Showing papers in "IEEE Wireless Communications in 2009"

A survey on vehicle-to-vehicle propagation channels

Abstract: Traffic telematics applications are currently under intense research and development for making transportation safer, more efficient, and more environmentally friendly. Reliable traffic telematics applications and services require vehicle-to-vehicle wireless communications that can provide robust connectivity, typically at data rates between 1 and 10 Mb/s. The development of such VTV communications systems and standards require, in turn, accurate models for the VTV propagation channel. A key characteristic of VTV channels is their temporal variability and inherent non-stationarity, which has major impact on data packet transmission reliability and latency. This article provides an overview of existing VTV channel measurement campaigns in a variety of important environments, and the channel characteristics (such as delay spreads and Doppler spreads) therein. We also describe the most commonly used channel modeling approaches for VTV channels: statistical as well as geometry-based channel models have been developed based on measurements and intuitive insights. Extensive references are provided.

OFDM for cognitive radio: merits and challenges

Abstract: Cognitive radio is a novel concept that enables wireless systems to sense the environment, adapt, and learn from previous experience to improve the quality of the communication. However, CR requires a flexible and adaptive physical layer in order to perform the required tasks efficiently. In this article, CR systems and their requirement of a physical layer are discussed, and the orthogonal frequency division multiplexing technique is investigated as a candidate transmission technology for CR. The challenges that arise from employing OFDM in CR systems are identified. The cognitive properties of some OFDM-based wireless standards also are discussed to indicate the trend toward a more cognitive radio.

Wake-up receivers for wireless sensor networks: benefits and challenges

Abstract: For successful data delivery, the destination nodes should be listening to the medium to receive data when the sender node starts data communication. To achieve this synchronization, there are different rendezvous schemes, among which the most energy-efficient is utilizing wakeup receivers. Current hardware technologies of wake-up receivers enable us to evaluate them as a promising solution for wireless sensor networks. In this article the benefits achieved with wake-up receivers are investigated along with the challenges observed. In addition, an overview of state-of-the-art hardware and networking protocol proposals is presented. As wake-up receivers offer new opportunities, new potential application areas are also presented and discussed.

Using mobile robots to harvest data from sensor fields

Abstract: We explore synergies among mobile robots and wireless sensor networks in environmental monitoring through a system in which robotic data mules collect measurements gathered by sensing nodes. A proof-of-concept implementation demonstrates that this approach significantly increases the lifetime of the system by conserving energy that the sensing nodes otherwise would use for communication.

Challenging issues in visual sensor networks

Abstract: Wireless sensor networks are an important research area that has attracted considerable attention. Most of this attention, however, has been concentrated on WSNs that collect scalar data such as temperature and vibration. Scalar data can be insufficient for many applications such as automated surveillance and traffic monitoring. In contrast, camera sensors collect visual data, which are rich in information and hence offer tremendous potential when used in WSNs. However, they raise new challenges such as the transmission of visual data with high computational and bandwidth requirements in mainly low-power visual sensor networks. In this article we highlight the challenges and opportunities of VSNs. We discuss major research issues of VSNs, specifically camera coverage optimization, network architecture, and low-power visual data processing and communication, and identify enabling approaches in this area.

Dynamic spectrum access in IEEE 802.22- based cognitive wireless networks: a game theoretic model for competitive spectrum bidding and pricing

Abstract: The emerging IEEE 802.22-based wireless regional area network technology will use the same radio spectrum currently allocated for TV service. This standard will use the concept of cognitive radio based on dynamic spectrum access to provide wireless access services in a large coverage area. A brief overview of the current state of the IEEE 802.22 standard is provided with a particular emphasis on the spectrum management (i.e., spectrum sensing and dynamic spectrum access) in this standard. Key research issues related to spectrum trading among TV broadcasters, WRAN service providers, and IEEE 802.22-based cognitive radio users are identified. To this end, a hierarchical spectrum trading model is presented to analyze the interaction among WRAN service providers, TV broadcasters, and WRAN users. In this model a double auction is established among multiple TV broadcasters and WRAN service providers who sell and buy the radio spectrum (i.e., TV bands), respectively. Again, multiple WRAN service providers compete with each other by adjusting the service price charged to WRAN users. We propose a joint spectrum bidding and service pricing model for WRAN service providers to maximize their profits. A non-cooperative game is formulated to obtain the solution in terms of the number of TV bands and the service price of a service provider. Numerical results are presented on the performance of this joint spectrum bidding and pricing model.

