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Wireless And Optical Communications Networks (WOCN), 2010 Seventh International Conference On

Date 6-8 Sept. 2010

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Displaying Results 1 - 25 of 74
  • Message from general chair, vice chairs and technical program co-chairs

    Publication Year: 2010 , Page(s): 1
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    Freely Available from IEEE
  • 6, 7 and 8th of September, 2010, Colombo, Sri Lanka

    Publication Year: 2010 , Page(s): 1 - 2
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  • Technical Program Committee

    Publication Year: 2010 , Page(s): 1 - 2
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  • Executive Committee

    Publication Year: 2010 , Page(s): 1
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  • WOCN2010 conference program Colombo, Sri Lanka

    Publication Year: 2010 , Page(s): 1 - 7
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  • Analysis of short term scintillation effects of Ku band satellite links in Sri Lanka

    Publication Year: 2010 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1140 KB) |  | HTML iconHTML  

    Scintillation effect is a dominant atmospheric impairment among the various contributing factors for low fade margin communication systems operating on high frequency bands such as Ku. This paper discusses the analysis of tropospheric scintillation effect under clear sky conditions where the other attenuation contributions such as rain, dense clouds is minimum. The experiment was setup at the University of Moratuwa, Sri Lanka using a a Ku band satellite downlink operating on a moderately high elevation angle of 45 degrees. The observed scintillation intensity was 0:027 dB over a short-term stationary period of 18:76 minutes The log amplitude and variance distributions showed a satisfactory conformance to the prediction models with the variance being better described by a loglogistic distribution. View full abstract»

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  • Sub gigahertz inter stage band pass filters for microwave transceiver systems

    Publication Year: 2010 , Page(s): 1 - 4
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    Inter stage band pass filters are essential entities in communication systems. Hence, the filter design and fabrication process has a remarkable effect on the performance of the overall system. This paper tries to analyze and understand the practical aspects of RF filter design and realization particularly in the sub GHz range. The analysis focuses on extracting the required performance of the band pass filter using the optimal number of components while keeping the cost of the filter at a minimum. View full abstract»

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  • A new generation of Very Small Aperture Terminal and satellite networks topology exploiting diversity of Multiple Antenna Sites

    Publication Year: 2010 , Page(s): 1 - 5
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    This paper presents a novel technique to enhance the link performance in satellite network. The technique exploits the location diversity of terminals in the ground segment (stations) and the Multiple Input Multiple Output (MIMO) mathematical frames (also known as `Network MIMO'). In this technique these diverse terminals are linked to a control unit (e.g. the hub) to coordinate the joint transmission detection in the up and down links respectively. The other pillar to this technique is the use of special antenna-site-distribution structures (in the form of Uniform Linear Arrays- ULA) to provide the Uncorrelated High Rank (UHR) channel in the presence of the strong Line Of Sight (LOS) as is usual in satellite links. The relation between the range, wavelength and the antenna separation products are examined for different ranges corresponding to different orbits from Low Earth Orbit (LEO) to Geostationary Earth Orbit (GEO)- this with respect to the proposed technique. The presented results are analysed. An outline of the applications of the technique and its merits is concluded with. View full abstract»

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  • Time series prediction of short term scintillations of Ku band satellite links in Sri Lanka

    Publication Year: 2010 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1420 KB) |  | HTML iconHTML  

    Scintillation effect is a dominant atmospheric impairment among the various contributing factors for low fade margin communication systems operating on high frequency bands such as Ku. Empirical analysis of scintillations can be done using signal strength measurements which can be treated as a time series prediction problem in forecasting the short-term scintillation effect. This paper discusses the time series based statistical prediction analysis of tropospheric scintillation effect. The experiment was performed under clear sky conditions where the other attenuation contributions such as rain, dense clouds is minimum. The experiment was setup at the University of Moratuwa, Sri Lanka using a Ku band satellite downlink operating on a moderately high elevation angle of 45 degrees. The time series analysis was performed using linear, non-linear, fuzzy and neural prediction techniques. The results show that though the error of prediction is low for a fuzzy predictor, the neural and non-linear predictors are better in analysing the statistical properties of the predictor results. View full abstract»

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  • A geographic based routing scheme for VANETs

    Publication Year: 2010 , Page(s): 1 - 5
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1215 KB) |  | HTML iconHTML  

    Routing in Vehicular ad hoc networks (VANETs) is considered to be an extremely challenging task due to the frequent and dynamic changes in the topology. The random speed and unpredictable movement of vehicular platforms causes the network to disconnect quite frequently. However as each vehicle in the network can obtain its exact location by using a Global Positioning System (GPS), position based routing protocols have started to play an important role in VANETs. In this paper we propose a position-based routing algorithm namely Position-based Routing with Nearest Forward Progress (PRNFP) which clearly enhances the performance of the system compared to flooding based routing protocols such as epidemic routing and Position-based Routing with Most Forward within Radius (PRMFR). Simulation results in terms of packet dropping probability and the total number of transmissions are compared for all three protocols. Moreover, the impact of selfish nodes is also studied. To evaluate the performance of the system, a 3×3 km Manhattan mobility model is presented. View full abstract»

