EG4217/EG7217 Advanced Communications Introduction

The laboratory work is intended to give students the opportunity to put the material in this           module into practice and to gain a critical understanding of the models presented in the lectures. The coursework component of the module consists of five work sheets, to be done in your own     time as there are no scheduled laboratory classes.  By necessity, these models are somewhat         simplistic, as the module covers a broad range of subjects.  A critical understanding of the models means not only knowing what inputs and outputs are relevant to each model, but also being able to comment on the relevance and accuracy ofthe output.  Marks will be awarded for all these        aspects.

The results, discussion and conclusions arising from this and subsequent exercises should be       written in an electronic lab-book (MS Word or similar), along with any graphical output from the programmes.  This is not a formal report, but it should still be clearly laid out and all variables      should be defined.  The results should be in sentence form, rather than just cut and pasted from   the Matlab window.  For example, the following is inadequate:

‘>> d=sqrt(2*a*ht)

d =

99.5359’

and should be replaced by:

‘The horizon distance was calculatedfrom theformula d=sqrt(2*a*ht), where a is the earth radius in km and ht is the antenna height in km.  It wasfound to be 99.5 km. ’

Matlab code should not be put in the lab-book.  If possible, please convert the finished lab-book to pdf format before uploading it to the EG4217/EG7217 Blackboard site.  The mark for the lab- book contributes 30% of the total marks available for the module.

You must upload the document by 12.00 noon on Friday  27th  November 2022.  Late                    submissions will lose 10% of the total possible mark for the first 24 hours or part thereof, and an additional 5% for each subsequent 24 hour period or part thereof.

You are reminded that while the outputs of the software will be the same for  many students, the discussions and conclusions must be your own work. All work that is not your own MUST be      referenced in your logbook.  When you submit your work you must include the following              paragraph at the beginning of your lab-book:

I declare that this assignment is my own work, that sources of reference are acknowledged and that it has not been submittedfor any other course. I understand that plagiarism is a serious offence        under the University’s regulations and that appropriate penalties will be applied if I amfound to      have submitted plagiarised work.

The software

The Matlab programs are available from the module Blackboard site.  They do not need to be        altered or edited.  To run a Matlab model, download it from the Blackboard site and place it in a   newly made directory called, for example, “AdvComCoursework”, which should be on your Z-       drive (your personal space on the UoL computer system that can be accessed from any computer on campus).  Then open Matlab and navigate to the AdvComCoursework directory.  You should    see the programme in the part of the Matlab window called “Current Folder” .

Now move your cursor to the part of the window marked “Command Window”  You should see     the prompt “>>” .  Type the name of the program, followed by round brackets and the value of any input parameters (as numbers), separated by commas.  If you’re unsure what the input                    parameters are, then double-click on the programme in “Current Folder” and the programme’s code will appear in the part of the window marked “Editor” .  The first line of code will tell you the required parameters and their correct order.

For example, to run freespace.m type freespace(1000,50)

This will return the calculated value of free-space loss for a 1000 MHz radio wave that travels 50km.

Some additional Matlab code may need to be written to present the results in the most                     appropriate format (see below). Many of the Matlab functions accept one of the input parameters in vector form, allowing the output parameter to be plotted in one line, e.g.

plot([1:20],freespace(1000,[1:20]))

will plot out the freespace loss from 1 to 20km in 1km steps for a 1GHz signal.  A slower, but a more C- or Fortran-like, alternative is

for  range=1:20

loss(range)=freespace(1000,range);

end

plot([1:20],loss,‘k’)  %‘k’  means  draw  line  in  black

All of the functions are sufficiently well documented by comments to explain what they do and  what inputs are required. You should have a reasonable grasp what each model does before       running the code. Please be careful to look at the units of each input variable and then use           appropriate values.   A few extra Matlab commands may be useful (look up the details using the online help, e.g. at the command line type help subplot):

• hold on : enables multiple lines to be drawn on the same axes

• subplot : can be used to generate multiple axes on the same piece of paper

• orient landscape (or tall) : sets the paper in the given orientation

• title, xlabel and ylabel : add the appropriate axis labels and title to your graph

• print –dtiff <filename.tif> : saves the current figure in tiff format (which can be imported into word).

