Locally Networked Satellite-Based Computer Labs for Tanzanian
Classrooms
Final Proposal
February 20, 2009
Sponsored By:
In Cooperation With:
University of Dar es Salaam
Michigan State University
ECE 480 – Design Team #2 – Spring 2009
Management
Webmaster
Document Prep.
Presentation/ Lab
Brian Holt
Daniel Newport
Steven Sadler
Kevin Bishop
Executive Summary
With the increasing dependency on technology there is a great demand to develop
affordable personal computers for remote and undeveloped areas. One potential region is rural
East Africa, specifically Tanzania. Before deploying a computer system into such harsh
conditions several obstacles must be overcome, including providing a reliable source of
electricity to the system, telecommunications, and the savannah climate. The Lenovo
Corporation has tasked this team to develop a computer workstation that can accommodate up to
eight users. The solution must be robust enough to withstand the harsh environment and also be
affordable for rural schools.
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TABLE OF CONTENTS
Technical Section
Introduction……………………....Page 3
Background……………………....Page 5
Design Criteria…………………...Page 6
Conceptual Design……………….Page 7
Ranking of Conceptual Design…..Page 10
Project Management Section
Project Management Plan………..Page 14
Costs Section
Approximate Costs…………..…...Page 15
Fast Diagram/ References
Fast Diagram………………..……Page 16
References………………………..Page 16
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Introduction
Many schools in rural Africa are without computers and network access, and have almost
no books for their students to use. Having internet access could greatly improve the current
situation of these schools. However, many schools are in locations with no electrical service or
network connectivity. While we may not be able to purchase books for these schools we are able
to provide a means to improve their education via computers and the use of the internet.
Lenovo has chosen to support the development of an eight-seat multi-user computer
workstation complete with network access. Since installing a computer system in rural Africa
will present many issues we will attempt to simulate, and educate ourselves as much as possible
on, as many of these issues as possible prior to our arrival in Tanzania.
We will begin this semester’s project by reviewing the previous semesters efforts to
install a similar system in Tanzania. While there are a few differences between the two projects,
such as the previous teams use of solar power, we believe we can use the previous project in
order to evaluate what measures they took in order to successfully install their system in
Tanzania, issues that they dealt with and had to overcome, and what we can do to improve upon
the previous design.
The following is the main criteria that we must consider in order to implement a
successful project design by May 9th, our scheduled deployment date.
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The system that we install must be robust and be able to perform under any weather
condition. This system must be reliable in heat that is typical in Africa, with an average
year round temperature of 85 degrees Fahrenheit and average highs of 110 degrees
Fahrenheit.
The system must also be able to operate under the most unpredictable of power
conditions. The secondary school that we will be installing this system in has access to a
power grid, however, that grid is subject to unpredictable power outages ranging in time
from a couple of minutes to full days. This power grid is also subject to varying voltages,
which could be harmful to the computer system and its components.
This system must be as maintenance free as possible. We are installing this system in an
area where neither the teachers nor the students have any previous experience with
operating a computer. If problems were to occur within the system debugging and fixing
these problems may not be possible for large amounts of time.
We will be routers equipped with modified antennas to create the gain and signal strength
necessary to accomplish the task of internet connectivity between location of the primary
school that last semesters team installed a workstation at and this semesters location at
the secondary school, which are separated by approximately two miles.
We are also designing this system so that it may easily be expanded beyond the two
schools that will have network access upon completion of this semester’s project. With
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the current multi seat system we are designing we will have two computers each
equipped with the ability to accommodate up to four users per computer. We are also able
to easily expand upon the current network connections due to the fact that the proposed
antenna design is capable of sending a usable signal up to five miles.
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Background
In the fall semester of 2008 the Lenovo Corporation made a unique opportunity available
to a design team in ECE 480. The task would be to introduce a low cost, low maintenance, solar
powered Linux based computer workstation into a primary school in rural Africa capable of
seating up to eight users. The team would face many obstacles while preparing to deploy the
system including the savannah climate, telecommunication and the lack of a reliable form of
electricity within the village in which the school was located. The team was able to use solar
panels to charge a small battery bank, which included a custom engineered management system
to monitor voltages and currents from the solar panels and the battery. The system was also able
to monitor the temperature within the case that stores the batteries and monitoring system, to
ensure that the system is shut down if an unsafe temperature is reached within the case.
