Sustainable Mobile Communication Networks: Green Communications Perspective

Visiting researcher: Prof. Liqiang Zhao (XDU)
Host researcher: Prof. Jie Zhang (Univ. of Sheffield) & Prof. Lajos Hanzo (Univ. of Southampton)
Duration: 3 months
Status: Ongoing

Biography of the visiting researcher

Liqiang Zhao obtained his PhD degree in Information and Communications Engineering from Xidian University (XDU), China in 2003. From 1992 to 2005, he was within the 20th Research Institute, Chinese Electronics Technology Group Corporation (CETC), China. His activities focused on mobile communication systems and spread spectrum technologies. From 2005 to 2007, he was within State Key Laboratory of Integrated Services Networks (ISN), Xidian University, China. His research focused on WiMAX, WiFi, and wireless sensor networks. In 2007, he was appointed as a Marie Curie Research Fellow at the Centre for Wireless Network Design (CWiND), University of Bedfordshire, UK to conduct research in the GAWIND project funded under EU FP6 HRM programme. His activities focused on automatic wireless broadband access network planning and optimization. After returning Xidian University in 2008, his research focuses on broadband wireless access, near space communications, and green communications. Moreover, he is researching inter-disciplinary topics, e.g., introducing game theory from mathematics and economics into broadband wireless access, and green networks.
Since 2005, he has been awarded more than 8 projects funded by a number of sources, e.g., Europe, Chinese government and direct industrial funding. His participation in various projects has yielded a number of concrete results including enormous high-level publications, patents, etc. Due to his excellent works in education and research, he was awarded by the Program for New Century Excellent Talents in University, Ministry of Education, China in 2008.

Background and motivation

It has become clear that 3GPP Long Term Evolution (LTE) is the preferred technology for the next generation mobile communications systems. Novel transmission technologies, such as multiple input and multiple output (MIMO), and orthogonal frequency division multiplexing (OFDM), will be adopted for LTE. However, the development of such mobile broadband communications systems comes at a significant energy cost, which is unsustainable and unsuitable for future-proof communications.
The aim of Green Communications is to investigate and create innovative methods for the reduction of the total power needed to operate the future mobile communications systems and to identify appropriate network architectures and radio technologies which facilitate the required power reduction.
Femtocell networks, as a low-cost and low-power two-tier cellular access network, have been proposed as a solution to the poor indoor coverage problem. With the aid of an energy efficient access network, in principle, energy savings can be achieved in two ways. Firstly, by improved deployment strategies, effectively reducing the number of active BSs/APs/FAPs required in the network to fulfill certain performance metrics, such as coverage and spectral efficiency. Secondly, by optimizing the parameters a femtocell, effectively reducing the operating energy in each active BS/AP/FAP.

Research Activities

Our primary goal is to cross-fertilize our expertise with that of Prof. Hanzo Lajos at Southampton and with Prof. Jie Zhang at University of Sheffield.
To investigate the mathematical theory of Green Communications
The continuous investment in research and development of the future mobile communications systems aims at improving the efficiency, and brings about a wealth of theoretical knowledge and practical engineering solutions. However, a widely accepted choice of a criterion characterizing the overall efficiency of a wireless network remains an open problem. In addition to the half-a-dozen established criteria, e.g., the b/s bandwidth efficiency, b/J power efficiency, b/TENU power efficiency, we present a novel concept of radio efficiency. In this project, we shall evaluate and compare the above existing efficiency metrics, and radio efficiency presented by the Visiting Fellowship.
Energy efficient radio resource management to reduce the operating energy of each BS/AP/FAP
For green femtocell networks, energy efficient radio resource management strategies are urgently needed. Five kinds of resources, time, frequency, code, space, and user domain resources, can be reused to reduce the energy consumption. We have explored the green spectrum allocation in macro-femto cellular networks to reduce the operating power of BSs/APs/FAPs. In this project, we will explore the strategies for green femtocell networks with optimizing these resources in time, frequency, and space domain simultaneously.
Energy efficient network topology to reduce active number of BSs/APs/FAPs
The number and position of active BSs/APs/FAPs can be also optimized for low-power Green Communications. The number and position of BSs/APs/FAPs are determined by the coverage and QoS when the network traffic is high. However, in low traffic, it is rather large cost of energy because there is no need to make all BSs/APs/FAPs active. A reasonable solution is to dynamically switch off some BSs/APs/FAPs with the variation of the network traffic. However, switching off some BSs/APs/FAPs cannot come with compromising of coverage and QoS.


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