Satellite Communication Systems

Assignment- Look Angles and Rain Attenuation

Introduction

This assignment is designed to reinforce some fundamental concepts learned in this subject. Students can work in a group of 2 or 3 and submit a final report for the assignment. However, it is STRONGLY in YOUR interest to attempt the assignment individually and ensure that you understand exactly how to calculate all of the required parameters.

You are encouraged to refer to the lecture notes and subject textbook, as well as books and other online sources such as Wikipedia - however these must ALL be fully and correctly referenced.

Show all working, calculations and Matlab/Octave script code - not just numerical results.

Your submission should be in the form of a single ZIP file containing (1) your report, preferably in PDF format, and (2) all source code in plain text format (do NOT try to paste it into a Word document or similar - I want to be able to run your code without having to fix it!).

No extensions will be granted except in exceptional circumstances.

Preparation

Perform the following calculation in Matlab or GNU Octave to select your satellite. Let N be your FULL student ID number and M be the month in which you were born (1-12). Now

phi = mod (N + M, 360)

For example, if N = 123456789, and M = 2 (i.e. February) then phi = 191^o.

Next, consult a database of geostationary satellites. Such information may be obtained from a variety of sources such as N2YO or Satellite Signals [1, 2]. Choose the satellite whose lon- gitude φss(i.e. the longitude of its sub-satellite point) is the closest to the phi that you have calculated. Note that if your angle is greater than 180^o, you may wish to convert it into a West longitude (i.e. if you calculate φ = 191^o, this is actually 191^oE or (360^o- 191^o) = 169^oW.

Finally, by consulting an atlas, choose any two cities from which this satellite should be visible. If, after going through the tasks in this assignment, you find that the satellite is not visible, re- peat the calculations with a different city (closer to the equator). The criterion for visibility is that the angle of elevation should be greater than 10^o.

Tasks

1. Record all of the parameters (including the satellite longitude and the coordinates of your chosen city). Show the calculations you have used to choose your satellite. Using a world map image (e.g. from Google Maps) indicate the location of your chosen cities and also the sub-satellite point.

2. Determine the satellite look angles from each of your chosen cities, assuming the receiver dish has two-axis (azimuth and elevation) adjustment capabilities. You can use the script developed in Week 4's workshop to do this.

3. Assume that your chosen satellite is identical to the Optus D3 commercial geosta- tionary satellite, in all aspects other than its position.

Specifically for this assignment you are interested in the BSS frequency plan listed on page 9). ?For horizontal, vertical and circular polarisations, and for Earth stations at the correct altitudes above sea level for both cities - you may find this information on Wikipedia or elsewhere online, calculate the rain attenuation which is exceeded for 0.1% of the time in any year, for a point rain rate of 8 mm/hour.

Choose any one pair of frequencies for the uplink and the downlink (a total of 12 calculations - 2 cities, 3 polarisations (horizontal, vertical and circular), 2 frequencies.

Assume that the rain height is 3500 m. The specific rain attenuation coefficients are provided in Table 1 - please note that you must interpolate between the values in this table to get the coefficients for the frequenies you have identified (linear interpolation is sufficient, although you are welcome to use a higher-order polynomial interpolation if you wish).

The Matlab/Octave function for this is interp1 (one-dimensional interpolation - if unsure type help interp1 at the command prompt and try the examples).

Path length reduction factors are listed in Table 2.