Investigation of a rural telecommunication system using VSAT technology in Malaysia

Mohammad Arif Abdullah', Emir Mauludi Husni2, Syed Idris Syed Hassan3 .

'School of Aerospace Engineering Universiti Sains Malaysia

Engineering Campus 14300 Nibong Tebal, Penang.

arif8 l79@yahoo.com

2School of Engineering & Information Technology Universiti Malaysia Sabah

Locked Bag No 2073 88999 Kota Kinabalu, Sabah.

ehusni@yahoo.com

3School of Electrical and Electronic Engineering Universiti Sains Malaysia

Engineering Campus 14300 Nibong Tebal, Penang.

s yed@eng.usm.my

Absfract- This study investigates the VSAT network that is applied to rural telecommunication network. The VSAT network is planned based on telecommunication demand as obtained from the survey. The network uses Measat-1 satellite and existing Hub of Maxis located at Shah Alam, Selangor. The network is also based on a star network using access of FDMA-MCPC inbound and a TDM outbound channels. To decide antenna diameter and HPA power of antenna, the satellite link budget is calculated based on the service requirement of BER at lo-', 64 kbps inbound information bit rate and BPSK modulation techniques. Rain attenuation is calculated by using the local measured rain rate with 0.01% time of the year that is exceeding 129 mm/h [l].

Keywords; telecommunication, rural, VSAT, satellite communication, star-shaped network.

I. INTRODUCTION

In recent years, the use of satellite technology has become more attractive for improving the telecommunication scenario in the rural areas. Numerous telecommunication studies on satellite-based have been carried out in the world. The results show that, a satellite-based telecommunication network can provide efficient long distance telecommunication services to rural communities at a lower cost than land-based wired networks in most cases [2].

The limitatipns to provide access of reliable telecommunication to the rural areas are including poor

geographic conditions, low-income levels, low population densities and lack of essential social and economic infrastructure such as health, education, electricity, clean water and roads.

In Malaysia, there are several options in providing telecommunication service to the rural people. Wireless Local Loop (WLL) technology for example, are now being used by Telekom Malaysia (TM) to bring telecommunication service to the rural people. Another wireless technology is by using a Very Small Aperture Terminal (VSAT) system that is provided by TM and also known as TM VSAT. Volunteers in Technical Assistance (VITA), US-based non-for-profit organization is also providing rural areas users worldwide with data only connectivity using their VITAsat satellite (store-and-fopvard e-mail based system).

However, the limitation of the existing systems is the charges were still high to the rural communities. -Other limitation is its coverage area. For'example, WLL system is usually covers only a few kilometers from base station. Another problem with existing satellite-based system is about rain attenuation for frequency above 10 GHz. The rain attenuation that has been used widely is ITU-R model. But some studies in tropical regions shows that the model underestimates significantly this value [3]. This makes the link performance are degraded below than predictable level.

0-7803-8114-9/03/$17.00 02003 IEEE. 883

11. METHODOLOGY

It is started with a survey to collect some data from selected rural population in Malaysia. The data needed are about users’ socio-economic background including their affordability, type of services they need and others.

From these inputs, the entire hardware configuration at the ground terminals will be defined. The procedures in designing communication system used in this work are as shown in Fig. 1 below.

Ground Station

Satellite User f+ Terminal

System Configuration

+ No Meet the

requirements

V P C

‘

1 I I Proposed Model

I I

Figure 1. Flowchart for satellite communication system prelimnary design

To achieve the lowest possible cost, related existing component either in space or ground segment in Malaysia were used in design and re-modeled.

111. DATA COLLECTION & ANALYSIS

A. Methods for Sampling The methods and processes used in conducting the survey

including the research design, survey result and data analysis are discussed in this section.

The survey design is selected because it is the best method to describe existing characteristics of a large group of people. The instrument used in the survey was a self-designed standard questionnaire that consists of statements in Bahasa Melayu to make it easier for the respondents to understand and answer those questions.

The target areas for this survey are the rural areas that is totally do not have or having insufficient telecommunication infrastructures ‘ and statistically, community’s data are balanced. Thus, it is more applicable and practical if sampling is made on suitable selected areas compared to random sampling. All selected areas are chosen after doing some discussions/consultations with the administrator of District

Office in each state. Three locations are surveyed but data is only collected once at each location.

In this study, a suitable respondent is self-chosen to meet the study objectives. This is known as reasoned sampling and it is suitable to be used when there is no sampling frame to study. Therefore, only selected respondent from selected population based on requirements given were allowed to answer the questionnaire.

