Noise based transmitted reference modulation for wireless sensor networks

Recent advances in the underlying technologies of wireless sensor networks (WSNs) have led to its use in different applications, from fields as diverse as battlefield applications to temperature control to healthcare. Research in the different aspects of WSNs is therefore in full swing, in both academia and the industry. In the Wireless Ad-hoc Links using robust Noise-based Ultra-wideband Transmission (WALNUT) project, modulation concepts (and relevant MAC protocols) are intended to be explored which allow for robust ad-hoc radio links with radio nodes implemented on a single CMOS chip

Design of Ad Hoc Wireless Mesh Networks Formed by Unmanned Aerial Vehicles with Advanced Mechanical Automation

Ad hoc wireless mesh networks formed by unmanned aerial vehicles (UAVs) equipped with wireless transceivers (access points (APs)) are increasingly being touted as being able to provide a flexible "on-the-fly" communications infrastructure that can collect and transmit sensor data from sensors in remote, wilderness, or disaster-hit areas. Recent advances in the mechanical automation of UAVs have resulted in separable APs and replaceable batteries that can be carried by UAVs and placed at arbitrary locations in the field. These advanced mechanized UAV mesh networks pose interesting questions in terms of the design of the network architecture and the optimal UAV scheduling algorithms. This paper studies a range of network architectures that depend on the mechanized automation (AP separation and battery replacement) capabilities of UAVs and proposes heuristic UAV scheduling algorithms for each network architecture, which are benchmarked against optimal designs.Comment: 12 page

Consistency Management Among Replicas in Peer-to-Peer Mobile Ad Hoc Networks

Recent advances in wireless communication along with peer-to-peer (P2P) paradigm have led to increasing interest in P2P mobile ad hoc networks. In this paper, we assume an environment where each mobile peer accesses data items held by other peers which are connected by a mobile ad hoc network. Since peers\u27 mobility causes frequent network partitions, replicas of a data item may be inconsistent due to write operations performed by mobile peers. In such an environment, the global consistency of data items is not desirable by many applications. Thus, new consistency maintenance based on local conditions such as location and time need to be investigated. This paper attempts to classify different consistency levels according to requirements from applications and provides protocols to realize them. We report simulation results to investigate the characteristics of these consistency protocols in a P2P wireless ad hoc network environment and their relationship with the quorum sizes

Performance analysis of variable Smart Grid traffic over ad hoc Wireless Mesh Networks

Recent advances in ad hoc Wireless Mesh Networks (WMN) has posited it as a strong candidate in Smart Grid's Neighbourhood Area Network (NAN) for Advanced Metering Infrastructure (AMI). However, its abysmal capacity and poor multi-hoping performance in harsh dynamic environment will require an improvement to its protocol stacks in order for it to effectively support the variable requirements of application traffic in Smart Grid. This paper presents a classification of Smart Grid traffics and examines the performance of HWMP (which is the default routing protocol of the IEEE 802.11s standard) with the Optimised Link State Routing (OLSR) protocol in a NAN based ad hoc WMN. Results from simulations in ns-3 show that HWMP does not outperform OLSR. This indicates that cross layer modifications can be developed in OLSR protocol to address the routing challenges in a NAN based ad hoc WMN

Multicast outing protocols and architectures in mobile ad-hoc wireless networks

The basic philosophy of personal communication services is to provide user-to-user, location independent communication services. The emerging group communication wireless applications, such as multipoint data dissemination and multiparty conferencing tools have made the design and development of efficient multicast techniques in mobile ad-hoc networking environments a necessity and not just a desire. Multicast protocols in mobile adhoc networks have been an area of active research for the past few years. In this dissertation, protocols and architectures for supporting multicast services are proposed, analyzed and evaluated in mobile ad-hoc wireless networks. In the first chapter, the activities and recent advances are summarized in this work-in-progress area by identifying the main issues and challenges that multicast protocols are facing in mobile ad-hoc networking environments and by surveying several existing multicasting protocols. a classification of the current multicast protocols is presented, the functionality of the individual existing protocols is discussed, and a qualitative comparison of their characteristics is provided according to several distinct features and performance parameters. In the second chapter, a novel mobility-based clustering strategy that facilitates the support of multicast routing and mobility management is presented in mobile ad-hoc networks. In the proposed structure, mobile nodes are organized into nonoverlapping clusters which have adaptive variable-sizes according to their respective mobility. The mobility-based clustering (MBC) approach which is proposed uses combination of both physical and logical partitions of the network (i.e. geographic proximity and functional relation between nodes, such as mobility pattern etc.). In the third chapter, an entropy-based modeling framework for supporting and evaluating the stability is proposed in mobile ad-hoc wireless networks. The basic motivations of the proposed modeling approach stem from the commonality observed in the location uncertainty in mobile ad-hoc wireless networks and the concept of entropy. In the fourth chapter, a Mobility-based Hybrid Multicast Routing (MHMR) protocol suitable for mobile ad-hoc networks is proposed. The MHMR uses the MBC algorithm as the underlying structure. The main features that the proposed protocol introduces are the following: a) mobility based clustering and group based hierarchical structure, in order to effectively support the stability and scalability, b) group based (limited) mesh structure and forwarding tree concepts, in order to support the robustness of the mesh topologies which provides limited redundancy and the efficiency of tree forwarding simultaneously, and c) combination of proactive and reactive concepts which provide the low route acquisition delay of proactive techniques and the low overhead of reactive methods. In the fifth chapter, an architecture for supporting geomulticast services with high message delivery accuracy is presented in mobile ad-hoc wireless networks. Geomulticast is a specialized location-dependent multicasting technique, where messages are multicast to some specific user groups within a specific zone. An analytical framework which is used to evaluate the various geomulticast architectures and protocols is also developed and presented. The last chapter concludes the dissertation

