Solar-Powered “Connect-on-Demand” Satellite/Radio Link for Tanzanian Schools (George and Vickie Rock and Dow

Chemical Company)

Pre-proposalFebruary 5, 2010

ECE 480 – Design Team #2 – Spring 2009 Management Rodney K. Singleton

Document Prep. Michael Edward MoultonPresentation Prep. Rafael Robert Ocampo

Lab Coordinator Luis Alfredo GarciaTeam Support Joe Larson

Facilitator Selin Aviyente

TABLE OF CONTENTS

Technical Section

Executive Summary…………..Page 2

Background…….……………..Page 3

Design Criteria ……………….Page 4

Conceptual Design……………Page 5

Project Management Section

Project Management Plan…….Page 8

Costs Section

Approximate Costs…………...Page 9

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Executive Summary

Across the world, at the turn of the century, businesses were trying to find ways to power their operations without exhausting the world’s resources. One decade later, the push for more environment friendly systems have spread throughout businesses, schools and residential buildings as well. However, with the implementations of these new power systems we are faced with the struggles of maintaining power efficiency. Specifically speaking about the solar-powered network currently installed in Tanzanian schools, there are worries about the quantity of sunlight being insufficient to run the satellite link and computer systems in place. In order to optimize the power usage, Dow Chemical has challenged the College of Engineering at MSU to design a solar-powered, “connect on-demand” satellite/radio link. With this new design in place, the system will draw minimum power from the batteries while optimizing the time of its usage. This will allow the Tanzanian users to gain the most out of their internet while staying well within their power limitations.

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Background

It is well known that a quality education is one of the key needs in helping populations of developing countries rise out of poverty. While there are plenty of schools in developing countries, such at Tanzania, many lack financial resources. The lack of financial capital results in a sever lack of textbooks for students to use. In order to avoid the cost of purchasing textbooks MSU's Department of Engineering and Department of Telecommunications, Information Studies, and Media have taken an interest in providing internet connectivity to provide the same information that can be found online. While this will lower costs in the long run, up front equipment costs can be very expensive. Resources must be used as efficiently as possible and this includes power used to operate networking equipment.

This project, to create on demand wireless internet connectivity, is closely related to two earlier ECE 480 projects in the fall semester of 2008 and spring semester of 2009. The 2008 project installed a multi-seat computer with internet connectivity provided through a VSAT in Baraka, Tanzania. The computer and the networking equipment were powered by solar panels and an Uninterrupted Power System (UPS) because the school was not on a power grid. The VSAT drew a significant amount of power and as a result solar panels and batteries where added to compensate.

In 2009, a similar multi-seat environment was installed at Manyara Secondary School, about 2 miles to the south of Baraka. In order to provide internet connectivity a wireless Ethernet bridge was installed between Baraka Primary School and Manyara Secondary School. Manyara Secondary School was on the local power grid and the amount of power available for consumption was not a concern for the overall system. The satellite and one end of the Ethernet bridge was still located at Baraka Primary School and as a result the internet connectivity at Manyara Secondary School was indirectly effected by the amount of power available at Baraka. While additional solar panels and batteries where added at Baraka Primary School, the internet could not be used at Manyara if the satellite had to be powered down.

In May 2010, a new multi-seat system will be installed at Rift Valley Secondary School. Internet connectivity will be shared on the same local area network that was established between Baraka and Manyara. To accomplish this, a WiMAX wireless bridge will be installed to connect Rift Valley Secondary School to Baraka Primary School. In doing so, this will create a problem faced by the Spring 2009 team, which was compensating for the additional power needed to operate networking equipment. Rift Valley Secondary School is also a residential school. As a result, providing the students with access to the internet at times that the muti-seat system at Baraka Primary School will be shutdown is the objective.

The goal for team 3 is to produce a solution that provides internet on demand so that resources can be used more efficiently. To do this the VSAT will power on with a request

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from any school for content on the internet and not be reliant upon the VSAT being turned on or off by the users at Baraka Primary School. Power will only be used to power the networking equipment when the network is in use by an end user. Finally, the networking equipment will power off when batteries powering it reach 40% capacity in order to preserve the overall life-cycle of the batteries.

