The Future

1. The Future Lecture-6 Presented By Laiq Akhtar Ch-15 p-

2. The Future • Satellite-based mobile-communication services are referred to by many different names, such as • Mobile Satellite Services (MSS), • Satellite Personal Communications Networks (S-PCN), • Global Mobile Personal Communications by Satellite (GMPCS). • The provisioning of personal communication services via satellites to users with handsets comparable in size to 2G (terrestrial) mobile handsets. • Have great potential

3. MSS • MSS is a mobile-telecommunication service in which the mobiles are linked directly to the satellite . • Provide global (or wide-area) coverage • Disadvantages • Limited system capacity, • Limited indoor service, high investment requirements, relatively • Long signal-propagation delays, • Relatively low data-transmission capacity.

4. MSS

5. The Market for MSS Networks • Complement the terrestrial cellular services • Also provide coverage in the countryside, on the sea and big lakes, • In countries without adequate telecommunication systems, and so on. • Customer segment intercontinental business users. 2G cellular systems were not global, but regional; thus, a business user travelling on another continent probably could not use his or her domestic mobile phone because the local cellular standard was different.

6. The Market for MSS Networks • The incompatibility between European and Japanese standards . • However, it is still true that there are so many different mobile phone standards in the world, building a multimode phone capable of handling all of them is not feasible. • The recent history of MMS consists almost entirely of bankruptcies. • There is nothing wrong with the technology; it is working fine.

7. MSS Networks • MSS networks typically use LEO or MEO orbits • LEO systems have the lowest orbit of all. They are located between a • Height of 200 km and 1,400 km, most often between 700 and 1,000 km. • • Low propagation delay; • • Low transmitter power requirement;

8. MSS Networks • The problems include the following: • • Satellites move fast in relation to the Earth, so frequent handovers • (HOs) are needed. • • A great number of satellites are needed to cover the Earth. • Globalstar and Iridium are both LEO MSS networks.

9. Iridium • Iridium was the first MSS system to be launched. • Its biggest investor was Motorola. • The system development started in 1990 • A fully functional Iridium system has 66 satellites. • There are altogether 6 orbits with 11 satellites per orbit. • Each satellite provides 48 cells or spot beams. • The cluster size is 12, so each frequency could be reused four times in each satellite. • The bandwidth allocation for the Iridium system is 5.15 MHz (1,621.35–1,626.5 MHz)

10. Iridium The system as designed could serve 1.4 million users. At the time of this writing, a large part of Iridium capacity is used by the U.S. Defence Department.

11. Globalstar • Globalstar’s commercial operation started at the end of 1999. • Its owners include space and telecommunication companies such as Loral, Qualcomm, Hyundai, and Alcatel. • The Globalstar system has 48 satellites in eight orbits. • The air interface technology is based on the IS-95 system (it is CDMA); • carrier bandwidth is 1.25 MHz. The system bandwidth allocation is 1,610 to 1,621.35 MHz in the uplink and 2,483.5 to 2,500 MHz in the downlink

12. Globalstar • The coverage area of a satellite is divided into 16 cells,

13. Teledesic • Teledesic was founded in 1990 by Bill Gates and Craig McCaw. • The Teledesic system is not a mobile communications system and will concentrate on broadband data traffic to fixed terminals. • It aims to provide fast (up to 64 Mbps in the downlink and only 2 Mbps in the uplink) broadband data services to areas that are not served by terrestrial fibre-optic networks.

14. Thuraya • Thuraya is a regional MSS system. It is a UAE (Abu Dhabi)–owned mobile satellite system. It will provide telecommunication services mainly to theMiddle East and Africa. • The Thuraya mobile satellite system is a turnkey project being built by Hughes at a cost of US $1 billion. • The radio interface technology isFDMA. The system is capable of handling as many as 13,750 simultaneous calls.

15. Restricted Coverage • Satellites systems are global, or at least regional with very large regions. This means that satellite network operators must get operating licenses from all countries within the planned coverage area • All countries may not want to grant operating licenses to satellite operators. • political reasons.

16. Diversity • Satellite signals are sensitive to fading due to shadowing. Any obstacles in the transmission path will cause severe signal attenuation. • Only a line-of sight (LOS) connection is typically good enough for satellite connections. • The same signal is duplicated in the network and relayed to the mobile station via more than one satellite. The mobile station receives these signals, and combines them into a composite signal, which most probably is of better quality than the component signals.

17. Diversity • The idea behind diversity is that if some obstacle causes shadowing to the mobile, another satellite in another direction can still serve the mobile station. • The drawback is that one logical connection uses more physical resources than a connection without satellite diversity.