This semester Lenovo Corporation has given our team the task of developing a similar
computer workstation, also capable of accommodating up to eight users. This workstation will
again be entered into the harsh climate of Tanzania but, contrary to last year’s workstation, will
accommodate users in a secondary school, approximately two miles from the primary school
location from last semester. However, this semester we will be able to utilize the fact that the
secondary school is located on the power grid.
While we are fortunate that the secondary school is located on the power grid we are still
forced to do with the reoccurring problem of unreliable power since this grid is subject to
unpredictable “blackouts” and varying voltages. To conquer the power problems we will incur
while attempting to place the workstation in Tanzania we will use an uninterruptible power
supply (UPS) system to charge a small battery bank, which will be used to run the workstation
when the power from the grid is unavailable. This will allow us to ensure that brief power
disruption does not cause injuries, data loss, or system failure. In the event that power is no
longer available from the grid the UPS will allow the user to continue normal operation on the
workstation for up to four hours. Ideally the UPS will include a monitoring system to warn the
user that the battery bank is running low, in order to ensure that important data is saved and the
proper shut down procedure is done in the event that power from the grid is not restored.
This semester we will also be installing modified antennas to two routers, one that will be
placed at the primary school and one at the secondary school. These antennas will allow us to use
the satellite router that was previously installed in the primary school location and access the
internet at the new location, which is approximately two miles away. We will also be moving the
satellite router to the secondary school, in order to release some of the power draw from the solar
power system.
This project will be completed throughout the course of this semester and will be
installed by the members of our team, as well as several members from the previous semesters
team, into the Tanzanian secondary school beginning on May 9th, 2009.
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Design Criteria

Low cost (priority: 4) – This is the most important design criteria. Since this system is
being designed for Third World countries to purchase, the cost needs to be as low as
possible. In particular, the computing solution will be designed to minimize the cost per
seat. Also, normal (store bought) wireless routers with modified firmware will be
attached to high-gain directional antennas so that a single internet connection can be
shared amongst multiple areas (schools).

Low maintenance (priority: 3-4) – Also one of the more important criteria. These
systems are being designed for areas that will have little to no available support. Thus,
they must be designed for robustness and require little maintenance. All materials used
for the antenna will be designed to handle a the expected harsh conditions. Furthermore,
the computing solution will be user friendly and secure. The uninterruptible power
supply (UPS) will help shield the computer from fluctuations in power, and the UPS
itself will be designed to handle an unpredictable energy supply.

Low power consumption (priority: 1-2) – Low power usage is less of an issue than in the
Fall 2008 project, however, a system that achieves this will increase the uptime of the
UPS should the power fail. The multi-seat computer system will help make this system
use less power by consolidating the required electronics into a single PC.
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Safety (priority: 3-4) – Safety is a high priority in more than just the physical sense. One
of the primary means of accomplishing this is the use of a white list on the computing
system to help control the content that school-aged children are allowed to view. The
white list will also make the system more maintainable by blocking sites that could
harbor malicious code. Also, the development of appropriate content for the system will
allow for an enriching yet safe experience.
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Expandability (priority: 2-3) – While the situation we are designing for is fairly unique,
the final system should be expandable so that it is usable as universally as possible. The
multi-seat system currently installed has four seats, but could be expanded to eight on the
same hardware. Furthermore, if a motherboard with more PCI slots was chosen the
system could possibly allow more than eight simultaneous users. The antenna will be
designed for a five mile hop so that it is usable in a multitude of situations.
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Conceptual Designs

Multi-seat computing system:
 There are a variety of options for the multi-seat computing system; one of the leading
items of debate is the choice of operating system. Candidates thus far are Ubuntu
Linux (used by the Fall 2008 team), Open Solaris, and Red Hat Linux. Initial testing
of Open Solaris showed that it was not as user friendly as needed for a system of this
nature. In an effort to maintain consistency the Spring 2009 group has again chosen
Ubuntu Linux as the candidate operating system. This choice ensures that the
environment will be intuitive and easily usable by young children. Also, this allows
for the continued use of the Multi-seat Display Manager (MDM) which may not be
usable in a non-Debian based operating system. Although less of a concern than those
previously mentioned, the use of Ubuntu makes the system easier to set up for an
administrator or anyone else responsible for maintenance.
