Song Mei

Link adaptation of wideband OFDM systems in multi-path fading channel

In OFDM systems, because channel fading on different sub-channels is different; when all OFDM sub-carriers use the same fixed modulation scheme, the error probability is dominated by the sub-carriers with the highest attenuation. Link adaptation can be used to enhance system throughput. According to the current link quality, the most appropriate modulation scheme can be selected on each sub-carrier to maintain acceptable error rate performance. In this paper, two link adaptation methods are considered. In the first method, a fixed number of weak sub-carriers which are highly attenuated are left out to improve the BER performance; in the second method, depending on the channel quality of each sub-carrier the modulation level on each sub-carrier is varied to adapt to the link conditions to improve the system throughput. The analysis and simulation results verify that the proposed link adaptation and coding scheme is effective in improving system throughput compared with the system with fixed modulation/coding.

Research on the SLA-based service management in mobile communication network

The paper proposes a flexible and effective service management method based on SLA. A new service modeling method is proposed. The service topology model is built from different points of view. The top down method is used to decide the SLA management policy and service alarm mechanism. Mobile communication network related simulation results demonstrate that by using the proposed service modeling approach, the service management system can do its utmost to reflect the influence of the network and elements to the service performance and it can also differentiate customers with different priority, which is useful for the future complex network environment.

Managing end-to-end QoS

Efficient network management can provide improved flexibility, scalability and robustness by distributing monitoring, analysis and control functionality throughout the networks. End-to-end (wired and wireless) QoS management faces big new challenges. The paper discusses both the online monitoring and the offline inter-network analysis. Monitoring methods in the core networks and the wireless access networks are analyzed respectively. From the analysis above, we infer that the different services and networks need to be measured by using different methods. The effective architecture to implement the end-to-end QoS management is proposed. The components of the integrated inter-network analysis process are discussed in order to provide end-to-end quality of service (QoS) guarantee. Simulation results show that these methods have good performance.

Research on Seamless Handover for WLAN with MIPv6

With the development of wireless technologies, WLAN (wireless local area network) has been widely deployed. However, because of the long delay of handover, WLAN can not meet the requirement of time critical service such as VoIP (voice over Internet protocol). Based on the analysis of the handover delay of WLAN with MIPv6 (mobile Internet protocol version 6) in layer 2 and layer 3, a new channel scanning is proposed to improve the delay characteristics of layer 2 and the handover performance of layer 3 is improved by the optimization of the handover flow of MIPv6. The improved solution was verified by the simulation and test

Considerations for the development of large scale mobile network management system

Mobile network systems have become more complex, especially large-scale mobile networks. Therefore, the performance of the NMS (network management system) becomes a challenge to software integration vendors. We summarize the problems encountered in our previous development of a large-scale mobile network management system. These problems can be mainly classified into two aspects: the interface between NMS and managed objects, that include not only network elements, but also the vendor EMS (element management system); the management data process pattern. To solve the first problem, a model driven mechanism is proposed. To solve the second problem, we suggest a loose coupling mode for the three main function sets (CM, PM and FM), which meets the requirement of a large-scale mobile network NMS better. We adopt the above two approaches in our real NMS which can manage 2G, 2.5G and 3G mobile networks. The results demonstrate that the two approaches can solve all problems analyzed at the beginning of the paper.

Capacity analysis of WCDMA-based packet data mobile cellular network with rate adaptation

Rate control is an important way to allocate radio resources when a packet data service is introduced in the CDMA cellular network. It can compensate some shortcomings when the system just uses power control and can improve the system capacity. In this paper, we focus on analysis of the CDMA system capacity when using the rate control method. We do a theoretical analysis and computer simulations on this issue. We give an expression of the mean inter-cell interference normalized by one cells throughput and discuss some factors influencing it. We also test the rate control method in a WCDMA-based packet data system, where we introduce a rate adaptation method to implement rate control procedure. From the simulation result, we prove that the system capacity can be improved obviously by using rate adaptation.