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  • Performance evaluation of a microcellular motorway vehicular network under realistic channel characteristics

    Publication Year: 2010 , Page(s): 1 - 5
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    The reliable and robust design of vehicular networks in a simulation environment requires accurate modelling of real vehicular traffic profiles obtained from experimental measurements (inductive loops or other sensors). Moreover, these models help to design wireless communication protocols and analyse their suitability for multimedia communications under different operating scenarios while maintaining the quality of service (QoS). To determine the key traffic parameters, in this paper firstly, we have carried out a statistical analysis of real vehicular traces recorded at the M4 motorway. Secondly, we evaluate and compare the performance of a modified packet reservation multiple access (M-PRMA) protocol with idealistic and realistic channel characteristics (real measurements) for a microcellular motorway communication system under varying network load. The results reveal that incorporating the realistic channel characteristics severely degrades the performance of the system however, the performance can be restored by adjusting the receiver power threshold. View full abstract»

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  • Performance of fixed and dynamic channel allocation schemes in a motorway environment

    Publication Year: 2010 , Page(s): 1 - 6
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    This paper aims to show the effects of road congestions arising from motorway roadworks on the performance of vehicular mobile networks. Using vehicular traces from loop Ids on a length of the M4 motorway in the UK, the impact of congestion due to speed control measures and lane closures in a section of the coverage area is simulated to show the resulting network effects on a fixed channel allocation (FCA) scheme. The performance of the system is then compared with a dynamic channel allocation (DCA) scheme to show how the load balancing nature of DCA mitigates the varying spatial distribution of traffic demand arising from road congestion. Furthermore the use of reservation slots to favour handoff requests is analysed for both FCA and DCA systems while considering a fixed and a dynamic number of slots reserved for handoff calls only. The considered area for the simulation consists of a linear array of five contiguous base stations in a cellular motorway network. The voice services considered use constant bit rate (CBR) data generation and have been modelled using a Poisson process with mean inter-arrival times and call duration periods generated for all vehicles independent of each other. The resulting degradation in the network performance in terms of blocked (call congestion) and dropped (handoff congestion) calls arising from the road congestion is evaluated. View full abstract»

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  • A cost effective intelligent solution to reduce traffic congestion

    Publication Year: 2010 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (977 KB) |  | HTML iconHTML  

    Major difficulty of finding a solution for heavily congested roads in city areas is the unpredictable nature of traffic flow rates at a given time. There can be variations due to unexpected accidents, breakdowns, events and other emergency situations which may occur due to political or environmental issues. Developing road infrastructure or imposing restrictions on motor vehicles entering city areas would not be cost effective solutions for this problem, especially in developing countries like Sri Lanka. This may be due to lack of funds to improve the infrastructure, the objections of the general public on applying restrictions on the inflow of vehicles or difficulties on acquiring lands to construct roads in highly populated areas. If it is possible to have proper traffic directing plans with the variation of traffic flow rates it is possible to reduce congestions with the existing infrastructure with minimal cost. This paper presents such a solution where new efficient traffic plans can be generated at real-time with the latest information which can be acquired with the latest communication technologies. Traffic conditions were transmitted using mobile or satellite communication channels as required from the pre-determined locations. Then a better traffic plan is achieved by identifying a congested junction or junctions in a city and rearranging the traffic flow in such a way that the interruptions to the continuous traffic flow are minimized at the congested location or locations. The proposed intelligent software tool can generate efficient traffic plans and can be used as a decision support system to reduce the traffic congestion. View full abstract»

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  • A novel method for jammer localization in large scale sensor networks

    Publication Year: 2010 , Page(s): 1 - 4
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    Sensor networks, by their very nature, are vulnerable to network security threats, with Denial of Service by radio jamming being one of the most common. It is more useful to detect jamming reactively than to proactively avoid it. We describe a method of countering jamming wherein some nodes just outside the jammed region form groups and transmit their locations to the Base Station for localization. These nodes are downstream in the hop-count based gradient broadcast routing sense. We also estimate the exact position of the jammer using the centre of curvature method. Simulation results show that the error in estimation of the jammer location is as low as 1.03m, accurate enough for real-time response. View full abstract»

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  • Adaptive atomic transaction support for service migration in wireless sensor networks

    Publication Year: 2010 , Page(s): 1 - 8
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB) |  | HTML iconHTML  

