Academic Journals Database
Disseminating quality controlled scientific knowledge

Guest Editorial

Author(s): Sudhanshu Gaur | Geoffrey Ye Li | Li-Chun Wang | Neelesh B. Mehta

Journal: Journal of Communications
ISSN 1796-2021

Volume: 6;
Issue: 4;
Start page: 271;
Date: 2011;
Original page

Keywords: Special Issue | Practical Physical Layer Techniques | 4G Systems & Beyond

If one looks at the last thirty years and measures the rate at which technological innovation is impacting human life, then it can be safely concluded that we are living in extremely exciting times. Wide-spread adoption of Internet triggered an information revolution that has changed the human society in fundamental ways. Subsequent development of cellular communication systems and the resulting ubiquity of cellphones enabled people to communicate while on the go, and within a decade, “anytime-anywhere” communications has become a normal service for majority of people in both developed and developing nations. Ever increasing penetration of smart phones, tablets etc. in mass markets has given users a taste of “anywhere-ubiquitous” access to information & entertainment, and this too will soon become a must have, commodity service for everyone.Meeting these growing user demands requires next generation cellular networks to have vastly improved spectral efficiencies and coverage. Thus there is a constant need for fundamental as well as applied research on the components and algorithms for forthcoming 4G systems and beyond. The aim of this special issue is to collect and present a set of cutting edge research contributions that would hopefully be representative of the wide spectrum of on-going activities on the Physical layer front for these next generation cellular systems.To this end, we have identified nine high-quality publications after a thorough peer-review process. The papers can broadly be divided into three categories. The first category groups contributions that present system level performance analysis of PHY techniques that have been recently proposed in the research literature. This category is quite important from a practical point of view because it tries to vet theoretically promising techniques by quantifying their real impact on a deployed system through simulations. Any research idea that aspires to be part of a 4G standard has to pass through such system level evaluations.  The second category focuses on resource management algorithms and mechanisms for LTE/OFDMA systems. The selected papers either present algorithms extending state of the art, or provide a better understanding of existing interference coordination mechanisms in LTE.  The third category consists of papers aiming to improve the power efficiency of cellular networks. The accepted contributions range from a paper proposing new power efficient PHY coding techniques, to a forward looking article comparing the efficiency or relay assisted networks versus user cooperation, and culminate with an invited survey article on green communications. In the paragraphs that follow, we will briefly summarize the basic ideas presented in each paper from this issue. The first three papers evaluate multi-user (MU) multiple-input multiple-output (MIMO) technique in the context of cellular networks. The first paper, “System-Level Impact of Multi-User Diversity in SISO and MIMO-based Cellular Systems” by R. Pupala, L.J. Greenstein, and D.G. Daut, considers several parameters in wireless multi-cell systems and evaluate their impacts on aggregate throughputs with different schedulers. This work attempts to quantify the benefits of multiuser diversity and excess degrees of freedom from multiple receive antennas. The second paper “Downlink System Throughput Statistics for Various MEA Configurations” by R. Pupala, Y. Yuan, Q. Bi, and L.J. Greenstein, investigates the merit in modifying a SISO link with added antenna elements at one or both ends. Practical considerations such as channel estimation overhead are considered to evaluate relative merits of various multi-antenna configurations. The third paper “Coverage Analysis for Multiuser MIMO Broadcast Systems” by L.C. Wang and C.J. Yeh, investigates the diversity gain and coverage of zero-forcing beamforing (ZFB) and zero-forcing dirty paper coding (ZF-DPC) techniques with/without the consideration of multiuser scheduling for multiuser MIMO broadcast channels. The proposed work shows that the use of multiuser scheduling can act as soft coverage enhancement technique without requiring additional transmit power.Next three papers focus on resource management algorithms and mechanisms for LTE/OFDMA systems. In the fourth paper, “A Practical Resource Allocation Approach for Interference Management in LTE Uplink Transmission” by L. Li, G. Wu, H. Xu, G. Li and X. Feng, the authors propose a novel resource allocation method for LTE uplink to reduce inter-cell interference. This paper investigates joint power control and resource allocation techniques for LTE uplink and proposes an efficient way to improve system performance, especially for cell edge users. In the next paper “Impact of CSI on Radio Resource Management Techniques for the OFDMA Downlink” by L. Sivridis, X. Wang and J. Choi, the authors propose sub-carrier allocation algorithm for OFDMA downlink. This work improves upon a previously known algorithm by reallocating the subcarriers of users who will not be able to meet their quality of service (QoS) requirements. The sixth paper “Understanding Static Inter-Cell Interference Coordination Mechanisms in LTE” by A. Mills, D.R. Lister, and M.D. Vos, considers modulation and coding scheme (MCS) based soft frequency reuse issue in cellular systems. Based on this metric the paper challenges the idea that cell edge users should have a high reuse factor.The remaining three papers focus on power-efficient system architectures and PHY techniques for cellular systems. The paper “Power-efficient Irregular Repeat-Accumulate Encoded BICM-ID for 16-ary Signal Constellations” by W.K. Han, S. Y. L. Goff, B. Sharif, and A. J. Al-Dweik presents novel results on the application of bit-interleaved coded modulation (BICM) along with irregular repeat accumulate and low-density parity-check codes to improve bit error rate (BER) performance over Rayleigh fading channels. The next paper “Dedicated-Relay vs. User Cooperation in Time-Duplexed Multiaccess Networks” by L. Shankar, G. Kramer, and N. Mandayam, investigates the performance trade-offs of cooperation in a multi-user uplink network. Two basic modes of cooperation are considered: user cooperation, in which users forward each other's messages, and dedicated relaying, in which a single dedicated relay forwards users' messages. This work explores whether user cooperation or dedicated relaying is more energy efficient, as measured by outage probability versus total transmit and processing power. Environmental impact and power usage are major concerns for next generation networks. An He et al., provide a survey of energy efficient advances in renewable and alternative energy resources for base stations in the ninth paper “Green Communications: A Call for Power Efficient Wireless Systems”. This paper is of tutorial nature and presents an interesting overview of technology and economics that could affect green communication systems.We feel that this special issue succeeds in its attempt to give readers an insight into on-going activities on fundamental as well as applied research on the Physical layer algorithms and system level design for forthcoming 4G systems and beyond. We would like to thank all the authors who submitted their work for consideration for this issue, and the reviewers for their timely and constructive feedback. We also thank the staff at the JCM Academy Publisher for their help in handling the manuscripts. Lastly, we would like to extend our sincere appreciation to Dr. Linda Xie, Editor of the Journal of Communications, for her great support, and Dr. Haohong Wang, Editor-in-Chief of the Journal of Communications for providing us the opportunity to organize this special issue.
Affiliate Program      Why do you need a reservation system?