Editorial - Advanced signal processing for wireless and mobile communications

Wireless and mobile communications have developed rapidly in recent years due to the endless demand for broadband multimedia Internet access and wireless connection anywhere and any time. Several 4G standards have been proposed such as WiMax, LTE and IEEE 802.11n. Signal processing plays a key role in the evolution of wireless and mobile communications. With the emergence of various 4G enabling technologies, advanced signal processing has become ever increasingly important for low complexity, low power and efficient physical implementations of future multimedia communication systems. Multi-antenna, multi-frequency, multi-user and cooperative technologies have emerged as powerful enablers for high date rate and highly reliable broadband communications. To harvest the benefits of these technologies maximally, both excellent opportunities and significant challenges are present in the research of signal processing. The aim of this special issue was to publish some most recent advances in the signal processing aspects of these wireless and mobile communication technologies. Five papers have been selected for the special issue. These papers cover various multi-antenna topics including MIMO detection, spacetime equalization, MIMO channel prediction and estimation, and space-time coding. Some papers also consider cooperative relay communications, OFDM, and multiuser systems.     

Medium Access Control for Integrated Multimedia Wireless Access with the Use of a Video Packet Discard Scheme

A well designed Medium Access Control (MAC) protocol for wireless networks should provide an efficient mechanism to share the limited bandwidth resources, and satisfy the diverse and usually contradictory Quality of Service (QoS) requirements of each traffic class. In this paper a new MAC protocol for next generation wireless communications is presented and investigated. The protocol uses a combined Packet Discard/Forward Error Correction scheme in order to efficiently integrate MPEG-4 videoconference packet traffic with voice, SMS data and web packet traffic over a noisy wireless channel of high capacity. Our scheme achieves high aggregate channel throughput in all cases of traffic load, while preserving the Quality of Service (QoS) requirements of each traffic type, and is shown to clearly outperform DPRMA, another efficient MAC protocol proposed in the literature for multimedia traffic integration over wireless networks. Dr. Polychronis Koutsakis was born in Hania, Greece, in 1974. He received his 5-year Diploma in Electrical Engineering in 1997 from the University of Patras, Greece and his MSc and Ph.D. degrees in Electronic and Computer Engineering in 1999 and 2002, respectively, from the Technical University of Crete, Greece. He was a Visiting Lecturer at the Electronic and Computer Engineering Department of the same University for three years (2003–2006). He is currently an Assistant Professor at the Electrical and Computer Engineering Department of McMaster University, Canada. His research interests focus on the design, modeling and performance evaluation of computer communication networks, and especially on the design and evaluation of multiple access schemes for multimedia integration over wireless networks, on call admission control and traffic policing schemes for both wireless and wired networks, on multiple access control protocols for mobile satellite networks, wireless sensor networks and powerline networks, and on traffic modeling. Dr. Koutsakis has authored more than 45 peer-reviewed papers in the above mentioned areas, has served as a Guest Editor for an issue of the ACM Mobile Computing and Communications Review, as a TPC member for conferences such as IEEE GLOBECOM, IEEE LCN and IEEE PerCom, will serve as Session Chair for the IEEE GLOBECOM 2006 Symposium on Satellite & Space Communications and serves as a reviewer for most of the major journal publications focused on his research field. Moisis Vafiadis was born in Elefsina, Greece, in 1980. He has recently completed his studies towards the Diploma in Electronic Engineering at the Technological Educational Institute of Crete, Greece. His research interests focus on wireless personal communication networks, and especially on the MAC layer and on the development and testing of wireless multimedia applications.     

Recent advances in cellular wireless communications

Testimonies of “wireless catching up with wireline” have begun. An information superhighway system is envisioned to fulfill the plethora of demand for wireless communications and the need for multimedia networks with multiservice requirements. The revolution in this technology will eventually free us, as communication users, from being tied down to a particular fixed location in a telephone network to person-to-person communications, via pocket-sized terminals, at an affordable price. This article briefly surveys the state of the art, standards, and technological growth experienced in mobile cellular (terrestrial and satellite) communications since the days of the ingenious inventions of Alexander Graham Bell and Guglielmo Marconi, over a century ago. Subsequently, we describe some emerging technological trends that can improve the capacity of third-generation systems and future outlooks for PCS networks in the next millennium     

Providing deterministic packet delays and packet losses in multimedia wireless networks

