Cost-effective Data-Enabled Network Design for the Ga-Rankuwa and Soshanguve Areas near Pretoria

P. Mailula and L. W. Snyman

Telkom - Alcatel Centre of Excellence in Radio planning, French South African Technical Institute in Electronics (F’SATIE), School of Electrical Engineering, Technikon Pretoria.

P/Bag X680,Pretoria, South Africa. Tel: +27(012) 318 4191 Fax: +27(012) 318 5294

E-mails: nkokoba@webmail.co.za , lsnyman@techpta.aq.za

Abstract – The Development of cost-effective and economically viable telecommunications solutions for rural underdeveloped areas has been a key problem to Africa and South Africa. Selecting an appropriate telecommunications technology and an appropriate network topology that could provide both voice and data communication solutions for these areas would be a major advantage for both the community and industries in these areas. Success lies in our ability to adapt selected technologies and implement it with a viable and affordable telecommunication solution. This paper proposes an appropriate telecommunications technology utilization of a cost effective network that can provide wide bandwidth for voice and data telecommunications solutions that are essential for the education, business and private multi-user needs for the Soshanguve and Ga-Rankuwa areas, North-West of Pretoria..

a. Introduction Although South Africa's fixed line telecommunication penetration is relatively high in comparison to other African countries, basic telephony and data-enabled services remain unaffordable and difficult to access for most of the South African population. Most of the data enabled services are centered in the economic epicenters of the country, making them inaccessible to underdeveloped areas. On average, the underdeveloped and rural areas of this country have a telephone penetration of less than one per 100 households [1,2]. The implementation of economically viable telecommunication infrastructure for underdeveloped and rural areas could have major high impacts on the education sector, community upliftment, industrial development and the social development of these areas.

This endeavour could enourmously stimulate economic growth in the northern regions of South Afroica, leading to a greater prosperity for all South Africas populations. It is therefore essential to develop cost effective telecom infrastructure that satisfy the target selected needs of a particular communities. The following approaches could hold the key to some possible solutions [3-5]: 1. An approach of combining wireless

telecommunication systems with fixed line technologies primarily for providing access to services cost effectively over large areas.

2. An approach of combining data-enabled services

with existing voice telecommunication systems. Data-enabled telecommunication systems can provide large scale stimulation in especially the educational and business environments in these areas.

3. An approach of providing telecommunications

services on a multi-user basis in underdeveloped communities instead of targeting the maximum number of individual subscribers. This would involve the development and utilization of so called “larger information and communication technology centers” in theser areas that could offer economic self-sustainability of the centre itself in the longer term.

4. Provision of by government of a core infrastructure

onto which a large number of low cost voice and data-enabled telecommunication systems could be connected to. Systems could then be supplied and installed by a number of entrepreneurial vendors in a particular area.

In this study, the following were achieved. 1. An appropriate telecommunication technology

survey was conducted. Systems that could support the provision of cost effective combined voice-data telecommunications services to rural areas in South Africa were focused on.

2. Subsequently, a telecommunications network was designed to support first iteration cost effective data telecommunications to the Ga-rankuwa and Soshanguve areas North of Pretoria, South Africa.

b. Telecommunication Technology Survey Results

To meet the voice and data-enabled telecommunications requirements for these areas, the selection of a combination of fixed lined and wireless technologies would be ideal. Figure 1: Example of a combined optical fiber backbone and RF microwave broadcast network for providing cost-effective high-bandwidth telecommunications to underdeveloped areas in South Africa. A number of access techniques are available with wireless systems such as time division multiple access (TDMA), code division multiple access (CDMA), and wide CDMA (w-CDMA). This together with radio technologies such as second-generation cordless telephony (CT2), The Global System for Mobile Telecommunications (GSM), Digital Enhanced Cordless Telephony (DECT), and newer technologies such as General Packet Radio Service (GPRS), Universal Mobile Telecommunication Systems (UMTS), Wireless Fidelity systems (WiFi) and Free Space Optical (Laser) Link systems could provide more economically viable telecommunication services as well as especially to date-enabled servics to these areas. [ 6–13 ] Furthermore, the deployment of wireless local loop systems, using a DECT air interface standard which