 A secondary design decision is regarding the hardware used in our proposed design
solution. Doing some rough estimation using data compiled by the previous
semester's team the cost to implement a thin-client based computing system would be
too high to justify switching to it over the current design. Although such a system
would be highly scalable, the cost per seat is significantly higher due to the thin client
hardware itself and the cost of a powerful central server to process the data. Again,
the Spring 2009 team has chosen to move forward using the same hardware as the
previous semester. The Lenovo ThinkStation S10 is a powerful workstation PC that
more than suits the needs of our target user, and gives us a lot of processing power to
run the multi-seat system. We have opted to use two S10 workstations minimally
running four seats each for Manyara Secondary School. This should help with
stability concerns, but at the same time allows for expansion up to a total of sixteen
seats. On site administration will hopefully be easier since each PC will be less
complex to set up.
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Antenna:
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The primary decision regarding the point to point link antenna is whether to buy a
commercially available one or to construct our own. A directional antenna designed
for the 2.4GHz band that could achieve our target distance of two miles would cost
upwards of $50. The advertised gain of such an antenna was generally around 20
dBi, but sometimes up to 25 dBi (the higher the gain the more costly the antenna).
There is no guarantee that a commercially bought antenna could actually reliably
transmit a signal that distance, and buying such an antenna would make it
unmodifiable (e.g. to make it more rugged to inclement weather).
Preliminary research regarding constructing our own antenna led us to a “Do It
Yourself” antenna constructed from an aluminum can. The can acts as a waveguide
feed, and would be directed into a parabolic dish to achieve even more gain. A
prototype dish could be constructed from thick gauge copper wire and aluminum
window screen for low cost, however the final design would need to be considerably
more sturdy for it to be deployed. Concerns over the sturdiness of this antenna led us
to seek advice from various antenna experts. The antenna prototype we are in the
process of constructing is a combination Yagi-Quad array constructed from the
handle of a hockey stick and other readily available parts. This design makes the
antenna more compact than a pure Yagi or Quad, and is anecdotally quoted at a range
considerably higher than our target (10 miles). Another attractive feature of the YagiQuad combination is that it is easier to achieve impedance matching with the router
which will allow for increased gain. Also, Yagi-Quad arrays generally provide better
gain than patch or parabolic dish antennas. Once our prototype has been properly
tested we will construct a version that can withstand adverse weather conditions.
Uninterruptible Power Supply (UPS):
 Again, one of the major decisions regarding this aspect of our project is whether to
purchase a UPS that is commercially available or to construct our own. Analysis of
the components required to construct our own UPS roughly price it at about $900
($400 for a deep cycle gel-cell battery, $300 for a DC to AC inverter, and $200 for a
gel-cell DC charger). This would create a UPS with an uptime slightly longer than
our target. However, this design does not take into account an interface to the
computer to let the users know how much time is left until the battery is dead. Also,
this design does not take into account the wide variation in voltage from the wall
outlets on the power grid (180VAC-240VAC), which could cause damage or at least
reduce the life of the gel-cell DC charger). Since high reliability and low cost are
important factors, this design is most likely out of the scope of this semester's project.
 Our other option is to purchase a commercially available UPS from a reputable
vendor. Such a system will be designed to handle extreme variation in input power,
and will also be able to interface directly with our computer system to notify the users
when they should shut the system down. Using a proven system will ensure that the
system can be shut down properly without losing data, and more importantly will
protect the hardware from an improper shut down. One current candidate UPS (built
by APC Power Systems) can provide around twenty minutes of uptime using our
proposed computer system, and costs around $500. We feel that although this stock
solution does not achieve the desired uptime, in terms of both cost and overall system
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lifespan this is a better option. There is a strong possibility that we could create a
battery bank to be hooked into this UPS, thus expanding the available charge capacity
significantly.

Router: The router will be a simple wireless device obtainable at any retail electronics
store. By flashing the firmware of this device with Open WRT we can greatly increase
the amount of administrative options that are available for the router to create a secure
and reliable networking base for our computing systems. Setting up the router in this
manner will allow us to install a filter and whitelist to control the content available to the
school children. We can also control the route of the network traffic so that it is only sent
to the appropriate destination, which as the network expands will greatly increase
efficiency. The router hardware being used is the Linksys WRT54G v8 home wireless
router which costs about $40. Low cost and proven compatibility with Open WRT are
the leading factors in this decision. Content filtering and traffic control will be achieved
using the Squid Caching proxy freely available for Open WRT. Our routers will be
retrofitted with custom made antennas to allow for an expandable network in even the
most remote of locations. By creating such an inter-networking scheme a single Internet
connection can be shared amongst multiple schools to help reduce costs even further.
