WiFi, WiMAX, and LTE Multi-hop Mesh Networks: Basic Communication Protocols and Application Areas

By Hung-Yu Wei, Jarogniew Rykowski and Sudhir Dixit

Wifi, WiMAX, and Cellular Multihop Networks presents an overview of WiFi-based and WiMAX-based multihop relay networks. As the first text to cover IEEE 802.16j multihop hop relay technology, this revolutionary resource explores the latest advances in multi-hop and ad-hoc networking. Not only does this reference provide the technological aspects, but also the applications for the emerging technology and architectural issues. Ranging from introductory material to advanced topics, this guidebook is essential for engineers, researchers, and students interested in learning more about WiFi and WiMAX multihop relay networks.

• Language: English
• Publisher: Wiley
• Release date: Mar 5, 2013
• ISBN: 9781118571118

Book preview

ABOUT THE AUTHORS

web_fbetwuf001

HUNG-YU WEI received a BS degree in Electrical Engineering from National Taiwan University in 1999. He received MS and PhD degrees in Electrical Engineering from Columbia University in 2001 and 2005, respectively. Dr. Wei was a summer intern at Telcordia Applied Research in 2000 and 2001. He was with NEC Labs America from 2003 to 2005. He joined the Department of Electrical Engineering at the National Taiwan University in July 2005 as an Assistant Professor, and he is currently Associate Professor in the Department of Electrical Engineering and Graduate Institute of Communication Engineering at National Taiwan University. He received the NTU Excellent Teaching Award in 2008 and the Recruiting Outstanding Young Scholar Award from the Foundation for the Advancement of Outstanding Scholarship in 2006. He was a consulting member of the Acts and Regulation Committee of the National Communications Commission during 2008∼2009. He has been participating in IEEE 802.16 and 3GPP standardization activities. His research interests include wireless networking, game theoretic models for communications networks, and mobile computing.

web_fbetwuf002

JAROGNIEW RYKOWSKI received an MSc degree in Computer Science from the Technical University of Pozna x144_rn , Poland in 1986 and a PhD degree in Computer Science from the Technical University of Gdansk, Poland in 1995. In 2008, he received a habilitation degree from the Institute of Computer Science, Polish Academy of Science (Warsaw, Poland). From 1986 to 1992, he was with the Institute of Computing Science at the Technical University of Pozna x144_rn . From 1992 to 1995, he worked as an Assistant in the Franco-Polish School of New Information and Communication Technologies in Pozna x144_rn . In 1995, he became an Associate Professor in the School. Since 1996, he has been with the Pozna x144_rn University of Economics, working as an Assistant Professor in the Department of Information Technology. He participated in several industrial projects concerning operating systems, networks, programming language compilers (assemblers and LISP), multimedia databases, and distributed systems for e-commerce. His research interests include software agents, with special emphasis put on personalized access to WWW servers by means of mobile devices and telecommunication networks. His recent interests have gone toward applications of Internet of Things and calm-computing devices, including intelligent buildings and workplaces, semantic support for IoT systems, telematics, ad-hoc and multi-hop networking, and related systems. He is the author and coauthor of 3 books, over 45 papers in journals and conference proceedings, and 2 patents.

web_fbetwuf003

SUDHIR DIXIT is the Director of Hewlett-Packard Laboratories, India. Prior to joining HP Labs in June 2009 in Palo Alto, California, Dr. Dixit held a joint appointment as CTO at the Centre for Internet Excellence and Research Manager at the Centre for Wireless Communications, both at the University of Oulu, Finland. From 1996 to 2008, he held various positions with Nokia: Senior Re­­search Manager, Research Fellow, Head of Nokia Research Center (Boston), and in the later years, as Head of Network Technology (USA) for Nokia Siemens Networks. He has also held the position of Senior Director at Research In Motion, and other senior management and technical positions at such companies as Verizon (previously NYNEX and GTE Labs), Motorola, Wang Labs, and Harris Corporation. Dr. Dixit received his PhD degree in Electronic Science and Telecommunications from the University of Strathclyde, Glasgow, UK, MBA degree from the Florida Institute of Technology, Melbourne, Florida, ME degree from the Birla Institute of Technology and Science, Pilani, India, and BE degree from Maulana Azad National Institute of Technology, Bhopal, India. He is an Adjunct Professor of Computer Science at the University of California, Davis, and a Docent (Adjunct Professor) of Telecommunications at the University of Oulu. He has published over 200 papers, edited 5 books, and holds 20 patents. He is a Fellow of IEEE (USA), IET (UK), and IETE (India).

