Lecture 05 Cellular Satellite Network WAP

8/2/2019 Lecture 05 Cellular Satellite Network WAP

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e u ar a e e e wore u ar a e e e wor

Dr. Nguyen Tuan NamDr. Nguyen Tuan Nam



•• First telephone system:First telephone system: – – A sin le radio transmitter A sin le radio transmitter

– – A single channel was used A single channel was used

– – Half Half--du lex: ress button to talk and releasedu lex: ress button to talk and releaseit to listenit to listen

••Cellular radio s stemCellular radio s stem

– – Analogue Analogue

– –

Nguyen Tuan Nam/WNC 2011Nguyen Tuan Nam/WNC 2011 22



--

•• Analogue Analogue•• Started in the 1980sStarted in the 1980s

•• No worldwide coordination for theNo worldwide coordination for the

development of technical standards fordevelopment of technical standards forthe systemthe system

•• Roaming was not possibleRoaming was not possible

•• Efficient use of the frequency spectrumEfficient use of the frequency spectrumwas not therewas not there




--

•• MiMi --1980s, t e European commission starte a series o activities to i era ize t e1980s, t e European commission starte a series o activities to i era ize t e

communication sector, including mobile communicationcommunication sector, including mobile communication•• Global System for Mobile Communication (GSM)Global System for Mobile Communication (GSM) – – First specificationsFirst specifications – – – – 1990s1990s – – Capable of providing all the basic services such as speech and data servicesCapable of providing all the basic services such as speech and data services

•• GSM and VAS (Value Added Service)GSM and VAS (Value Added Service) – – Voice Mail System (VMS) Voice Mail System (VMS) – – Short Message Service Center (SMSC): proved to be incredibly commercially successfulShort Message Service Center (SMSC): proved to be incredibly commercially successful

•• GSM and GPRS (General Packet Radio Services)GSM and GPRS (General Packet Radio Services) – – Possible to send packet data on the airPossible to send packet data on the air--interfaceinterface

•• GSM and EDGE (Enhancement Data rates in GSM Environment)GSM and EDGE (Enhancement Data rates in GSM Environment)

– –•• 2G phone systems were characterized by2G phone systems were characterized by – – Digital circuit switched transmissionDigital circuit switched transmission – – Introduction of advanced and fast phoneIntroduction of advanced and fast phone--toto--network signalingnetwork signaling

••


..



--

•• In EDGEIn EDGE – – Packet transfer on airPacket transfer on air--interface behaves like a circuitinterface behaves like a circuitswitch callswitch call low efficiencylow efficiency

– – Standards for developing the networks were differentStandards for developing the networks were differentfor different parts of the worldfor different parts of the world

•• -- processingprocessing – – Not standardize on a technologyNot standardize on a technology

– – ,,rate)rate)

•• WCDMA for UMTSWCDMA for UMTS




--

•• Not discussed hereNot discussed here




•• Radio network made up of a number of Radio network made up of a number of radioradio

cellscells ((cellscells))

•• ac ce serve y a eas one xeac ce serve y a eas one xe -- oca onoca on

transceiver (known as cell site or base station)transceiver (known as cell site or base station) radio coverage over a wider area than a cellradio coverage over a wider area than a cell

be used in any one cell and moved throughbe used in any one cell and moved through




•• Mo i e station MS : A evice use to communicate over t e ce u arMo i e station MS : A evice use to communicate over t e ce u ar

network.network.•• Base station transceiver (BST):Base station transceiver (BST):

– –interface section of the network.interface section of the network.

– – Fair amount of computing power, correcting errors in the receivedFair amount of computing power, correcting errors in the received

signal and encrypting the conversationsignal and encrypting the conversation

up and maintains calls made over the network.up and maintains calls made over the network.•• Base station controller (BSC): Controls communication between aBase station controller (BSC): Controls communication between a

group of BSTs and a single MSC.group of BSTs and a single MSC.

•• Pu ic switc e te ep one networ PSTN : T e an ase sectionPu ic switc e te ep one networ PSTN : T e an ase sectionof the network.of the network.





.