Price-Based Optimal Resource Allocation in Multi-Hop Wireless Networks

Recent advances in wireless communications and digital electronics have enabled rapid development of a variety of wireless network technologies. The undeniable popularity of wireless network is due to its ubiquity and convenience, which is appreciated by the users. In this dissertation, we study the problem of resource allocation in multihop wireless networks (so called ad hoc networks). A wireless ad hoc network consists of a collection of wireless nodes without a fixed infrastructure. Two wireless nodes communicate with each other directly, if they are within the transmission range of each other. Otherwise, the communication is achieved through the relays of intermediate nodes. Compared with traditional wireline networks, the unique characteristics of wireless networks pose fundamental challenges to the design of effective resource allocation algorithms that are optimal with respect to resource utilization and fair across different network flows. Particularly, the following issues of wireless networks need fresh treatment: (1) Interference of wireless communication. Flows not only contend at the same node (contention in the time domain), but also compete for shared channel if they are within the interference ranges of each other (contention in the spatial domain). (2) Multiple resource usage. Sending data from one wireless node to another needs to consume multiple resources, most notably wireless bandwidth and battery energy. (3) Autonomous communication entities. The wireless nodes usually belong to different autonomous entities. They may lack the incentive to contribute to the network functionality in a cooperative way. (4) Rate diversity. Wireless nodes can adaptively change the transmission bit rate based on perceived channel conditions. This leads to a wireless network with rate diversity, where competing flows within the interference range transmit at different rates. None of the existing resource allocation algorithms in wireless ad hoc networks have realistically considered end-to-end flows spanning multiple hops. Moreover, strategies proposed for wireline networks are not applicable in the context of wireless ad hoc network, due to its unique characteristics. In this dissertation, we propose a new price-based resource allocation framework in wireless ad hoc networks to achieve optimal resource utilization and fairness among competing end-to-end flows. We build our pricing framework on the notion of maximal cliques in wireless ad hoc networks, as compared to individual links in traditional wide-area wireline networks. Based on such a price-based theoretical framework, we present a two-tier iterative algorithm. Distributed across wireless nodes, the algorithm converges to a global network optimum with respect to resource allocations. Further, we present a price pair mechanism to coordinate multiple resource allocations, and to provide incentives simultaneously such that cooperation is promoted and the desired global optimal network operating point is reached by convergence with a fully decentralized self-optimizing algorithm. Such desired network-wide global optimum is characterized with the concept of Nash bargaining solution, which not only provides the Pareto optimal point for the network, but is also consistent with the fairness axioms of game theory. Finally, we present a channel aware price generation scheme to decompose the bit rate adjustment and the flow rate allocation. The allocation result achieves channel time fairness where user fairness and channel utilization is balanced. The major achievements of this dissertation are outlined as follows. It models a system-wide optimal operation point of a wireless network, and outlines the solution space of resource allocation in a multihop wireless network; It presents a price-based distributed resource allocation algorithm to achieve this global optimal point; It presents a low overhead implementation of the price-based resource allocation algorithm; It presents an incentive mechanism that enables the resource allocation algorithm when users are selfish

A service-oriented middleware for composing context aware mobile services

Recent advances in wireless networks and mobile devices have brought about new scenes for the provision of services to end-users. Besides traditional services, new ones may be provided that transparently adjust and adapt to the user context. The user would have more choice and flexibility if, besides using the services, he could also compose his own services in an ad-hoc way. This paper presents iCas, an architecture to create context-aware services on the fly and discusses its main components. Also an application scenario is briefly described

