides a new call’s acceptance (or not), (2) selects which call to accept according to the pre-established services priorities, (3) the decision should be taken in the shortest time. 13