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Ranking of Conceptual Design
Computer System:
Criteria
Thin Client Based Multi-seat System
System
with 8 Monitors
Lenovo
ThinkStation S1
Server: $1200
Lenovo
ThinkStation S1
Server with 4
Graphics Cards:
$1300
Lenovo L197
LCD
Monitor: $239
each
Low Cost
(Priority: 4)
Keyboard/Mouse:
$30 each
Expandability/Flexibility
(Priority: 2-3)
Low Maintenance
(Stability)
(Priority: 3-4)
Performing
maintenance may
be difficult on the
thin client.
Lenovo L197 LCD
Monitor: $239 each
Keyboard/Mouse: $30
each
Cost per Seat: ~$594
Cost per Seat:
~$431
Cost per Seat:
~$704
System is quite
expandable, but at
a higher cost. May
need to upgrade
the central server
(costly) if too
many clients are
connected.
Lenovo ThinkStation S1
Server with 4 Graphics
Cards: $1300
Lenovo L197
LCD
Monitor: $239
each
Keyboard/Mouse:
$30 each
Diskless
Workstation Thin
Client: $285 each
Two Server Multi-Seat
with 4 Monitors Each
Possible to expand
this system to
contain up to 8
Use half as many seats on
seats. Could use a
each server, allows
more powerful
system to be expanded in
server to get more the future. Slightly more
seats than this, still
costly.
lowest overall
cost.
Centralized point
Two points of
of configuration,
configuration; however,
however, also a
they are mirrored so
single point of
complexity stays the
failure. If system
same. Even if one PC
goes down there
goes down there will still
will be no
be 4 (or possibly more)
computers.
seats available for
Antenna:
Criteria
Commercially
Parabolic Dish with
10
Yagi-Quad Array
Low Cost
(Priority: 4)
Expandability
(Priority: 2-3)
Low Maintenance
(Rugged Design)
(Priority: 3-4)
Purchased
Cost per Antenna:
~$60, could be more
dependent on gain
(need to do further
testing). Also need to
include cost for cables
to run to the router,
should be
approximately the
same for each antenna
(~$15)
"Cantenna" Feed
Cost per Antenna:
$15
(made from an
aluminum coffee can
available from most
stores, thick gauge
copper wire, and
aluminum window
screen scraps)
Cost per Antenna:
$20
(made from some
base material (i.e.
hockey stick handle),
copper wire for the
Quad elements, and
threaded rod for the
Yagi elements)
Unsure if a
commercially built
antenna will provide
us with enough gain to
properly transmit our
signal.
Unsure if gain will be
high enough for our
needs. Could have
issues with
constructing a well
designed antenna.
The gain for such an
antenna if well
designed is
anecdotally quoted at
a range well beyond
our requirement (10
miles). This should
provide for a highly
expandable point-topoint mesh network.
Materials used to
build the antenna may
not be sufficient for
the climate in
Tanzania. May not be
able to easily modify
without messing up
antenna
characteristics.
Initial prototype
materials would most
certainly not
Initial prototype
withstand the
should be fairly
elements in Tanzania.
ruggedly designed.
A more rugged design May have to do some
would be possible, but minor treatment of the
the cost would rise
materials to protect
significantly. Also,
them from the
we would likely have
climate. Compact
to completely
footprint should also
redesign the final
help this design.
product in terms of
impedance matching.
Uninterruptible Power Supply:
Criteria
Low Cost
(Priority: 4)
Commercially Purchased
UPS
APC UPS Cost: ~$500
Battery Cost: ~$500
Additional Battery Cost:
$150
DC-to-AC Inverter Cost:
$300
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Self-Built UPS
DC Charger Cost (AC
Input): $300
Cost could vary dependent
upon the power needs for a
particular application (e.g.
might need a more powerful
inverter for a higher overall
wattage system)
Expandability
(Priority: 2-3)
Low Maintenance
(Priority: 3-4)
Safety
(Priority: 3-4)
The stock UPS supports
approximately 20 minutes of
The self-built UPS would give
uptime using our current
a high amount of
electronic configuration.
expandability. The only
However, this UPS supports
requirement would be to
the installation of additional
ensure that the DC charger is
batteries to increase uptime.
powerful enough to properly
This feature should help us
charge the battery bank.
meet our desired uptime
requirement.