B. Results The number of total respondents is 112 and the fraction of

respondents according to those three places is shown in Table 1 below. TABLE 1 . SELECTED AREAS AND THE NUMBER OF RESPONDENTS

The data collected from the questionnaire in this study was analyzed and summarized using appropriate descriptive statistics based on the objectives of the survey.

The result obtained from this study shows that, the percentage of male respondents was 80.4 while the female respondents were 19.6%. More than 44% of the respondents completed Standard 6 as their highest education qualification. 23.2% of the respondents were farmers, 5.4% was fisherman and the rest of the respondents were doing other jobs. It is also obtained that 50% of the respondents had income below than RM 500 and 16.1% of the respondents had income between RM 501 to RM 1000 per month. Almost all houses are supplied with electricity and clean water.

Five types of communication system were asked to the respondents to know the frequency of using these systems daily. It is including public phone, home telephone, letter, e- mail and facsimile. The result shows that, more than 60% of the respondents had never used the public phone and only 34.8% of the respondents had used a public phone between 1 to 4 times daily. For the home telephone, more than 90% of the respondents had never used it. Only 8.9% of the respondents had using home telephone between 1 to 4 times daily. More than 70% of the respondents had never used letter and almost 100% of the respondents also had never used e- mail. For facsimile system, more than 85% of the respondents had never used it.

The reasons of never used the communication services answered by respondents were includes don’t have it, not related to their daily activities and very limited usage. The estimated telecommunication expenses per month shows that 71.4% of the respondents had expensed below than RM 25 and 58.0% of the respondents were willing to pay more for using the telecommunication services in future. 63.7% from the total 71.4% of the respondents that had expensed below RM 25 per month were willing to pay and only 7.5% were not willing at all.

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There are three types of communication that can be offered to rural people, which includes data, voice and video communication. From all these types of communication, data and voice communication are most needed. However home telephone is most demanded by respondents (as a voice communication tool). This is shown by 97% of the respondents needs home telephone compared with only 80% of the respondents needs data communication. More than 85% of the respondents were not needs the video communication.

The percentages of all additional hnctions according to respondents' need are as follows;

1. It must be useful in the field of health (92.8%)

2. It must be usehl for village affair (90.2%)

3. It must be useful for their children's education (83.9%)

4. It must be useful in bringing information

related to their works (80.3 yo)

IV. SATELLITE COMMUNICATION SYSTEM DESIGN

This section will discuss about satellite communication system designed for rural telecommunication purposes and based on the result obtained from the survey. Satellite communication system can be defined as a configuration of satellite and earth station, in a space system that will send the information to each other. Communication type that used in design is only to provide voice communication over Ku-band VSAT terminal. The reason for only offering voice communication is because of its demand is higher than data and video communication, as obtained in survey. Meanwhile, by using Ku-band frequency, terrestrial interference can be avoided but interference from adjacent satellite still remains.

A. Network Topology and Traflc Requirements Two-way full star-shaped network topology was selected to

provide duplex communication between a central Hub and multiple remote sites. This topology allows all remote nodes to interconnect to the Public Switch Telephone Network (PSTN) through Hub. The Hub station has a larger antenna size than that of a VSAT, which allows many remote sites to be configured with smaller and less costly antennas. This topology was selected by assuming that the users would like to connect to the PSTN more than to each other. Fig. 2 shows a simplified diagram for full star-shaped VSAT network topology.

The total network capacity is estimated to be 800 full duplex pre-assigned MCPC channels. Total peak network capacity therefore, is 6.7 Mbps.

Some general parameters for Measat-I satellite, Hub and VSAT terminal are shown in Table 2. VSAT terminal is located at Padang Terap, Kedah (assumed) and it will be used in all related analysis to represent all VSAT terminals in the proposed network.

Satellite channel

VSAT I

VSAT I

U w g u r e 2. Star-shaped VSAT network

TABLE2. SOME GENERAL PARAMETERS FOR SPACE AND GROUND SEGMENTS

Parameter 1. Measat- 1

Launch date Satellite lifetime Satellite longitude Frequency

Transponder bandwidth Polarization

Location Coordinate

2. Hub

Location Coordinate

Value

13 January 1996 12.2 years 91.5'E fu = 13.75 to 14.5 GHz f~ = 10.95 to 11.2 GHz 54 MHz Vertical

Shah Alam, Selpgor . 101.55OE 3.23" N

Padang Terap, Kedah 100.75OE 6.25'N

The network is composed of a central Hub terminal and comprises of multiple remote sites scattered within Measat- 1 coverage area. Each VSAT has an own frequency band and accessing the transponder in Frequency Division Multiple Access (FDMA) mode. Fig. 3 illustrates the star-shaped network with multiplexed duplex connections. In this mode of operation, individual carriers are assigned with specific frequency slots on a permanent basis, which is very efficient for unintempted circuit requirements.

