Call Admission Control And Downlink Resource Allocation For Mobile Celluar Netwrok

With the wide application of internet and development of mobile communication technology, various high-speed rate services represented by multimedia applications increase continuously and gradually become the core service of future mobile communication system. However, due to the scarcity of wireless resource, users’mobility and time-variant character of wireless channel, wireless resource management faces more and more severe challenges. In order to manage the wireless resource efficiently, two aspects should be considered. Desired quality of service (QoS) should be assured from the point of users’view. Meanwhile, the utilization of wireless resource should be improved as high as possible from the service provider’s perspective. Nowadays, how to manage the limited wireless resource has become an interest and hot research field in mobile cellular system. The research on wireless resource management is very important both in theory and in practice. Wireless resource management involves many aspects such as call admission control, handover control, packet scheduling, subcarrier allocation and power control. In this paper, we are focused on call admission control and downlink scheduling and resource allocation for future mobile cellular system. As to the two problems, we have done the following works.1. A new call admission control scheme based on fuzzy logic is proposed for present CDMA system. Besides, we design a fuzzy logic controller (FLC) which can adaptively adjust signal to interference plus noise threshold (SINRth) to realize the tradeoff between the signal quality and network utilization according to the number of active users (AUs) in a cell and average arrival traffic intensity (AATI) in Erlang per cell. Numerical results show that the proposed scheme based on FLC has better performance than the optimal fixed threshold CAC scheme.2. A dynamic and hybrid CAC scheme integrated cutoff priority with handoff queue for mobile cellular network is proposed for the diversity of services of future mobile cellular system and some performance metrics are derived. The unique characteristic of the proposed CAC scheme is that it can support any number of service types and that the cutoff thresholds for different types of handoff call are dynamically adjusted according to the number of service types, the number of channels in a cell and service priority index. By modeling the proposed CAC scheme with a one-dimensional Markov chain (1DMC), some performance metrics including new call blocking probability (Pnb), forced termination probability (PF), average queue length, average waiting time in queue, offered traffic utilization, wireless channel utilization and system performance are also derived. In order to validate the correctness of the derived analytical performance metrics, extensive simulations are performed. It is shown that simulation results match closely with the derived analytic results in terms of Pnb and PF. At last, to show the advantage of1DMC modeling for the performance analysis of our proposed CAC scheme, the computing complexity of multi-dimensional Markov chain (MDMC) modeling in performance analysis is analyzed in detail. It is indicated that state-space cardinality, which reflects the computing complexity of MDMC, increases exponentially with the number of service types and total channels in a cell. However, the state-space cardinality of our1DMC model for performance analysis is unrelated to the number of service types and increases linearly with the number of channels in a cell and with the queue capacity of the highest service index in a cell.3. Downlink scheduling and resource allocation for multiuser single-cell OFDMA system under perfect channel state information (CSI) is isummarized. Firstly, a general form of downlink scheduling and resource allocation is presented. Then, to keep a tradeoff between spectrum efficiency and fairness among users, rate-based and average-delay-based utility function are used to perform downlink scheduling and resource allocation from solely PHY layer and cross PHY-MAC layers respectively. Besides, a cooperation game theory based downlink scheduling and resource allocation scheme is also investigated.4. A downlink scheduling and resource allocation scheme with minimum and maximum rate constraints for multiuser single-cell OFDMA system under partial (imperfect) CSI is investigated. The proposed downlink scheduling and resource allocation scheme, which can satisfy user’s minimum rate requirement, keep fairness among user and assure the system outage probability, consists of two phases. In the first phase, joint scheduling and subcarrier allocation is performed to satisfy users’ minimum rate requirements with the consideration of long term fairness among users. In the second phase, power adjustment is carried out among subcarriers of users whose maximum rates are satisfied. Without changing users’ maximum rates, the saved power is reallocated to the users whose maximum rates are not satisfied to increase the system throughput. Simulation results show that the proposed scheme achieves the highest mean system fairness compared with Max C/I and MPF scheme, realizes a higher system throughput than a MPF scheme by allocating the saved power through power adjustment among subcarriers of maximum-rate-satisfied users to the users whose maximum rate are not satisfied. Besides, when the average SNR is beyond15dB, the average outage probability of the Max C/I and MPF scheme increase sharply, however, that of the proposed scheme still keeps a low level.