LIST OF FIGURES

LIST OF TABLES

1 

Introduction

Nowadays, a global trend is to make our lives easier. To reach this goal, we freely apply new technologies to develop personal, organizational, and social solutions. We even create new technology domains and their applications, such as cellular telephony or Internet. And it looks like that this trend is only going to accelerate, as new technologies lead to new multidisciplinary innovations with a multiplier effect. The rapid change is akin to what Arthur C. Clarke described as magic—any sufficiently advanced technology is indistinguishable from magic (Clarke, 1962). And humans, for the most part, have begun to believe in that magic such that with technology and innovation almost everything is possible.

With the mass introduction of, first, the Internet, and, now, cellular telephony, a new need has arisen to be able to communicate with everybody (or everything), at anytime, from anywhere, including access to the Web. Magical mobile communication has been accepted as a norm around the world, and this nomadic lifestyle has prompted a serious look at the business and personal environment. However, the magic is unfortunately constrained by several technical and economic obstacles. Even if we do believe that unrestricted communication is a must, we are still faced with many challenges, for example, poor signal quality and range, and high calling costs. Satellite phones would probably work better to provide universal coverage (e.g., in rural and mountainous regions), but the cost will be prohibitively high. Similarly, a bigger battery would substantially reduce the need for frequent recharging, but it is going to severely impact portability.

As we become aware of our continuously expanding needs and expectations, we naturally tend to ignore the limitations. In general, two ways are possible: either we simply wait for an introduction of a new technical/organizational/social solution, new infrastructure, device, and so on, or we try to adapt the existing solutions for new challenges, even if this is a temporary solution; alternatively, we apply a mixed approach—first we try to accomplish the best from the existing solutions, and later search for a new solution to better fulfill our needs.

This book is devoted to applying such mixed approaches to mobile communication and internet access with the main objective to significantly improve coverage and minimize cost. Recently, wireless computer networks, such as WiFi and WiMAX, on the one hand, and mobile communication, such as general packet radio service/enhanced data rate for global evolution (GPRS/EDGE), high speed packet access (HSPA), and Long Term Evolution (LTE), on the other hand, have opened up new possibilities to meet the objectives. However, to build such a network, significant investment in the infrastructure is required, not to mention of the physical restrictions (such as the ability of the radio signals to penetrate through physical structures). From the organizational point of view, the connected equipment (mobile stations) must authorize itself prior to accessing the network, and there is a serious issue of potential denial of service attack between a server (i.e., network element serving the client devices) and a client. The advent of ad-hoc and multi-hop networking has only compounded the problem.

A mobile ad-hoc network (MANET for short) is defined as a self-organized set of wireless, mobile nodes with no fixed topology of connections. In general, wireless mesh network can be of two types (Fig. 1.1): MANET and infrastructure-based immobile network. MANETs are typically peer-to-peer networks with mobile client devices communicating with each other directly or through other nodes in multi-hop configuration (Fig. 1.1a). Here client nodes may function as routing nodes for others that are not within each other’s communication range. In immobile wireless mesh network, the access radio nodes and gateway nodes are stationary, and the client devices connect to the access node (Fig. 1.1b). MANET organization may vary in time—nodes are being connected and disconnected, they replace their point of connection (their neighborhood evolves), and dynamically adapt themselves to the topology changes. As a matter of fact, nothing is fixed; in contrast to classical networking, a MANET node may disappear at anytime, causing serious disruptions to the neighboring nodes. Furthermore, routing of the information must be planned in a dynamic manner so as to be able to deal with the evolving network topology (the route for the outgoing packet and the incoming packet between a pair of nodes may be different, as the topology may change even during the period of a single transmission).

