Research

Project: " A pricing strategy in slotted Aloha"

In this project, slotted aloha is analyzed using game theory. By introduce pricing, the transmission probability of each can be optimized.

Project: “Cooperative transceiver architecture and MAC scheme for broadband ad hoc networks”

In this project, a new cooperative transceiver architecture combined with MIMO, OFDM and space-time coding is proposed. To fully utilize the physical layer, from the view of cross layer design, a new MAC scheme MARI-BTMA is also proposed. Performance analysis and simulation results show much better performance compared with traditional MIMO-OFDM, RI_BTMA and CSMA/CA.

Project: “New soft handover scheme for WCDMA”

In this project, a new soft handover scheme was proposed and evaluated for WCDMA. This new scheme aimed to provide fairness between soft handover links and other links when it is admitted into the target cell. This scheme was compared with the traditional ReleaseConnOffset method. The effects on downlink carrier power, uplink noise rise, dropping rate and blocking rate were evaluated.

Project: “WCDMA speech admission control parameter optimization”

In WCDMA, admission control is important for checking that the admittance of a new connection does not sacrifice the planned coverage area or the quality of the existing connections. In this project, the admission control algorithm with different carrier power admission thresholds and different estimations of power consumption of a new link were evaluated for speech users.

Project: “Speech capacity evaluation of a WCDMA system”

This project concentrated on the influence of the admission control algorithm and dropping the control algorithm on speech capacity. Different from the above projects focused on signal processing, this project used the network perspective for a wireless network system.

▪ Project: “Transceiver design in MIMO CDMA system”

This project used multiple input multiple output (MIMO) scheme to improve the data rate in CDMA systems. In the transmitter, vertical Bell Laboratories Layered Space Time architecture (V_BLAST) was combined with CDMA. An improved receiver based on the detection algorithm of V_BLAST and Rake receiver was proposed. To improve the system capacity, a multi-carrier was also incorporated.

Project: “Combined array processing and space-time codes”

As space-time codes can improve the system performance with space diversity while array-processing techniques such as V_BLAST can increase the data rate of the system, the combination of space-time codes with array processing was studied in this project. By extending STBC with the introduction of linear correlation among the multiple transmit antennas, the performance of the system outperforms traditional STBC. Furthermore, the scheme of partitioning the transmit antennas into small groups and using individual space-time trellis codes (STTC) for each group was investigated combined with CDMA in the multipath fading scenario. A receiver named Group Interference Suppression Maximum Ratio Combining (GIS_MRC) was designed to combat the multipath fading. To further improve the system performance, parallel Concatenated Convolutional Codes (PCCC) and Serial Concatenated Convolutional Codes (SCCC) were combined with this scheme.

Project: “Design high efficient channelization code and multiple code detector for LAS-CDMA2000 System”

Large area synchronous CDMA (LAS-CDMA) is well known for its novel multiple access schemes, which are different from all known traditional CDMA. The auto-correlation functions of all LAS-CDMA codes are ideal, and there exists an interference free window (IFW) or a zero correlation zone (ZCZ) in their cross-correlation functions of its access codes around the origin. Due to the existence of this IFW or ZCZ, LAS-CDMA system can have much higher system capacity and spectral efficiency than traditional CDMA. To further improve the spectral efficiency and find more complementary codes, OFDM, multi-carrier CDMA were introduced in the creation of the new codes. After trying many code extended methods, one novel kind of code was found which doubled the number of orthogonal LS codes in one set. The new codes were designed as channelization codes in LAS_CDMA2000. Meanwhile, the receiver was re-designed. Various multiple user detector (MUD) algorithms, especially the algorithms based on zero forcing (ZF) and minimum mean-square-error (MMSE) were investigated intensely. According to the characteristics of the new codes, a new multiple code detector (MCD) was proposed. Simulation results showed excellent performances with a slight degrade over the ML receiver and much less computational complexity. It was written into the specification of LAS_CDMA2000.

Project: “Channel estimation in LAS-CDMA2000+ System”

Classic channel estimation methods, including linear channel estimation, feedback channel estimation and interpolation channel estimation were investigated. Specifically, one space-time channel estimation method suitable for the multiple transmitting antennas in LAS_CDMA20000+ was studied. Various orthogonal transmitter and diversity schemes, such as space-time transmit diversity (STTD) based on space-time blocking code (STBC), were considered. By designing the adaptive location of a pilot symbol and its proper orthogonal transmition configuration, an adaptive space-time channel estimation scheme was proposed. The simulation on COSSAP showed its good performance and later it was used in the prototype of LAS_CDMA2000+.

Research resource

Localization in Sensor network Cross layer design

Localization in Sensor network

1. A kernel-based learning approach to ad hoc sensor network localization

2. A Self-Localization Method for Wireless Sensor Networks

3. ACOUSTIC SOURCE LOCALIZATION IN DISTRIBUTED SENSOR NETWORKS

4. ADAPTIVE DISTRIBUTED MULTIDIMENSIONAL SCALING FOR LOCALIZATION IN SENSOR NETWORKS

5. An Experimental Study of Localization Using Wireless Ethernet

6. Automatic Online Localization of Nodes in an Active Sensor Network

7. Distributed Camera Network Localization

8. Dynamic Localization Protocols for Mobile Sensor Networks

9. Energy-Aware Target Localization in Wireless Sensor Networks