VERY SMALL APERTURE TERMINAL (VSAT) BASED RURAL/Remote NETWROK

May, 2007

KING FAHD UNIVERSITY OF PETROLEUM & MINERALS

DEPARTMENT OF ELECTRICAL ENGINEERING

EE 672: Satellite Communications Project

Project Overview

Project AgendaVSAT Overview

Proposed System

Propagation Effects

Link budget for inbound link

Link budget for Outbound link

Hub Earth Station

VSAT Antenna

Multiple Access Scheme

System Applications with respect to Remote Areas

Delay considerations and cost estimates

Rural/Remote Areas Scenarios

System Application Scenario (HASSAI)

Conclusion and future work (IRAQ scenario – GSM over VSAT)

VSAT Based Rural Network

Introduction

Many inhabitants of rural remote areas currently have no way of communicating locally or with the outside world as no services are available in their poor remote regions. As a solution, a VSAT associated with a local loop is employed.

Voice and data communications are essential to the economic development of a region, and it has been shown that traffic increases rapidly as soon as the service is available.

Why VSAT VSATs guarantee seamless global communication even across the last mile.

A VSAT Network can be provided through a lease arrangement with fixed transmission costs regardless of distance .

VSAT Networks offer superior flexibility and performance. Adding a site is quick and easy. Mobility is an other advantage

VSATs service charges depend on the bandwidth, which is allocated to network in line with your requirements. Whereas in a leased line, you get a dedicated circuit in multiples of 64 Kbps whether you need that amount of bandwidth or not.

Due to their high demand and mass production, VSAT terminals prices are falling, which makes it affordable and the choice to most business sites.

Why WLL•Shorter implementation time

•The costs to connect a customer are independent of the distance

•Higher flexibility

•Lower maintenance costs

Proposed System The types of customers the system is targeting are residence/non residence/corporate

offices.

The system consists of a single hub Earth station, a geostationary satellite ( ARABSAT 30.5 E global coverage) and a number of VSAT terminals.

Each VSAT earth station send and receives 64 Kbps data stream to and from the hub using BPSK and half rate error correction (FEC) coding giving a bit rate of 128 Kbps.

Using filters (0.25) gives a channel bandwidth of 160 KHZ. Adding 40 KHZ guard band between channels gives a total bandwidth of 200 KHZ per channel.

Data from VSAT to hub (inbound link) is (SCPC-DAMA) .

Data from hub to VSAT is sent using a continuous time division multiplexing (TDM) stream of packets.

The system can be used to transmit voice, data and fax.

System capacity is approximately 566 available 64 Kbps trunked channels with 5% blocking probability. Can reach up to 5540 channels if voice is compressed to 9.6 Kbps.

Proposed System - Continued

Satellite used ARABSAT 2B 30.5 E (KU band)

ARABSAT transponder EIRP 47 dBW

Transponder Bandwidth 36 MHZ

Transponder Noise Temperature (Ts) 500 k

Maximum antenna gain (TX & RX) 34 dB

Uplink frequency (inbound - VSAT to SAT) 14 GHZ

Downlink frequency (inbound - SAT to Hub) 12.521 GHZ

Uplink frequency (outbound - Hub to SAT) 14.02 GHZ

Downlink frequency (outbound – SAT to VSAT) 12.539 GHZ

Range to VSAT terminals 38000 Km

Max Hub transmission power 200 W

Noise temperature of Earth station 150 K

Hub antenna gain 50dB (uplink) & 49 dB (downlink)

VSAT transmission power 2 W

VSAT antenna gain 47.5 dB uplink & 46.5 dB downlink

VSAT antenna diameter 2 meter

VSAT antenna efficiency 65 %

VSAT noise temperature 147.8 K

Total inbound C/N at Hub 17.7 dB over 10 dB threshold

Total inbound C/N at VSAT 12.96 dB over min 6.0dB threshold

System Bandwidth 36 MHZ (1 transponder), 18MHZ inbound and 18MHZ for outbound link.

System capacity (5% blocking) 566 channels (up to 5400 if 9.6 kbps)

Multiple Access Scheme

Star hub configuration with frequency division multiple access, demand assigned single carrier per channel (DAMA SCPC).

A pool of satellite channels are used, which are available for use by any station in that network. On demand, a pair of available channels is assigned So that a call can be established.

Once the call is completed, the channels are returned to the pool for an assignment to another call. Since the satellite resource is used only in pro-portion to the active circuits and their holding times, this is ideally suited for voice traffic and data traffic in batch mode.

Delay Considerations

Processing delay at the VSAT terminal = 50 ms

Retransmission delay due to error (BER 10*-6) = 0 (Negligible)

Satellite delay = 253 ms (one way round trip)

Other terrestrial and processing delays = 50 ms (may be longer for database applications)

Approximate 1 way trip delay = 50+50+253 = 350 ms = 0.35 seconds.

This will be doubled (0.70 seconds) if the call is from VSAT site to VSAT site.

Cost Considerations

VSAT     Cost/5 years Cost Per Month

  Equipment $2,000.00 $2,000.00 $33.33

  Installation $700.00 $700.00 $11.67

  Spare parts $200.00 $200.00 $3.33

  Maintenance per Year $500.00 $2,500.00 $41.67

         

Hub        

  Lease Cost Per Year $40,000.00 $200,000.00 $3,333.33

         

Satellite (36 MHz) Bandwidth Lease/Year $1,800,000.00 $9,000,000.00 $150,000.00

         

License One Time Fee (Approx) $8,000.00 $8,000.00 $133.33

         

Total Total Estimated Cost   $9,213,400.00 $153,556.66

Cost per channel (90)     $102,371.11 $1,706.19

Channel cost/min $0.04      

System Scenarios

VSAT/WLL Applied Scenario (Hassai – Sudan)

population 30*30 km is approximately 6335.

Hassai – Sudan: VSAT/WLL Solution

Call charges

Estimated population 6335

Estimated Subscribers (15%) 1000

Average calls/day within loop 15 Minutes

Average calls/day within Network 5 Minutes

Monthly Fee/user $3.00

Call cost/min within loop $0.10

Call cost/min within Network $0.35

Total income/Month $100,500.00

Operation Cost for 45 trunked channels(50%)/Month $76,776.67

Revenue from Hassai Area only $23,723.33

Conclusion and Future Work Similar Systems already tested successfully in rural areas in Peru, many parts of

Africa, India, Malaysia and other countries.

System can be upgraded to deploy GSM through VSAT (Iraq scenario), ATM machine, POS, DBS, etc.

More work can be done to reduce the overall system cost and improve system delay, by considering LEO orbits or using a space loop for example.

References

[1] INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING

Int. J. Satell. Commun. Network. 2005; 23:307–321. Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/sat.819

[2] VSAT NETWORKING FOR BANKING D.J. Atkinson

[3] www.arabsat.com

[4] VSAT Networks, 2nd Edition, G. Maral

[5] http://www.nitehawk.com/rasmit/offset.html (offset antenna design)

[6] www.googleearth.com

[7] www.tracks4africa.com

[8] INTELSAT Satellite-based rural telephony: effective solutions for infrastructure development

[9] THE WLL/VSAT RURAL TELEPHONY TRIAL IN PERU

[10] Cable and Wireless Global VSAT – Iraq Case Study

[11] VSAT Networks – G. Maral