‘Anytime, anywhere’ communication, information access and processing are much cherished in modern societies because of their ability to bring flexibility, freedom and increased efficiency to individuals and organizations. Wireless communications, by providing ubiquitous and tetherless network connectivity to mobile users, are therefore bound to play a major role in the advancement of our society. Although initial proposals and implementations of wireless communications are generally focused on near‐term voice and electronic messaging applications, it is recognized that future wireless communications will have to evolve towards supporting a wider range of applications, including voice, video, data, images and connections to wired networks. This implies that future wireless networks must provide quality‐of‐service (QoS) guarantees to various multimedia applications in a wireless environment. Typical traffic in multimedia applications can be classified as either Constant‐Bit‐Rate (CBR) traffic or Variable‐Bit‐Rate (VBR) traffic. In particular, scheduling the transmission of VBR multimedia traffic streams in a wireless environment is very challenging and is still an open problem. In general, there are two ways to guarantee the QoS of VBR multimedia streams, either deterministically or statistically. In particular, most connection admission control (CAC) algorithms and medium access control (MAC) protocols that have been proposed for multimedia wireless networks only provide statistical, or soft, QoS guarantees. In this paper, we consider deterministic QoS guarantees in multimedia wireless networks. We propose a method for constructing a packet‐dropping mechanism that is based on a mathematical framework that determines how many packets can be dropped while the required QoS can still be preserved. This is achieved by employing: (1) An accurate traffic characterization of the VBR multimedia traffic streams; (2) A traffic regulator that can provide bounded packet loss and (3) A traffic scheduler that can provide bounded packet delay. The combination of traffic characterization, regulation and scheduling can provide bounded loss and delay deterministically. This is a distinction from traditional deterministic QoS schemes in which a 0% packet loss are always assumed with deterministically bounding the delay. We performed a set of performance evaluation experiments. The results will demonstrate that our proposed QoS guarantee schemes can significantly support more connections than a system, which does not allow any loss, at the same required QoS. Moreover, from our evaluation experiments, we found that the proposed algorithms are able to out‐perform scheduling algorithms adopted in state‐of‐the‐art wireless MAC protocols, for example Mobile Access Scheme Based on Contention and Reservation for ATM (MASCARA) when the worst‐case traffic is being considered. Copyright © 2002 John Wiley & Sons, Ltd.     

无线Mesh技术和网络

无线网状网（WMN）是近年被高度重视和快速发展的新型网络技术,支持宽带高速多媒体业务服务。文章就无线Mesh网络技术和应用进行讨论,综述无线Mesh网络的发展由来、基本技术、典型应用和现在的发展。随着未来无线分布技术和无线分布网络的发展,无线Mesh技术和网络将会成为无线移动通信的基本网络技术和网络结构,渗透到各种无线网络中,发挥更大作用。     

Cross-layer wireless multimedia transmission: challenges, principles, and new paradigms

Wireless networks are poised to enable a variety of existing and emerging multimedia streaming applications. As the use of wireless local area networks spreads beyond simple data transfer to bandwidth-intense, delay-sensitive, and loss-tolerant multimedia applications, addressing quality of service issues become extremely important. Currently, a multitude of protection and adaptation strategies exists in the different layers of the open systems interconnection (OSI) stack. Hence, an in-depth understanding and comparative evaluation of these strategies are necessary to effectively assess and enable the possible trade-offs in multimedia quality, power consumption, implementation complexity, and spectrum utilization that are provided by the various OSI layers. This further opens the question of cross-layer optimization and its effectiveness in providing an improved solution with respect to the above trade-offs. In this article we formalize the cross-layer problem, discuss its challenges, and present several possible solutions. Moreover, we also discuss the impact the cross-layer optimization strategy deployed at one station has on the multimedia performance of other stations. We introduce a new fairness concept for wireless multimedia systems that employs different cross-layer strategies, and show its advantages when compared to existing resource allocation mechanisms used in wireline communications. Finally, we propose a new paradigm for wireless communications based on competition, which allows wireless stations to harvest additional resources or free up resources as well as optimally and dynamically adapt their cross-layer transmission strategies to improve multimedia quality and/or power consumption.     

Introduction to the Special Issue on Models, Theory, and Codes for Relaying and Cooperation in Communication Networks [Guest Editorial]

The thirty-four papers in this special issue are devoted to models, theories, and codes for relaying and cooperation in communication networks. The demand for large, more efficient, reliable, and cost effective communication networks is motivating new network architectures for cellular and wireless communications as well as cognitive radio and sensor networks.     