have already been implemented in some areas North West of Pretoria, could be examples of optimum utilization of existing networks onto which expansions could probably be implemented. DECT, or possibly other wireless technologies, provides a complete wireless access solution for new and expanding telecommunication networks with seamless integration of both voice and data services. In this study a few technologies were selected as possible ideal technologies to be used in the network design of this project as outlined above. These included fixed-line fiber optic technology, a free space optical link system and the DECT technology system. The key characteristics associated with each technology are outlined below.

Fiber Optic Technology

o Large Bandwidth o Transmission rate of 2Gbps over tens of km o Low signal attenuation o Immunity to EMI, RFI and cross talk o Very high level of data security

Free Space Optical Link Technology

o Simple and low cost implementation o Speed transmission rate of 20Mbps over 2 km o Efficient and reliable data transfer o Low power requirements o No frequency allocation o Directed, point-to-point connectivity o Easy management and maintenance

DECT (1.8 GHz) Technology

o Low cost o Transmission speed of up to 2Mbps o Capable of handling up to 100 000 users per

km2 in an office environment o No interference from other technologies o Services are compatible with GSM, ISDN and

UMTS o Low power requirement

c. Estimated cost/kilometer/subscriber analysis for selected telecommunication technologies

Table 1 shows approximate cost estimates based on surveys conducted for fixed-lined optical fiber, free space optical link, GSM and DECT technologies. The information was obtained from sources based on a client enquiry approach of vendors in South Africa.

Optic Fiber Back Bone

Tx

RF Broadcast Tx Tx

The optical fiber technology proved to be an ideal technology for providing large bandwidth to individual subscribers on a point-to-point basis. However, the installation costs in high-density underdeveloped areas in South Africa would be quite enormous and would not be in the economic reach of many possible subscribers. The free space optical link technology proved to be a viable technology for implementation in these areas. A significant installation cost savings would be made since it transmits data at high bandwidth by means of infrared laser through air and with a range of up to 4km in a point-to-point configuration. It, however, has a disadvantage of the signal being affected by smoke in the underdeveloped areas. This system could be utilized most effectively for reaching out to local schools, which are in most cases not easily accessible by fixed line technology.. If appropriate interrupt protocol procedures are installed between the transmitter and the receiver, the high bandwidth transmission capabilities would outweigh the disruptions due to atmospheric interference effects. The GSM and DECT technologies proved to be suitable for deploying data-enabled telecommunications in high-density, underdeveloped suburban areas in South Africa due to their ability to cover large areas penetrating high densities of potential subscribers with low capital outlay costs. These technologies could, therefore, be ideal solutions for underdeveloped areas. Satellite ground-based station technology that provides linkages with service providers in a hopping link approach over larger distances is another viable option. This technology could provide links to larger local area networks in distant centers. Direct access to

international service providers in a deregulated future telecommunication environment would provide a further attractive option. The cost implications associated with these technologies are, however, speculative. A particular viable option is a combination of the above quoted technologies in order to serve specific needs. Optical fiber and FSOL systems are used to connect different individual users requiring high bandwidth telecommunication facilities, whereas wireless technologies such as GSM or DECT that are data-enabled could be used to reach out to areas with a moderate subscriber density providing telecommunication services on a point to multi-point basis.

