Satellite CommunicationsSatellite Communications

Alison Griffiths – Room C203, Alison Griffiths – Room C203, Beacon BuildingBeacon Building

a.l.griffiths@staffs.ac.uka.l.griffiths@staffs.ac.uk

MCCSMCCS

What we will look atWhat we will look at What are satellite phonesWhat are satellite phones How do they operateHow do they operate

How do they integrate into the PSTN How do they integrate into the PSTN networknetwork

Who operates this phone networkWho operates this phone network

MCCSMCCS Over the next few weeks we will look at Over the next few weeks we will look at

mobile telecommunicationsmobile telecommunications 2G, 2.5G, 3G, 4G2G, 2.5G, 3G, 4G These are all designed to operate within a These are all designed to operate within a

proximity of a transmitter / receiver (base stations)proximity of a transmitter / receiver (base stations) Now consider what happens in areas where there are no Now consider what happens in areas where there are no

base stationsbase stations This could be for financial reasons, as in there is just not This could be for financial reasons, as in there is just not

enough use to justify the base stationenough use to justify the base station Practical reasons as in it is impossible to install a base Practical reasons as in it is impossible to install a base

station, like the middle of the Pacific oceanstation, like the middle of the Pacific ocean For these users an alternative needs to be offeredFor these users an alternative needs to be offered

For a lot of people it unacceptable to be disconnected from For a lot of people it unacceptable to be disconnected from the world for long periods of timethe world for long periods of time

This is becoming increasingly true in the wired worldThis is becoming increasingly true in the wired world

MCCSMCCS Areas where cellular communications are not Areas where cellular communications are not

possible Satellite phones are an optionpossible Satellite phones are an option Original theorised by Arthur C. Clarke in 1945Original theorised by Arthur C. Clarke in 1945

Paper called “Extra Terrestrial Rays”Paper called “Extra Terrestrial Rays” A number of private sector businesses are investing A number of private sector businesses are investing

in this infrastructurein this infrastructure They are hoping to gain access to the large majority of the They are hoping to gain access to the large majority of the

world who do not have access to Mobile telecommunicationsworld who do not have access to Mobile telecommunications They also want to gain the travelling business peopleThey also want to gain the travelling business people

Although as we will discuss over the new few weeks any Although as we will discuss over the new few weeks any standard of telecommunications after 2G are supposed to be standard of telecommunications after 2G are supposed to be compatible outside of the host country there are still problems compatible outside of the host country there are still problems in realityin reality

Local roaming agreements are needed with each of the Local roaming agreements are needed with each of the countries which are not always in placecountries which are not always in place

Different countries use different technologiesDifferent countries use different technologies

MCCS - CompaniesMCCS - Companies

Only a few companies control the Only a few companies control the worldwide satellite marketworldwide satellite market Some of them are listed belowSome of them are listed below

IridiumIridium GlobalstarGlobalstar ICOICO EllipseEllipse Asian Cellular System (ACES)Asian Cellular System (ACES) ThurayaThuraya TeledesicTeledesic

MCCS - CompaniesMCCS - Companies There are three kinds of satellite used There are three kinds of satellite used

for these communicationsfor these communications LEOLEO

Low Earth OrbitLow Earth Orbit 350 to 1400 Km above the Earth350 to 1400 Km above the Earth

MEOMEO Medium Earth OrbitMedium Earth Orbit

6,000 to 20,000 Km above the Earth6,000 to 20,000 Km above the Earth Global Positioning System is a user of these satellitesGlobal Positioning System is a user of these satellites

GEOGEO Geostationary Earth OrbitGeostationary Earth Orbit

36,000 Km above the equator36,000 Km above the equator

MCCS - SatellitesMCCS - Satellites

GEOMEO

LEO

MCCS - CompaniesMCCS - Companies The closer the satellite is to the Earth the less The closer the satellite is to the Earth the less

area is covered by each onearea is covered by each one GEO orbit GEO orbit

A minimum 3 satellites are needed to cover the planetA minimum 3 satellites are needed to cover the planet The satellite will remain in one location rotating with the The satellite will remain in one location rotating with the

EarthEarth The company ACES uses this technologyThe company ACES uses this technology

ACES actually only uses 1 satellite as they only offer services ACES actually only uses 1 satellite as they only offer services over Asia, not globallyover Asia, not globally

Relatively a Large amount of power is needed to transmitRelatively a Large amount of power is needed to transmit LEOLEO

A large number of satellites are needed to cover the A large number of satellites are needed to cover the planetplanet

Iridium, uses 66 satellites for global coverage + spares in Iridium, uses 66 satellites for global coverage + spares in case of problemscase of problems