•• The very first switchesThe very first switches – – Human manning a switchboardHuman manning a switchboard

– – You phoned the switchboard You phoned the switchboard

– – Told them which line you wanted to be connectedTold them which line you wanted to be connected – –

socketsocket

••

– – Invented by StrowgerInvented by Strowger

– – RelaRela







•• Pro em:Pro em:

– – Only one transmission can be used on any given frequencyOnly one transmission can be used on any given frequency – – Number of available frequencies is very limitedNumber of available frequencies is very limited

•• “ “S ectrum is like real estateS ectrum is like real estate – – the ust don’t make it an morethe ust don’t make it an more” ”

– – A cellular operator has typically been given A cellular operator has typically been given•• 25MHz of radio spectrum25MHz of radio spectrum

•• Each individual requires 25KHz in order to make a callEach individual requires 25KHz in order to make a call,,

•• Solution:Solution: – – Same frequency can be reused in a different area for a completelySame frequency can be reused in a different area for a completely

different transmissiondifferent transmission

– – There must be at least a one cell gap between cells which reuse theThere must be at least a one cell gap between cells which reuse thesame frequencysame frequency




•• T e requency reuse actorT e requency reuse actor:: – – The rate at which the same frequency can be used inThe rate at which the same frequency can be used in

the network.the network. – – It is 1/K (or K according to some books) where K isIt is 1/K (or K according to some books) where K is

the number of cells which cannot use the samethe number of cells which cannot use the samefrequencies for transmission.frequencies for transmission.

– – Common values for the frequency reuse factor areCommon values for the frequency reuse factor are1/3, 1/4, 1/7, 1/9 and 1/12 (or 3, 4, 7, 9 and 121/3, 1/4, 1/7, 1/9 and 1/12 (or 3, 4, 7, 9 and 12depending on notation).depending on notation).

•• N sector antennasN sector antennas – – One base station can have N sector antennas, eachOne base station can have N sector antennas, each

with different directionwith different direction




F1

F3

F1

F1

F2

F4

F2

F2

F3

F1

F3

F1

2

F4

2




•• Adjacent base station sites use the same Adjacent base station sites use the samefrequenciesfrequencies

•• The different base stations and users areThe different base stations and users are

separated by codes rather than frequenciesseparated by codes rather than frequencies•• Requires certain signalRequires certain signal--toto--noise ratio to operatenoise ratio to operate

•• NearNear--far problemfar problem::

– – As receiver moves away from transmitter As receiver moves away from transmitter thethepower transmitted is reducedpower transmitted is reduced signal becomessignal becomes

corru ted and unusablecorru ted and unusable




•• Reduce power usageReduce power usage•• Lar er covera e areaLar er covera e area

•• Increase capacityIncrease capacity

Since most mobile phones use cellular network cell phones

In cities, cell site range is shorter compared to rural areas




•• Po ing sc emePo ing sc eme

– – A control channel exists permanently between mobile stations and base station A control channel exists permanently between mobile stations and base station – – Base station send a request for a call setup to mobile station using the controlBase station send a request for a call setup to mobile station using the control

channelchannel – – o e s a on con nua y po c anne or connec on requeso e s a on con nua y po c anne or connec on reques – – If mobile station and radio resources are availableIf mobile station and radio resources are available a dedicated voice circuit isa dedicated voice circuit is

setupsetup voice circuit only exist when necessary, and then get destroyedvoice circuit only exist when necessary, and then get destroyed

•• Original analogue representation of speech is encoded into digitalOriginal analogue representation of speech is encoded into digital

– – Well known pulse code modulation (PCM) encoding scheme used in most publicWell known pulse code modulation (PCM) encoding scheme used in most publicswitched telephone networks (PSTN) output data at a rate of 64 kbpsswitched telephone networks (PSTN) output data at a rate of 64 kbps

– – GSM only 34kbpsGSM only 34kbps RPERPE--LC encoding scheme at 25kbps (added overhead)LC encoding scheme at 25kbps (added overhead)

•• – – No data is transmitted during a user's silent periodNo data is transmitted during a user's silent period – – Each person on average speaks no more than 40% of the timeEach person on average speaks no more than 40% of the time effectiveeffective




•• Mobile transceiver moves from one cell toMobile transceiver moves from one cell toanother during ongoing continuousanother during ongoing continuouscommunicationcommunication switch from one cellswitch from one cell

frequency to a different cell frequencyfrequency to a different cell frequency•• IntraIntra--cell handoff vs. intercell handoff vs. inter--cell handoff cell handoff

-- ..