Security in service-oriented vehicular networks

Abstract: Service-oriented vehicular networks support diverse infrastructure-based commercial services including Internet access, real-time traffic concerns, video streaming, and content distribution. The success of service delivery in vehicular networks depends on the underlying communication system to enable the user devices to connect to a large number of communicating peers and even to the Internet. This poses many new research challenges, especially in the aspects of security, user privacy, and billing. In this article we first identify the key requirements of authentication, privacy preservation, and billing for service delivery in vehicular networks. We then review the existing industrial and academic efforts on service- oriented vehicular networks. We also point out two security challenges, minimizing vehicleto- infrastructure authentication latency and distributed public key revocation, which are considered among the most challenging design objectives in service-oriented vehicular networks. A novel fast vehicle-to-infrastructure authentication based on a vehicle mobility prediction scheme and an infrastructure-based short-time certificate management scheme are then proposed to address these two challenges.

Cognitive radio for next-generation wireless networks: an approach to opportunistic channel selection in ieee 802.11-based wireless mesh

Abstract: 'Cognitive radio' has emerged as a new design paradigm for next-generation wireless networks that aims to increase utilization of the scarce radio spectrum (both licensed and unlicensed). Learning and adaptation are two significant features of a cognitive radio transceiver. Intelligent algorithms are used to learn the surrounding environment, and the knowledge thus obtained is utilized by the transceiver to choose the frequency band (i.e., channel) of transmission as well as transmission parameters to achieve the best performance. In this article we first provide an overview of the different components to achieve adaptability in a cognitive radio transceiver and discuss the related approaches. A survey of the cognitive radio techniques used in the different wireless systems is then presented. To this end, a dynamic opportunistic channel selection scheme based on the cognitive radio concept is presented for an IEEE 802.11-based wireless mesh network.

Providing location security in vehicular Ad Hoc networks

Abstract: It is fair to say that most, if not all, VANET applications rely on accurate location information. It is therefore imperative to provide mechanisms that ensure the integrity, availability, and confidentiality of location information. In this article we present a number of location security mechanisms specifically designed for VANETs. Proposed mechanisms for location integrity range from the use of onboard radar devices and GPS to simpler methods that rely on information fusion. We also address ways to enhance the availability of location information by selecting and maintaining stable routing paths. Finally, we discuss a mechanism that promotes location confidentiality through encryption/decryption and access control using geographical information. Our location information security mechanisms meet the requirements of the Confidentiality, Integrity, and Availability (CIA) information security model.

Enabling secure service discovery in mobile healthcare enterprise networks

Abstract: Advances in wireless networks, sensors, and portable devices offer unique chances to deliver novel anytime anywhere medical services and information, thus enabling a wide range of healthcare applications, from mobile telemedicine to remote patient monitoring, from location-based medical services to emergency response. Mobile e-health has great potential to extend enterprise hospital services beyond traditional boundaries, but faces many organizational and technological challenges. In pervasive healthcare environments, characterized by user/service mobility, device heterogeneity, and wide deployment scale, a crucial issue is to discover available healthcare services taking into account the dynamic operational and environmental context of patient-healthcare operator interactions. In particular, novel discovery solutions should support interoperability in healthcare service descriptions and ensure security during the discovery process by making services discoverable by authorized users only. This article proposes a semantic-based secure discovery framework for mobile healthcare enterprise networks that exploits semantic metadata (profiles and policies) to allow flexible and secure service search/retrieval. As a key feature, our approach integrates access control functionalities within the discovery framework to provide users with filtered views on available services based on service access requirements and user security credentials.