MCCS – GEOMCCS – GEO Using a GEO satelliteUsing a GEO satellite

Means that if 2 people wish to communicate in the Means that if 2 people wish to communicate in the same area a ground station is not requiredsame area a ground station is not required

The signal can be received and transferred back to the The signal can be received and transferred back to the recipientrecipient

Due to the distance involved with GEODue to the distance involved with GEO Delay may occur within the callDelay may occur within the call About 260 ms delay in what is said before it can be returned About 260 ms delay in what is said before it can be returned

to the other party.to the other party. If both parties in the call are on satellite phones this will get If both parties in the call are on satellite phones this will get

longer and more noticeablelonger and more noticeable

Person 1

Person 2

MCCS – ConnectingMCCS – Connecting Using a LEO satelliteUsing a LEO satellite

These satellites are closer to EarthThese satellites are closer to Earth Each one will cover a small areaEach one will cover a small area

Referred to as the “footprint”Referred to as the “footprint” This has large advantages in the respect frequencies can be This has large advantages in the respect frequencies can be

reused in different parts of the planet at the same timereused in different parts of the planet at the same time This is the same basis that cellular communications operate This is the same basis that cellular communications operate

uponupon Due to the distance to satelliteDue to the distance to satellite

The latency issue is less of a concern average 10 msThe latency issue is less of a concern average 10 ms This is similar delay as you would get on any land base PSTNThis is similar delay as you would get on any land base PSTN

Less power is required to transmit to the satelliteLess power is required to transmit to the satellite

MCCS – ConnectingMCCS – Connecting Two types of satellites exist for LEO Two types of satellites exist for LEO

designsdesigns Repeaters (also known as “bent pipe”)Repeaters (also known as “bent pipe”)

These just receive a signal and forward it to a These just receive a signal and forward it to a ground station to be routed to the destinationground station to be routed to the destination

Very simple operation and rely on the fact that a Very simple operation and rely on the fact that a ground station is within transmission distanceground station is within transmission distance

This is seen in the following diagramThis is seen in the following diagram

MCCS – LEO - RepeaterMCCS – LEO - Repeater

Person 1

Person 2

MCCS – ConnectingMCCS – Connecting Two types of satellites exist for LEO Two types of satellites exist for LEO

designsdesigns RoutersRouters

These operate like a router in a computer These operate like a router in a computer networknetwork

The destination of a packet is inspectedThe destination of a packet is inspected This allows inter satellite handover or call routingThis allows inter satellite handover or call routing

The removal of the transmission to the ground station The removal of the transmission to the ground station removes a potential problem for the network.removes a potential problem for the network.

Ground stations only need to be informed at the end for Ground stations only need to be informed at the end for call charging purposescall charging purposes

MCCS – LEO - RouterMCCS – LEO - Router

Person 1

Person 2

MCCS – ConnectingMCCS – Connecting The way that each of the methods The way that each of the methods

communicate varies with each of the communicate varies with each of the companiescompanies The satellites use a variety of standards to The satellites use a variety of standards to

allow communication with the handsetsallow communication with the handsets TDMA/FDMA and CDMA are predominant TDMA/FDMA and CDMA are predominant

technologiestechnologies These will both be covered in a later lectureThese will both be covered in a later lecture

Each of the companies are issued with a Each of the companies are issued with a range of radio frequencyrange of radio frequency

These are reserved and offered by the ITUThese are reserved and offered by the ITU International Telecommunications UnionInternational Telecommunications Union

More about this organisation will be discussed in the GSM More about this organisation will be discussed in the GSM lectureslectures

MCCS – FrequenciesMCCS – Frequencies Operating frequenciesOperating frequencies

A number of frequencies are issuedA number of frequencies are issued Each of these frequency ranges are issued a letter to designate Each of these frequency ranges are issued a letter to designate

the frequency and the potential usethe frequency and the potential use The use depends on the intention of the satelliteThe use depends on the intention of the satellite

CC 4 GHz – 6 GHz4 GHz – 6 GHz

LL 390 MHz – 1.55 GHz 390 MHz – 1.55 GHz GPS SystemGPS System Iridium Iridium

KKuu 12 – 18 GHz12 – 18 GHz

KKaa 18 – 40 GHz18 – 40 GHz

XX 5.2GHz – 10.9 GHz5.2GHz – 10.9 GHz

VV 50 GHz – 75 GHz50 GHz – 75 GHz

MCCS – ConnectingMCCS – Connecting Ground stationsGround stations

Depending on the technology affects the Depending on the technology affects the number of ground stationsnumber of ground stations

OperationsOperations Link satellites into the PSTNLink satellites into the PSTN Send/receive control signalsSend/receive control signals Control billing / access informationControl billing / access information