Figure 1.1. Examples of (a) mobile ad-hoc (infrastructureless) mesh network and (b) immobile (infrastructure-based) mesh network.

web_c01f001

When we speak about MANETs, we think about mesh networking. A wireless* mesh network can be in general configured as a hierarchical network made up of home area network (HAN), Neighborhood Area Network (NAN), and wide area network (WAN), each utilizing the most suitable wireless technologies for their needs. For HAN, IEEE 802.11- and IEEE 802.15.4-based ZigBee (ZigBee Alliance, 2012) are thought of as most suitable. In the majority of cases, a single access point (AP) or ZigBee host is sufficient in the home scenario. If the source and destination nodes do not reside within the same NAN, the traffic from the various HANs is routed to one or more gateway nodes that backhaul the traffic utilizing high speed mobile data technologies, such as 3G, HSPA/HSPA+, LTE, LTE-A, or WiMax (3GPP Specifications, 2012; IEEE Wireless MAN [WiMax], 2012; WiMax Forum, 2012). The preferred solution to cover a wide area (resulting in a NAN), such as a neighborhood, a campus, or a city is to use IEEE 802.11x WLAN (aka WiFi) in mesh configuration. Figure 1.2 shows a generic wireless mesh network depicting the various scenarios. Figure 1.3 shows the use of lower frequency white spaces between the TV channels (which is at much lower frequencies than 2.4 GHz) in the ultra-high frequency (UHF) band (470–890 MHz) to create longer distance Internet connections that easily penetrate through the physical obstructions. These are still unlicensed and therefore their use is free and similar to WiFi and Bluetooth. This type of networking technology is called Super WiFi by the Federal Communications Commission (FCC) (Regulators, 2012; Segan, 2012). It should be noted that there is no similarity with the WiFi technology, and the use of Super WiFi is confusing and controversial with the Wi-Fi Alliance (WiFi, 2012; US regulators, 2012).

Figure 1.2. Use of long range WLAN (Super WiFi) mesh to extend coverage to larger areas.

web_c01f002

Figure 1.3. Use of long range WLAN (Super WiFi) mesh to extend coverage to larger areas.

web_c01f003

Traditionally, wireless network design is based on the centralized architecture where the base stations control the operation of the wireless services delivered to subscriber stations. In the conventional wireless cellular architecture, a base station is the centralized controller of each cell, as shown in Figure 1.4a. The base station transmits and receives data packets and signaling messages to and from subscriber stations through a one-hop direct wireless link. On the other hand, a multi-hop relay wireless paradigm has emerged in recent years. In multi-hop wireless relay networks, wireless nodes may transmit and forward packets through one or several wireless relay hops, as shown in Figure 1.4b. In this multi-hop relay network configuration, a distributed design approach may be applied to enable multi-hop relay signaling and data transport. A third wireless network paradigm integrates the previous two approaches as shown in Figure 1.4c. Both direct one-hop wireless connections and multi-hop wireless relays are present in this hybrid architecture. This hybrid wireless network architecture leverages the benefits of both the conventional cellular architecture and the multi-hop relay architecture to provide efficient centralized wireless network control and flexibility of multi-hop relaying.

Figure 1.4. Networking paradigms: (a) conventional wireless cellular network, (b) multi-hop wireless relay network, and (c) hybrid wireless network integrating cellular structure and multi-hop relay.

web_c01f004

As the hybrid architecture could take advantages of both the conventional centralized cellular architecture and the emerging relay architecture, there are several design benefits that could be exploited. Some of the key advantages of this hybrid wireless multi-hop relay architecture are as follows:

leveraged benefits of cellular architecture and multi-hop relay architecture

extended wireless network coverage at cell boundary

enhanced signal reception quality and throughput

improved load balancing

flexible deployment with fixed or mobile relay stations.

