Veselin Rakocevic

Improving the Performance of the Distributed Scheduler in IEEE 802.16 Mesh Networks

Wireless mesh networks are a viable solution to provide broadband wireless access (BWA) in a cost efficient and flexible manner. The IEEE 802.16 standard is currently one of the most interesting BWA standards. Besides the popular point-to-multipoint mode it defines an optional mesh mode. This paper evaluates the performance of the coordinated distributed scheduler (C-DSCH), defined by the IEEE 802.16 standard for mesh mode. Analytical as well as simulation results show, that this mechanism has a scalability problem that leads to poor performance in dense networks and aggravates QoS provisioning. To solve this, a dynamic adaptation mechanism is proposed, that is able to reduce the contention and to enhance the performance (throughput) in dense networks.

Review: A1: An energy efficient topology control algorithm for connected area coverage in wireless sensor networks

Energy consumption in Wireless Sensor Networks (WSNs) is of paramount importance, which is demonstrated by the large number of algorithms, techniques, and protocols that have been developed to save energy, and thereby extend the lifetime of the network. However, in the context of WSNs routing and dissemination, Connected Dominating Set (CDS) principle has emerged as the most popular method for energy-efficient topology control (TC) in WSNs. In a CDS-based topology control technique, a virtual backbone is formed, which allows communication between any arbitrary pair of nodes in the network. In this paper, we present a CDS based topology control algorithm, A1, which forms an energy efficient virtual backbone. In our simulations, we compare the performance of A1 with three prominent CDS-based algorithms namely energy-efficient CDS (EECDS), CDS Rule K and A3. The results demonstrate that A1 performs better in terms of message overhead and other selected metrics. Moreover, the A1 not only achieves better connectivity under topology maintenance but also provides better sensing coverage when compared with other algorithms.

Poly: A reliable and energy efficient topology control protocol for wireless sensor networks

Energy efficiency and reliability are the two important requirements for mission-critical wireless sensor networks. In the context of sensor topology control for routing and dissemination, Connected Dominating Set (CDS) based techniques proposed in prior literature provide the most promising efficiency and reliability. In a CDS-based topology control technique, a backbone - comprising a set of highly connected nodes - is formed which allows communication between any arbitrary pair of nodes in the network. In this paper, we show that formation of a polygon in the network provides a reliable and energy-efficient topology. Based on this observation, we propose Poly, a novel topology construction protocol based on the idea of polygons. We compare the performance of Poly with three prominent CDS-based topology construction protocols namely CDS-Rule K, Energy-efficient CDS (EECDS) and A3. Our simulation results demonstrate that Poly performs consistently better in terms of message overhead and other selected metrics. We also model the reliability of Poly and compare it with other CDS-based techniques to show that it achieves better connectivity under highly dynamic network topologies.

IMS based IPTV services: architecture and implementation

This paper presents a novel architecture for providing converged IP-based TV (IPTV) services specified by ETSI TISPAN standardisation for IPTV in ongoing NGN release 2 specifications. The described IPTV architecture is based on utilisation of the IP Multimedia Subsystem concept used by NGN architectural framework and its adaptation to provide the IPTV specific functionalities and services. Using the foundation provided by the IMS based architecture, we propose a new functional architecture to enhance the functionalities and features needed for scalable converged networks, flexible media delivery and advanced IPTV service scenarios. The proposed architecture, leveraging on the FMC architecture that operators may deploy to provide IPTV service across different access networks in future deployments (mobile, wireless, fixed) has prototypically been implemented in the ScaleNet* demonstrator testbed. This paper analyses in detail the main principles for such a converged reference architecture. The paper also presents the IPTV service scenario prototype called Click-to-Multimedia which shows some basic features and advantages implemented on top of the presented architecture by prototyping demo applications as proof of concept reference.

Timestamp authentication protocol for remote monitoring in eHealth

Remote monitoring is fundamental in eHealth and introducing mobile devices in the remote monitoring process can provide additional benefits to both patients and medical personnel. For mobile remote monitoring systems to be successful, however, the authentication process must be in place to prevent the misuse of the system. In this paper we analyse the use of timestamps in the authentication process, showing many advantages timestamps have over other authentication methods. The paper presents the design principles for timestamp based authentication protocols in remote monitoring systems and proposes a specific protocol to implement such a system.

