Distance Measurement Using RSSI Method in WSN

Distance Measurement apply RSSI system in WSNDistance Measurement Using RSSI Method in radio receiver demodulator NetworksAkhand Pratp Singh, Devesh Pratap Singh, Santosh KumarAbstract. RSSI method gives hold pulsement among beacon inspissations and unknown inspissation. RSSI is Range-based location principle depends on the assumption that the absolute standoffishness between a organiseer and a receiver can be presaged by one or more features of the communication forecast from the sender to the receiver. RSSI measurement is non more relevant because the RF ratify is affected by the environment, the exact surmount between the leaf nodes cannot obtain by RSSI measurement by RSSI.Keywords Received mansion Strength indicator method, RSSI method, Distance Measurement by RSSI.Introduction piano tuner detector Networks can be generally defined as network of nodes that hand and glove sense and control the environment enabling interaction between persons or raters and th e surrounding environment. WSNs argon mostly used in military surveillance, industrial crop control and environmental monitoring. thickener localization is a big problem of wireless sensor networks applications 1.According to estimation of node localization 23, the localization algorithms3 can be divided into two categories range-based and range-free. Range-based method calculates the localization between neighboring sensors. Several ranging techniques are possible for range measurement, such as time of arrival, time dispute of arrival, angle of arrival, or the receive signal potentiality indicator (RSSI) 3. Range free techniques solution depends only on the contents of received messages, which does not estimate the distance or angle between the nodes. Typical range-free localization algorithms 7 included Centroid, DV-Hop, Amorphous, MDS-MAP14 and APIT, and so on 3. Localization algorithm 7 based on range-based has higher the true but requires additional hardware on sensor node s.Localization of Wireless Sensor NetworksLocalization 8 is the process by which sensor nodes determine their location. In uncomplicated terms, localization is a mechanism for discovering spatial relationships between objects. The various approaches taken in literature to solve this localization problem differ in the assumptions they specify about their respective network and sensor capabilities. A detailed, but not exhaustive, list of assumptions made include assumptions about device hardware, signal propagation models, measure and energy requirements, com note of network via homogeneous vs. heterogeneous, operational environment via indoor vs. outdoor, beacon density, time synchronization, communication costs, error requirements, and node mobility 9. Localization of WSNs is classified in two approaches 5.Direct ApproachesThis is also known as absolute localization. The direct approach itself can be classified into two types Manual configuration and 8GPS-based localization 5. Th e manual configuration method is very cumbersome and expensive. It is neither practical nor scalable for large scale WSNs and in particular, does not adapt wellhead for WSNs with node mobility. The GPS-based localization method, apiece sensor is equipped with a GPS receiver. This method adapts well for WSNs with node mobility 6. However, thither is a downside to this method. It is not economically feasible to equip each sensor with a GPS receiver since WSNs are deployed with 100 of 1000 of sensors. This also increases the size of each sensor, rendering them unfit for pervasive environments. Also, the GPS receivers only work well outdoors on earth and have line-of-sight requirement constraints. Such Wireless Sensor Networks cant be used for underwater applications kindred home ground monitoring, water pollution level monitoring, tsunami monitoring 5, etc.Indirect ApproachesThe indirect approach 5 of localization is also known as relative localization 4 since nodes position themse lves relative to other nodes in their vicinity. The indirect approaches of localization were introduced to overcome some of the drawbacks of the GPS-based direct localization techniques 9 while retaining some of its advantages, like accuracy of localization. In this approach, a small subset of nodes in the network, called the beacon nodes, are either equipped with GPS receivers to compute their location or are manually configured with their location. These beacon nodes whence send beams of signals providing their location to all sensor nodes in their vicinity that dont have a GPS receiver. Using the transmitted signal containing the location information4, sensor nodes compute their location. This approach effectively reduces the overhead introduced by the GPS-based method. However, since the beacon nodes are also operating in the same hostile environment as the sensor nodes, they overly are vulnerable to various threats, including physical capture by adversaries. This introduces n ew security threats concerning the honesty of the beacon nodes in providing location information Since they could have been tampered by the adversary and misbehave by providing incorrect location information. Within the indirect approach, the localization process can be classified into the following two categories.A. Range-basedIn range-based 5 localization, the location of a node is computed relative to other nodes in its vicinity. Range-based localization depends on the assumption that the absolute distance between a sender and a receiver can be estimated by one or more features of the communication signal from the sender to the receiver. The accuracy of such estimation, however, is subject to the transmission sensitive and surrounding environment. Range based techniques usually rely on complex hardware which is not feasible for WSNs since sensor nodes are highly resource-constrained and have to be produced at throwaway prices as they are deployed in large numbers. Some range-bas ed localization