    In recent years, much research has been done in the area of wireless sensor networks (WSNs). Nevertheless, the programming of sensor nodes is still a time-consuming and tedious task. One paradigm which seems to be qualified to simplify the programming of sensor networks is the service oriented architecture (SOA). The composition of simple services to more complex ones can be a convenient way to design applications. But to enable the sophisticated techniques known from SOAs like replication and migration of services, a transactional model for WSNs is needed. In this paper, we describe our implementation of consistent and stateful service migration in wireless sensor networks via atomic commit protocols. We show that different commit protocols offer advantages under changing networks environments and explain how the appropriate protocol can be selected (a) at compile time and (b) adaptively at runtime. We show that the best results in terms of transmitted bytes per commit decision can be achieved if the appropriate protocol is chosen adaptively during runtime. View full abstract»

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  • Early detection congestion and control routing in MANET

    Publication Year: 2010 , Page(s): 1 - 5
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (542 KB) |  | HTML iconHTML  

    Ad hoc mobile networks are composed of mobile nodes communicating through wireless medium, without any fixed backbone infrastructure. In these networks, Congestion occurs in any intermediate nodes when data packets travel from source to destination and they incur high packet loss and long delay, which cause the performance degradations of a network. This paper presents the early detection congestion and control routing protocol for wireless Ad-hoc networks called as EDAODV. EDAODV detects congestion at a node level by calculating queue_status value and finding congestion status. Based on a congestion status, EDAODV utilizes the non-congested predecessor and successor nodes of a congested node and initiates route finding process bi-directionally to find alternate non-congested path between them for transmitting data. The process finds more non-congested alternate paths and chooses a best single path for transmitting data. View full abstract»

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  • An efficient hybrid routing based on contact history in delay tolerant networks

    Publication Year: 2010 , Page(s): 1 - 6
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (622 KB) |  | HTML iconHTML  

    In this paper, we propose a novel contact-based hybrid routing scheme for delay tolerant networks (DTNs). The scheme combines utility and centrality metrics to make forwarding decision. The utility and centrality metrics are defined with two kinds of contact history, the ages of last encounter and the cumulative contact durations between the nodes in the network, respectively. We evaluate the performances of the proposed routing scheme using three real connectivity trace data sets. The simulation results show that the routing scheme achieves better performance in terms of delivery, delay and overhead, compared to PROPHET and SimBet Routing. View full abstract»

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  • Super high speed Hybrid technology challenges for smart solution in spectral-efficient high data-rate wireless networks

    Publication Year: 2010 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (829 KB) |  | HTML iconHTML  

    The realization of wireless communication providing high speed, high capacity and high quality information exchange between two portable terminals that might be located anywhere in the world is still the communication challenge. For the development of future wireless communication systems, an extremely spectrum-efficient transmission technology is required. In this paper, we interface OFDM with CDMA and then integrate this CDMA-OFDM to MIMO to generate a system which is functionally superior to other multicarrier systems. We investigate the effect of multipath signal propagation on the capacity, under both single and multi user channel on the conventional MIMO, MIMO-OFDM and spread MIMO-OFDM. The obtained results show that the multipath signal propagation has more influence on the capacity of MIMO than MIMO-OFDM and spread MIMO-OFDM. In addition, the capacity of spread MIMO-OFDM is higher under the condition of the multi user channel scenario. Finally we implement the CDMA-OFDM-MIMO technology as an integrated system taking all the desirable qualities of these system architectures, thus yielding a very robust and strong system. Therefore, Hybrid technology can offer a very powerful and affordable solution for real life wideband multimedia system targeting Giga-bit speed wireless transmission and ITS applications. View full abstract»

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  • Congestion adaptive routing in Wireless Mesh Networks

    Publication Year: 2010 , Page(s): 1 - 5
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    The main reason for packet loss in Wireless Mesh Networks (WMNs) is due to congestion. Presently, routing in WMNs is not congestion-adaptive. Routing may let a congestion happen which is detected by congestion control. The way in which the congestion is handled results in longer delay and more packet loss and requires significant overhead if a new route is needed. Hence, we propose a congestion adaptive routing protocol (CARP) for WMNs with such properties. Our ns-2 simulation results confirm that CARP can successfully achieve a high packet delivery ratio with lower routing overhead and latency in WMNs. View full abstract»

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  • Mobile optical wireless systems employing beam angle and power adaptation with diversity receivers

