| With the ever-growing investigation and development of versatile wireless access technologies, different types of wireless networks may co-exist in the same geographic area across common communication media, where a heterogeneous wireless network (HWN) environment is formed. Meanwhile, due to the characteristic of scalability, the multimedia service would be applied widely and become one of the most important service types in HWN. However, the Radio Resource Management (RRM) policies in HWN are very complicated, and the HWN would provide wireless access service for large amount of users, moreover, the data resources of multimedia service might widely exist in HWN with versatile Quality of Service (QoS) requirements, and the traffic loads of multimedia service may be unevenly distributed in HWN. All these factors bring in a great challenge to the reliability and efficiency of multimedia service during its resource lookup phase, service access phase and data transmission phase. In the thesis, some of the key problems while applying multimedia service in HWN are analyzed, and the corresponding novel solution mechanisms are proposed. Theoretical analyses and Simulation results demonstrate that the proposed mechanisms could effectively improve the QoS of multimedia service in HWN. The main content and contributions of the thesis are as follows:1. The cross-layer optimized P2P lookup protocol for Mobile Ad hoc Network (MANET) is proposed.Firstly, the application of structured P2P lookup protocol in MANET is analyzed, and it is observed that the P2P-overlay might be separated into several independent parts due to the mobility of MANET nodes and could not converge again, namely the "Separated P2P-overlay problem", which would seriously impact the reliability of P2P lookup protocol. Meanwhile, the logic neighbor nodes in P2P-overlay and topologic neighbor nodes in network layer are not actually the same; therefore the query routing packets would be circularly routed in MANET, namely the "Query Routing Mismatch (QRM) problem", which would seriously impact the efficiency of P2P lookup protocol. To solve these problems, a Cross-layer optimized Structured P2P-overlay (CoSP) architecture is proposed in the thesis, which could obtain the information of topologic neighbor nodes and facilitate the task of improving the reliability and efficiency of P2P lookup protocol.Secondly, under the CoSP architecture, explicated with Chord protocol, the Separate Logic ring Detection and Convergence (SLDC) algorithm is proposed, which utilizes the information of topologic neighbor nodes to effectively detect the separate P2P-overlay (or refered to as logic ring in Chord protocol) in MANET and then start the convergence procedure. Both theoretic analyses and simulation evaluations demonstrate that the SLDC algorithm could effectively improve the reliability of P2P lookup protocol.Thirdly, under the CoSP architecture, explicated with Chord protocol, the Query Routing Mismatch Alleviation (QRMA) algorithm is proposed, which utilizes the information of topologic neighbor nodes to find a more appropriate Alternative Next Hop (ANH) node and alleviate the QRM problem. The probability of ANH node and influence factors are discussed through theoretic analyses, and the simulation results prove that QRMA algorithm could effectively improve the efficiency of P2P lookup protocol.2. The service-aware proactive spectrum resource sharing algorithm and access network selection algorithm are proposed.Firstly, the conventional spectrum resource management policy is analyzed, which is not suitable for HWN since the traffic load of multimedia service is unevenly distributed, and the utilization ratio of spectrum resource is compromised. Therefore, a HWN architecture is established in the thesis, which could manage the leisure spectrum resource through a Joint Radio Resource Management unit by utilizing the cognitive radio technique and spectrum pool technique. In this architecture, a Multimedia Traffic Rate Prediction (MTRP) model is designed to facilitate the task of proactively adaptive to the variation of traffic load distribution, which could predict the traffic rate of multimedia service by learning the statistic information of multimedia service traffic.Secondly, the Service-aware Proactive Spectrum Sharing (SPSS) algorithm is proposed, which would proactively evaluate the utilization states of spectrum resources in all wireless networks according to the prediction results of MTRP model. By designing a service-aware system optimization objective function, the SPSS would optimize the spectrum sharing and scheduling decisions. Simulation evaluations demonstrate that the SPSS could effectively improve the utilization ratio of spectrum resource and the service access ratio, and decrease the average access delay.Thirdly, the Service-aware Proactive Vertical Handoff (SPVH) algorithm is proposed, which would proactively evaluate the traffic load states of all available access networks according to the prediction results of MTRP model. By designing a service-aware access decision optimization objective function, the SPVH would optimize the access network selection decisions. Simulation results prove that SPVH could effectively improve the utilization ratio of spectrum resource and the service access ratio, and decrease the average access delay.3. The optimal modulation solution set based Spectral efficient Layered Broadcast/multicast Mechanism for multimedia service is proposed.Firstly, the conventional broadcast/multicast mechanism is analyzed and it is observed that the spectral efficiency is badly compromised since the system needs to transmit in a low rate due to the diversity of user channel conditions in applications. Therefore, a Spectral efficient Layered Broadcast/ Multicast (SLBM) mechanism is proposed, which could classify the multimedia service data into several layers and modulate each layer of data into corresponding layer in the modulated symbol in order to achieve various transmission rate for users depending on their own channel conditions, respectively.Secondly, the conception of modulation solution is defined, and the evaluation function of the spectral efficiency of a modulation solution in layered broadcast/multicast mechanism is deduced. Base on this, the system optimization objective function is designed.Thirdly, the conceptions of Enhanced Modulation Solution (EMS) and Primary Modulation Solution (PMS) are defined, and the close-form equations of their parameters are deduced. Based on EMS and PMS, the conception of Optimal Modulation Solution Set (OMSS) is defined as well, and it is further proved that OMSS would be valid to achieve the highest spectral efficiency while only containing limited number of optional modulation solutions.Fourthly, the optimal Layered Modulation Solution Selection algorithm is proposed based on Markov Decision Process, which could effectively select optimal modulation solution from OMSS.Finally, the simulation results demonstrate that the SLBM mechanism proposed in the thesis could effectively improve the spectral efficiency and enhance the QoS while the fairness of multimedia service is guaranteed. |
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