• plot : see the help for details of how to add plot symbols, introduce dashed lines, etc.

Coursework 1

Task 1

freespace.m

This programme calculates free space loss assuming isotropic antennas.  We shall investigate the effect of frequency and distance on the loss.

Plot the free-space loss for ranges between 1 km and 60 km for radio frequencies 100 MHz and 1 GHz.

To make this curve easy for the reader to view and understand:

Plot these curves in different colours on the same graph using ‘hold on’ .

Add a graticule using the command ‘grid on’

Add a legend using the command ‘legend’ .

Add axis labels using ‘xlabel’ and ‘ylabel’, not forgetting units.

Add a figure number and caption to the plot

Add some text, referring to Figure 1 and describing the trend.

Explain why loss increases with distance.

(Subsequent outputs should also all have these embellishments to make them clear.)

Task 2

planereflec2.m

This function calculates the loss associated with propagation over a plane earth using the two-ray   ground model and assuming isotropic antennas.  Please Note: This programme requires all                 distances in km, as can be seen by double-clicking on the programme in the Matlab ‘Current Folder’ pane and examining the code in the Editor pane.

a)    Plot the loss as a function of Tx-Rx distance for distances between 10km and 100 km, transmit and receive antennas of height 80 m and frequencies 500 MHz and 1 GHz.

b)   What physical factors limit the values of range for which the model can be used?

c)    Explain why the loss values form peaks at certain distances

Task 3

No Matlab programme needed

Plot a graph of the maximum distance for which two antennas of equal height can maintain a        line-of-sight link, assuming a smooth spherical earth.  The graph should show maximum distance in km as a function of antenna height in m for antennas of height 5 to 100m.  Use the formula d = sqrt(2* R* ht) + sqrt(2* R* hr), where ht and hr are the heights of the transmit and receive             antennas respectively and R is the effective earth radius, as shown in the lecture.

Task 4

p526.m

This programme implements the modelfound in ITU Recommendation P526 (on the Bb site) for    propagation loss beyond the radio horizon.  It outputs the extra loss in dB due to diffraction of the radio signal over the curvature of the earth for over-the-horizon radio links.

Plot the diffraction loss predicted by this model as a function of distance for a vertically polarised radio wave of frequency 6 GHz travelling over the sea and antenna heights of 100m.  How much   diffraction loss is caused at the maximum LOS distance ?

Task 5

Using all the programmes mentioned above

Figure 1 shows the Channel Islands, which are situated in the English Channel between the UK      and France.  An omnidirectional antenna with 2dB of gain transmits vertically polarised radio        waves with a power of 30 watts and a frequency of 500 MHz from the highest point on the island  of Jersey (150 m above the mean sea level).  Jersey is marked as the dot next to the letter J in          Figure 1.  The transmitter broadcasts a radio service to Guernsey (marked G in Figure 1),                 Alderney (marked A) , Portland (P) and Leicester (L).  One more receiver (not shown on the map) is placed at location J2, in sight of the transmitter antenna at 300 m distance for diagnostic              purposes.  Between it and the transmitter antenna the ground is hilly and tree covered.                    All receive antennas have 2 dB gain.  Gains are not included in the loss values given in the table.

Complete the following table using the three programmes already introduced:

L1 = loss calculated using freespace.m,

L2 = loss calculated using planereflec2.m,

L3 = loss calculated using p526.m,

In the last column, consider the three different loss estimates given by the models, and choose    which one you think applies best to the path in question (L1, L2 or L3).  Then do a power budget calculation using this value to get the value of Received power (Best Estimate) in dBW.

State reasoning for each case.  High precision is not expected in this exercise.

Please remember that the output of planereflec.m includes free-space loss, whereas p526.m does not.

In this task, you should assume

1 degree of latitude = 111km

1 degree of longitude = 72 km at this latitude

53

52.5

52

51.5

51

50.5

50

49.5

49

48.5

48

-

7             -6             -5             -4             -3             -2             -1              0               1              2              3

Degrees East

Figure 1 The Channel Islands