Each VSAT can transmit and receive K channels equivalent to the connections of the terminals to the VSAT terminal. The Hub must be able to transmit and receive NK channels to-and- from all the VSATs.

outbound I 1 2

Utilised

band

Figure 3. FDMA-MCPC inbound/TDM outbound [4]

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With Multiple Channels Per Carrier (MCPC), each VSAT will transmit only one carrier that multiplexed their channel in the time. This allows the channel to be shared by several users by multiplexing of up to 8 or 10 Time Division Multiplex (TDM) user channels into single 64 kbps carrier (8 or 10 TDM compressed voice channels).

B. System Configuration Configuration of equipment for this system can be divided

into two parts i.e. one for Hub and another one for VSAT terminal. The Hub terminal consists of an 11 m antenna dish, 200 W High Power Amplifier (HPA) rated power, modems and multiplexing equipment. Network Management System (NMS) has also been provided at the Hub, which monitors and controls the links, perform call processing and integrated with existing billing platforms.

It is important to know that for small satellite networks, it is better to lease Hub capacity and connectivity on a larger existing Hub from a different network, since owning a Hub may not be economically acceptable for a small network.

VSAT station consists of two parts; the indoor unit (IDU) that interface to the user segment and the out door unit (ODU) that interface to the space segment. Coherence modulation scheme, Binary Phase Shift Keying (BPSK) is used.

C. Link Budget The network uses FDMA-MCPC/TDM access type with

inbound information bit rate of 64 kbps. Using inbound and outbound code rate of 0.5, thus the inbound transmission rate is 128 kbps and outbound transmission rate become 512 kbps. The modulation used is BPSK with a 0.7 bpsHz spectral efficiency.

Links analysis for proposed VSAT network is summarized -in Table 4. Uplink and downlink frequencies are fu = 14.032 GHz and fD = 10.982 GHz respectively. The service requirement is a Bit Error Rate (BER) = and this mean a required E,,” without coding is 11.3 dB. The BER of lo-’ is selected for a typical digital transmission and it is an acceptable quality for voice communication application [4].

The value for Output Back Off (OBO) is assumed -5 for both VSAT and Hub terminals by using Traveling Wave Tube Amplifier (TWTA). From this link budget, a required diameter for proposed VSAT terminal is 3.6 m with 100 W HPA rated power.

D. Total Cost The costs of a VSAT depend directly on the total number

of VSAT in the network. The larger the network size, the lower the unit cost for each VSAT terminal but then makes a larger cost for the overall system. Tabk 5 illustrates the budget headings of a proposed VSAT network. (Refers to a network of 100 VSAT stations and a shared Hub for a 5-year period).

The estimated total cost for this system is about USD 10M. This means, for a typical 8 users per VSAT, the cost for each user would be about USD 7 per day.

TABLE 4. CALCULATED LINK ANALYSIS

Inbound Outbound

Uplink Earth station EIRP (dBW) Path loss (dB) Gain of ideal 1 m2 antenna (dB) Operating flux density (dBW/m*) Saturation flux density (dBW/m*) Input back-off (dB) per carrier Total input back-off (dB) Satellite G/T (dB/K) Uplink C/lv, at saturation (dBHz) Uplink C/N, (dBHz)

Downlink Saturated satellite EIRP (dBW) Path loss (dB) Earth station G/T (dBiK) Downlink CN,, (dBHz) Total output back-off (dB) Output back-off (dB) per carrier Operating EIRP (dBW) per carrier Downlink UNo (dBHz)

Intermodulation (dBHz) Interference (dBHz)

Total link C/N, (dBHz) per camer Required EdNo (dB) (no coding) Coding gain (dB) Required EdNo (dB) (with coding) Required CNo (dB)

66.80 245.88 44.39 -134.69 -86.91 -47.78 -10.00 8.90 106.20 58.42

58.39 225.18 34.45 96.26 -6.00 -38.50 19.89 57.76

79.71 246.59 44.39

-122.49 -90.10 -32.39 -10.00 12.10 106.21 73.82

56.87 224.81 25.17 85.83 -6.00 -24.65 32.22 61.18

82.48 94.81 81.21 83.84

55.05 60.95 11.30 11.30 5.50 5.50 5.80 5.80 53.86 59.88

I Margin (dB) 1.19 1.07

TABLE 5. THE ESTIMATED TOTAL COST

Cost per unit Units Total Cost per month (USD) (Over 5 years)(USD) (USD)

VSAT Equipment 8000 100 800000 13333 Installation 1000 100 100000 1661 Spare parts 1000 100 100000 1667 Maintenance 1000 100 100000 1667 per VSAT per year

