Research On Key Technologies Of Radio Resource Management In Hierarchical Heterogeneous Networks

The rapid developments of both telecommunication technologies and wireless services drive the evolutions of radio access technologiesand mobile terminal technologies continuously. Promoted by radio access heterogeneity and mobile terminal mode diversity, heterogeneity, cooperation and convergence are the most promising trends of the future wireless communication system, which will integrate and manage multiple heterogeneous radio access networks. This wireless communication system aims at fully meeting the users' growing demands under different application scenarios by providing multi-mode terminals a universal heterogeneous radio access environment. Therefore, radio resource management(RRM) is the key technology to realize the orderly organization and efficient utilization in heterogeneous wireless convergent networks. In hierarchical heterogeneous networks, radio resource management can be considered as a whole integrated distribution and use of radio resources. By using reconfigurable technology to measure services, the RRM strategies conduct service split between different access networks, and joint access control and resource scheduling in access networks with different characteristics. On the basis of meet the business requirements, the RRM strategies improve the efficiency of resource allocation and scheduling, and then achieve optimal use of heterogeneous network resource.To solve the problems above effectively, this dissertation focuses on the topic of radio resource management in hierarchical heterogeneous convergent networks and does research on it.We focus on researchloss performance model and efficient algorithm, optimal resource allocation with multi-services, call admission control(CAC) and vertical handovers algorithmsin heterogeneous convergent network. And then, we analyzed heterogeneous network convergence system capacity. By the above works, we aim to effectively improve the performance of wireless communication system in heterogeneous convergent network environment, ensure customers' Quality of Service(QoS), and make full use of different configuration of network resources.In hierarchical heterogeneous networks, the inter-tier overflow traffic is bursty in nature, and traditional analysis for Poisson traffic in multiservice loss systems is no longer available for the non-Poisson overflow traffic. Existing approximation methods include the use of Markovmodulated Poisson process(MMPP) or its variants to approximate the overflow process. However, when facing the large-scale complex networks, the major concern with the MMPP model is the high computation effort involved in solving multi-dimensional equilibrium state equations. This dissertation proposes a new computationally efficient numerical method for the loss probability approximation in hierarchical heterogeneous wireless networks, which derive the moments of multiclass overflow traffic with different service time distributions. We allocate the bandwith's resource to each service traffic or call connection by equivalent unit bandwith method. Further, according to the results of the above derivation, we develop the multiclass traffic loss model for a hierarchical heterogeneous overlay system. We obtained the numerical solution of the call blocking probability for each type of traffic. Verified by simulations, the performance and accuracy of the proposed numerical method is evaluated in a two-tier hierarchical cellular network and compared with an existing approximation method based on multi-dimensional Markov-Modulated Poisson Process.In hierarchical heterogeneous wireless networks, call admission control technology can decide which radio access network to admit new call service request. And CAC want to minimize the impact generated from the new call sevice to the existing service connections, so as to avoid network congestion and guarantee QoS services. This dissertation propose a probabilistic CAC algorithm based on the traffic load in the WLAN and the velocity of the cellular mobile users, which allows the WLAN to limit Downward Vertical Handovers(VHOs) from the cellular network to reduce unnecessary VHO processing. We derive the expressions of new call blocking rate and DVHO blocking rate. Simulation results demonstrate that our CAC scheme reduces the unnecessary VHO processing while keeping the DVHO blocking rate within acceptable limits. And this algorithm maintains reasonable throughput and improves the overall performance of the system.Future broadband wireless networks are expected to support a wide variety of communication services with diverse Quality-of-Service(QoS) requirements, such as delay-sensitive, guaranteed throughput. On the other hand, the proportional user rate constraint is considered as a fairness criterion, which balances the tradeoff between the system sum-rate and user fairness. We focus on the RRM in heterogeneous networks with Orthogonal Frequency Division Multiple Access(OFDMA), and aim to maximize the system sum-rate and meet QoS requirements under the proportional-fairness constraint of user rate. The previously proposed resource allocation schemes, which do not differentiate the traffic types or consider the fairness performance, may result in inefficient allocation of radio resources. To tackle this problem, we present an analytical model which takes consideration of two types of the traffic including the Delay-Constraint(DC) traffic and the Best-Effort(BE) traffic, and then formulate the RRM problem as a linear programming(LP) problem. We propose an efficient iterative algorithm to find the optimal solutions by converting this combinatorial problem with exponential complexity into a convex problem or showing that it can be solved in the dual domain. Numerical studies are conducted to evaluate the performance of the proposed algorithm in terms of achievable transmission rate for the DC traffic and fairness for the BE traffic, multiuser diversity, and system throughout.Hierarchical heterogeneous wireless networks will consist of heterogeneous radio access technologies(RATs). A major issue on service-differentiated radio resource management(RRM) is how to jointly utilize the resources in an more efficient manner while simultaneously achieving the desired QoS and minimizing the service cost. This paper proposes an adaptive Common RRM(CRRM) scheme to integrete the UTMS and WLAN access technologies. The prosposed scheme considers several key parameters, including service type, user mobility and location information, and jointly utilize the resources of heterogenous networks. The performance of the CRRM scheme is analyzed by using Markov chain. The analysis shows that the scheme can meet the QoS requirement, and in the meanwhile, minimize the service cost. Numerical results validate that the CRRM scheme can dramatically decrease the rate of unnecessary vertical handoffs, improve the system throughput, and therefore can be deployed in practical heterogeneous networks.