A still-growing trend is to spend large sums of money on the development of ad-hoc and multi-hop technologies. However, it is worth noting that these ideas are not quite new. The very first research on these topics was undertaken in the late 1960s. Then, ALOHA protocol was proposed to control the access to telecommunication channels. Although it considered only stationary nodes, communicating in a single-hop mode, it was the first step toward spontaneous and unrestricted networking. In 1973, DARPA initiated the PRnet (Packet Radio Network) project based on multi-hop transmission. This proposal clearly showed that using multi-hops may substantially extend the network range, improve efficiency (especially by division and parallel transmission of signal parts), and reduce energy consumption. Nowadays, MANETs are capable of multi-hop information routing even when the network topology and traffic are dynamically changing, while employing narrow and temporal channels. Several companies now offer global solutions, prime examples being Intel, CISCO, Mitsubishi, BMW, Nokia, and Deutsche Telecom. Despite technical, organizational, societal, and legislative issues (some of them discussed in this book), the global trend is clear. Using ordinary nodes as routers substantially improves network range and efficiency. Each device already connected to the network may in turn become an access point for other devices, even those not operating directly in mesh topology. The replacement of one-to-many access mode by many-to-many opens up new connection and transmission possibilities. Local instead of long-distance communication reduces network traffic and improves coding and noise/error reduction while also eliminating interference among devices and improving radio bandwidth sharing. Local communication also protects the environment—less power is needed to transmit the signals at a short distance. These advantages compensate the necessity to use own energy for serving other network nodes.

As in other modern technologies, the army was the first big client of mobile ad-hoc, multi-hop networking. A need for efficient local transmission among the soldiers at the battlefield seems to be the ideal case for testing networking mode needing no central and/or server node. Even if marked as top secret for obvious reasons, the technologies had to migrate, sooner or later, to the civilian world. Businessmen see themselves as business soldiers, and they have similar needs. And even ordinary users would welcome network efficiency and range. So why not adapt the army-related solutions to everybody? Linked with personal firewalls and ciphering (virtual private networking, VPN), ad-hoc and multi-hop access is a need in many situations at home and at work. In addition, the network operators may significantly improve customer satisfaction. The users themselves may also apply mesh networking to new application areas, including self-managed community networks outside the control of the network operators/administrators.

Problems and questions emanating due to the success of ad-hoc and multi-hop networking create their own challenges. This book is intended to address both the technologies of mesh and ad-hoc networking and quality of service issues. The book adopts the following approach. First, potential application areas of ad-hoc and multi-hop networking are discussed, with emphasis on privacy, security, anonymity, trust management, traffic filtering, information searching and addressing, quality of services, personalization, and other aspects. We try to enumerate the biggest potential application areas, including telematics, public transportation, telemedicine, environment protection, public safety, marketing and shopping guidance. Last but not least, in this part of the book, we discuss the most important economic aspects of multi-hop and ad-hoc networking, both from the point of view of the network provider/operator and the end user.

Second, we describe several technical aspects of multi-hop networking while limiting the scope to three key networking technologies: WiFi (IEEE 802.11*), WiMAX (IEEE 802.16*), and LTE. Starting from the introduction of network architecture and basic terminology, we move on to discuss some important technical details, such as routing and node addressing, MANET multi-hop extensions, such as WiFi mesh networking 802.11s, enhancements to physical and media access control (MAC) layers for 802.16j protocol, and recent proposals toward efficient LTE relaying.

The book is addressed to a wide audience, from students of computer science and related domains to engineers and system designers. The book introduces the emerging multi-hop relay wireless networking technology and its applications. An engineer, who works for a wireless network service provider, would benefit from the complete coverage of the wireless multi-hop mesh technologies.

The book not just covers technology aspects, it also addresses applications, as well as some important architectural issues, such as searching for information in local ad-hoc networks, extended addressability for both the network nodes and the information published via/by these nodes, anonymous and ad-hoc access, and so on. In addition, the book covers several integration issues, such as integration with backhaul connection, and WiFi and WiMAX multi-hop relay integration. Several deployment scenarios and applications are also illustrated. Engineers and technical managers could realize the deployment options and the trade-off between application scenarios and the technology to be chosen.

The book covers a wide range of system architecture and protocol design issues in WiFi, WiMAX, and LTE multi-hop mesh networks. Readers would get a head start in the latest WiMAX multi-hop relay networking technology and be ready for the future research in WiMAX-based multi-hop relay research and development (including IEEE 802.16j and the multi-hop relay extension for the next-generation IEEE 802.16m). Engineers would find the various system architecture design trade-offs useful. To research and develop the future mesh multi-hop relay technologies, researchers and engineers would benefit by the design considerations of various system protocol components, such as mobility management, multi-hop relay path management, location management, paging protocol design, network entry process, power efficient design, medium access control protocol design, service flow QoS management, system auto-configuration, and so on.

