• Study Resource
• Explore

Survey

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Transcript
Maa-6.3289 GNSS-technologies (5 cr)
Course work assignment, “Performance Analysis of a GPS software defined receiver”
In this course work, you are asked to use an open source software-defined GPS receiver developed by Prof. Kai
Borre and his colleagues [1], [2]. You are asked to carry out certain tasks with the receiver. The software
receiver is developed in Matlab, and a brief description of the software can be found in [2]. Please read
through the article carefully for a better understanding on the receiver.
Live data collection
A 60 seconds long raw GPS data in the form of In-phase and Quad-phase (I/Q) is provided to you for analysis.
The data was collected on December 01, 2014 via an RF front-end from Nottingham Scientific Limited [3]. The
front-end configuration for this data set is provided in Table 1.
Parameters
GNSS signal
Intermediate frequency
Sampling frequency
Front-end bandwidth
Signal type
No. of Quantization bits
Values
GPS
6.39 MHz
26 MHz
4.2 MHz
Real
2
The receiver was static for the whole data duration, and the true WGS84 coordinates are:
trueLatitude = 60.1610902666670 N;
trueLongitude = 24.5454277833330 E;
trueHeight = 54.1970000015572 [meters];
You need to use the true coordinate of the receiver as a reference when comparing the performance with the
estimated position solution.
Plot the frequency domain spectrum of the received GNSS signal. What is the approximate 3-dB bandwidth of
the received signal? You may find spectrum plot in probedata.m function.
How many satellites were acquired with the given data set? What is the number of coherent integration time
used for acquisition? Make a three-dimensional acquisition plot of one acquired satellite, for example, a 3D
acquisition plot for PRN 8. (hint: you may use ’mesh’ command in Matlab for 3D acquisition plot). You need to
use debug option in order to step into the acquisition file. You can have a break point in line 178, when the
satellite is acquired. Use ‘mesh’ command with the variable ‘results’ in order to see the acquisition metric. In Xaxis, you can see the code delays in samples, and in y-axis, you can see the frequency steps with respect to
intermediate frequency and in z-axis, you can see the correlation value of all the possible code delay-frequency
combinations.
Make a table of the acquired satellites with the following information filled:
Acquired PRN Number
PRN 8
?
?
?
Estimated Code Delay in Chips
? (a/26000)*1023
?
?
?
Estimated Doppler in Hz
?
?
?
?
Plot the tracking result for PRN 8. Describe each of the sub-plots in your own words.
Plot the positioning error in local East-North-Up (ENU) frame at 1 Hz rate.
Compute the tracking error variances of PRN 8 in the following three cases:
i.
ii.
iii.
with correlator spacing 1 chips
with correlator spacing of 0.5 chips
with correlator spacing of 0.25 chip
Which of the above three cases has the least tracking error variance? Compute also the 3D Root Mean Square
Error (RMSE3D) of the position solution in the above three cases. You may need to save the trackingResults.mat
file for three different cases.
Plot a sky-plot of the satellites which are used in the navigation solution. Are all the GPS satellites acquired?
Compare the sky-plot you have with the sky-plot of Trimble GNSS planner given in the following site:
http://www.trimble.com/GNSSPlanningOnline/#/Settings ). You have to look for sky-plot of December 01, 2014
at around 17:30 o’clock. Select GPS satellites only with elevation mask of 10 degrees. How can you acquire
more satellites in a GPS receiver?
Describe the logical flow diagram of the GPS software-defined receiver. Mention the basic functionalities of the
following three processes in the context of the receiver:
i.
ii.
iii.
Acquisition
Tracking
What code discriminator (i.e., DLL) is used in the receiver? What other code discriminator based algorithms
exist in the literature? You may look at tracking.m function for the required information.