d. Radio planning considerations for wirelless

network designs The incorporation of wireless technologies such as GSM and DECT systems with high bandwidth data systems to underdeveloped areas requires extensive radio planning to be executed as part of network planning exercise for a new rolled out system. Such systems would use a combination of point-to-point technologies and broadcast technologies. This process especially becomes important and more critical at higher frequencies of transmission since it becomes more sensitive to the effects of absorption, multi-path reflection and interference. Radio frequency based data transmission is also more susceptible to the detrimental effects of interference from adjacent cells. Radio planning tools are used to provide an accurate simulation of network designs that are to be rolled out. Atoll [16] is a radio planning software that integrates advanced information technology techniques and propagation algorithms to develop and plan radio networks. In the network development, the DECT system is simulated using the WLL propagation model in Atoll to predict signal strength and coverage. The Atoll software helps in the prediction of radio coverage by using propagation models that may help in the designing and optimization of wireless networks. Atoll supports applications such as cellular systems, PCS, Wireless Local Loop systems, paging, broadcast systems, microwave etc. The Wireless Local Loop (WLL) propagation model was used in this project since previous research showed that it provided the best correlation between predicted results

Technology Estimated

Capital Layout required for Transmission Equipment and Commisioning (Rand)

Bandwidth available (MHz) / Throughput (kbps)

Typical Range (km)

Potential subscriber enrolment per practical reception site / area

Estimated System Cost per Throughput per Sub-scriber (Rand/kbps/ subscriber)

Optical Fibre

107

200 000 / 200 000

100 (line)

102

5

GSM (900 MHz)

107

10 / 14.4

20 (radius)

105

6.9

Free Space Optical Link

5 x 104

200 / 2 000

0.3 – 4 (line)

102

0.025

DECT (1.8 GHz)

106

200 / 2000 (potentially)

20 (radius)

105

0.005

Table 1: Estimated System Layout Cost per Data Download Rate for telecommunications provision with different technologies in underdeveloped suburban areas in South Africa.

PR = PTGTGRλ2 / 4ππππr2 ……………(1)

and actual measurements in the field in comparison with models such as the ITU-526 model. By simulating wireless DECT networks in Atoll that uses digital maps such as digital terrain maps (DTMs) and clutter maps, the comparison of predicted coverage can be accurately done before any implementations and capital outlay is made. Radio planning is therefore one of the most critical issues to be executed in the network planning of future networks for high and medium density suburban and rural areas in South Africa.

e. The Free Space Propagation (broadcast) Model

The free space propagation model is used to predict received signal strength when the transmitter and receiver have a clear, unobstructed line-of-sight path between them. The free space power received by a receiver antenna which is separated from a radiating transmitter antenna by a distance d, is given by [ 13-15 ]: where PT is the transmitted power, PR is the received

power which is a function of the Transmitter-Receiver (T-R) separation, GT is the transmitter antenna gain, GR is the receiver antenna gain, r is the T-R separation distance in meters and λλλλ is the wavelength in meters Most radio Planning models use the following formula to estimate the attenuation of the transmitted signal.

A = 32.45 + 20 log (F) +20 log (d) ……….(2)

where F is the frequency used for the radiation and d is the distance from the transmitter.

The WLL model, which is based on the ITU 526-6 model, takes into account the terrain profile as well as the height of clutter components in the environment. Attenuation for the WLL model is given by

A = (32.45+k)+20 log (F) + 10 n1 × log (d) + DL ………(3)

where k and n1 are constants with values of k = 0.67, n1 = 2.06. DL is the diffraction losses due to obstacles in the environment and varies according to the obstacles in the environment.

f. Prediction of RF Coverage Predictions were done with Atoll Radio Planning Software [ 16 ] for the Ga-rankuwa and Soshanguve areas in the North West region of Pretoria. The WLL propagation model was used for the simulations in conjunction with available digital terrain maps and clutter maps for the selected areas. Hypothetical DECT transmitters at 1.8GHz were created at the highest points in selected favorable sites in the area. Analysis of the network design was performed to obtain the maximum coverage for the selected areas using the minimum number of transmitters. A particular popular approach that has been adapted is the use of high power directional antennas that direct 15 dBi of radiated signal along an elongated shallow valley in areas between adjacent hills. It was observed that this approach provided the optimum coverage for the given terrain in the areas and required the least number of transmitters to be set up. The specifications for a typical DECT transmitter as deployed for the basis of the planning exercise were as follows. Height : 35m Antenna Type : omni directional Power : 24dBm Tilt : 0 degrees Figure 2 gives an example of the typical terrain of the areas under study. Darker regions depict areas that are “shadowed” and represents hills and mountainous areas, while sharper line contoured features are indicative of valleys and rivers.