A Mobility Enabled Inpatient Monitoring System Using a ZigBee Medical Sensor Network

This paper presents a ZigBee In-Patient Monitoring system embedded with a new ZigBee mobility management solution. The system enables ZigBee device mobility in a fixed ZigBee network. The usage, the architecture and the mobility framework are discussed in details in the paper. The evaluation shows that the new algorithm offers a good efficiency, resulting in a low management cost. In addition, the system can save lives by providing a panic button and can be used as a location tracking service. A case study focused on the Princes of Wales Hospital in Hong Kong is presented and findings are given. This investigation reveals that the developed mobile solutions offer promising value-added services for many potential ZigBee applications.

Securing electronic health records with novel mobile encryption schemes

Mobile devices have penetrated the healthcare sector due to their increased functionality, low cost, high reliability and easy-to-use nature. However, in healthcare applications the privacy and security of the transmitted information must be preserved. Therefore applications require a concrete security framework based on long-term security keys, such as the security key that can be found in a mobile Subscriber Identity Module (SIM). The wireless nature of communication links in mobile networks presents a major challenge in this respect. This paper presents a novel protocol that will send the information securely while including the access privileges to the authorized recipient.

Multihop Wireless Networks

In cellular and wireless local area networks, wireless communication only occurs on the last link between a base station and the wireless end system. In multihop wireless networks, there are one or more intermediate nodes along the path that receive and forward packets via wireless links. Multihop wireless networks have several benefits: Compared with networks with single wireless links, multihop wireless networks can extend the coverage of a network and improve connectivity. Moreover, transmission over multiple ‘‘short’’ links might require less transmission power and energy than that required over ‘‘long’’ links. Moreover, they enable higher data rates resulting in higher throughput and more efficient use of the wireless medium. Multihop wireless networks avoid wide deployment of cables and can be deployed in a costefficient way. In case of dense multihop networks, several paths might become available that can be used to increase robustness of the network. Unfortunately, protocols developed for fixed or cellular networks as well as the Internet are not optimal for multihop wireless networks. This is in particular the case for routing protocols, where completely new unicast, multicast, and broadcast routing protocols have been developed for (mobile) ad hoc and sensor networks. On the transport layer, the Transmission Control Protocol (TCP) is the de facto standard in the Internet, and, in order to allow interoperability, TCP must be supported in multihop wireless networks as well. However, many protocol mechanisms such as congestion control and error control based on acknowledgments do not work efficiently in multihop wireless networks due to various reasons such as contention and control packet overhead. Even on the application level, new concepts are required to support discovery of available applications and services.

Performance analysis of bandwidth allocation schemes in multiservice IP networks using utility functions

Abstract The Internet needs to evolve from a single-service data network into the multiservice intelligent network capable of satisfying diverse performance requirements. The way network resources, primarily bandwidth, is shared, is one of the key issues in this evolution. This paper analyses the concept of bandwidth partitioning, in which each link in the network is partitioned into a number of sublinks, each sublink serving a single traffic class. We analyse a new approach to bandwidth partitioning, Dynamic Bandwidth Partitioning . In this scheme bandwidth partitioning is related to the average level of end-user satisfaction with the network performance according to a simple linear control algorithm. The scheme is user-oriented and adaptive, designed to maximise the overall end-user utility. Furthermore, this paper observes a number of bandwidth allocation schemes in the mutliservice Internet environment, and compares their performance by comparing the average connection utility —the quality of service level which a user of an Internet application derives from the network performance. Our analysis shows that Dynamic Bandwidth Partitioning generates higher overall utility in the multiservice Internet environment than the current best-effort scheme, mainly because it takes account of the quality of service requirements of the real-time Internet traffic.

Distributed road traffic congestion quantification using cooperative VANETs

The well-known traffic congestion problem in urban environments has negative impact on many areas including economy, environment, health and lifestyle. Recently, a number of solutions based on vehicle-to-vehicle communications were proposed for traffic congestion detection and management. In this paper we present an algorithm designed to enable each vehicle in the network to detect and quantify the level of traffic congestion in completely distributed way, independent of any supporting infrastructure and additional information such as traffic data from local authorities. Based on observations of traffic congestion by every vehicle, and by adapting the broadcast interval, it enables dissemination of the traffic information to other vehicles. The algorithm also makes every vehicle aware about the congestion level on the streets that are spatially separated from their current location by several streets. Its robustness keeps the vehicles overall knowledge about congestion consistent, despite the short-term changes in vehicles motion. Since the quantification of congestion is based on per-vehicle basis, the algorithm is able to operate even when only 10% of vehicles in the network are VANET enabled. Data aggregation and adaptive broadcasting are used to ensure that vehicles do not send redundant information about the traffic congestion. The simulations are conducted in Veins framework based on OMNeT++ network simulator and SUMO vehicular mobility simulator.