On Improving the Robustness of Partitionable Internet-Based Mobile Ad Hoc Networks

Recent technological advances in portability, mobility support, and high speed wireless communications and users' insatiable interest in accessing the Internet have fueled to development of mobile wireless networks. Internet-based mobile ad hoc network (IMANET) is emerging as a ubiquitous communication infrastructure that combines a mobile ad hoc network (MANET) and the Internet to provide universal information accessibility. However, communication performance may be seriously degraded by network partitions resulted from frequent changes of the network topology. In this paper, we propose an enhanced least recently used replacement policy as a part of the aggregate cache mechanism to improve the information accessibility and reduce the access latency in the presence of network partitioning. The enhanced aggregate cache is analyzed and also evaluated by simulation. Extensive simulation experiments are conducted under various network topologies by using three different mobility models: random waypoint, Manhattan grid, and mo -di -fied random waypoint. The simulation results indicate that the proposed policy significantly improves communication performance in varying network topologies, and relieves the network partition problem to a great extent

Network-Layer Resource Allocation for Wireless Ad Hoc Networks

This thesis contributes toward the design of a quality-of-service (QoS) aware network layer for wireless ad hoc networks. With the lack of an infrastructure in ad hoc networks, the role of the network layer is not only to perform multihop routing between a source node and a destination node, but also to establish an end-to-end connection between communicating peers that satisfies the service level requirements of multimedia applications running on those peers. Wireless ad hoc networks represent autonomous distributed systems that are infrastructure-less, fully distributed, and multi-hop in nature. Over the last few years, wireless ad hoc networks have attracted significant attention from researchers. This has been fueled by recent technological advances in the development of multifunction and low-cost wireless communication gadgets. Wireless ad hoc networks have diverse applications spanning several domains, including military, commercial, medical, and home networks. Projections indicate that these self-organizing wireless ad hoc networks will eventually become the dominant form of the architecture of telecommunications networks in the near future. Recently, due to increasing popularity of multimedia applications, QoS support in wireless ad hoc networks has become an important yet challenging objective. The challenge lies in the need to support the heterogeneous QoS requirements (e.g., data rate, packet loss probability, and delay constraints) for multimedia applications and, at the same time, to achieve efficient radio resource utilization, taking into account user mobility and dynamics of multimedia traffic. In terms of research contributions, we first present a position-based QoS routing framework for wireless ad-hoc networks. The scheme provides QoS guarantee in terms of packet loss ratio and average end-to-end delay (or throughput) to ad hoc networks loaded with constant rate traffic. Via cross-layer design, we apply call admission control and temporary bandwidth reservation on discovered routes, taking into consideration the physical layer multi-rate capability and the medium access control (MAC) interactions such as simultaneous transmission and self interference from route members. Next, we address the network-layer resource allocation where a single-hop ad hoc network is loaded with random traffic. As a starting point, we study the behavior of the service process of the widely deployed IEEE 802.11 DCF MAC when the network is under different traffic load conditions. Our study investigates the near-memoryless behavior of the service time for IEEE 802.11 saturated single-hop ad hoc networks. We show that the number of packets successfully transmitted by any node over a time interval follows a general distribution, which is close to a Poisson distribution with an upper bounded distribution distance. We also show that the service time distribution can be approximated by the geometric distribution and illustrate that a simplified queuing system can be used efficiently as a resource allocation tool for single hop IEEE 802.11 ad hoc networks near saturation. After that, we shift our focus to providing probabilistic packet delay guarantee to multimedia users in non-saturated IEEE 802.11 single hop ad hoc networks. We propose a novel stochastic link-layer channel model to characterize the variations of the IEEE 802.11 channel service process. We use the model to calculate the effective capacity of the IEEE 802.11 channel. The channel effective capacity concept is the dual of the effective bandwidth theory. Our approach offers a tool for distributed statistical resource allocation in single hop ad hoc networks, which combines both efficient resource utilization and QoS provisioning to a certain probabilistic limit. Finally, we propose a statistical QoS routing scheme for multihop IEEE 802.11 ad hoc networks. Unlike most of QoS routing schemes in literature, the proposed scheme provides stochastic end-to-end delay guarantee, instead of average delay guarantee, to delay-sensitive bursty traffic sources. Via a cross-layer design approach, the scheme selects the routes based on a geographical on-demand ad hoc routing protocol and checks the availability of network resources by using traffic source and link-layer channel models, incorporating the IEEE 802.11 characteristics and interaction. Our scheme extends the well developed effective bandwidth theory and its dual effective capacity concept to multihop IEEE 802.11 ad hoc networks in order to achieve an efficient utilization of the shared radio channel while satisfying the end-to-end delay bound