Figure 2: Digital Elevation Map and contour data for Ga-Rankuwa and Shoshanguve Regions

Ga-RankuwaRegion

Shoshanguve Region

Figure 3 shows the digital terrain map overlaid with a scanned map giving a more descriptive overview of the region being considered.

Figure 3: Digital Elevation Map overlaid with a Scanned Map of the same region showing built structures, roads, railways etc. Figure 4 provides the detail of typical clutter data that is incorporated into the predictions. This study concentrated, however, took into account the coverage on a macro level for the selected area. The detailed fluctuations caused by absorption and scattering of the received signal strength as a result of specific clutter types such as buildings, vegetation, etc. were not studied.

Figure 4: Overlay of Clutter maps onto DTM and Scanned Map. Figure 5 gives a description of the clutter categories that were considered.

Figure 5: Clutter Categories considered in this study

g. First Iteration Network Design for the Ga-rankuwa and Soshanguve areas North West of Pretoria

A solution to the problem of non-access in many of these areas is to provide RF based access such as DECT at 1880Hz. In the first iteration network design for the Ga-rankuwa and Shoshanguve areas, DECT transmitters were placed at Technikon North West and Technikon Northern Gauteng campuses, primarily due to the ease of access to these sites, and in the Mabopane area respectively. Omni directional antennae were used at the different sites. Figure 6 shows our first iteration network design with an emphasis of providing low cost data enabled telecommuincation to the Garankuve, Soshanguve and Mapopane areas nort of Pretoria. The network includes a combination of existing optical fibre line to the Rosslynnn Industrial area, and a diginet line to the Technikon Northern Gauteng. Since this line already supports fast core data enabled telecommunications it is only necessary to follow an add on approch by adding on data-enabled wireless DECT (or UMTS) network components. Obviously capacity cabilities of the network would decrease in the wireless and outer outshirts of the network. Where dedicated high bandwitdh data enabled services are required , e.g at largeer educational institutions, schools, and isolated business complexes , the utilisation of Free Space Optical Link Systems offer ideal high bandwidth (2Mbps) point -to- point linkagres. The signal strength in the RF is strong were the threshold is –45 dBm (red) , and is very weak where the threshold is –80 dBm.(blue) The DECT system can be easily adapted as a telecommunication solution to schools, clinics and businesses in the area under study. Bandwidth of up to

50 Kbps could be provided to individual subscribers in these areas using the DECT technology. The French South African technical Institute in Electronics at Technikon Pretoria currently has diverse programs in radio planning of telecommunication networks. They also currently further develop and provide cost efficient telecommunication systems, such as the infra-red based Free Space Optical Link System to diverse clients.

h. Conclusions 1. A cost effective combined voice and data-enabled

network based on optic fiber backbone, Free Space Optical Link and RF telecommunications such as the DECT technology has been designed for the currently underdeveloped areas of Ga-rankuwa and Soshanguve North West of Pretoria. The implementation of the Free Space Optical Link seems especially attractive and revolutionary.

2. An ‘add-on’ approach was followed, in which appropriate telecommunication technology systems were added to the existing telecommunications infrastructure in the area so as to provide basic access to telecommunication services in these areas.

3. This network is shown to be highly cost-efficient in

supplying initial high bandwidth requirements in the area that would be normally anticipated for normal house holds, entertainment, business and education

purposes. It would also have a great potential to stimulate the economic development and business activities in the area.

i. Acknowledgements This project was the primary result from a B. Tech research and development project at FSATIE at the the Technikon Pretoria with Mr Peter Mailla as the student and with Prof L Snyman as supervisor. The Authors

Optic Fiber Back Bone (Existing)

Diginet Line (Existing)

Free Space Optical Links

10km Technikon

Pretoria

Technikon Northern Gauteng

Technikon North West

Figure 6: First Iteration coost effective data enabled Network Design for the Garankuva, Soshanguve andMabopane areas nort of Pretoria.

