MAC architecture for broadband satellite access systems

In recent Years, the telecommunications industry has expanded tremendously. A tendency of integrating various business revenues with the conventional communication systems is becoming more and more popular to achieve global information services. The integration is triggered by increasing demands of costumers to access various types of broadband multimedia services. The access system can be implemented on many platforms; from line feed as cable, fiber, or copper networks to wireless as radio or satellite networks. Broadband satellite access is a leading candidate to contribute to such development due to satellites' distinctive features of global coverage over single hops and distance insensitivity. However, as satellite networks possess rather longer delays and bounded resources, a MAC layer that can efficiently share resources over a minimum possible bandwidth is mandatory to the success of satellite access. Existing MAC protocols are not able to achieve optimum performance. Hence, design of a new MAC becomes inevitable. The new MAC should introduce a novel structure with certain behavioral sequences and an efficient access technique. In this thesis, we propose a MAC architecture that aims to address such requirement. We utilize a novel access technique based on an enhanced CFDAMA protocol. We also introduce a new concept of two level differential scheduling. We present formal models based on SDL to verify the validly of the devised system. Finally, we build an OPNET simulation model to demonstrate quantitative system operation and serve as a nucleus model for possible future research involving performance optimization in satellite networks over the devised architecture

Satisfied-user based capacity analysis in wideband and multi-carrier CDMA cellular networks

Future generations of cellular networks envision unprecedented growth in capacity requirements essential to handle the tremendous evolution of multimedia services. Code division multiple access (CDMA) has been one of the premium candidates to lead the charge in supporting packetized multimedia traffic within mobile cellular networks. This dissertation presents an analytical framework to derive system capacity of CDMA-based cellular networks on the basis of the satisfied-user criteria recommended by universal mobile telecommunications systems (UMTS). The proposed criteria stretch beyond system-level outage probability that has been commonly adopted in the CDMA literature and proceed to focus on evaluating the percentage of outage during the lifetime of each individual session. Special emphasis is devoted for the downlink as it is considered to be the limiting direction in future cellular systems. The foundation of the proposed analysis is established by recognizing one of the main features of wireless communication channels. Large-scale path-loss depicts measurable/controllable parameters that exhibit high correlations over the scale of consecutive frames. On the other hand, small-scale fading represents fast fluctuations that cannot be reliably predicted. Accordingly, the devised analysis relates the satisfied-user probability to the correlated outage behavior of small-scale fading channels with respect to an effective protection margin set over the large scale.The analytical platform is expanded for capacity evaluation of multi-carrier CDMA (MCCDMA). Multi-carrier CDMA (MC-CDMA) has recently emerged as an extremely promising technology to support higher system capacities for its combined advantages of multi-carrier modulation techniques and CDMA in a frequency-selective fading environment. The analytical approach leads to the proposal of power allocation and channel assignment strategies that share the objective of diminishing the effects of multiple access interference (MAI) and increasing system capacity. In particular, an effective margin-based power control operating over the large-scale is introduced for speech services. The base stations target an effective protection margin and avoid allocating un-necessary power to compensate for intra-cell interference that shares the same small-scale fading paths as the target signal. Moreover, a channel assignment strategy based on large-scale interference measurements is used to investigate the migration from MC-CDMA to Grouped MC-CDMA systems. Capacity analysis of Grouped MC-CDMA systems triggers the development of an iterative simulation platform to incorporate the effects of coupling and dependencies of channel assignments and power allocations across base stations of the cellular network