Traffic Prioritization in Sensor Networks using Bandwidth Scavenging

This chapter presents a history-based statistical channel access mechanism for enabling traffic prioritization in wireless sensor networks. Prioritized access is realized such that low priority non-real-time sensors can access channel bandwidth that is unused by high priority real-time traffic. The key idea is for the low priority sensor nodes to first observe and statistically model the channel usage pattern by the high priority traffic, then make advantageous probabilistic transmissions so that the non-priority traffic throughput is maximized while protecting the high-priority traffic from disruptions. The chapter details a practical whitespace measurement scheme and presents a channel history based prioritization protocol. The access mechanism is implemented in a TelosB mote-based sensor testbed in which the non-priority motes continually measure the RSSI to infer the channel usage pattern and probabilistically access the channel while different types of traffic are sent by high-priority TelosB motes.

Multimedia Broadcasting in LTE Networks

Long Term Evolution (LTE) constitutes the latest step before the 4th generation (4G) of radio technologies designed to increase the capacity and speed of mobile communications. To support Multimedia Broadcast/Multicast Services (MBMS), LTE offers the functionality to transmit MBMS over Single Frequency Network (MBSFN), where a time-synchronized common waveform is transmitted from multiple cells for a given duration. In MBSFN transmissions, the achieved Spectral Efficiency (SE) is mainly determined by the Modulation and Coding Scheme (MCS) selected. This study proposes and evaluates four approaches for the selection of the MCS that will be utilized for the transmission of the MBSFN data. The evaluation of the approaches is performed for different users’ distribution and from a SE perspective. Based on the SE measurement, the approach that either maximizes or achieves a target SE for the corresponding users’ distribution is determined.

Adaptive Scheduling for TCP-Fairness in Wireless Broadband Networks

The exponential growth in multimedia traffic (Cisco Visual Networking Index, 2010), predominantly on UDP transport, poses a threat to the TCP’s best effort throughput. This problem is more acute in last mile broadband wireless access networks (Bakshi, Krishna, Vaidya, & Pradhan, 1997). Most scheduling algorithms discuss improving the combined TCP and UDP throughput or improving the TCP throughput without studying the effects of inelastic traffic such as UDP. This chapter furthers the necessity for TCP throughput protection and proposes a novel dynamically adapting Weighted Fair Queue (WFQ) based scheduling mechanism that provides a higher degree of TCP protection. This is accomplished by differentiating between TCP and UDP flows, buffer provisioning for each flow, and prioritizing TCP ACK packets. The simulation results show that the proposed mechanism yields a relative improvement of up to 29% of TCP goodput and 7.5% of aggregate MAC throughput over the mechanism without the proposed improvements.

Mobility Challenges and Management in the Future Wireless Heterogeneous Networks

The organization of this chapter is as follows: It begins by analyzing the mobility challenges under the multi-accessing wireless heterogeneous environments. Next the chapter gives a brief introduction of the mobility management. Afterwards it introduces the state-of-art of the mobility management solutions and describes the respective approaches and compares their advantages and disadvantages. The last section concludes this chapter.

Adaptive Coexistence between Cognitive and Fiber Networks

Cognitive radios are proposed as secondary users of spectrum to provision for the growth in mobile users and services. However, the dynamic changes in the wireless environment and spectrum availability are blocking the success of online communications for future cognitive mesh networks. As a solution, Cognitive Radio over Fibre (CRoF) subnet is developed through combining selected Base Stations (BSs) with the radio over fibre network. These CRoF-BSs attract the neighborhood cognitive BSs to send data through fibre whenever they are unable to formulate their own wireless links. This leads to the network splitting into many zones of services in which cognitive BSs are controlled by CRoF-BS zones. Therefore, a new paradigm for local resource sharing emerges through these architectural network modifications. In this chapter, the multi-zone structure is analyzed in order to formulate the rules of adaptation between the CRoF zones and the traditional cognitive networks.