Using a proven design will
The self-built UPS gives no
ensure that the UPS functions
guarantee that it will properly
properly. One of the more
handle the varying input
important features is an
power from the grid (could
interface directly to the PC to
cause damage to the system or
inform users of the
at least lower its lifespan).
approximate amount of power
Also, there is no built in PC
left. This will give ample
interface, so one would have
warning for when to shut
to be designed. Failure of this
down the system to avoid data
component could lead to
loss and help protect the
damage to the hardware (both
hardware from improper
UPS and computer system).
shutdown.
The commercially bought UPS
is already in an enclosure so
that the electric components
A self-built UPS would
are not in plain view. This will require a proper enclosure to
increase the safety of the
ensure that it is safely isolated.
system in case anyone
attempts to modify it.
Proposed Design Solution:
Given the above conceptual designs, and our understanding of the system requirements,
Team 2 has selected an overall design to move forward with. The basis will be a similar
computer system used by the previous semester's team. There will be two ThinkStation S10
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workstations powering four seats each in the Manyara Secondary School. Each of these
workstations will run Ubuntu Linux, and will be configured into a multi-seat system using the
Multi-seat Display Manager (MDM). By using two workstations with only four seats each the
system will be expandable if desired, and possibly more stable. Four additional seats will be
added to the system currently installed in the Baraka Primary School.
The satellite Internet link currently installed in the Baraka Primary School will be moved
to the Secondary School so that it can be on the power grid. In turn, a wireless link will be
created between the two schools using cheap, off-the-shelf wireless routers with modified
antennas so that a single Internet connection can be shared. The routers selected are the Linksys
WRT54G v8 routers and will be "flashed" with an Open Source firmware so that their
administrative capabilities are expanded. The firmware used will be OpenWRT, and will allow
us to put the Squid Caching proxy directly on the router to help control available content. A
whitelist will be implemented on the router, and will be accessible from any of the terminals
using a simple SSH connection (Administrators only). Also, we will be able to more tightly
control network traffic thereby making the network more efficient (forward packets only to their
actual destination). The antenna design will consist of a combination Yagi-Quad directional
antenna to achieve both the gain and impedance required to efficiently transmit our signal.
Range estimates thus far indicate that a wireless link could extend well beyond our two mile
target; however more testing is required to get an accurate maximum distance.
All of the above will be connected to a properly sized Uninterruptible Power Supply
(UPS) to handle both fluctuating input voltage (from the power grid), and complete power loss.
The UPS chosen from American Power Conversion (APC) is estimated to provide about twenty
minutes of uptime off the shelf, but can be expanded using additional batteries. Our goal is to
allow our computer system to remain active for one hour in the event of complete power failure.
The diagram below illustrates our proposed overall solution.
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Project Management Plan
Personnel
Daniel Newport
(webmaster)
Kevin Bishop
(Presentation/Lab)
Steven Sadler
(Documentation)
Brian Holt
(Management)
Shared Projects
Components
Quagi Antenna
UPS
2 Computers
Filtering Routers
Secondary
Routers
8 screens
4 Video Cards
Operating system
Filtering Router
software
Secondary router
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Tasks
Installing operating system
o Set up multi-seat
Program installation
Programming router
o Install Filtering Software
Program installation
Designing / building antenna
Selecting UPS
Designing / building antenna
Selecting UPS
Selecting Routers, video cards
Resources
 Hockey stick
 Welding rod
 Nuts and bolts
 Coaxial cable
 Connector
VR 1500i
Think Station S10
Wireless G router
Wireless G router
Source
ECE shop
L157
GeForce 8400 GS
Ubuntu Linux
Open WRT
Lenovo
NVIDIA
Free open source
Free open source
Open WRT
Free open source
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APS
Lenovo
Linksys
Linksys
Costs (Approximate)
Computer:
Lenovo Thinkstation S10 - $1190
Video Card - $64
Keyboard/Mouse - $30
Lenovo Monitor - $239
Router - $50
Antenna - $70 dollar per if bought
Antenna - $20 if built
UPS - $550
Software:
Ubuntu- $0
Multi-seat Display Manager- $0
Xephyr- $0
X windows- $0
All Software is open source
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Fast Diagram
References
Images
All images on the cover sheet of this document were obtained from Wikipedia.
All other images were created using Microsoft Visio.
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