Multipath video transport over ad hoc networks

Real-time multimedia transport has stringent bandwidth, delay, and loss requirements. It is a great challenge to support such applications in wireless ad hoc networks, which are characterized by frequent link failures and congestion. Using multiple paths in parallel for a real-time multimedia session (called multipath transport) provides a new degree of freedom in designing robust multimedia transport systems. In this article, we describe a framework for multipath video transport over wireless ad hoc networks, and examine its essential components, including multistream video coding, multipath routing, and transport mechanisms. We illustrate by three representative examples how to extend existing video coding schemes in order to fully explore the potential of multipath transport. We also examine important mechanisms in different layers for supporting multipath video transport over ad hoc networks. Our experiments show that multipath transport is a promising technique for efficient video communications over ad hoc networks.     

Evolution of aeronautical communications for personal and multimedia services

The demand to make air travel more pleasant, secure, and productive for passengers is one of the winning factors for both airlines and the aircraft manufacturing industry for which aeronautical communications is one of the enablers. This article describes current trends in the area of aeronautical passenger communication toward personal and wireless in-cabin communications and multimedia data networks. Technological challenges are summarized as well as market potentials and regulatory issues.     

A cross-layer scheduling algorithm with QoS support in wireless networks

Scheduling plays an important role in providing quality of service (QoS) support to multimedia communications in various kinds of wireless networks, including cellular networks, mobile ad hoc networks, and wireless sensor networks. The authors propose a scheduling algorithm at the medium access control (MAC) layer for multiple connections with diverse QoS requirements, where each connection employs adaptive modulation and coding (AMC) scheme at the physical (PHY) layer over wireless fading channels. Each connection is assigned a priority, which is updated dynamically based on its channel and service status; the connection with the highest priority is scheduled each time. The authors' scheduler provides diverse QoS guarantees, uses the wireless bandwidth efficiently, and enjoys flexibility, scalability, and low implementation complexity. Its performance is evaluated via simulations.     

Internet delivery of MPEG-4 object-based multimedia

Object-based multimedia communications demand a much more sophisticated delivery framework for delivering synchronized, multiplexed, media object streams across the Internet or wireless networks. We describe the Moving Picture Expert Group's Delivery Multimedia Integration Framework (DMIF) and examine several remote retrieval issues. We also describe our design and implementation of a DMIF-based MPEG-4 multimedia streaming system.     

New concepts and technologies for achieving highly reliable andhigh-capacity multimedia wireless communications systems

The rapid growth of multimedia wireless communications services forces the development of advanced digital wireless systems with high reliability and high speed as well as flexibility for varying traffic conditions. To achieve such advanced wireless systems. New system design concepts different from the conventional ones aiming at increasing system capacity for voice transmission would be required. Since multimedia wireless communications require high quality, high speed, and high flexibility as well as temporary and spatial control of traffic under severe fading environments, the so-called conventional system design concept will be insufficient. New system design concepts and techniques for achieving highly reliable and high-capacity multimedia wireless communications are discussed using both time division multiple access (TDMA) and code division multiple access (CDMA) systems. The demands for high-speed and high-reliability mobile, personal, and multimedia wireless communications services strongly require matching with the trunk network constructed by a broadband optical fiber system or wired system     

The future generations of mobile communications based on broadband access technologies

The forthcoming mobile communication systems are expected to provide a wide variety of services, from high-quality voice to high-definition videos, through high data rate wireless channels anywhere in the world. The high data rate requires broad frequency bands, and sufficient broadband can be achieved in higher frequency bands such as microwave, Ka-band, and millimeter-wave. Broadband wireless channels have to be connected to broadband fixed networks such as the Internet and local area networks. The future-generation systems will include not only cellular phones, but also many new types of communication systems such as broadband wireless access systems, millimeter-wave LANs, intelligent transport systems, and high altitude stratospheric platform station systems. Key to the future generations of mobile communications are multimedia communications, wireless access to broadband fixed networks, and seamless roaming among different systems. This article discusses future-generation mobile communication systems.     

