== Indoor Localization ==

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== Introduction ==

The use of GPS services is growing just as fast as the development and accessibility of mobile  devices. A GPS device, which used to be a significant investment, is now included in every smartphone that emerges on the market. These services have assisted many as they navigate themselves from place to place outdoors.

Although GPS is well-defined outdoors, localization indoors is still an active research problem. GPS signals indoors tend to be weaker; even if they are usable, the accuracy associated with GPS signals is not up to par. Large errors (on the order of meters) associated with GPS generally do not affect the user's ability to navigate to buildings, parks, landmarks, etc. Errors on the order of meters indoors, however, could mean that somebody is in a different room or different building altogether. A fine-grained service, down to the centimeter, is needed to localize indoors.

=== Motivation ===

An effective, low-cost, easy-to-implement solution to the indoor localization problem will have immediate impacts on everyday life, especially commercial retail. Based on movements of people in a store, retailers could determine where to place their best-selling items. They could place products effectively to accommodate shoppers and increase profits. In addition to commercial applications, indoor localization could help emergency responders efficiently respond to calls indoors, or help the elderly navigate inside a large building. Once the technology is fully developed, there are plenty of applications.


=== What is ORBIT Lab? ===
The ORBIT facility consists of a 20 x 20  grid of programmable radio nodes used to test wireless protocols and applications. Certain nodes in the facility, as well as certain sandboxes (part of the lab but not the grid), contain Universal Software Radio Peripherals (USRP), which are software defined radios that transmit and receive signals.

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Founded in 2003 and launched in 2005, this lab provides the world's largest academic testbed for wireless communications. As of 2014, there are over 1000 registered users who have logged ~200,000 experimentation hours since the lab's founding.

=== Overall Approach ===

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<td><center><img src="http://www.orbit-lab.org/raw-attachment/wiki/Other/Summer/2015/aSDR1/trilateration.gif" height=200>
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Trilateration is the method of determining location of an object through relative distances of points and geometry of spheres. It is a method that is used in Global Positioning Systems but we intend to use the same principle in indoor localization.   
As illustrated below, knowing an object's relative distance from Boise, Minneapolis and Tucson, one can derive that that object is in Denver. Similarly, knowing a person's location from three USRPs enables us to roughly estimate his position in an indoor place.
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<center><b> Trilateration </b> </center>
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=== Resources ===

USRP:

ESG Signal Regenerator:

Wiserd:

Spectrum Analyzer:



=== Procedure ===
Using the USRPs as both transmitters and receivers, we measure the received signal power of a certain transmitted signal and plot this measurement against the distance between the node and transmitter. We hope to obtain many distance-power measurements, which would allow us to accurately predict the the distance (but not direction) between a transmitter and receiver based on the signal power. 



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       <center><b> The location of the transmitter and the various receivers </b></center>
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<b><font color = "red">Experiment one: </b></font> Detecting noise and signals using the nodes 
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The photos below show what occurs before the signal is transmitted and after the signal is transmitted. The ASCII art below gives us a general idea of the signal amplitude, which is then measure directly with OMF (ORBIT Management Framework) commands.




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    <center><b> The noise in the ORBIT lab</b></center>
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    <center><b> the signal received by a node </b></center> 
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<b> Analysis: </b> The left image shows signal reception when there is no signal transmitted. This is the noise that is present while we conduct experiments in the ORBIT room. The peak that is visible in the right image is the frequency that the transmitted signal is received at the receiver nodes. 
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<font color="red"><b>Experiment two:</b></font> I/Q Samples<br><br>
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IQ samples are often used in RF applications. In signal processing, I/Q samples are the real and imaginary components of a transmitted signal. The in-phase component is the "i" and the out of phase component, shifted by 90 degrees, is "q". These samples were used to calculate the power of the signal and figure out the relationship between signal power and distance. 
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    <center><b> Real and Imaginary Signals</b></center>
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    <center><b>Verifying Reception using FFT</b></center>
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'''Analysis:''' We used USRPs to collect the IQ samples that are portrayed in Figure 1. The graph has time on the x axis and amplitude on the y axis for both the real and imaginary components of the signal. Figure 2 verifies the reception of this signal using Fast Fourier Transform in Matlab. IQ samples are often used for modulation and demodulation of the signal that is being analyzed. We used these samples to calculate the power of the signal at known distances. 