Towards Carrier-Grade Quality in Heterogeneous Wireless Mesh Networks

Current backhaul networks typically comprise a wired middle mile and a wireless last mile part. The wireless part is almost exclusively based on tree topologies. However, a lot could be gained by deploying mesh-based backhauls. Meshes allow better network capacity exploitation due to load balancing and offer inherent resilience to link degradations or failures. Yet meshes come with increased complexity in terms of radio configuration, routing, or mobility management. This chapter proposes architecture and mechanisms for carrier-grade mesh-based wireless backhauls. One special focus is that it supports heterogeneous backhauls, which encompass multiple different wireless technologies. The proposition has been successfully deployed in a test network.1

Multi-Access Communications in Wireless Mesh Networks by Virtualization

This chapter presents an architecture for context-aware Virtual Networks (VNs) that provides user-driven multi-access communication. The architecture is dedicated and appropriate for the flexibility provided by Wireless Mesh Networks. According to this architecture, VNs with different context characteristics such as Quality of Service (QoS), mobility, and security are built to support communications with different characteristics that best fit the users’ needs. The architecture is modeled both through a probabilistic and an optimization approach to provide quantitative insights into its performance. The probabilistic model quantifies the overhead on the architecture in terms of networking delays induced due to the VN management (searching, creation, and management). The optimization model provides insights into the competition of the VNs for the limited bandwidth resources. Indicative results of the models show the feasibility of the architecture, the upper bounds in terms of number of supported VNs to achieve good quality communications, and the relative placement of the flows in different, competing VNs.

Multi-Access Environments in Next Generation Networks

Wireless heterogeneous environment is becoming increasingly popular because of its ability to support multi access technologies, which keeps the mobile users always connected. The fourth generation (4G) of wireless environment consists of dissimilar technologies like Worldwide Interoperability for Microwave Access (WiMAX) and Long Term Evolution-Advanced (LTE-A). Coexistence of these standards presents technological challenges. Other challenges towards heterogenous 4G environment include coexistence of third generation (3G) and 4G and coexistence of Wireless Local Area Network (WLAN) and 3G/4G technologies. This chapter presents the technical overview of the 4G (WiMAX and LTE-A) standards and identifies the challenges and research issues (i.e., mobility management, network selection, handover, and Quality of Service [QoS]) toward a multi-access environment that consists of 3G, 4G, and WLAN technologies. The chapter also discusses future directions and some research solutions.

Heterogeneous Meshed Wireless Back-Haul Network Integrating Unidirectional Technologies

Wireless Mesh Networks (WMNs) have matured in recent years and the visibility of WMN deployments has attracted commercial operators to investigate this technology for applicability in their networks. Having their roots in the Mobile Adhoc Network (MANET) world and rather cheap off-the-shelf single-radio WLAN routers, WMN routing protocols were not designed for applicability in carrier-grade back-haul networks. For example, protocols such as OLSR or B.A.T.M.A.N. can not address the QoS-requirements of a modern operator back-haul network with its increasing demand for triple-play content. Although numerous solutions have been proposed to introduce QoS-awareness at the protocol or the technology level, traditional WMNs fail to meet commercial operator requirements in terms of reliability, traffic engineering and QoS guarantees. This chapter proposes a novel approach combining an IEEE 802.21-based control plane and an MPLS-based data plane. To provide support for ubiquitous high-bandwidth multi-media services, it seamlessly integrates unidirectional broadcast technologies such as DVB into the heterogeneous multi-radio WiBACK architecture.

Multiple Attributes Decision Making Algorithms for Vertical Handover in Heterogeneous Wireless Networks

The envisioned heterogeneous wireless systems are expected to integrate multiple access networks over a common IP platform. In such systems, since mobile users expect to achieve the Always Best Connected (ABC) experience, heterogeneous systems have to support the vertical handover of users among different access networks. On the other hand, the field of Multiple Attribute Decision Making (MADM) has proved to be a suitable tool to study the vertical handover process. This chapter presents a survey of MADM algorithms that have been proposed for vertical handover. First, the authors describe the procedures of methods such as SAW, MEW, TOPSIS, ELECTRE, and VIKOR. Then, the chapter compares them by mean of simulations and performance analysis for an heterogeneous system integrated by WLAN, UMTS, and WiMAX networks, when users conduct different applications. The chapter concludes with a summary of open issues and future research directions in the area of vertical handover.