IrBurst Modelling and Performance Analysis in the Presence of Transmission Errors

IrBurst is a session/presentation layer protocol dedicated for high speed large volume information transfer over IrDA links. The protocol is developed by IrDA in order to complement the existing protocol OBEX which is best suited for small files. This paper presents a mathematical model for IrBurst over the IrDA protocol stacks taking into account the presence of bit errors and multiple simultaneously applications. The performance of IrBurst is examined considering TinyTP buffer sizes and the number of IrBurst application connections as parameters. The contribution of this work is to develop a mathematical model for IrBurst, investigate the compatibility of IrBurst to low layer protocols, as well as providing suitable design guidelines for IrDA devices for high performance of IrBurst. Pi Huang received the B.Sc. degree in Electrical and Electronic Engineering from University of Central Lancashire, U.K., in 2001, the M.Sc. degree in Telecommunications from University College London, U.K., in 2002 and the Ph.D degree in the Personal Wireless Networks and Outdoor Optical Links from Bournemouth University, U.K., in 2006. He is currently working in wireless solution division of British Telecom. His research focuses on performance modelling and analysis as well as discrete-event simulation of wireless communication protocols and wireless communication networks. He has published over 20 papers in the areas of wireless communications. Anthony C. Boucouvalas has worked at GEC Hirst Research Centre, and became Group Leader and Divisional Chief Scientist until 1987, when he joined Hewlett Packard (HP) Laboratories as Project Manager. He joined Bournemouth University in 1994 and became a Professor in Multimedia Communications in 1996, and in 1999 became Director of the Microelectronics and Multimedia Research Centre. His current research interests span the fields of wireless communications, optical fibre communications and components, multimedia communications, and human-computer interfaces, where he has published over 200 papers. He has contributed to the formation of IrDA as an industry standard and he is now a Member of the IrDA Architectures Council. He is a Fellow of Fellow of the Royal Society for the encouragement of Arts, Manufacturers and Commerce, (FRSA) and a Fellow of IEE, (FIEE). In 2002 he became a Fellow of the Institute of Electrical and Electronic Engineers (FIEEE), for contributions to optical fibre components and optical wireless communications. He is an Editor of numerous Journals and in the Organising committee of many conferences.     

Distributed Medium Access Control Next-Generation CDMA Wireless Networks

The next-generation wireless networks are expected to have a simple infrastructure with distributed control. In this article, we consider a generic distributed network model for future wireless multimedia communications with a code-division multiple access (CDMA) air interface. For the medium access control (MAC) of the network model, we provide an overview of recent research efforts on distributed code assignment and interference control and identify their limitations when applied in next-generation wireless networks supporting multimedia traffic. We also propose a novel distributed MAC scheme to address these limitations, where active receivers determine whether a candidate transmitter should transmit its traffic or defer its transmission to a later time. Simulation results are given to demonstrate the effectiveness of the proposed distributed MAC scheme.     

基于混沌序列的视频保密通信

随着网络和多媒体技术的快速发展,信息安全技术成为了人们关注的一个热点课题。图像视频信息保密通信是混沌应用的一个新领域,混沌加密在计算机网络和视频通信方面的应用为解决信息安全问题开辟了一种新的途径。根据一个离散时间混沌序列,运用驱动—响应式同步方法对视频数据进行实时加密和解密,最后通过Wi Fi网络传输实现了无线混沌视频保密通信。     

Centralized Resource Allocation for Multimedia Traffic in IEEE 802.16 Mesh Networks

The IEEE 802.16 standard provides a high degree of flexibility for setting up and operating wireless broadband networks in metropolitan environments. The standard supports numerous capabilities, including mesh topologies and multimedia communications. In this paper, we study these two features by investigating how efficiently an IEEE 802.16 mesh network can treat distributed multimedia traffic by providing differentiated quality of service (QoS). A key component of the system is the ldquoenhanced frame registry tree schedulerrdquo (E-FRTS) that provides QoS-aware resource allocation using a tree structure to prepare the creation of time frames and reduce processing requirements at the beginning of each frame. Simulation results show that distributed multimedia traffic can be efficiently supported in mesh 802.16 networks, provided efficient scheduling and a reasonable number of hops.     

Hybrid QoS based routing protocol for inter and intra wireless mesh infrastructure communications

Quality of service (QoS) in wireless mesh networks is an active area of research, which is driven by the increasing demand for real-time and multimedia applications, such as Voice over IP and Video on Demand. In this paper, we propose a novel QoS based routing protocol for wireless mesh infrastructure, called Hybrid QoS Mesh Routing (HQMR). It is composed of two QoS based routing sub-protocols: a reactive multi-metric routing protocol for intra-infrastructure communications and a proactive multi-tree based routing protocol for communications with external networks. The proposed routing protocol enables forwarding real-time and streaming applications with QoS guarantee in a mesh wireless environment, by assigning a specific routing path for each defined service class. To this end, three different QoS service classes are defined, depending on the applications requirements. We analyze in this paper the simulation results of different scenarios conducted on the network simulator ns-3 to demonstrate the effectiveness of the HQMR protocol and to compare it to other routing protocols while forwarding real-time applications with QoS guarantee.