Research On The Key Technology For QoS Guarantee In Heterogeneous Multi-Link Systems

The main structure of future communication systems will be the IP-based heterogeneous network, in which intelligent multi-mode terminals can connect multiple different networks simultaneously to obtain better user experience for diverse services. This kind of heterogeneous multi-link systems is composed of network equipments, communication technologies and intelligent multi-mode terminals. With increasing diverse service requirements, quality of service (QoS) becomes one of the bottlenecks restricting the development of hetergeneours multi-link systems in the direction of personality and intelligenty. Therefore the research on QoS guarantee has received extensive attention.There are three main characteristics in the heterogeneous multi-link system:multiple options of target access network, diversity of link characteristics and mobility. These characteristics have brought significant challenges to QoS guarantee in the heterogeneous multi-link system. This thesis proposes algorithms and solutions for QoS guarantee to tackle these challenges. The research contents include:link selection technology in the scenario of single service on one bearer, QoS technology in the scenario of single service on multiple bearers, and the mobility management technology in the scenario of multiple bearers scenario. Specifically, this study covers the following aspects:Firstly, the heterogeneous multi-link system is introduced briefly. The challenges of achieving QoS guarantee in the heterogeneous multi-link system are summarized. Then the states of the arts of tackling the technology challenge mentioned above are reviewed. Detailed analysis produces the research emphases of this thesis. As for the selection of the target access network, a link selection algorithm based on virtual target network (VTN) and multiple attribute decision making (MADM) theory is proposed. The network which is similar with VTN is selected as the access target network, so that the continuity of service and QoS are guaranteed with the minimum cost and the network resource is fully utilized. Furthermore, an algorithm of weight allocation to different link attributes is also proposed. This algorithm is based on information entropy theory and it is practical. Two novel weighted Markov chain (WMC) approaches based on rank aggregation are proposed as for the situation that the network information is not complete or inaccurate measurement happens. By using the proposed approaches, partial knowledge due to incomplete measurement can be easily used.As for the diversity of link characteristics, the solutions in the user side and the network side for QoS guarantee are proposed respectively. On the user side, a load distribution algorithm is proposed. It optimizes the end-to-end delay by decreasing packet reordering delay. The pivotal idea of this algorithm is as follows:when the error between theoretical distribution and practical transmission capabilities of the links is under the predefined threshold, the traffic is split proportionally for all available links; when the error between theoretical distribution and practical transmission capabilities of the links is over the predefined threshold, the traffic is split proportionally for selected links. On the network side, a network control method is proposed. It also optimizes the end-to-end delay by decreasing packet reordering delay. In this method, decision-making function is placed on network side. The packet transmission is controlled by this function based on the state information of packet arrival. This method can optimize the reordering delay and save power consumption for the terminal.As for the mobility aspect, a novel type of mobility management architecture is proposed for heterogeneous multi-link system. This architecture is composed of trigger module, multi-link management module and handover module. These modules are logical function modules, which achieve the mapping to 3GPP evolved network architecture and the protocol stack. An efficient handover scheme based on MIH services is also proposed. It performs the opration by allowing the cooperation between the handover initiated interface and other activated interfaces on the same terminal.A summary is given at the end, where the future research directions related to this thesis are also pointed out.