Deployment of a Wireless Mesh Network for Traffic Control

Wireless mesh networks (WMN) have attracted considerable interest in recent years as a convenient, new technology. However, the suitability of WMN for mission-critical infrastructure applications remains by and large unknown, as protocols typically employed in WMN are, for the most part, not designed for real-time communications. In this chapter, the authors describe a wireless mesh network architecture to solve the communication needs of the traffic control system in Sydney. This system, known as SCATS and used in over 100 cities around the world — from individual traffic light controllers to regional computers and the central TMC —places stringent requirements on the reliability and latency of the data exchanges. The authors discuss experience in the deployment of an initial testbed consisting of 7 mesh nodes placed at intersections with traffic lights, and share the results and insights learned from measurements and initial trials in the process.

CORM

Designing future computer networks dictates an eclectic vision capable of encompassing ideas and concepts developed in contemporary research unfettered by today’s operational and technological constraints. However, unguided by a clear articulation of core design principles, the process of network design may be at stake of falling into similar pitfalls and limitations attributed to current network realizations. This chapter presents CORM: a clean-slate Concern-Oriented Reference Model for architecting future computer networks. CORM stands as a guiding framework from which several network architectures can be derived. CORM represents a pioneering attempt within the network realm, and to the author’s knowledge, CORM is the first reference model that is bio-inspired, accounts for complex system characteristics, and applies a software engineering approach to network design. Moreover, CORM’s derivation process conforms to the Function-Behavior-Structure (FBS) engineering framework, which is credited to be applicable to any engineering discipline for reasoning about, and explaining the process of design.

Precoding for Multiuser MIMO

Future Wireless Networks are expected to adopt multi-user multiple input multiple output (MU-MIMO) systems whose performance is maximized by making use of precoding at the transmitter. This chapter describes the recent advances in precoding design for MU-MIMO and introduces a new technique to improve the precoder performance. Without claiming to be comprehensive, the chapter gives deep introduction on basic MIMO techniques covering the basics of single user multiple input multiple output (SU-MIMO) links, its capacity, various transmission strategies, SU-MIMO link precoding, and MIMO receiver structures. After the introduction, MU-MIMO system model is defined and maximum achievable rate regions for both MU-MIMO broadcast and MU-MIMO multiple access channels are explained. It is followed by critical literature review on linear precoding design for MU-MIMO broadcast channel. This paves the way for introducing an improved technique of precoding design that is followed by its performance evaluation.

Spectrum Sensing and Throughput Analysis for Cognitive Radio An Overview

Cognitive radio (CR) is a new technology introduced to deal with the issues of spectrum scarcity and underutilization. Since the spectrum is limited, the unlicensed secondary users (CR users) opportunistically access the underutilized spectrum allocated to the licensed primary users (PUs) of the network. This chapter first gives a brief overview on spectrum sensing and its impact on the system throughput in a cognitive radio network. Later, cooperative relays are introduced in the network to improve spectrum efficiency and mitigate interference to PU. A detailed analysis of power allocation is demonstrated where the transmit power of CR is kept within such limit so that it can maintain low interference to PU. This optimal power allocation can achieve high throughput, which is also presented in this chapter.

MAC and PHY-Layer Network Coding for Applications in Wireless Communications Networks

Network coding (NC) is a promising technique recently proposed to improve network performance in terms of maximum throughput, minimum delivery delay, and energy consumption. The original proposal highlighted the advantages of NC for multicast communications in wire-line networks. Recently, network coding has been considered as an efficient approach to improve performance in wireless networks, mainly in terms of data reliability and lower energy consumption, especially for broadcast communications. The basic idea of NC is to remove the typical requirement that different information flows have to be processed and transmitted independently through the network. When NC is applied, intermediate nodes in the network do not simply relay the received packets, but they combine several received packets before transmission. As a consequence, the output flow at a given node is obtained as a linear combination of its input flows. This chapter deals with the application of network coding principle at different communications layers of the protocol stack, specifically, the Medium Access Control (MAC) and physical (PHY) Layers for wireless communication networks.

Secure Communications over Wireless Networks

Nakagami-m fading channel is chosen to analyze the secrecy capacity for fading channels since the Nakagami-m distribution can model fading conditions, which are more or less severe than that of Rayleigh and has the advantage of including Rayleigh as a special case. At first, secrecy capacity is defined in case of full channel state information (CSI) at the transmitter, where transmitter has access to both the main channel and eavesdropper channel gains. Secondly, secrecy capacity is defined with only main channel CSI at the transmitter. Then, optimal power allocation at the transmitter that achieves the secrecy capacity is derived for both the cases. Moreover, secrecy capacity is defined under open-loop transmission scheme, and the exact closed form analytical expression for the lower bound of ergodic secrecy capacity is derived for Nakagami-m fading single-input multiple-output (SIMO) channel. In addition, secrecy capacity is defined for the AWGN channel in order to realize the information-theoretic security of wireless channels with no fading. Finally, analytical expressions for the probability of non-zero secrecy capacity and secure outage probability are derived in order to investigate the secure outage performance of fading channels.

Introduction to Wireless Networks

Wireless networks offer mobility and elimination of unsightly cables and utilize radio waves or microwaves to maintain communication. It is rapidly growing in popularity for both home and business networking. Wireless technology keeps on improving and at the same time the cost of wireless products are continuously decreasing. The demand for ubiquitous personal communications is driving the development of wireless networks that can accommodate mobile voice and data users who move throughout buildings, cities, or countries. The objective of this chapter is to provide the fundamentals of wireless networks so that the general readers can be able to easily grasp some of the ideas in this area.

Creating Realistic Vehicular Network Simulations

A key component for Vehicular Ad-Hoc Network (VANET) simulations is a realistic vehicular mobility model, as this ensures that the conclusions drawn from simulation experiments will carry through to the real deployments. Node mobility in a vehicular network is strongly affected by the driving behavior such as route choices. While route choice models have been extensively studied in the transportation community, the effects of preferred route and destination on vehicular network simulations have not been discussed much in the networking literature. In this chapter, the authors describe the effect of route choices on vehicular network simulation. They also discuss how different destination selection models affect two practical ITS application scenarios: traffic monitoring and event broadcasting. The chapter concludes that selecting a sufficient level of detail in the simulations, such as modeling of route choices, is critical for evaluating VANET protocol design.

Adaptation of Algebraic Space Time Codes to Frequency Selective Channel

The Algebraic Space Time Codes (ASTC) are constructed based on cyclic algebras; they showed a good spectral efficiency, a full diversity, and a full rate under non selective channel condition. However, the radio - mobile channel is a selective channel whose features vary during the time. This selectivity is owed to the multi-path phenomenon and generates interferences between symbols (IES). The overall objective of this chapter is to proof that ASTC is adapted to channel selectivity, in order to analyze and improve its performances in wide-band system.

Spectrum Access and Sharing for Cognitive Radio

Cognitive radio (CR) has emerged as a smart solution to spectrum bottleneck faced by current wireless services, under which licensed spectrum is made available to intelligent and reconfigurable secondary users. CR technology enables these unlicensed secondary users to exploit any spectrum usage opportunity by adapting their transmission parameters on the run. In this chapter, the authors discuss the characteristic features and main functionality of CR oriented technology. Central to this chapter is Spectrum sensing (SS), which has been identified as a fundamental enabling technology for next generation wireless networks based on CR. The authors compare different SS techniques in terms of their sensing accuracy and implementation and computational complexities along with merits and demerits of these approaches. Various challenges facing SS have been investigated, and possible solutions are proposed.