Prof. LI Ping (李坪)

Prof. Li Ping received his Ph.D. degree at Glasgow University in 1990. He lectured at Department of Electronic Engineering, Melbourne University, from 1990 to 1992, and worked as a research staff at Telecom Australia Research Laboratories from 1993 to 1995. Since January 1996, he has been with the Department of Electronic Engineering, City University of Hong Kong, where he is now a chair professor of information engineering. Prof. Li Ping received the IEE J J Thomson premium in 1993, the Croucher Foundation Award in 2005 and a British Royal Academy of Engineering Distinguished Visiting Fellowship in 2010. He served as a member of the Board of Governors for IEEE Information Theory Society from 2010 to 2012 and is a fellow of IEEE.

• Iterative Signal Processing
• Mobile Communications
• Coding and Modulation
• Information Theory
• Numerical Methods

Research Activities

(1) Coding and modulation schemes for communication systems

Coding and transmission techniques are crucial in modern communication systems. The progress in information theory and signal processing techniques has a tremendous impact on coding and modulation techniques. Recent advent in iterative decoding, codes on graphs, hybrid coding/modulation and loss recovery codes have shown that both capacity and performance of communication systems can be significantly enhanced. We have developed some very low complexity code and hybrid coded modulation methods, which can be ten times cost effective than the best existing schemes, yet with comparable or even better performances.

(2) Multiple access techniques of wireless cellular communication systems

The capacity of a cellular mobile communication system is limited by multi-user interference, from both same-cell users and other-cell users. Multiple access techniques, such as FDMA, TDMA and CDMA, are techniques to treat this interference problem. One basic approach (such as FDMA and TDMA) is to prevent interference by adopting orthogonal waveforms. Another quite different approach (such as CDMA) is to use random signals so as to reduce the correlation among signals from different users. Interference cancellation methods have also been widely studied to handle the problem. Our work in this area has revealed that the advantages of these methods can be combined so that the system architecture can be much simpler, the transmitter and receiver can be considerably simpler, and the performance can be greatly enhanced.

(3) Transmission and routing techniques for Internet and wireless data networks

As the broadband Internet keeps increasingly growing at speed, delivery of multimedia contents is expected to be one of the most popular broadband services in the near future. Handling multimedia contents is a very challenging issue as it involves a huge amount of storage capacity and a very wide transmission bandwidth. The current Internet architecture, however, uses a best effort delivery. It is not optimized for delivering multimedia contents because all types of data are treated as the same. To improve the performance of data delivery, designers of communication systems must pay special attention to each type of multimedia content. The delivery systems designed must also handle each type of contents in a unique way so as to provide optimal performance. Such systems can be called "content based multimedia delivery systems". We are currently studying and developing design strategy, performance analysis and demonstration prototypes for such systems.

Simulation Package

1. Zigzag Codes

Zigzag codes are a family of very simple error correction codes with perfomance close to theortical limit. They are suitable to median to high rate coding applications. The principle of zigzag codes can be found in "Zigzag codes and concatenated zigzag codes", IEEE Trans. Inform. Theory, special issue on codes on graphs, vol., IT-47, no. 2, pp., 800-807, Feb. 2001.

Simulation Package for Zigzag Codes

Simulation Package for Zigzag Coded IDMA

2. IDMA Systems

Interleave-division multiple-access (IDMA) is a new multi-access scheme. The principle of IDMA can be found in "Interleave-Division Multiple-Access," IEEE Trans. Wireless Commun., vol. 5, no. 4, pp. 938-947, Apr. 2006. The simulation software package for IDMA is available below.

Simulation Package for IDMA

3. Final Year Projects

The following simulation packages are developed by my final year project students. They are revised and improved by Kevin Ong at University of Michigan as his 2012 summer project.

Simulation Package for OFDM-IDMA. The principle can be found in "The OFDM-IDMA approach to wireless communication systems", IEEE Wireless Commun. Mag., pp. 18-24, June, 2007.

Simulation Package for Superposition Coded Modulation. The principle can be found in "Superposition coded modulation and iterative linear MMSE detection," IEEE J. Select. Areas Commun., vol. 27, no.6, pp. 995-1004, Aug. 2009.

Research Group

Former Students

• Dr. Wai Kong LEUNG
• Dr. Keying WU
• Dr. Lihai LIU
• Dr. Xiaojun YUAN
• Dr. Qinghua GUO
• Dr. Peng WANG
• Dr. Jun TONG
• Dr. Hao WANG
• Dr. Chongbin XU
• Dr. Zhonghao ZHANG
• Dr. Jianwen ZHANG
• Dr. Junjie MA
• Dr. Sai JIN
• Current Graduate Students
• Mr. Yang Hu
• Mr. Chengfei Huang
• Mr. Shansuo Liang
• Current Postdoctoral Fellows
• Dr. Haiyang Liu
• Dr. Chulong Liang
• Dr. Junjie MA