Chapter 1-introduction 24th May

CHAPTER 1 INTRODUCTION 1.1 MOTIVATION Wireless sensor networks provide an economical, fully distributed and computing solution for environments where conventional networks are impractical. WSNs are composed of small, cheap, self-contained, and disposable sensor nodes. WSNs are constrained by low power, dense deployment, and limited processing power and memory. Sensor networks have different constraints than traditional networks. Energy constraints are paramount in sensor networks since nodes can often not be recharged, so any wasted energy shortens their useful lifetime. Reliable data transport in sensor networks is a multifaceted problem. The emphasis on energy conservation in sensor networks implies that poor paths should not be artificially bolstered. Path maintenance, on the other hand benefits from wellengineered recovery at the transport layer. Recovery should not be costly however, since many applications in sensor networks are impervious to occasional packet loss. The aspects of reliable data transport include the provision of guaranteed delivery and fragmentation/reassembly of data entities. Reliable data transmission in WNSs is difficult due to the following characteristics of WSNs: •

Limited processing capabilities and transmission range of sensor nodes.

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Close proximity to ground causes signal attenuation or channel fading.

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Dense deployment of sensor nodes creates significant channel contention and congestion.

1.2 OBJECTIVE The main objective of the project is to provide reliable data transport in sensor networks. To achieve reliability, there is a need for transport layer protocol to handle the packet loss recovery. Reliable multisegment transport (RMST) protocol provides reliable transmission of data.

1.3 OVERVIEW OF THE PROJECT The project mainly deals in providing reliable data transport in sensor networks. Reliable multisegment transport protocol provides the reliability. It is meant to operate on the top of directed diffusion. Directed diffusion is the communication paradigm used in sensor networks. It supports data-centric routing and applicationspecific processing inside the network. In the proposed work routing of data is done by one phase pull diffusion algorithm. It is a part of directed diffusion protocol. Routing is performed when the sink initially sends interest messages to all the sensor nodes. The sensor node which receives the interest message will forward the interest to its neighboring nodes. Source receives the interests from the sink through the neighboring nodes with varying latencies. The interest message with low latency is selected and that path is chosen implicitly as the preferred gradient. The data is sent from the source to sink, along the preferred gradient. Reliable multisegment transport protocol, in conjunction with one phase pull diffusion provides reliable data transmission. It includes caching mode and noncaching mode providing hop by hop and end to end recovery. It benefits from one phase pull diffusion routing, adding minimal additional control traffic. RMST is energy efficient, since it sends a single NACK for a list of lost fragments.

1.4 REPORT OVERVIEW Chapter 2 presents the Literature Survey for my work. Chapter 3 presents the detailed functioning of Directed Diffusion. Chapter 4 presents the detailed information about Reliable multisegment transport protocol. Chapter 5 presents the implementation details of one phase pull diffusion and RMST. Chapter 6 presents, Coding and simulation results. Chapter 7 presents the conclusion