would like to thank Telkom SA and Alcatel Pty Ltd for assisting with site detail and transmitter specifications of their DECT transmitters in the underdeveloped areas North West of Pretoria. The authors would also like to thank all fellow radio planning students who assisted with this project. These include Mathews Mathibela, Ndivhuwo Mugwedi, Boitumelo Mooke, Livhuhani Ntsandeni and Kariem Tope. j. References [1] “ Africa reaches historic telecom milestone” in

ITU Telecommunication Indicators Update,. July 2001

[2] Keynote address, President of South Africa, Opening of parliament, February 2001.

[3] “Training –based implementation of DECT and GSM networks in underdeveloped areas in South Africa” by L. W. Snyman and J . Ehrhart. Quantum (SA ) : Journal for the Electronics Professional , pp 27 – 29 , February 2002.

[4] Snyman, L.W., “The design of distance training systems for South Africa with an emphasis on cost and didactical efficiency” Proceedings of IEEE COMSIG Conference, pp224-230, 1993.

[5] Snyman, L.W., "Low cost and localised distance training systems in South Africa, using television as medium” South African Journal of Higher Education, Vol. 9 No1,1995 pp. 199-203.

[6] The Network Age - Transmission Technologies” by : McDowell-Romero,California, Mc Graw Hill ,1996.“ETSI Telecom Standards” at http://www.etsi.org/frameset/home.html/pressroom/Media_Kit/DECT.htm,, 2001.

[8] Rapport, T.S. , “Wireless Communications, Principles and Practice” 2nd Edition ( ISBN 0-13-042232-0) , p 29- 54, 2002”

[9] Optical Fiber Communications 2nd Edition: John M SeniorFiber Optics Technology at http://floti.bell.ac.uk, 2002.

[10] “Hands-On Networking Essentials with Projects” by Michael J. Palmer at http://wwww.fsona.com/technology.php?sec=fso_primer, 2002

[11] GSM Architecture” at http://www.cs.uct.ac.za/Research/DNA/GiSMo/docs/reportmaster/node10.html#gsmnetwork., 2001

[12] “DECT Forum” at http://www.dectweb.com/dectforum/publicdocs/TechnicalDocument.PDF, 2002

[13] Rapport, T.S. , “Wireless Communications, Principles and Practice” 2nd Edition ( ISBN 0-13-042232-0) , p 107, 2002”

[14] Parsons J.D, “ The Radio Propagation Channel “ 2nd Edition , J Wiley and Sons Ltd, 1992.

[15] Krauss, J.D., Fleisch, D.A., “Electromagnetics with Applications” 5th Edition Mc Graw Hill , Chapter 4, 1999.

[16] Atoll Radio Planning Manual, release 1.7, FORSK France, October 2000.

Biographies Mr. N.Peter Mailula was a B Tech student in Electrical Engineering

(Telecommunication Technology) at F’SATIE) at Technikon Pretoria during 2002. He was previously working for the Department of Environmental Affairs and Tourism as a meteorological Technician

before joining the Technikon. He spent fourteen months on Gough Islands and another fourteen months on Marion Island doing Meteorological Observation for the South African Weather Service. He studied for Bachelor of Science degree in Physics and Mathematics at the University of the North.

Professor Lukas Willem Snyman is Head of Department of Electronic Engineering at the Technikon Pretoria and is also associated as researcher at the French’ South African Technical Institute in Electronics at Technikon Pretoria. During 2002 he was the program manager for the

Telkom–Alcatel Center of Excellence in Radio Planning at FSATIE with about 15 B’Tech students and 3 masters students studying at the center. Professor Snyman has published about 40 papers in the fields of semiconductor physics, microelectronics, and telecommunication technologies in conference proceedings and scientific journals, most of them international. During the period 1991 to 1995, he made initiating contributions towards the introduction of interactive tuition by means of web-based and MMDS interactive television tuition at the University of Pretoria, South Africa.