Note

* To simplify the description, we consider wireless connections only.

2 

Architectural Requirements for Multi-hop and Ad-Hoc Networking

In the introduction, we briefly discussed several aspects of ad-hoc and multi-hop networking. The discussion was mainly devoted to possible implementations of physical and logical connections in an ad-hoc network of devices. However, taking into account a wider point of view, there are many other important issues in ad-hoc networking. Let us assume a user is trying to get useful information from a network. Before anything else, there is one important task—that is, how to pick an access device. For example, a user may decide to use a smartphone, a tablet, or a notebook, and so on. However, in this book, we will not worry about the choice of a device, since there exists a wide spectrum of devices to choose from. Instead, we are going to concentrate on other ad-hoc user activities, mainly: ad-hoc authorization or authentication mechanism, including a trade-off between the anonymity and the security, ad-hoc searching for an information/service, including fuzzy queries, and ad-hoc choosing and accessing the just-found information/service.

In the remainder of this chapter, we are going to discuss these topics after a general discussion on the needs and expectations, on the one hand, and possible restrictions and limitations, on the other hand, of ad-hoc and multi-hop networking.

2.1. WHEN AND WHERE DO WE NEED AD-HOC NETWORKING?

Let us leave aside networking for a while and raise a more general question—when and where do we need ad-hoc activities? At home? Probably not—everyday activities are usually quite stable and repeatable. At work? For most jobs, probably not, because the work environment is pretty well provided. Aside from the earlier examples, we all have to travel everyday between home and work. We have to do incidental and weekly shopping. We have to visit local administration offices from time to time, we go places on holidays, and many more. Most of these activities are usually performed in an ad-hoc manner. While traveling, we also interact with other drivers, pedestrians, and road infrastructure. What is common with all these activities? First of all, we use our senses, for example, sight, smell, and hearing. And we do it only locally, as our senses work only in a local environment. Second, usually, we do not have enough information how to proceed further, and we are continuously looking for more hints and instructions. Third, usually, we are overloaded with nonessential information that must be filtered out to achieve better results on what matters most.

Now, going back to networking, at home and work, we usually have access to a stable network connection, with classical login, user names, passwords, and so on, so ad-hoc networking is not a necessity. And what about the rest of our activities? It looks like there is a place for ad-hoc networking. After all, ad-hoc networking is a natural extension of ad-hoc activities mentioned earlier. For example, we would like to use our smartphone to take a look into a part of a road in front of us to discover the reason for a traffic jam ahead of us. Naturally, we use our sight; however, if it is too far and we are not able to leave our car, we would like to ask someone who is better informed, for example, a driver at the very beginning of the traffic jam. So, why not to ask this driver for a photo to be sent via a local (ad-hoc) network to our smartphone? Why not ask him by a Skype call? However, we neither know the phone number nor an IP address of this driver’s device. So, we are forced to establish an ad-hoc connection with the drivers in a local neighborhood to reach the driver of interest, hoping some of them are better informed. Thus, there is certainly a place for ad-hoc and multi-hop networking.

Let us now try to answer the question raised in the title of this section: when do we apply ad-hoc networking? The answer is simple—for all our everyday ad-hoc activities, as much as we can: traveling, shopping, meeting with incidental people, reacting in impromptu situations, and so on. The second question is: where? The answer is similar—everywhere we usually perform our ad-hoc activities. And even at home and at the workplace, we can apply ad-hoc networking. For example, the smart buildings can provide sophisticated infrastructure to improve the way of interaction with humans. Ad-hoc networking may be used for dynamic adjustment of human possibilities, especially for incidental users—imagine a person being guided to an office via a personal handheld device, without having to ask anyone. Or simply imagine that you use your mobile as a TV pilot, working with all kinds of TV sets irrespective of where you are. Also, at work, especially in dynamic environments, for example, a hospital, ad-hoc networking may substantially improve access to the information. Where am I? Where is the nearest doctor