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Diary of Tuesday, 22st February 2005

Prepared by: ing. Jared Baraza

1rst Session
Lecturer: Prof. Dr. R. Struzak
Period: 9 AM to 10 AM
Topic: Frequency Management.

Professor Struzak started his lecture by defining what frequency management is all about by giving a historical development of physics in the frequency domain.

History of Radio Spectrum: Before Fourier formulated the Fourier transformation, there was nothing of importance to the physicists in the frequency domain. All physics research was based on the time-space domain. Fourier transformation and later on James Clark Maxwell's theory (1864) transformed this standpoint that led to the study of frequency spectrum.
Later on Heinrich Hertz (1888) used the findings of electromagnetic theories of Maxwell and Fourier to discover the transmission of signals by radio waves. This opened the new field of radio communication that became very popular in the 19th century. Radio equipment was built by people like Marconi for long distance communication.

In the earlier times the radio spectrum was considered as a common and readily available resource that could be used by anybody anyhow. During this time a lot of innovations were made for example the Trans-Atlantic radio. Later on the radio spectrum became a scarce resource because many users were occupying the available frequencies. Interference became the order of the day due to lack of regulation. This was the beginning for the need of spectrum regulation that eventually led to what is now commonly known as spectrum management.

As from 1925 there was no more free frequency available according to the US department of commerce. In 1932 the International community sat together and established the International Telecommunication Union (ITU) under a treaty. The ITU had the following roles to play: prevent conflicts among members, convey policy goals, formulate regulations and resolve disputes among members. The member states have their own internal regulations and licensing rules that are independent of ITU. The ITU operates under strict observance of:
(a) Sovereignty
(b) common heritage
(c) consensus
(d) equitable access
(e) seniority
(f) special needs of developing countries.

Of importance to the participants is the ITU Radio Regulation RR S04 that governs spectrum and frequency allocations to administrations and operators worldwide.

Prof. Struzak highlighted during this lecture that the changing environment dictates usage of radio spectrum. He also emphasized that the spectrum is scarce and should be used for the common good by everybody. Last but not least, it was noted that the spectrum should be properly managed and utilized both internationally and nationally. The member states and operators are not forced to follow regulations of the ITU, but to follow national regulations in respective countries.

The ITU has a standing committee on Radio Spectrum management called World Radio Conference (WRC). WRC has divided the world in three regions for the purposes of radio frequency allocation and management. There are some other sectors in charge of standards, development, etc. Different frequency bands are assigned for different applications e.g. for space, satellite, fixed, land mobile among others. Prof. Struzak is a former Vice Chairman of the World Radio Commission (WRC) at ITU in Geneva.

2nd Session
Lecture
Time 10.30 to 11.00 hrs
Lecturer: Dr. Sebastian Buettrich & Tomas Krag
Topic: Wireless Road show:

The two lecturers from Denmark introduced their organization wire.less.dk based in Denmark to the participants. They summarized the activities of the organization as follows:
developer of wireless solutions for NGOs and civil societies in developing countries
work in collaboration with entities in developing countries to teach, learn, help, and build community wireless networks
Conduct workshops in wireless technology and Linux for groups, NGOs and civil society organizations in developing countries
Cooperate with entities from developing countries in funding and rollout of pilot community networks.
It was emphasized in the discussion that developing countries should collaborate with the organization in introducing wireless technology in respective countries.

Wire.less.dk is ready to discuss with the representatives from developing countries further in the matter. They can be reached on the Internet at: http://thewirelessroadshow.org

3rd Session
Time 11.30 to 12.30 Hrs
Topic: Link Budget Planning
Lecturer: Marco Zennaro

Mr. Zennaro started off by highlighting important parameters and factors that must be considered when planning a wireless link. First of all he reminded the participants of the Decibels and the Milli watts and how they are inter- related in the so called dB mathematics that the participants are now all familiar with.

Different power measurement units were highlighted as follows:

  • 1 dB: 10 x log (P2/P1)
  • dBi: Power level measured with reference to isotropic Antenna
  • dBW: Power measured in dB with reference to 1 Watt
  • dBm: Power measured in dB with reference to 1 Mill watt
  • +3 dB: double the power
  • +10 dB ten times power
  • -3dB halve power
  • -10 dB one tenth power

It was noted that the dB measure is important because it is easier to add and subtract relative power levels instead of calculations involving real power (watts/Militates). He went further and introduced a so called "Intentional Radiator".
Intentional radiator is by definition consists of a Transmitter, a Cable and everything else before the Antenna. Another important parameter in radio communication is the EIRP; Equivalent Isotropic Radiated Power. The Freznel zone was also mentioned as very important in setting up a radio line of sight.
Participants were told that the radio line of sight is not necessarily the same as the visual line of sight. The main RF signal from the transmitter can only reach the receiver if the Freznel zone is not blocked by any obstruction.