Prediction in wireless networks by Markov chains

Abstract: Discrete sequence modeling and prediction is an important goal and a challenge for pervasive computing. Mobile clients' data request forecasting and location tracking in wireless cellular networks are characteristic application areas of sequence prediction in pervasive computing. This article presents information-theoretic techniques for discrete sequence prediction. It surveys, classifies, and compares the state-of-the-art solutions, suggesting routes for further research by discussing the critical issues and challenges of prediction in wireless networks.

Traffic pattern detection in a partially deployed vehicular Ad Hoc network of vehicles

Abstract: Knowledge about traffic conditions on the road play an important role in route planning and avoiding traffic jams. With recent developments in technology, it is possible for vehicles to be equipped with communication and GPS systems. Equipped vehicles on the road can act as nodes to form a vehicular ad hoc network. These nodes can collect information regarding traffic conditions such as position, speed, and direction from other participating nodes. Depending on the number of participating nodes in the ad hoc network, this collected information can provide useful information on driving conditions to the node collecting this information. With proper analysis this information can be used in detecting and/or predicting traffic jam conditions on freeways. In this article the traffic information gathered by a node in an ad hoc network is viewed as a snapshot in time of the current traffic conditions on the road segment. This snapshot is considered as a pattern in time of the current traffic conditions. The pattern is analyzed using pattern recognition techniques. A weight-of-evidence-based classification algorithm is presented to identify different road traffic conditions. The algorithm is tested using data generated by microscopic modeling of traffic flow for simulation of vehicle or node mobility in ad hoc networks. Test results are presented depicting different percentage levels of vehicles equipped with communication capability.

European research on future Internet design

Abstract: Future Internet has become the federating theme for European research on communication networks and services. At the core lies research on communication networks toward an efficient, scalable, and reliable future Internet coupled with research on the underlying technologies, in particular mobile and wireless access and optical networks. This article first presents the motivation for a bold initiative for future Internet research in Europe. In this context a changing business environment for telecommunications and the Internet, and the opportunities to provide future Internet services are discussed. From a technical perspective the limitations of the current Internet technology are outlined. The research activities that address the challenge of future Internet research are introduced under three main lines: future Internet architecture and network technologies, spectrum-efficient access to future networks, and converged infrastructures in support of future networks. Examples of the first promising approaches to significantly change the principles of the Internet architecture and protocols are presented.

Scalable video coding over RTP and MPEG-2 transport stream in broadcast and IPTV channels

Abstract: The ITU-T and ISO/IEC standard for scalable video coding was recently finalized. SVC allows for scalability of the video bitstream in the temporal, spatial, or fidelity domain, or any combination of those. Video scalability may be used for different purposes, such as saving bandwidth when the same media content is required to be sent simultaneously on a broadcast medium at different resolutions to support heterogeneous devices, when unequal error protection shall be used for coverage extension in wireless broadcasting, as well as for rate shaping in IPTV environments. Furthermore, it may also be useful in layered multicast transmission over the Internet or peer-to-peer networks, or in any transmission scenario where prioritized transmission for network flows is meaningful. In order to make usage of SVC in the aforementioned use cases, standards for defining the transport format and procedure are required. Therefore, we give a detailed overview of the recently finished SVC standards on transport over IP/RTP and the MPEG-2 transport stream. Both standards are important for IPTV and video on demand, where the first is important for SVC transport over mobile broadcast/multicast channels, and the latter is also important for SVC transport over traditional digital broadcast channels.

Control-based scheduling with QoS support for vehicle to infrastructure communications

Abstract: This article is focused on data transmission scheduling in V2I communications, where a central station, the roadside beacon, decides how to allocate system resources among the vehicles under coverage. We consider non-safety applications whose commercial appeal is expected to accelerate the deployment of VANETs. In this case the main objective is to deliver as much information as possible during the connection lifetime of the vehicles, which is limited by their speed and the length of the road sections under coverage. In this environment the contention free poll-based access mechanism of the 802.11e standard included in current VANET specifications is especially suitable. The design of a scheduling mechanism is addressed in this article from a control theory point of view with the additional novelty of using an optimal control formulation comprising resource constraints. This design strategy allows QoS differentiation, assuring a fixed amount of bandwidth for each QoS class. The resulting algorithm not only maximizes the amount of data delivered, but also reduces performance differences between users traveling along different roads.

