Research On Cognitive-Based Resource Management Method In Heterogeneous Converged Network Environment

With the growing demands for high bandwidth services, diversity in content forms, intelligent ways for information service provision, future wireless network is developing rapidly with the features of higher transmission rate, broader coverage, integration of heterogeneous access networks and effective coordination with various perimeter networks. However, key technical challenges still exist in terms of efficient network resource usage, especially the efficient use of spectrum resources, the network energy-efficiency of data transmission and the cognition and adaptation to the network variability.On the one hand, with a significant increase of the spectrum-based wireless services and terminal equipment, the demand for spectrum resources is growing rapidly, which leads to the "spectrum scarcity" becoming one of the main factors for constraining the development of next generation wireless communication systems. In this case, how to allocate network resources, especially for efficient dynamic spectrum allocation and management of wireless networks, has become an urgent problem to be solved. On the other hand, considering the end-users in wireless network has limited energy, in addition to the efficient resource usage, how to effectively reduce the energy consumption of the whole system as well as prolonging the network lifetime under the premise of satisfying users’ own reliable data transmission, which is also the challenge of wireless network faced currently in terms of energy conservation. Moreover, facing to the complex and changeable service requirements and external environment, it’s urgent need to break through the existing wireless network design by introducing cognitive and learning ability, and through exchanging information with the environment, it is also required to design the heterogeneous converged network architecture with context-aware features as well as the corresponding user context-aware reasoning mechanism to solve the contradiction between static network mode and dynamic demands.In order to effectively address above problems and challenges, on the one hand, by focusing on the merits of cognitive radio technology in terms of efficient spectrum resources usage and wireless network adaptation, this dissertation focus research on the dynamic spectrum management mechanism and user context-aware reasoning technique. On the other hand, on the basis of taking advantages of cooperative communication technology in terms of the improvement of system combating fading performance, channel capacity and transmission reliability, this dissertation mainly combines above two technologies and investigates the joint optimization of radio resources incluing channel allocation and power control. The main contributions of this dissertation include following aspects:Considering a wireless network environment in which multiple primary users and secondary users coexist, a multistage game-theoretic framework is proposed for jointly modeling the inseparable intra-stage spectrum allocation and inter-stage spectrum trading process. In this framework, on the one hand, the improved K-M algorithm based on multi-user sharing mechanism is presented in intra-stage spectrum allocation from the perspective of system utility maximization. On the other hand, according to the spectrum allocation results within the previous stage, the multiuser interactions and user-centric strategy adaptive adjustment mechanism are mainly focused on the inter-stage spectrum trading. Also, from the perspective of individual payoffs, the spectrum-selection algorithm based on evolutionary game for secondary users and strategy adjustment mechanism based on non-cooperative game for primary users are proposed respectively, and the equilibrium solutions of above hybrid game model are obtained, which can not only satisfy users’own needs but also guarantee the fairness among users on different region (group). Finally, for a specific spectrum trading exemplification, the existence and stability of evolutionary equilibrium for secondary user and Nash equilibrium for primary user are analyzed and elaborated, respectively. A number of simulation results reveal the network dynamics and adaptation of hybrid game model and their equilibrium status under different systems parameters, and investigate the effect of user strategy adjustment behavior on system performance.Considering a multi-terminal cooperative communication scenario in cognitive wireless networks, the dissertation implements the parallel data transmission based on various transmission modes (direct transmission, multiplexing (dual-hop) transmission, and relay transmission). In addition, on the basis of various types of transmission coexistence, the joint optimization scheme for channel allocation and power control based on transmission capacity and network lifetime maximization are proposed respectively under different channel allocation models, which has the purpose of improving system transmission capacity, reducing energy consumption and extending the network lifetime. Simulations compare the performance of system transmission capacity among different channel allocation modes and analysis the superiority of parallel transmission over single transmission in terms of system energy-consumption cost and network lifetime simultaneously. More importantly, by introducing the energy price incentive mechanism, under the condition of the same parallel transmission, the dissertation also elaborates the influence of the factors that transmission rate allocation proportion and energy price on system energy-consumption cost and network lifetime respectively.As for the cognitive relay network and licensed network coexistence scenario, taking full account of different cognitive user’s transmission power over each channel and their mis-detection or false alarm probability of licensed users, the dissertation makes in-depth analysis of the spectrum sensing and data transmission phase in the cooperative transmission system, and on this basis, the joint optimization scheme for sensing-transmission time allocation and power control is proposed to improve the transmission bits of per unit of energy. Simulation results show the superiority of relay-assisted transmission mode over non-relay transmission mode in terms of system transmission energy-efficiency, and with sensing-transmission time allocation ratio decreasing, system performance of energy-efficiency can be further improved. Moreover, observing time durations of both spectrum sensing and data transmission are within a strict interval, it is proved that optimal strategy of sensing-transmission time and power allocation can be tractable by sequential optimization effectively.As for the cognition and adaptation of network issue in heterogeneous converged network environment, the dissertation describes the characteristics of context in the converged network environment and analysis the content of user context-awareness. Based on establishing the heterogeneous converged network architecture with user context-aware features, user context-aware functional entities and their interaction mechanism are designed, and the corresponding context-aware reasoning process is also elaborated. Moreover, as for the common reasoning mechanism like BP neural network which has the shortcomings such as low convergence rate and easy plunging into local minimum, an improved BP algorithm is proposed with construction of the composite error function and dynamical adjustment of different learning rates, also the convergence of the improved algorithm is analyzed based on the principle of Lyapunov stability and the algorithm process is described simultaneously. Theoretical analysis shows that the improved BP algorithm can overcome the shortcomings of traditional BP neural network effectively and has the property of stable convergence, so it is an effective method for the user context-awareness and reasoning.A summary is given at the end, where the future research directions related to this doctoral dissertation are also pointed out.