Energy is one of the most important and scarce resources in Wireless Sensor Networks (WSN). WSN nodes work with the embedded operating system called TinyOS, which addresses the constrains of the WSN nodes such as limited processing power, memory, energy, etc and it uses the collection Tree Protocol (CTP) to collect the data from the sensor nodes. It uses either the four-bit link estimation or Link Estimation Exchange Protocol (LEEP) to predict the bi directional quality of the wireless link between the nodes and the next hop candidate is based on the estimated link quality. The residual energy of the node is an important key factor, which plays a vital role in the lifetime of the network and hence this has to taken as one of the metric in the parent selection. In this work, we consider the remaining energy of the node as one of the metric to decide the parent in addition to the link quality metrics. The proposed protocol was compared with CTP protocol in terms of number of packets forwarded by each node and packet reception ratio (PRR) of the network. This work was simulated in TOSSIM simulator and the same was tested in Crossbow IRIS radio test bed. The results show that our algorithm performs better than CTP in terms of load distribution and hence the increased lifetime
Deep Dive into Energy and Link Quality Based Routing for Data Gathering Tree in Wireless Sensor Networks Under TINYOS - 2.X.
Energy is one of the most important and scarce resources in Wireless Sensor Networks (WSN). WSN nodes work with the embedded operating system called TinyOS, which addresses the constrains of the WSN nodes such as limited processing power, memory, energy, etc and it uses the collection Tree Protocol (CTP) to collect the data from the sensor nodes. It uses either the four-bit link estimation or Link Estimation Exchange Protocol (LEEP) to predict the bi directional quality of the wireless link between the nodes and the next hop candidate is based on the estimated link quality. The residual energy of the node is an important key factor, which plays a vital role in the lifetime of the network and hence this has to taken as one of the metric in the parent selection. In this work, we consider the remaining energy of the node as one of the metric to decide the parent in addition to the link quality metrics. The proposed protocol was compared with CTP protocol in terms of number of packets forw
Wireless Sensor Networks (WSN) consist of potentially large tiny sensor nodes, which are capable of sensing the parameters of interest, processing the data locally and communicating the processed information over the radio. WSN networks are having huge potential applications in the area of environmental monitoring, military surveillance and reconnaissance, structural monitoring, habitat monitoring, health monitoring and home automation. The main aim of the WSN nodes is to sense, process the parameter of interest at its close proximity to the place where it got generated, and transmit in wireless mode to the collection centre at low cost. Also, it should reach any type of unreachable terrains like huge hills and deep valleys, dense forests and narrow gaps in machineries, etc. Due to these objectives, the nodes are designed to be tiny and also of low cost. Hence, the sensor nodes are designed to have a low processing power, low memory and use low power radio. The nodes are mostly unattended hence the battery power is more precious [1] [2]. The conservation of the battery power is the most challenging task in the protocol design and this can be done at any layer.
TinyOS is a free and open source component-based event driven operating system, which addresses these issues of the WSN motes. TinyOS is implemented using nesC (Network Embedded System C) language, which supports the event based concurrent model of TinyOS [3]. The applications are developed from tiny reusable components, which are specific to the application, and the size of the code is in the order of kilobytes. TinyOS provides components for packet communication, sensing, scheduling, routing and medium accessing etc. The routing protocols supported by this operating system is Collection Tree Protocol (CTP), it estimates the quality of the link based on either one of the link estimator protocols such as LEEP or four-bit link estimator.
The quality of the link is measured with two parameters namely Received Signal Strength Indicator (RSSI) and Link Quality Indicator (LQI). Many of the radio chips like CC2420, RF230, etc provide the reading for both parameters and any one of the parameters can be taken as a metric to estimate the link quality. RSSI is the measure of the signal power from the received packet over 8 symbols whereas the LQI is the measure of the chip error rate over 8 bit period after the start of frame delimiter. The LQI has good correlation with Packet Reception Ratio (PRR) and thus it gives the better estimate of link quality over time [4]. Also, the LQI is not a fixed quantity, even though the distance between the nodes is unchanged, it varies over the time due to fading. The causes for fading are the multipath reflections from the obstacles present in the surrounding and the interference from other sources. Hence, the LQI is the important metric to decide the next hop and it should be calculated dynamically. The LEEP protocol measure the link quality based on the packet reception ratio (PRR), but not considering the packet acknowledgement, results in increased retransmissions. The four-bit link estimator considers the information from physical, link and network layer information to find the link quality [5]. Hence the Collection Tree Protocol (CTP) based on the four-bit link estimator is considered in our work. The CTP protocol decides the parent node merely based on the link quality and thus the nodes with good quality link will always be selected as the parent candidate. It is apparent that a node with good wireless link will involve in more communication and be drained out quickly. These nodes will be exhausted soon and the network will be disconnected. Thus the balancing the traffic among the nodes is necessary and this can be achieved by considering the residual energy of the node as one of the metric in the routing strategy. This approach will choose the parent by considering the varying nature of the wireless link as well as the residual energy of the node and thus improves the lifetime of the network. This algorithm is simulated with TOSSIM, which is a discrete event simulator for TinyOS applications [6]. The same algorithm is tested in the test bed consisting of nine IRIS motes, which are WSN motes from Crossbow Technology. It is based on Atmega 1281 microcontroller and having 8KB RAM, 128KB programmable memory and 512KB flash memory. It uses ATRF230 radio chip for communication [7]. This mote is supported under TinyOS2.x, which is the de facto standard development platform for the resource constrained embedded Sensor Network.
The rest of the paper is organized as follows: Section 2 gives the survey of existing routing protocols, Section 3 describes the proposed protocol section 4 elaborates the implementation of the proposed algorithm in the simulator and the testbed section 5 gives the performance evaluation of the proposed protocol. Finally Section 6 gives the conclusion.
Many energy based routing protocols are propos
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