UNIVERSITY OF NEW HAVEN
Tagliatela College of Engineering
Spring 2017
TO:
FROM:
SUBJECT:
Engineering Data Support Team Members (EASC 1112 Students)
Supervisor of Engineering Data Support Team (EASC Instructor)
Project 2 - Information Needed for Cell Tower Design and Location
You are working as an engineering in the Data Support group of ACME Wireless Communications,
Inc. Recent housing development has created the potential for new customers in the region west of
a particular metropolitan area. You have been asked to perform some analysis and provide
information to company management who will decide if and where to build new cellular
communication towers. You are asked to develop a population density model and to prepare a table
that estimates the number of potential customers reached as a function of tower location and
transmitter strength. You will also recommend a location and power level to maximize the number
of new customers. The results of your work should be summarized in a technical memo (2 to 3
pages length, not including attachments) written to your supervisor. ASSUME your supervisor is
NOT an engineer but MBA.
Background Information In cellular communications the cell tower antenna and the cell phone
each act as transmitters and receivers. For a system to work well the signals exchanged between a
user and the tower must be at a sufficient power level. Furthermore the placement of towers must
assure that signal strength is adequate throughout the coverage area as users move from location to
location and thus switch from one tower to another. Density of tower placement must provide
enough overlap of signals from multiple towers to support users, but must not be so saturated as to
cause interference. Design of a cell tower includes specification of the tower height, geographical
location, antenna type, transmitter power and other parameters. In this project you will focus on
tower location and transmitter power, with other parameters already specified. You are required to
set the transmitter power level within the given range and to specify the location (East/West
position) of the tower.
Demographics and Service Area Requirements
Demographic information has been obtained for the geographical area to be served by the new
tower. The area has been divided into 7 regions, with land area and population as shown in table 1.
Region
Length, m
people
Table 1 Demographic Data for New Service Area
1
2
3
4
5
1000
3000
5000
6000
6000
7500
4500
2500
1200
800
6
6500
600
7
8000
500
Length values are East-West dimensions. A width of 1 kilometer will be used for each region in your
analysis. Eventually, a series of towers will be built along a North-South line to service the new area.
Your analysis will set the pattern for future installations by considering this 1 kilometer wide
segment.
Each of the regions will be divided in half for the purpose of determining the number of potential
customers. For each possible cell tower location, you will calculate the signal reached at the
boundaries of each of the 14 sub-regions and include the population of that sub-region only if the
signal strength meets the provided criteria. For example, consider the case of a tower is located at
Michael Collura, University of New Haven, Spring 2016 (modification of original project by Eric Brisart)
the center of region 6 (see Figure 1) with a certain transmitter power level. It is found that signal
level at the center of region 1 is within specifications, but the signal level at eastern border is too
low. The number of potential customers will include the number assigned for the west half of
region 1 but not the number assigned to the eastern half of this region.
Figure 1 Cell Tower Location in New Subscriber Area
N
W
E
S
Area 7
Area 6
Area 5
Area 4
Area 3
Area 2
Area 1
Another
cell tower
500 People
600 People
800 People
1200
People
2500
People
4500
People
7500
People
Length
8000 m
Length
6500 m
Length
6000 m
covers
area East
of Area 1
Length
6000 m
Length
5000 m
Length
3000 m
Length
1000 m
Position Z=0
Z
For reliable service in the target area a signal level of -90 decibels must be available at both
borders of the sub-region. In addition, Region 1 (both halves) there is an additional restriction that
the signal level cannot be too strong or it will cause interference problems. Thus the signal in this
region cannot exceed a maximum is -85 decibels. All designs must provide for full service in
Region 1. Service to other regions is desirable, but will depend on the overall economics of the
project. Select your tower location and transmitter power so as to maximize the number of
potential customers.
Scope of Work
To provide the needed information, you should perform the following tasks:
1. Create a population density model that allows prediction of people/km2 as a function of
distance west of the eastern boundary of region 1. The model should be in the form of a
power law equation, with population density (people/km2) as a function of position west of
the eastern border of region 1. From the data in Table 1 determine the population density in
each region using a 1 km width and the center of each region for the distance variable. You
will want to create a table in Excel with the borders of each region (East and West) as well
as the distance to the center. Use appropriate plots and regression methods to determine
the model constants and to show how well the model matches the demographic data
provided using methods learned in class.
2. Create a table that begins with position zero and has a row for the center and for the
western border of each region (15 rows). Note that the western border of a region is also
the eastern border of the adjacent region. Thus each row (except the first) will correspond
to the information for the sub-region bounded by the location in the row above and the
location in this row. Add a column for the area of the sub-region and the number of people
in it. The latter should be determined from the population density model. Add a column for
each possible cell tower location. This includes the center of regions 2, 3, 4, 5 and 6. Regions
1 and 7 are not being considered.
