With the increasing requirement on QoS of data service, the long term evolution (LTE) of 3G is being researched and standardized to provide higher bit rates with lower latency, lower cost and improved coverage. In this paper，a novel network topology optimization of UMTS access networks combining mobility management and improved authentication schemes is proposed to support these requirements. The architecture presents a concept of URA (UMTS Terrestrial Radio Access Network Registration area) self-control system in control plane (C-plane) of access network, so that the handover process of C-plane can be independent of that of user plane (U-plane), which significantly reduces the handover latency. Moreover, a novel layered tunnels topology method is proposed in U-plane to achieve load equilibrium in access gateway (AGW). Based on the proposed network architecture, we give examples of signaling sequence combining fast handover process and proposed authentication scheme, and shows that their performance is generally superior to current 3G network architecture, in terms of reducing handover latency and increasing data security and integrity.

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In order to combat multipath fading in the wireless networks and increase the system capacity, the idea of spacetime coding devised for multiple antenna systems is applied to the two-hop non-regenerative (NR) relaying system. The proposed cooperative relaying system (CRS) is based on twohop protocol, in the 1 st hop the transmitter encodes original information into distributed linear dispersion codes (LDC) and in the 2 nd hop, the relaying nodes amplify the received signals and forward them to the receiver. Besides the capacity analysis of two-hop NR relaying system in the presence of LDC, we present some conditions based on maximum LDC capacity to optimize the proposed CRS performance. Theoretic analysis and numeric results show that the proposed CRS performance not only outperforms that of earlier proposed methods, but also obtains the maximum channel capacity.

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As existing wireless network, system, and standards evolve to beyond 3G capability, the ability to roam between heterogeneous wireless networks becomes increasingly desirable. However, when attempt is made to achieve the vision of seamless handover between heterogeneous wireless networks, a number of formidable barriers appear due to unreasonable roaming strategy. In this paper, we propose a novel roaming solution which takes into account the call activity rates and moving speed of users, and analyze the impact of the different parameters on the rate of inter-networking handover and the fraction of calls undergoing call setup delay. Theoretic analysis and numeric results demonstrate that the proposed scheme can obtain better performance than traditional roaming strategy, in terms of improving the capability of inter-networking roaming and reducing the signaling cost of handover