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<font color="red"><b> Experiment Three: </b></font> Calculating power <br><br>
Calculating signal amplitude and power is the next step in the process. The IQ samples, as mentioned above, gives the real and imaginary amplitude (y-axis) as it is related to time. Therefore, using the real amplitude on the x axis and the imaginary amplitude on the y-axis would result in the amplitude of the signal at a given time (hypotenuse). We can also calculate power from the similar calculation.
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    <center><b> Amplitude using IQ samples</b></center>
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    <center><b>Power Program</b></center>
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<b> Analysis: </b> The figure on the left is the main principle of this power program. Using the phase, frequency and the phase angle of the sine wave, we can figure out the power of a signal by graphing the real amplitude on the x axis and the imaginary amplitude on the y axis. The hypotenuse is the amplitude of the signal. In this manner, we can figure out the power of the signal at each of the times in the domain using the program on the right. Using the average power, thereby cancelling out interference and propagation errors, we can figure out each of the powers at each distance between the receiver and the transmitter. The next step is to figure out the relationship between the two.

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<font color="red"><b> Experiment four: </b></font>Relating Signal to noise ratio to distance
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Signal to noise ratio is an important part in this localization process. To maintain a high SNR at higher distances means a greater chance of better localization data since there is more signal to collect and analyze. Even in the real world, people look for gadgets and devices with a higher SNR since that provides them with greater aural experience. Due to these reasons, it is very important to analyze SNR to validate the results and conclusions of the experiments.<br>
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    <img src="http://www.orbit-lab.org/raw-attachment/wiki/Other/Summer/2015/aSDR1/SNR%20vs%20Dist.png" height=320> 
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     <b> Signal-to-Noise ratio versus distance and the fitted curve(red) </b></br>
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    Using the  measured signal power, along with the distance between the transmitted and receiver, we obtained a signal amplitude-distance pair. We many of these pairs using different transmitters and receivers. We then plotted these items on a graph and found the exponential fit for the graph, as shown below. </br></br>
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    <td><img src="http://www.orbit-lab.org/raw-attachment/wiki/Other/Summer/2015/aSDR1/SNR%20fit.png" height=230>
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<b> Analysis: </b> As shown in this experiment, the line of best fit follows a generally negative and exponential curve but some of the points are no where close to the curve. The scattering of the data points signify either an error in signal processing or simply not enough data points. We believed the latter might have had a hand in this error.
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=== Weekly Presentations ===
Presentations are done on a weekly basis before other research interns or professors. Presentations include the group's accomplishments over the past week as well as goals for the following week



[https://docs.google.com/presentation/d/19tk2BQUCDE6SibGhI5q5ZbgrDVxeivjv-o5k8SRUtpU/pub?start=false&loop=false&delayms=3000 Week 2][[BR]]
[https://docs.google.com/presentation/d/1bB5xOKHx_YjLfJ1QgAFkz9POWl7zakhP11L4NGwn4Mg/pub?start=false&loop=false&delayms=3000 Week 3][[BR]]
[https://docs.google.com/presentation/d/1Zwrn0vNEuN4WQPvoh9i3Pk9lSppQn_kekqOq8mlOKdM/pub?start=false&loop=false&delayms=60000 Week 4][[BR]]
[https://docs.google.com/presentation/d/1g_KbZgF6W24HXhJNMXTMtkahgETWTUDOlhRXyfhY3hA/pub?start=false&loop=false&delayms=3000 Week 5][[BR]]
[https://docs.google.com/presentation/d/1I1gc6wtnZkyP5FN9h_qYw-3CHTYzYk9VVXQfDYBt-Ps/pub?start=false&loop=false&delayms=5000 Week 6] [[BR]]
[https://docs.google.com/presentation/d/1uMwQwDnEYL5DdNjgX7N-VyOxOZOs_KBcetloV3CQlbA/pub?start=false&loop=false&delayms=5000 Week 7] [[BR]]
[https://docs.google.com/presentation/d/1VErJIzLNoOnpdwJVy60t8QTDD7V3giSe0EcwfRldJS0/pub?start=false&loop=false&delayms=5000 Week 8][[BR]]
[https://docs.google.com/presentation/d/1vls9I32fbq7ubQY-pouM0mt68GfNYfKto1SNjZ_iURA/pub?start=false&loop=false&delayms=5000 Week 9][[BR]]
[https://docs.google.com/presentation/d/1bl6XcSzHVppZVYgLfC7Zobgx1fosXx3bSCTkBhmmabg/edit?pli=1#slide=id.p Final Week][[BR]]

=== Team ===

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    <td align='center'><b>Rahul Hingorani </b> <br> University of Michigan <br> Industrial/Electrical Engineering</td>
    <td align='center'><b>Vineet Shenoy </b> <br>Rutgers University <br> Electrical and Computer Engineering </td>
    <td align='center'><b>Karan Rajput </b> <br> Rutgers University <br> Electrical and Computer Engineering </td>
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