3. For the table created in task 2, add a row for the transmitter power near the top of the table,
so it can be varied for each tower location (column in table). Create a formula that can be
Michael Collura, University of New Haven, Spring 2016 (modification of original project by Eric Brisart)
copied down and across to determine the level of signal reached at each border, using the
signal distance from the tower to the border. Details of how to do these calculations are
attached as an appendix.
4. Add a row at the bottom of the table to show the number of potential customers reached. A
region can be included in the count only if both of its borders meet the signal requirements.
This set of calculations will require the use of a logic function (Excel’s IF function) and will
require the use of 1 or 2 auxiliary tables to hold intermediate values. Some class time will be
used to discuss approaches to this part.
5. Use your model to determine the optimal transmitter power to use and the number of
potential customers reached for each possible tower location. Present this data as part of
your report and make a specific recommendation for the tower location and transmitter
power.
Report Requirements and Calculation Procedures
In doing this work you are to prepare a spreadsheet that can be used in the future for similar
analysis with minor changes. Thus you should do all calculations using data from specific, labeled
cells in the spreadsheet that can easily be changed, rather than inserting the value of parameters
into equations in the cells. Never type parameter values into your equations. Instead place those
values in labeled data cells and use cell references to refer to the values. Do the same thing if you
are using the results of a prior calculation in another calculation. Thus: when you change any input
value, all your calculated data and your results would instantly update with no intervention by you.
In setting up the excel spreadsheet, make sure you follow the guidelines from class. Your report
should be in technical memo format, following the PITCH guidelines. It should include the
following:
•
•
•
•
•
Heading: identify author, course, project, date, etc.
Summary (opening) Paragraph: Brief summary of problem, and brief summary of solution
including major numerical results
Discussion:
o Details of the problem
o Details of the results from your research
o Documentation of calculations
o Table of inputs, parameters, variables and constants, including units
Conclusion: In the conclusion (final paragraph) of your memo, address the following
reflection question: From doing this project, what you have learned: about using Excel,
about engineering design, about cellular communications, about yourself?
Attached project spreadsheet :
o Two spreadsheet pages should be attached as an appendix to your memo. One of
these should show the work for the population density model. The other should
show the table with signal received in each region. Both sheets should be properly
organized and documented.
This project is due on the published due date at the beginning of class. Submit via Blackboard,
with the memo submitted to Turn-It-In and the spreadsheet file to Blackboard. Use the file name:
EASC1112-Proj2_YourName.xlsx, replacing YourName with your name.
Michael Collura, University of New Haven, Spring 2016 (modification of original project by Eric Brisart)
APPENDIX 1: Assumptions and equations:
To help design the cell tower, please keep the following in mind:
• Your system consists of a base station (cell tower), a mobile unit (cell phone), and the air
link between them.
• While the electromagnetic signal flows in both directions (uplink – mobile to base station
and downlink – base station to mobile), we will follow the engineering practice of assuming
both links follow the same path – thus, only calculate the signal strength of the downlink.
•
•
•
•
•
Assume all signal propagation from base station to mobile is line-of-sight.
Cellular frequency = 850 MHz, thus for each wave, the is wavelength = 0.3529 m
Height of the tower will be 250 ft. = 76.2m
4𝜋𝑑
Path loss equation: 𝐿 = 20 𝑙𝑜𝑔10 ( 𝜆 )
o L is path loss in dB
o Lambda is the wavelength in m
o D is the distance between mobile and base station antenna in m. Remember to use
the correct equation (trigonometry??) to calculate distance from mobile to the top
of the tower – it is not the distance measured on the ground. While this calculation
is only really needed when you are closer to the tower, you need to include it for all
areas in case you move your tower during the design process.
Link budget equation: Prx = Ptx + Gtx – Ltx – Lfs – Lm + Grx - Lrx
o Prx = received power by mobile (dB)
o Ptx = base station transmitted power (dB): use range of 10 to 40 dB
o Gtx = base station antenna gain (dB): use 10.0
o Ltx = base station cable and equipment power losses (dB): use 10 dB
o Lfs = path loss (dB)
o Lm = misc. losses (dB): use 5 dB
o Grx = mobile unit antenna gain (dB): use 12 dB
o Lrx = mobile unit internal component losses (dB): use 2 dB
Michael Collura, University of New Haven, Spring 2016 (modification of original project by Eric Brisart)
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