A networking framework for teleoperation in safety, security, and rescue robotics

Abstract: Safety, security, and rescue robotics is an important application field that can be viewed as a prototypical example of a domain where networked mobile robots are used for the exploration of unstructured environments that are inaccessible to or dangerous for humans. Teleoperation, based on wireless networks, is much more complex than what one might expect at first glance because it goes well beyond mere mappings of low-level user inputs - like joystick commands - to motor activations on a robot. Teleoperation for SSRR must move up to the behavior and mission levels where a single operator triggers short-time, autonomous behaviors, respectively, and supervises a whole team of autonomously operating robots. Consequently, a significant amount of heterogeneous data - video, maps, goal points, victim data, and so on - must be transmitted between robots and mission control. In this article, a networking framework for teleoperation in SSRR is presented. It was evaluated in a series of field tests and competitions, including the European Land Robot Trials and RoboCup events.

Using robot mobility to exploit multipath fading

Abstract: Communication-aware motion control allows mobile networked robots to increase the average communication throughput. We exploit that in a multipath fading channel, robots can measure the SNR and adapt their motion to spend slightly more time at positions where the channel is good. Two new such cross-layer strategies are analyzed and evaluated: periodic stopping, where the stop duration is a function of the SNR, and controlled stopping, where the robot stops when the communication buffer is filling up. It is shown that the expected average channel capacity can be twice as high as when no cross-layer information is utilized. Experimental evaluation of the strategies confirms the theoretical results.

Wireless traffic service platform for combined vehicle-to-vehicle and vehicle-to-infrastructure communications

Abstract: Vehicular wireless communications and vehicular ad hoc networks are nowadays widely identified enablers for improving traffic safety and efficiency, and a large number of suggestions for vehicle-to-vehicle and vehicle-to-infrastructure communication have been presented. The focus is typically on bilateral communication between two vehicles or on broadcasting information from one vehicle or infrastructure to vehicles in the surrounding area. In the Carlink project [1, 2] of the European Celtic program call 3 we have developed an intelligent hybrid wireless traffic service platform between cars supported by roadside wireless base stations. Communication between cars will be arranged in an ad hoc manner, supported by wireless base station connection to the backbone network whenever possible. The platform consists of a specific set of services (e.g., local road weather service and incident warning service), but a variety of services can be integrated to this kind of a system. The ultimate goal was to enhance traffic safety and smoothness, but also to generate a completely new communication entity, allowing new types of applications, services, and business opportunities. In this article we present the concept and example services of the Carlink platform. The platform simulations, field tests, and analysis show that the platform operability and efficiency are suitable for a large-scale traffic system, to be verified in the pilot system deployment.

DV-Loc: a scalable localization protocol using Voronoi diagrams for wireless sensor networks

Abstract: Localization systems have been identified as a key issue in the development and operation of wireless sensor networks. DV-Hop, a well-known localization algorithm, has recently been proposed for WSNs. Its basic idea relies on transforming the distance to all beacon nodes from hops to meters by using the computed average size of a hop. Despite its advantages, the DV-Hop algorithm has some limitations, mainly due to its high communication cost and energy consumption, which unfortunately limit its applicability to small or medium-sized sensor networks. The scalability issue of DV-Hop is a challenging problem that needs to be addressed. In this article we propose a novel localization-based protocol and show how Voronoi diagrams can be used efficiently to scale a DV-Hop algorithm while maintaining and/or reducing further DV-Hop's localization error. In our localization scheme, nodes can also be localized by their Voronoi cells. In order to evaluate the performance of our scheme, we present an extensive set of simulation experiments using ns-2. Our results clearly indicate that our proposed algorithm performs and scales better than DV-Hop.

Security, privacy, and accountability in wireless access networks

Abstract: The presence of ubiquitous connectivity provided by wireless communications and mobile computing has changed the way humans interact with information. At the same time, it has made communication security and privacy a hot-button issue. In this article we address the security and privacy concerns in wireless access networks. We first discuss the general cryptographic means to design privacy-preserving security protocols, where the dilemma of attaining both security and privacy goals, especially user accountability vs. user privacy, is highlighted. We then present a novel authentication framework that integrates a new key management scheme based on the principle of separation of powers and an adapted construction of Boneh and Shacham's group signature scheme, as an enhanced resort to simultaneously achieve security, privacy, and accountability in wireless access networks.