    Publication Year: 2010 , Page(s): 1 - 6
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    In this paper, we propose a mobile optical wireless (OW) system that employs beam angle and power adaptation in a line strip multibeam spot diffusing configuration in conjunction with an angle diversity receiver (APA-LSMS). Our goal is to improve the signal to noise ratio (SNR), reduce the delay spread and increase the received optical power under multipath dispersion, background noise and mobility. Our results demonstrate that the proposed system (APA-LSMS) at a bit rate of 50 Mbit/s achieves 43 dB SNR gain over a power adaptive line strip multibeam system (PA-LSMS) and 18 dB SNR gain over the power adaptive beam clustering method (ABCM) at 6 m transmitter-receiver horizontal separation. The results also show that APA-LSMS reduces the delay spread by a factor of 5 over ABCM. These improvements can enhance our system and enable it to operate at a higher data rate. View full abstract»

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  • An adaptive genetic algorithm method for mobile multi spot diffusing optical wireless systems

    Publication Year: 2010 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (801 KB) |  | HTML iconHTML  

    Multi-beam spot diffusing optical wireless systems have been shown to offer performance improvement over conventional diffuse systems. In this work, the authors build on the genetic algorithm multi-spot diffuse technique introduced in by adaptively optimising the distribution of transmit power among the spots. Our aim is deliver superior SNR and delay spread results compared to other existing systems in an indoor mobile communication scenario. This paper examines the boundaries of the maximum SNR that can be achieved in an indoor wireless system. It is demonstrated that the SNR can improve by as much as 50 dB compared to conventional diffuse systems and 20 dB compared to the state of the art adaptive systems. The proposed system offers the possibility of adapting the number, pattern and power distribution of the spots as either the receiver or transmitter move. View full abstract»

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  • Hybrid-power IP over WDM network

    Publication Year: 2010 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1095 KB) |  | HTML iconHTML  

    In this paper we propose a “hybrid-power” IP over WDM network where renewable energy is used to reduce the CO2 emissions. A novel heuristic is proposed to improve renewable energy utilization. Compared with routing in the electronic layer, the results show that routing in the optical layer coupled with renewable energy significantly reduces the CO2 emission of the IP over WDM network considered by 47% to 52%, and the new heuristic introduced hardly affects the QoS. The results also show that the nodes at the centre of the network have more impact than other nodes if they use renewable energy sources. View full abstract»

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  • Effect of SRS and FWM on performance of optical star WDM networks: A deterministic approach

    Publication Year: 2010 , Page(s): 1 - 4
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (637 KB) |  | HTML iconHTML  

    In all optical WDM network the signal remains in optical domain between source and destination without optical to electrical (O-E) conversion at intermediate nodes. As the signal propagates through the network the fiber nonlinearities like four wave mixing (FWM), and stimulated Raman scattering (SRS) degrades the signal quality. This paper investigates the combined effect of FWM and SRS on the performance of WDM all optical networks. Performance comparison in terms of signal to noise ratio of the worst affected channel has been carried out when (a) thermal, shot, FWM and (b) thermal, shot, FWM and SRS noise are present. Numerical results are presented in the graphical forms for the practical values of parameters. View full abstract»

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  • A coverage restoration scheme for wireless sensor networks within Simulated Annealing

    Publication Year: 2010 , Page(s): 1 - 5
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    This paper presents a simple but an effective approach to restore the coverage within a wireless sensor network (WSN) when sensors fail without adding new sensors. We have considered a sensor node failure due to electrical faults or malfunctions during the initial deployment. Each sensor has a limited energy supply, and the failure of a sensor results in extra overhead during restoration of the uncovered regions of the failed sensors on the active sensors. Therefore, we have proposed a restoration problem, which is to find the nearest and most apt neighbor in order to cover the uncovered region and at the same time maintain the lifespan of WSN to an accepted level. We have developed a restoration scheme within an optimization search algorithm, Simulated Annealing- a generic probabilistic metaheuristic algorithm. Our scheme searches the neighborhood space of the failing sensors in west-first counterclockwise. Our algorithm analyzes all the categories of failed nodes and the computational results show that our algorithm assists to increase the coverage area of the failing sensors with optimized energy consumption. View full abstract»

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  • A novel permission-based reliable distributed mutual exclusion algorithm for MANETs

    Publication Year: 2010 , Page(s): 1 - 6
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (165 KB) |  | HTML iconHTML  

    Distributed mutual exclusion provides access to shared critical resources amongst different mobile nodes in a MANET. Several solutions for fixed networks like token-based and permission-based algorithms have been proposed in the literature. In this paper, we have come up with a novel permission-based algorithm for solving the problem that can handle site failures. Our approach introduces a new message called HOLD message to ensure that the requesting nodes be aware of the node currently executing in the critical section. Our algorithm doesn't predetermine the timeouts as static values like the earlier algorithms in the literature. We use an adaptable timeout mechanism so that we can deal with critical sections having varying execution times. This paper presents an algorithm that can handle situations where the node in critical section itself can fail, with the help of the HOLD message and the adaptive timeout mechanism. We have also given the correctness of our algorithm. View full abstract»

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