Day 8, 03/03/2010

Wednesday, 3 March 2010

At 09.00

The morning lecture was started by reviewing the design of the antenna and the installation.

Typical installation.

The equipments required for typical installation were discussed. This included:

One or more wireless routers

Antennas and mounting brackets

50 ohm transmission line (LMR 400)

POE injector and twisted pair cable ( UTP, FTP, STP).Noted that outdoor environment requires a conduit or special cable called folded twisted or shielded.

Appropriate connectors or adaptors

Lightening arrestors and grounding cable

Self amalgamating tape.

Lecture two was focused on:

Base station mounting considerations.

In a point to multi point deployment, the location of the base station was by far the most important concern.

Important Considerations were discussed which included :

Access to the power grid

Physical security of equipment

Accessibility of the site

Antenna placement on the building or tower

Third lecture ( 10:00 – 11:00)

The types of antennas were listed and discussed on.

Types included:

Self supporting towers. Noted that self supporting towers are often the best choice for base station. That under this design, twisted pair cable on Ethernet cable should be used.

Guyed towers. That a climbable guyed tower is normally made of aluminum, with a triangular cross section, about 30cm per side.

Free- standing pole. That this type was less expensive to build as compared to tower antenna. Built cheaply built by attaching foot rests to any sizeable pole. That with this type, wind speed calculation must be done in order to avoid the collapsing of the antenna.

Another topic discussed was on Tower installation safety which involved the following:

Always work on the towers with a partner

Wear a harness securely attached to the tower when working at heights.

Avoid working on towers during strong winds or storms.

Avoid working in the dark.

Give yourself a plenty of time to work during day.

Penetrating roof mounts was also talked on.

That care should be taken when mounting in order not to let water penetrate the roof. That this could be achieved by using non- penetrating roof mounts.

The next topic was on installation tips which included:

Do your AP and client configuration in the lab, not in the field

Keep coax line cables short that is not more than 15m.

Tape and secure all connectors

Use weather proofing tape but not electrical tape.

That try to use conduits for cables

That shield the radio from water or sun if possible

Considerations of weather proof enclosures were also discussed.

The next lecture was on grounding.

GROUNDING.

Grounding was defined as a conducting connection, whether intention or accident between an electrical circuit or equipment and the earth, or to some other conducting body that serves in place of the earth.

Electrostatic damages were talked about. That this was brought about by current passing from one object to another. That this involves large voltage but low current.

Lightening characteristics were also discussed.This included:

Instataneous power- 1 mega watt

Sound pressure - up to 90 atmospheres

Rise time - 0.1 up to 5 micro seconds

Average current - 30 KA

Duration - 300us

Grounding system components and grounding electrodes were also talked on

Grounding system components

Under this, an area of grounding was talked on. This included:

Grounding of equipment system ( Safety ground)

Grounding of electrode system ( Earthing system)

Grounding Electrodes

Under this, types of grounding electrodes were talked on.This included:

Ground rod

Ground ring

Ground plate. And etc.

Lightening arrestors were also talked on.

Where by lightening conductors is a conductor installed at the top of a tower or tall building intended to attract lightening away from sensitive equipment and divert the strike directly to the ground.

At 11: 20 am.

After tea break we resumed with lectures.The first was on:

Long distance link requirements

It was stated that

One should simulate the link and perform a site survey first.

One should use suitable structures to hang antennas so that the Fresnel zone and earth curvature can be cleared.

One should choose special purpose equipment or modify short short distance equipment.

One should use proper antenna alignment techniques.

Review on maximizing the power budget was later talked on.

Under this, practical link budget considerations was talked on.This included:

Legal regulations on maximum EIRP

Realizing of high power and very expensive radios , which couldn’t be recommendable

Avoiding use of amplifiers as it is very expensive.

Avoiding use of very high gain antenna, as it is expensive and not easy to transport.

Timing issues was also talked on.

The hidden node was also discussed.

That when two clients are in range of the same access point but not each other, their transmissions can interfere with each other. This condition is called a hidden node problem.

That hidden node is alleviated somewhat by CTS/RTS.

CTS/RTS adds overhead, so you can specify a maximum packet size above which CTS/RTS is used.

Long distance strategies were also talked on.

That you could make use of repeaters.Where repeaters are anodes that are desired to over come traffic.That adding repeaters could reduce the complexity of planning a single link, but adds additional hardware and maintenance overhead to the net work.

Afternoon program (2.00pm) 3rd march 2010.

OUTDOOR AND LONG DISTANCE TO MUGGIE

At 2.00pm we sent off to Muggie using a bus organized by ICTP.

Almost all the participant were involved.

We arrived at the station at exactly 2.25 pm.Before doing anything, the first thing was to indentify all the requirements we had listed down.

Having ensured that everything was ok, we had to test the DC power supply voltage, using a digital multimeter.The voltage read was 13.3V without load.

This was followed with the setting of the spectrum analyzer using a laptop then configuration of the radio station.

Mounting of the horizontal plane and vertical plane.

Materials used :

One pipe of 3 m long

Three pipes of each 1m long

Adjustable spanner

Bolt spanner

Clamps

Leveling spirit

The mounting of the horizontal pipe was done on already designed basement.

The horizontal pipe was mounted on the base using the clamps. The clamps were fixed using bolts and nuts while using the adjustable and bolt spanners. The three vertical pipes were then mounted leaving a spacing of equal centimeters apart. The mounting of vertical planes were done due to the three radios involved.

Mounting of radio station.

Materials required were:

Radio station

Compass

Zip tie clip (two pieces)

Nozzle plier

Since there was already a reference point with respect to Galileo guest house, a compass was not used.

For group two, radio station was mounted on the vertical pipe placed in the middle by clamping it on the pipe using a zip tie clip. With the aid of the nozzle plier, both pieces were tightened. The alignment was done by rotating the radio station with respect to the reference point.

Powering of the radio station

The radio station was powered by connecting it to the power pack. The lap top was then connected to it through the USB cable. Having fulfilled all the connections, the testing of the communication between the laptop and radio was done.

A frequency of 2412MHZ was applied.

The angle set was 340 degrees. When the computer was run a report of -93dBm was measured thus indicating a very low signal.

Several trials were made by slightly rotating a radio station to different angles but the much it could go was -89 degrees Celsius. Still the signal was too low to make the radio communicate.

There was a point when the radio station could indicate a floating value. For example 54dBm.

We couldnot try any further because of time.So by 6pm, we had to make our way back to ICTP.

Assumptions

We assumed that, an external reflector would have been used so that the signal could be improved.