Downlink scheduling for multimedia multicast/broadcast over mobile wimax: connection-oriented multistate adaptation

Abstract: With its comprehensive QoS support and ubiquitous coverage, the mobile WiMAX network offers promising opportunities for unwiring the last mile connectivity to Internet. However, stringent QoS demands of multimedia applications entail studies on service-oriented radio resource management. This article systematically examines the design issues and the state of the art of multimedia downlink scheduling in the multicast/broadcast-based WiMAX system. We propose a viable end-to-end framework, connection-oriented multistate adaptation, by considering cross-layer adaptations in source coding, queue prioritization, flow queuing, and scheduling. Its performance is confirmed by simulations on important metrics, showing that the framework can effectively accommodate heterogeneity in link variations, queue fluctuations, and reception diversities.

Seamless service provision for multi heterogeneous access

Abstract: The key enabling function for seamless mobility and service continuity among a variety of wireless access technologies is the handover. Handovers within the same radio system are addressed by the standardization bodies involved in the development of the corresponding technologies (e.g., 3GPP, 3GPP2, IEEE, DVB), while handovers between heterogeneous systems are managed by protocols developed by the IETF. However, the interoperability between radio access systems that is required to realize the vision of Beyond 3G calls for coordinated actions and integrated solutions combining individual strengths. This article reviews emerging protocols and architectures aiming to support intersystem handovers between nextgeneration wireless systems and presents an optimized handover framework built around the functionality introduced by the IEEE 802.21 standard. Mapping of this framework to the entities of the 3GPP evolved system architecture is discussed and handover procedures involving key entities of this architecture are presented.

Key technologies for IMT-advanced mobile communication systems

Abstract: WINNER is an ambitious research project aiming at identification, development, and assessment of key technologies for IMT-advanced mobile communication systems. WINNER has devised an OFDMA-based system concept with excellent system-level performance for flexible deployments in a wide variety of operating conditions. The WINNER system provides a significant step forward from current 3G systems. Key innovations integrated into the system concept include flexible spectrum usage and relaying, adaptive advanced antenna schemes and pilot design, close to optimal link adaptation, hierarchical control signaling, and a highly flexible multiple access scheme. The end-to-end performance assessment results demonstrate that the WINNER concept meets the IMT-advanced requirements.

IMS-based presence service with enhanced scalability and guaranteed QoS for interdomain enterprise mobility

Abstract: Enterprise mobility and IP multimedia system corporate services are becoming more relevant; in particular, the IMS-based presence service is starting to provide different kinds of seamlessly mobile services, with context awareness in a wide range of enterprise-deployment scenarios. However, the deployment of presence-based enterprise services in wide and heterogeneous wireless networks still faces several challenges. First of all, scalability and differentiated quality are considered crucial, especially under heavy traffic conditions and when dealing with inter-domain mobility scenarios. This article presents an overview of very recent research contributions about the standard IMS presence service and some novel proposals for scalability and quality optimization. In addition, we propose a novel presence service solution that presents three original extensions for scalability and quality: a federated model to optimize inter-domain distribution of notification messages through locality-based aggregation, a proposal for differentiated quality levels, and an extension of client-side buffering for reliable delivery of presence messages, even during user roaming. The prototype of the enhanced presence service has been deployed and validated by obtaining performance results of improved scalability in terms of CPU and memory usage in infrastructure nodes and message traffic. The prototype is openly available to the IMS community for possible refinement and extension.

Securing resource-constrained wireless ad hoc networks

Abstract: Huge interest in and demand for services over the information superhighway have pressed various telecommunications research fronts and led to a new form of future Internet consisting of wired and wireless segments where resource-constrained devices such as mobile devices, smart phones, palm pilots, and wireless sensors may become integral parts of the Internet rather than access-only platforms. One of the key design problems is the security in such heterogeneous networks, particularly over wireless networks with resource constraints. In this tutorial article we discuss a novel approach to addressing security issues, and articulate why and how ID-based cryptography can be effectively applied to address various security problems in resource-constrained wireless networks.