Design Criteria

Low power consumption (priority: 1) – With this new integrated system, after running off of solar power during the day, at night, the system will be operating off of battery power. Once battery power reaches 40% the battery life will be preserved by shutting down power to the whole network. This system itself will consume very little power at Baraka where solar power will be utilized.

Durability/Robustness (priority: 2) – Certain precautions need to be taken into

consideration give the fact that this device will be installed in a hot climate with very little moisture. Added steps must be taken to ensure that no dust or any particulate matter enters the systems and causes malfunctions. Furthermore, steps will be taken to account for any animals (i.e. rats, millipedes, termites… etc) that might interfere with system functionality.

Low maintenance (priority: 3) – With the assumption that there will be a few trained technicians in the area; nothing can be left to chance. Problems will occur and these problems can escalate and cause error in the network. In order to minimize this chance for malfunction this design must produce a minimized set of error. A user-friendly design will be implemented. This design will not only be robust, but also include an override.

Safety (priority: 4) – Added security will be beneficial to prevent any unwanted

damage caused to the network. Batteries will be added, in doing so, they must be encased to prevent the possibility of tampering and resulting in death.

Low cost (priority: 5) – MSU’s interest in Tanzania are more concerned with developing a proof of concept that provides end user computer terminals at the lowest cost. The internet would be provided by 3G cellular data cards. The 3G coverage in Tanzania is currently underdeveloped, and is why a VSAT with wireless bridges must currently be used. Since the “internet on demand system” that is being designed will be outside the scope of a multi-seat system MSU hopes will be adopted by the Tanzanian government, cost is not a primary concern at the moment.

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Conceptual Design

Figure 1: Design Diagram

Design Overview

Figure 1 is a simplified diagram of the system Anything connected in blue is a typical network connection. The signals dealing with the proposed control system are in red. First a user would try to access the internet. A software program would cache the packet and send a signal to the AM transmitter. The AM receiver will demodulate the signal and send it to the decoder. The decoder will decode the message and decide which school the request came from. This information will be sent to a microcontroller. The microcontroller is the command center. It decides what to turn on and off and when. Also there will be an input from the battery charge controller to the microcontroller. Devices will be powered on and off using relays.

End user software:

At the end user machine (Lenovo S10/20) software will be running in the background that will capture and analyze packets originating from the client machine. If the packet is determined to have originated from user input the application will send a request to turn on the wireless network bridge at Baraka. If the end user computer does not have internet connectivity then the packets generated by the user will be cached in memory until a network connection has been established. To determine if a request is user generated the software will examine the destination port of TCP headers. To determine if the computer has a network connection the software will check the IP address.

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Microcontroller:

In the design, a micro-controller will be used to handle all switching functions at the site of the satellite link in Baraka. The micro-controller will decide whether or not to turn on/off the satellite links based on four different inputs. The first input is an alert from the battery system, proclaiming that the battery life is falling lower than 40%. At this notice, the micro-controller will turn off the system and go into an idle state. The microcontroller will then wait for another alert from the battery system, proclaiming the battery life to be above 60%. At this instance, the microcontroller will power up everything for internet usage. The second input will be a decoded message from either Baraka, Manyara or Rift Valley requesting access to the internet. Whenever a user from either location sends packets to the internet, the microcontroller will receive these requests via radio-link and tell the satellite to tell the pseudo-router to turn on. The third input will be a reset timer which will be clocked internally through the microcontroller. As soon as the microcontroller receives a high value to turn on the system, the clock will reset and count down 15 minutes. After the countdown is complete, the microcontroller will realize that the system is not being used and it will send a relay to power down the system. The fourth and last input is another timing signal based on what time of the day it is. The microcontroller will be synchronized to an external clock at Baraka. When that clock reads 11pm, the microcontroller will shut down the system for the night and enter in a hibernation mode. The external clock will then begin a countdown until morning, or 6am. When the countdown ends, it will send a high signal to the microcontroller, causing the microcontroller to relay the message for the system to turn on.