Hub

Lease cost per 50 000 5 250000 4167

Hub-to-host 25 000 5 150000 2083 Year

connection cost per year

Satellite Transponder lease 1 600 000 5 8 000 000 133 333

Licence One-time fee 8 000 1 8 000 133

per year

Licence charge per 100 5000 500000 8 333 VSAT per year

Total cost 10 008 000 166 800 Cost per VSAT per month 1668

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V. PROPOSED MODEL

From the result obtained, it shows that the proposed system is suitable to be implemented in Malaysia. Hub station belonging to Maxis at Shah Alam, Selangor will be used in this network. While each user’s house will be connected to VSAT station by common terrestrial cable. Ordinary telephone 2-wire copper line will be installed between the VSAT and subscriber’s premises. Fig. 4 shows a simplified block diagram for the MCPC equipment configuration.

1

lndmr Unlt Outdoor Unit

Figure 4. The configuration of equipment

The Hub transmits a channel divided into time slot (TDM), which is received by all VSATs, but can be addressed to specific VSAT terminal. With TDM, a number of independent signals in digital format can be transmitted through a common channel by interleaving pulses in time. Thus, there are two main channels on the satellite -a TDM outbound from the Hub to VSATs and an FDMA-MCPC inbound from VSATs to the Hub.

The cost and prices for each equipment and services should be as low as possible. As obtained from the survey, users are only willing to pay not more than RM 25 per month. Thus, the cost should be below than that to attract the rural communities.

Government by its company can be major parties to support the total initial cost of proposed system. This is because telecommunication was a policy principle applied to achieve telecommunication services among lower income population by making use of subsidy mechanisms. Thus, the government resources have to use for the development of rural telecommunications.’ By this step, the cost for users have to

solution to the rural cbmmunities. pay will decrease c nd this of course can give attractive

The involved parties, in its entirety are includes;

0 The users (rural communities)

The VSAT network operator (may be a telecom company like TM)

The VSAT network provider (may be a national telecom operator)

0 The equipment provider (may be the network provider or different party)

The various known services that can be developed by the

0

proposed system are includes;

Tele-education

Medical data transfer

Emergency services

Sales monitoring and stock control

Agribusiness

CONCLUSION The rural telecommunication network must be configured

according to the user’s requirements. Foremost in this, the network must always be available and capable of providing voice service in meeting the user’s expectation. The satellite technology gives more advantages and has higher reliability than any other wire line or wireless technologies. Its capability in providing coverage over the large coverage areas and relatively immune to topography makes this technology become more attractive for improving the telecommunication system in the rural areas. This study was conducted to preliminary design a satellite-based telecommunication system using VSAT for rural area in Malaysia. The network uses Measat-1 satellite and existing Hub of Maxis. The network also based on a star-shaped network using access of FDMA- MCPC inbound and a TDM outbound channels. A 3.6 m VSAT terminal is needed to be located in rural area to get 99.99% link availability in rain condition. With a good marketing. strategy, the proposed model shall attract the majority of the population. In additions, such missions can become an important factor in bringing the benefits of education and social development to all rural people.

ACKNOWLEDGMENT I owe special thanks to my supervisor, Assoc. Prof. Dr.

Emir Mauludi Husni, for giving me the opportunity to pursue exciting research opportunities and also to my co-supervisor, Prof. Syed Idris Syed Hassan for helping me in this research. Last but not least, I acknowledge with gratitude the support of Ms Nor Hanim Salwa Abd Rahman, who has provided constant encouragement during my study.

REFERENCES Syed Idris Syed Hassan, Kajian Perambatan Isyarat SatelittKe Arah Sistem Perhubungan Global rang Berkualiti. Sin syarahan umum perlantikan Profesor. Pulau Pinang: Penerbit Universiti Sains Malaysia, 2002. E. Hudsen, When Telephones Reach the Village: The Role of Telecommunications in Rural Development. Nonvood, NJ: Ablex Publishing Corporation, 1984. A. Yagasena, Satellite-to-Earth Signal Propagation Through Rain At Ku-Band In Malaysia. Ph.D Thesis. Universiti Sains Malaysia, 2000. G. Maral, VSAT Networks. Chichester, England: John Wiley & Sons, 1995. R. Conte, Satellite Rural Telephone Network design: A Methodology for Performance Optimization. Ph.D Thesis. Virginia Polytechnic Institute and State University, 2000. R. Elbert, The Satellite Communication: Ground Segment and Earth Station Handbook. Boston: Artech House, Inc., 2001. T. Pratt and W. Bostian, Satellite Communications. New York John Wiley & Sons, 1986.

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