A middleware architecture supporting seamless and secure multimedia services across an intertechnology radio access network

Abstract: This article presents a middleware architecture to support multimedia services across intertechnology radio access networks in a secure and seamless manner. The proposed architecture uses the media-independent handover framework, where the handover decision function is based on triggering/collecting statistics from the physical, network, and application layers so that an ongoing multimedia session (video) can be transferred seamlessly and securely (using context transfer) across intertechnology radio access networks. Simulation results show that when a vertical handover is based on the proposed MIH framework (including the context transfer of AAA information), handover latency is reduced by 38 percent during WiFi to UMTS handover and 20 percent during UMTS to WiFi handover compared to a non-MIH-based handover scheme.

Certificate status validation in mobile ad hoc networks

Abstract: Certificate validation is much more complex in mobile ad hoc networks than in conventional networks because online access to trusted authorities is not always guaranteed. For this reason, we require new solutions to overcome both the lack of infrastructure and the limited capabilities of several user devices. In this article we study the application of different mechanisms for certificate validation in MANETs and present a cooperative mechanism for certificate validation suitable for MANETs.

Sharing government spectrum with private users: opportunities and challenges

Abstract: Measurements of spectrum occupancy typically confirm the expectation that spectrum assigned to government entities often has low average utilization in urban areas despite its potential for peaks during emergencies. By contrast, spectrum assigned to the private sector is usually most heavily used in urban areas. The second generation of government spectrum sharing started in 2004 with cognitive-radio-based sharing of the 5.25-5.35 and 5.47-5.725 GHz radar bands by unlicensed Wi-Fi-like systems. This sharing is called dynamic frequency selection (DFS) in regulatory and standards publications. Although DFS enabled sharing, the technical criteria were very conservative due to the fact that the military radar systems were not designed for sharing and the fact that interference to these radar systems had to be kept to a negligible likelihood.

Clustering-driven wireless data broadcasting

Abstract: The performance of a push-based system relies heavily on the proper scheduling of the broadcast data. To this end, the Broadcast Disks method is most commonly employed. It defines a procedure consisting of four separate algorithms: one to provide and handle the clients' feedback, another to group the data objects into disks, a third one to define their spinning velocities, and finally a Broadcast Sequence constructor algorithm. In this article we introduce and evaluate Clustering-Driven Wireless Data Broadcasting (CWDB), a complete instantiation of the Broadcast Disks method. The proposed CWDB procedure addresses the major omissions of preceding schemes, including the total lack of feedback mechanisms, extremely limited variety of spinning velocity definition algorithms, and no thorough and realistic testing of complete combinations of algorithms under various client configurations. A new efficient clustering-driven data grouping algorithm is also introduced. Extensive simulation results are presented, which indicate that the proposed CWDB is absolutely dominant over other classical methods in the vast majority of the test cases and led to very important conclusions that were previously overlooked.

Vertical QoS mapping over wireless interfaces

Abstract: This article focuses on the problem of quality of service mapping between layers in a cascade. Protocol stacks in telecommunications networks are composed of functional layers. QoS provision depends on the performance achieved at each layer and is based on functions performed at layer interfaces. In practice, QoS derives from reliable physical and link layers that can offer specific transport services to upper network layers. The data flows (or bundles of flows) generated by the upper layers (e.g., the network layers) are forwarded down to a physical interface that transports the information along a channel that provides, if possible, the expected QoS to the upper layers. The action is called vertical QoS mapping and poses many challenges for a communication scientist, in particular if it is applied to wireless interfaces. This article states the definition of vertical QoS mapping, proposes a formal separation between technology-dependent and technology-independent layers, models each functional layer as a battery of buffers, generalizes the relation between layers through a chain of buffers in a cascade, formalizes the theoretical problems of vertical QoS mapping, and suggests possible solutions that use dynamic bandwidth allocation schemes.