PDF Localization for Ad Hoc Networks Using Zigbee

I hereby certify that I am responsible for the work submitted in this project, that the original work is mine except as noted in the references and acknowledgments, and that the original work contained herein has not been taken or performed by unspecified sources or persons. This report will present the progress that has been made and the future work that will be done to complete this project. An ad hoc network is a wireless network that consists of a decentralized structure consisting of nodes.

Therefore, there will be no central administration and each node can freely participate in transmission. To apply the positioning system in ad hoc network, localization is one of the most essential technologies to obtain accurate location information. There are many methods in localization technologies and one of them is by using the signal strength of each node.

GPS (Global Positioning System) is one of the systems that used localization technologies that included satellites. Thus, the aim of this project is to design a cheap and low-cost localization technique in ad hoc network using ZigBee mesh network.

INTRODUCTION

Project background
Problem statement
Objectives
Scope of Study

A local positioning system is a navigation system that allows the network to collect information about its location and update this location to neighbors via a wireless broadcast. There are many techniques used by this local positioning system, namely Angle-of-Arrival (AOA), Received-Signal Strength (RSSI) and propagation-time based systems. Zigbee is one of the network protocols that has a channel bandwidth of 1MHz and became another alternative in building a local positioning system.

Due to its low cost, the technology of Zigbee itself can be widely deployed in wireless control and monitoring applications. This protocol is suitable in applications that require low data rates and can be used in coordination systems such as local positioning systems. Therefore, there is a need to build an inexpensive and reliable local positioning system using low-cost microcontroller boards and wireless modules and implement localization technique on this system.

The scope of the study requires ZigBee module for local positioning system using localization technique. Once the data has been collected, the data must be analyzed in order to draw conclusions.

LITERATURE REVIEW

Localization Techniques

Each sphere indicates the range that the receiver can cover, while the blue node in the middle is the transmitter to be localized. These formulas cannot be solved using a simultaneous equation because they are independent and non-linear. Using Dixon's method [3], the X-coordinate and Y-coordinate can be defined using the equation below.

By this method of calculation, the values of X and Y are the accurate position in two dimensions (2D) for the blind node. b) Triangulation. The position of a node in space is calculated based on the angular distance between three different pairs of anchor nodes is called Triangulation [4]. Based on Figure 3, the triangulation system can be solved using trilateration technique as shown in Figure 4 as long as the information given or collected is sufficient enough.

The location of two nodes that are already known can be used to calculate the length between them using the Sine Rule [5].

Figure 3: Angle of Arrival and Angle of Transmission [5]

Estimating Distances

Based on Figure 5 and Figure 6, the localization for the angle of arrival with and without orientation method can be solved using triangulation. The Angle of Arrival (AOA) method provides more accurate results than the RSSI technique, but the disadvantage of this technique is the requirement of many antennas with an anisotropic radiation pattern that will lead to high cost [11] [12].

METHODOLOGY

Project Methodology
Tools Required
Project Gantt-Chart
Key-Milestone
Experimental Setup
Implementation of Trilateration in Arduino

Important information about these techniques is collected based on the previous study and the experiment of the project is carried out. For the software, Arduino programming plays an important role in calculating distances based on the value of the signal strength. The ZigBee module will communicate with the Arduino to measure the distance based on the signal strength from consecutive nodes.

Estimate and analyze signal strength by comparing experimental results with theoretical values. Based on Figure 8, three XBees will be Routers and another will act as a Coordinator. Then the coordinator will measure the force signal and process the signal to determine the location of the coordinator.

The receiving nodes identify the coordinator based on the same PAN ID. a) XBee configuration on XCTU. This step is called calibration because based on equation 1.7, the RSSI value for 1 meter must first be determined as a reference. Before these Xbees measure signal strength, it must be configured using the same software, XCTU.

Since these Xbees are connected in series with a computer, there is no need to program them to measure the signal strength. The range test and the RSSI value indicate the relationship between the distances between two consecutive Xbees and the signal strength measured. Based on previous configuration of Xbees on XCTU, these Xbees are calibrated and configured as router and coordinator.

With this encoding, it enables the transmitter to send data based on interval time. Multiple readings of data will be taken to obtain the average value of RSSI and to minimize the error. To obtain the RSSI value in the Arduino Serial Monitor, a program based on AT mode must be uploaded to the Arduino Board.

There are a few requirements to be met in order to collect RSSI value in Arduino Serial Monitor. i) The Arduino board must have at least two serial ports for communication. The serial port consists of two pins: RX for receiver and TX for transmitter. Based on Figure 13, the XBee shield schematic shows that when the shield is stacked on the Arduino board, the Xbee digital output and digital input pin is connected to the RX and TX pin of the Arduino board. plate.

Table 3 shows the description about the hardware that used in the project:- Table 2: Tools required

RESULTS AND DISCUSSIONS

RESULTS

Based on the collected signal strength, the signal strength value for 1 meter of -36.3 dBm is used as a reference for another distance. After obtaining the value for 1 meter, the experiment is carried out to test the range up to 12 meters with different value of propagation constant, n. The values of n tested are and 3. The comparison is made between the actual and measured values and the propagation constant 2 is chosen because it has the smallest error of 1.12% as shown in Table 8 and is closest to the actual values. Based on the collected data, RSSI values decrease as distances increase.

From the calibration step, each router will have the same value for the same distance, but each router must be tested first to ensure accuracy during the Trilateration experiment. Based on Figures 17 and 18, the XBees should be placed at the same level from the ground. If the positions of the XBees are not the same, the data collected will be completely different.

So with this testing the signal strength can be accurately measured and the Arduino can calculate the distance and execute the trilateration algorithm correctly. Thus, each router can calculate the distance very well based on the measured signal strength. From this result, the collected data can be used in 2D trilateration for ad hoc localization.

After a few range tests are done, the Trilateration algorithm will be implemented as shown in Figure 20 in Arduino programming using AT command. The experiment is set up as shown in Figure 21 without any obstacle or any obstacles that may increase the power loss during transmission of the signal. The experiment is set up as shown in Figure 22 with a few obstacles or obstructions that can increase the power loss during transmission of the signal.

From the data tabulated in Tables 10 and 11, for Free space with line of sight, the coordinate calculated is quite accurate with minimal error of 22%. The power received by XBee may not be sufficient enough to measure the signal strength. Although every router has obstruction to communicate with the coordinator, these XBees are able to send signal efficiently.

Based on the table above, the measured coordinate is not exactly the same as the coordinate of the real one, but the percentage error obtained from the experiment is quite low, which is 22% to 28%. For Free Space case, the experiment was set up to obtain the power received without any obstruction that could interrupt the transmission.

FUTURE WORKS

CONCLUSION AND RECCOMENDATION