User authentication is a crucial service in wireless sensor networks (WSNs) that is becoming increasingly common in WSNs because wireless sensor nodes are typically deployed in an unattended environment, leaving them open to possible hostile network attack. Because wireless sensor nodes are limited in computing power, data storage and communication capabilities, any user authentication protocol must be designed to operate efficiently in a resource constrained environment. In this paper, we review several proposed WSN user authentication protocols, with a detailed review of the M.L Das protocol and a cryptanalysis of Das’ protocol that shows several security weaknesses. Furthermore, this paper proposes an ECC-based user authentication protocol that resolves these weaknesses. According to our analysis of security of the ECC-based protocol, it is suitable for applications with higher security requirements. Finally, we present a comparison of security, computation, and communication costs and performances for the proposed protocols. The ECC-based protocol is shown to be suitable for higher security WSNs.

Abstract-Vehicular Ad-hoc NETworks (VANETs) adopting Dedicated Short-Range Communications (DSRCs) have emerged as a preferred choice of network design for the Intelligent Transportation System (ITS). A possible application of the ITS is to disseminate emergency messages by multihop broadcast. Due to the high density and high mobility of vehicles, it is difficult to design an efficient broadcast protocol for VANETs in urban areas. In this work, we propose a broadcast protocol, named Streetcast, to provide efficient broadcast service. Street maps are used to assist the selection of relay nodes, and multicast RTS (Request-To-Send) is adopted to protect wireless communications for providing high reliability. In addition, an adaptive beacon control heuristic is proposed to reduce beacon overheads. At last, we evaluate our broadcast protocol in a real roadmap scenario with real traffic flows. The simulation results show that the proposed broadcast protocol has a superior performance in terms of packet delivery ratio and the number of collisions under various traffic load patterns.

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Abstract. The research of Video Streaming has often focused on the methodologies of P2P protocols, such as peer selection, network structure, group organization, etc. In addition, streaming mechanism and system deployment are significant to provide a Video Streaming service. Research in this field, however, is scant. On the other hand, the layered video codec provides scalability when environment is divergent due to different transmission rate, computational power, and so on. Recently, Scalable Video Coding (SVC), which is a layered video codec, has been standardized and caught much attention. The study is to explore how to provide Video Streaming service by employing P2P and SVC. A system architecture which involves video layering, dynamic Segment seeding and scheduling, and Segment downloading and sharing is developed. To provide high quality Live or On-demand P2P Video Streaming service, a Video Streaming system, GaiaSharp, is implemented and deployed, and the experience is shown to explain the importance of layered video codec.

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