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Vehicular Ad Hoc Networks (VANETs) is an emerging area of research and have been gaining significant attention over recent years due to its role in designing intelligent transportation system. It includes vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) message flows, supported by wireless access technology such as, IEEE 1609 WAVE and IEEE 802.11p. One of the major scientific challenge in VANET implementation, is the design of routing protocol that could provide efficient and reliable node-to-node packet transmission. Routing in VANETs is a complex task in urban environment. This paper reports the overall performance evaluation of two existing routing protocols namely, Ad hoc On-Demand Distance Vector (AODV) and Dynamic Source Routing (DSR) for VANETs. This study aims at optimizing the selection of best possible routing protocol for providing reliability to data packet dissemination in an efficient way. The impact and effectiveness of existing topology based routing protocol for VANETs application has been evaluated through the use of NetSim software tool. The simulated results shows that a combination of proper channel model together with an efficient routing protocol enhance the link throughput of the VANET for a fixed network size. Further, performance evaluation also demonstrate the impact of network sizes and routing protocols on packet loss, packet delivery ratio, average end-to-end delay and overhead transmission.

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A distributed sensor system employing spontaneous Raman scattering with use of correlation-coding techniques and a single-detector scheme is discussed and experimentally characterised. A sensing distance of up to 8 km is achieved with high spatial and temperature resolutions; use of correlation-coding significantly reduces measurement time and allows use of low-power laser sources.Introduction: Fibre-based distributed temperature sensor (DTS) systems have been intensively studied for several years, because of the advantages they can provide compared to conventional sensors, and to optical fibre multiplexed sensor systems (such as grating-based sensors); most common applications include pipeline monitoring (for oil and gas transportation), oil well monitoring and power cables as well as fire detection systems [1].Spontaneous Raman scattering effect is commonly exploited to implement DTS systems [2]. In Raman-based schemes, the ratio of Raman antiStokes (AS) line to Stokes line intensities is usually used for temperature monitoring, since it allows for measurements which are independent of major fibre loss effects and loss changes owing to fibre ageing and other effects. Temperature sensing along the fibre is then generally achieved through optical time domain reflectometry (OTDR), where light pulses are coupled into the fibre, and backscattered Stokes and AS light are detected. One drawback of such implementation schemes is that, owing to low Raman backscattering power, high peak power and long measurement time must be used to ensure good spatial and temperature resolution. Coding techniques can be used in OTDR to overcome the resolutionrange trade-off and improve signal-to-noise ratio (SNR) [3].In this Letter we deal with the implementation and characterisation of a novel distributed Raman-based DTS (Agilent DTS N4385A= N4386A -proprietary technology) using for first time complementary-correlation (CC) coded OTDR techniques with a single photodiode receiver scheme. Use of correlation coding allowed overcoming of the resolution-range trade-off by enhancing SNR, resulting in a high-performance DTS over 8 km multimode (MM) sensing fibre. The newly proposed single photodetector receiver scheme allows for high measurement repeatability over a wide temperature range. Experimental characterisation has shown temperature sensing over 4 km (8 km) of MM fibres with 1 m (3 m) spatial resolution and 0.3 K temperature resolution.

Abstract-A distributed temperature sensor based on spontaneous Brillouin scattering and employing optical pulse coding has been implemented and characterized using a direct-detection receiver. The signal-to-noise ratio (SNR) enhancement provided by coding is analyzed, along with the influence of coding in stimulated Brillouin threshold. Simplex-coding using 127 bit codeword provides up to 7 dB SNR improvement, allowing for temperature sensing over 21 km of dispersion shifted fiber with 3.1 K resolution and 40 m spatial resolution, permitting to avoid the use of optical pulse amplification.Index Terms-Brillouin scattering, distributed-fiber sensor, optical time-domain reflectometry (OTDR).