PSTN

MCCS – ConnectingMCCS – Connecting

Communications neededCommunications needed Communicate with another satellite phoneCommunicate with another satellite phone Communication with another satellite phone in a Communication with another satellite phone in a

different positiondifferent position Communications with phone attached to the PSTNCommunications with phone attached to the PSTN

This will include Mobile phones as these will be routed This will include Mobile phones as these will be routed through the PSTN through the PSTN

MCCS – ConnectingMCCS – Connecting

Technologies used for LEO with Inter satellite handoverTechnologies used for LEO with Inter satellite handover Mean that it is POSSIBLE to hand only one ground station for all Mean that it is POSSIBLE to hand only one ground station for all

calls being handledcalls being handled This would however meanThis would however mean

A single point of failure within the networkA single point of failure within the network Routing PSTN calls further than requiredRouting PSTN calls further than required Increased inter satellite communicationsIncreased inter satellite communications

In the event of a single satellite failing all worldwide communications In the event of a single satellite failing all worldwide communications could be effectedcould be effected

Using multiple ground stations allows forUsing multiple ground stations allows for More controlMore control Redundancy in the networkRedundancy in the network Reduced cost of connecting to the PSTNReduced cost of connecting to the PSTN

MCCS – ConnectingMCCS – Connecting Single Ground stationSingle Ground station

Someone in China phoning a PSTN in ChinaSomeone in China phoning a PSTN in China

China CanadaPSTN

MCCS – ConnectingMCCS – Connecting Multiple Ground stationsMultiple Ground stations

Someone in China phoning a PSTN in ChinaSomeone in China phoning a PSTN in China

ChinaPSTN

MCCSMCCS

Satellite phonesSatellite phones Need a clear line of sight to operate properlyNeed a clear line of sight to operate properly

The line of sight is towards the satelliteThe line of sight is towards the satellite This is usually towards the horizon, where the best This is usually towards the horizon, where the best

opportunity is available to receive a satellite signalopportunity is available to receive a satellite signal

MCCS - HandsetsMCCS - Handsets

Current generation if handsets look like Current generation if handsets look like cellular phonescellular phones An aerial must be used to get the best signalAn aerial must be used to get the best signal Voice quality is not as good as the GSM networkVoice quality is not as good as the GSM network The phones are slightly bulkier than the new slim The phones are slightly bulkier than the new slim

line GSM devicesline GSM devices Battery life is lower than GSM devicesBattery life is lower than GSM devices There are multiple standard at the moment for There are multiple standard at the moment for

phonesphones Devices which work with one satellite group may not Devices which work with one satellite group may not

work with anotherwork with another http://www.highspeedsat.com/motorola-9505.htmhttp://www.highspeedsat.com/motorola-9505.htm

MCCS - FutureMCCS - Future Future use of Satellite based phones will be Future use of Satellite based phones will be

seenseen Most of the current companies are having financial Most of the current companies are having financial

problemsproblems Iridium went bankrupt and was bought out in 1999/2000Iridium went bankrupt and was bought out in 1999/2000

Other companies are scaling down planned growth Other companies are scaling down planned growth of the systemsof the systems

The IMT-2000 specifications for 3G communications The IMT-2000 specifications for 3G communications does include a discussion on Satellite phones to does include a discussion on Satellite phones to make them compatible with cellular handsetsmake them compatible with cellular handsets

The intention is to attempt to allow a “standard” 3G The intention is to attempt to allow a “standard” 3G compliant phone operate anywherecompliant phone operate anywhere

MCCS - FutureMCCS - Future

IMT-2000 Vision

http://cis270.williamson.cx/3G.2/imt_2000_Concept_imsi.gif

MCCS - FutureMCCS - Future IMT-2000IMT-2000

Looking at using Satellite phones for areas Looking at using Satellite phones for areas where cellular communications will not be where cellular communications will not be possiblepossible

These phones will offer increased voice quality and These phones will offer increased voice quality and data ratesdata rates

144 Kbps actual rates will define once operators start to 144 Kbps actual rates will define once operators start to use this technologyuse this technology

Current Data Rates are about 8Kbps for satellite phonesCurrent Data Rates are about 8Kbps for satellite phones Different sorts of Satellite communications can be used for Different sorts of Satellite communications can be used for

high speed data transfer in the region of 2 to 45 Mbpshigh speed data transfer in the region of 2 to 45 Mbps New technology starting 2005 is Icomera, which is New technology starting 2005 is Icomera, which is

providing wireless LAN access via satellite to trains providing wireless LAN access via satellite to trains in Europein Europe

http://www.icomera.com/default.asp http://www.icomera.com/default.asp

MCCSMCCS

ConclusionConclusion Looked at satellite technologyLooked at satellite technology

Different types of satellitesDifferent types of satellites ConsiderationsConsiderations

Future of satellite phone technologyFuture of satellite phone technology