UHF radio link:

To let the microcontroller know that a user is making an internet request from one the satellite schools (Manyara or Rift Valley), a tone signal will be transmitted from one of these schools to Baraka via AM radio. Since this radio will be sending much less data and will be at a much lower frequency than the internet link, it will consume less power at the satellite school than if the WiFi or WiMAX link was up. More importantly, it will consume less power at the Baraka end because there only needs to be a receiver and decoder. The signal being transmitted will be an summation of tones. When a user tries to access the internet, the computer program will send a short signal composed of three tones. (Each satellite school will have its own tones so the microcontroller knows which link to establish.) This signal will be amplitude modulated and transmitted to Baraka. At Baraka, the signal will be received, demodulated, and decoded. Once the signals are decoded, the microcontroller will know which school sent the request.

UHF AM radio

The AM radio will operate on what recreational 'walkie-talkies' work on, in the 462 MHz range. This frequency is advantageous because it is unlicensed in Tanzania, and open for public use so testing is possible in America. 462 MHz is also advantageous because it allows for a directional antenna. At very low frequencies, directional antennas would not be practical because the size of an antenna is proportional to the inverse of the frequency.

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Antenna

Directional antennas will be implemented at the satellite schools to lower the transmitting power. These antennas will most likely be simple Yagi-Uda arrays. Baraka's receiving antenna will be an omni-directional monopole since it requires receiving signals from multiple sources.

Decoder

The decoder will be an analog circuit with a band pass filter for each frequency that is expected to be received. A peak detector and transistor will create a logical 1 if this frequency is received. These bits will be go through a logical AND gate to make sure all three tones are present. This bit will be sent to the microcontroller. The reason for three signals being sent is to ensure the microcontroller does not receive an undesired signal.

Risk Analysis:

We will probably have to look into having more than one microcontroller to carry out all of these functions. Also, the microcontroller may not have the ability to perform two different timers at once. If that is the case, then external timers must be used. We will also have to look into how much power usage will be consumed for the microcontroller to power up the system. If this is not negligible, we will have to look for better methods to conserve power in a dynamic system.

This system will be deployed to a region where teams from MSU only travel to ever 4 to 8 months and trusted technical support is hard to find locally. As a result contingencies must be considered in the event of a failure or malfunction. In a worst case scenario such a malfunction could prevent a school from being connected to the network. As a result not only would end user functionality be impacted, but the ability to remotely diagnose and fix the problem would be compromised. As a result we plan to create an override functionality, which will disable our power management system. The satellite, router, and network bridges will have to be manually powered up and down.

The current multiseat implementations have also been adversely effected by environmental factors in Tanzania. These range from dust to animals, such as rats. In the past the best way to protect against the dust is to have rugged designs that are inexpensive and easy to replace in the event of a failure. In the past rats have chewed through power and data cables. While proving to be persistent creatures the best way to mitigate this risk is through a tiered approach. First trying to prevent access into the room where the system will be housed through the installation of a ceiling and patching any holes in the walls. Then, inside of the room place all devices inside of a metal box. Finally, any wires that have to be exposed must be placed in conduit.

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This implementation is meant to support existing mutiseat deployments and the system team 4 will be installing. Consequently, if team 4 fails in their implementation one of the nodes that would be supported by this system would not be connected. This could reduced the realized value provide by team 3’s system. .

Project Management Plan

Personnel (primary tasks)o Joe Larsen (Team 3 Support):

Program installation, programming, software developmento Rafael Ocampo (Presentation):

Team organization, design layout and presentationo Michael Moulton (Documentation Preparation):

Assisting software developmento Rodney Singleton (Management):

Microcontroller research and designo Eric Hatch (Webmaster):

Radio link research and design, assisting microcontroller designo Luis Garcia (Lab):

Procurement, assisting hardware designo Shared projects

Selecting WiFi/WiMAX, physical control switches, routers/servers, etc…

Resourceso WiFi/WiMAX, radio link hardware

Purchasing High-gain antennas Transmitter/receiver (AM band) Routers/web servers

Open-source code TCP destination port detection Locally cache packets during system boot-up

o Microcontroller ECE Shop

o Additional Hardware Relay switches Power cords and splitters Circuit breakers

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Costs (Approximate)

Computer:3 Timers: $5 – $10Micro Controllers: $10 – $20Am transmitter and receiver: $12 – $803 Op Amp: $6 – $10WiMax: $2,000 – $2,500Wires: $15 – $30Power Strip: $6 – $20Project Enclosures: $10 – $80

Software:Python - $0Libpcap - $0

All Software is open source

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