The lecture also focused on the propagation basics including FSL, attenuation due to air, scattering, cable losses, multipath fading, diffraction and the possibilities of reflections on water. It was observed that propagation of radio signal is so much dependent on the environmental and geographical factors. A good link budget planning must therefore take into consideration not only the system parameters but also the environment into consideration. Mr. Zennaro went further and introduced important parameters that are used as a measure of link budget:

  • Link margin: this is a measure of link quality of the equipment
  • Minimum RSL: this is the minimal Receiver Signal level in dB (also known as Squelch)
  • Range: how far the signal can reach
  • Availability: how reliable is the link (99.999999%)
  • Path loss: total power lost in the link expressed in dB

Finally there was a demonstration of a real- time link budget analysis that produced a GIF of the following:

  • Freznel Zone
  • Path Profile
  • Link budget

Mr. Zennaro concluded his lecture by emphasizing that the link budget calculation using some software is just a simulation and a prediction. A lot of factors are assumed in the prediction model. An accurate link budget can only be achieved after carrying out field tests and site surveys.

4th Session
Time 12.30 Hrs to 13.00 Hrs
Topic: Radio Mobile Software
Lecturer: Prof. Pietrezemoli

Prof. Pietrezemoli started his lecture by introducing public domain software that can be used for radio network planning. He explained that the software can run on any PC with Windows platform but requires digital maps and digital elevation maps. The maps can be acquired from NASA shuttle. The software can calculate link budget parameters that are important for us in radio planning in the 20 KHz to 200 GHz frequency spectrum. The software can only work once a user has given the following inputs:

  • Coordinates of transmitter and receiver site (from GPS/topographical maps of the areas)
  • Antenna centerlines at both sites
  • Transmitter Power
  • Altitude of both transmitter and receiver sites
  • Transmitter frequency
  • Antenna gains for both transmitter and receiver (dBi)
  • Feeder type
  • Feeder cable length (dB/100m)
  • Receiver threshold (Squelch)
  • Fade margin
  • Earth radius factor ( assumed 4/3)
  • Terrain type
  • Polarization
  • Antenna type /pattern

In summary we can get the following results from this software:

  • Line of sight analysis displayed as graph
  • Path loss
  • Link Budget
  • System margin
  • Availability
  • Range/Coverage
  • Visual coverage

It was noted that the DEM does not show coastline. It only shows the elevation. The software is available as a public domain resource for download at: http://www.cplns.org/rmw/english.html

5th session:
Time: 1400 HRS to 1600 HRS
Topic: PEBBLE LINUX, LECTURER: MR. Rob Flickenger

Mr. Rob introduced a new wireless ready Linux version called Pebbles. Features of the software:

  • Drivers and tools are pre-installed
  • Updated drivers
  • Linux 2.4 kernel included
  • Read only file system supported
  • Standard system library based on Debian 3

Metrix pebble:

  • Features:
  • Many new tools and updates
  • Fine tuned for Soekris motherboard

Of importance to wireless networking is the WIFI Admin function: the WIFI Admin has the following functions:

  • System services
  • Wireless settings
  • Network interfaces
  • Statistics
  • Routes
  • Users

1. LINUX LABORATORY EXPERIMENTS:

The first lab was to connect an Access Point using Power over Internet. The second experiment was to configure the wireless link to access the internet using Metrix pebble. All groups managed to hook up to the internet via the wireless network

6th Session
Time 1630 Hrs to 1830 Hrs
TOPIC: RADIO LAB
Tutor: Prof. Pietrezemoli

Activities for the groups:

  • Downloading the radio mobile planning software
  • Downloading digital elevation maps
  • Planning and setting up two radio links using the software between Adriatic guesthouse and Trieste.
  • Analysis of the Link results
  • Change different inputs and observe results (simulation of real time situations) e.g. change antenna heights, change frequency, change transmit power, change antenna gain, change terrain model

All groups managed to download and manipulate the functions of the software without any serious difficulties.

Notes:
There was a small problem with the digital elevation maps that require a long time to download. Most participants want things to move extremely fast. This depends also on the processing speed of the computer and the internet.

The results of this simulation and prediction are not 100% accurate. The prediction do not take into consideration all physical features and environmental matters. In order to set up a link a site visit and survey must b carried out and sometimes a radio propagation test to see how much the transmit signal is degraded over the link.

This marked the end of a very busy day for the participants.


This Report was prepared by:
Dipl. Ing. Jared Baraza
Manager Transmission Network,
Telkom Kenya Ltd,
11th Floor Telposta Plaza
Kenyatta Aveue
P.O. Box 30301
Narobi.
Tel: +254-20-3232880
Email: ochiengjerry@yahoo.com
Email: obaraza@ictp.it