techniques are as follows Angle of Arrival, Received Signal Strength Indicator (RSSI), Time of Arrival and Time Difference of Arrival. In this paper we are discussing about the RSSI technique 1215, RSSI technique does need require additional hardware, which depart not increase the hardware cost and the size of the nodes. However, due to RF signals influenced by the environment, the exact distance between the nodes cannot obtain by using RSSI 1011, so the localization accuracy of nodes are not high.B. Range-freeRange-free5 localization never tries to estimate the absolute point to point distance based on received signal strength or other features of the received communication signal like time, angle, etc. This greatly simplifies the design of hardware, making range-free methods very appealing and a cost-effective election for localization in WSNs. Typical range-free localization algorithms7 included Centroid ,DV-Hop, Amorphous, MDS-MAP14 and APIT,etc.Received Signal Strength Indicator (RSSI) Measurement PrinciplesRSSI measurement 3 calculates the signal loss in the scattering process with the theory or experience loss of signal propagation model and distance calculated between transceiver to receiver by path distance conventione. Some measure terms which are important role in RSSI measurement as followsPath Loss ModelPath loss models 3 are free space propagation model, the logarithmic distance path loss model, Hata model, etc. the logarithmic distance path loss model 3 is shown by formula (1) (1)Where d is distance from transmitter to receiver and its unit is km, n is path loss exponent that measures the rate at which the RSSI decreases with distance and the value of n depends on the specific propagation environment, X is a zero mean Gaussian distributed random variable whose mean value is 0 and it reflects the change of the received signal indicant in certain distance, d0 is reference distance and usually equals 1 meter, PL(d0) is a known reference power value in dBmilliwatts at a reference distance d0 from the transmitter.Received Signal Power at Reference distanceSuppose A is the received signal power in the distance d0 between trans- mitter and receiver, the formula (2) can be generated. (2)Where Pt is power of transmitter and PL(d0) is a known reference power value in dBmilliwatts at a reference distance d0 from the transmitter.Distance Calculated by RSSI measurement The RSSI Value at the certain distance is calculated by the given formula. (3)Where RSSI is the received signal power. A is the received signal power in the sdistance of 1meter,n is the path loss index and relates to the environment. Then we select maximum RSSI value and then we convert it into distance by given formulae. After calculating the RSSI values we can obtain the maximum value of the RSSI which is known as RSSImax. (4)Where RSSImax is the maximum received signal power selected from all the RSSI values. A is the received signal power in the distance of 1meter,n is the path loss index and relates to the environment.RSSI Measurement AlgorithmsWhen we go through the RSSI method then we have to go through the following step of the algorithms as followsResult and AnalysisOur simulation is done in 10m x 10m two dimensional environment. Node deployment accuracy is very important. 9 nodes are deployed randomly we can get their coordinate and count on one known node as unknown node and then we can find the distances, path loss, Gaussian distributed value 3.Figure 1 Random deployed nodeWhere + unknown node* Beacon nodeIn the simulation we assume (x1,y1) (3.4855, 2.7068) as unknown Node and further we calculate the distance, maximum RSSI value in Scenario of 9 node where one node suppose to be mobile6 by RSSI Method when n=2 ,A=8.4734 dBm and power loss at reference distance is 31.5266 dBm.Table1.Distance CalculationWhen we simulate we found that distance measure by RSSI principle is 1.5726 meter, but when we applied the distanc e formulae for the Coordinate we found that exact distance is 5.4825.So we found that there is measure margin of error.Figure2. Error in distance calculated by RSSIIn figure1 we can see that the distance calculated by RSSI is not accurate, because the error percentage is 71.35.ConclusionsLocalization performance will depend on many things, including the localization algorithm used, the quantity of prior coordinate information, the method selected, and the accuracies possible from those measurements in the environment of interest12. The RSSI measurement is studied in this paper, but this method is not more accurate because the radio frequency signals is affected by the environment1213, the exact distance between the nodes cannot obtain by RSSI measurement. observational measurement and simulation results show that the distance is obtain, but measurement is not accurate. The proposed method is a good option in wireless sensor node localization, because of low cost and less complexity of the simulation. In future we can work on improving the RSSI method for the more accuracy because sometimes there is problem of accurate distance and it depends only on the measurement parameter model. The result shows that in future if we work through the RSSI method for the specific scenarios like war (soldier) and forest fire then the method may provide the specific result and maybe there is need of some more approach in this proposed method because some time the result shown by experiment is out of bound so there is need of some more improvement.References1 Yick J., Mukherjee B. and Ghosal D., Wireless Sensor Network survey, ElsevierComputer Network, vol.52, pp. 2292 2330, 2008.2 Mao G., Bars F. and Anderson B.D.O.,Wireless Sensor Network Localization Techniques, Elsevier Computer Networks, vol.51,pp. 25292553, 2007.3 Zheng J., Wu C., Chu H. and Xu Y., An Improved RSSI Measurement In WirelessSensor Networks, Elsevier Procedia Engineering, vol.15, pp. 876 880, 2011.4 Patwari N., Aah J. 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