Per-user location caching

Pointer forwarding

Local anchoring




•• A service t at ena es customers o a particu ar A service t at ena es customers o a particu arnetwork operator to make calls from areas notnetwork operator to make calls from areas notserved b that network o eratorserved b that network o erator

•• Network operator within the area of the callNetwork operator within the area of the call

initiation contacts a Gateway MSC (GMSC),initiation contacts a Gateway MSC (GMSC),

•• Using mobile station ISDN number (MSISDN),Using mobile station ISDN number (MSISDN),which uniquely identifies a mobile stationwhich uniquely identifies a mobile station

•• MSISDN consists of a country code (CC),MSISDN consists of a country code (CC),national destination code (NDC) and anational destination code (NDC) and a




•• Quiz: higher frequency better or worse?Quiz: higher frequency better or worse?Why?Why?

•• Effect of frequency on cell coverage andEffect of frequency on cell coverage and

bandwidthbandwidth different frequencies servedifferent frequencies servee er or eren uses:e er or eren uses: – – Low frequencies such as 450Mhz serve wellLow frequencies such as 450Mhz serve well

– – GSM 900 is suitable for light urban coverageGSM 900 is suitable for light urban coverage

– –


. .. .



•• SMSSMS

– – Store and forward principlesStore and forward principles•• GPRSGPRS

– –every time transmit a small amount of dataevery time transmit a small amount of data

– – Allow user to connect to packet Allow user to connect to packet--switched data network switched data network user pay foruser pay for

the amount of data, not the time spent connected to the network the amount of data, not the time spent connected to the network – – -- ,,

•• EDGEEDGE – – Up to 500 kbpsUp to 500 kbps

•• WAPWAP

– – WAP gateway between web server and WAP clientWAP gateway between web server and WAP client – – HTML translated into WML and compressed into binary formHTML translated into WML and compressed into binary form – – Client has WAP browserClient has WAP browser




•• Geosync ronous servicesGeosync ronous services

– – Satellites in geosynchronous orbit, remain in a fixed position in the sky at allSatellites in geosynchronous orbit, remain in a fixed position in the sky at alltimestimes – – Can maintain nearCan maintain near--continuous global coverage with only three or four satellitescontinuous global coverage with only three or four satellites

– – 22,00022,000 miles (35,000miles (35,000 km)km) a noticeable delay present while making a phonea noticeable delay present while making a phonecall or using data servicescall or using data services

– – The user will need to find an area with lineThe user will need to find an area with line--of of--sight before being able to use thesight before being able to use thephonephone

•• Low Earth orbitLow Earth orbit – – Altitude of 400 Altitude of 400--700 miles (640700 miles (640--1120 kilometers), and provide coverage cells of 1120 kilometers), and provide coverage cells of

about (at a 100about (at a 100--minute orbital period) 1740miles (2800km) in radiusminute orbital period) 1740miles (2800km) in radius – – A usable pass of an individual LEO satellite will typically last 4 A usable pass of an individual LEO satellite will typically last 4– –15 minutes on15 minutes on

averageaverage – – If the signal is blocked by an obstacle, one can wait a few minutes until anotherIf the signal is blocked by an obstacle, one can wait a few minutes until anothersatellite passes overheadsatellite passes overhead


en o use w c






2525Nguyen Tuan Nam/WNC 2011Nguyen Tuan Nam/WNC 2011



•• Satellite network vs. Cellular Network?Satellite network vs. Cellular Network?




Wireless Application ProtocolWireless Application Protocol

Dr. Nguyen Tuan NamDr. Nguyen Tuan Nam

[email protected]@yahoo.com



Examples of Interactive DataExamples of Interactive DataServices for PDA Services for PDA

•• EmailEmail•• Stock trackinStock trackin

•• Sport resultsSport results

•• Music downloadsMusic downloads

•• Social networksSocial networks•• Instant messen ersInstant messen ers




•• Wireless Application ProtocolWireless Application Protocol•• A lication la er A lication la er network communicationsnetwork communications

in a wireless environmentin a wireless environment

mobile phone or PDA (Personal Digitalmobile phone or PDA (Personal Digital

Why do we need WAP?




Wireless Application Environment

Wireless Transaction Protocol

Wireless Transport Layer SecurityWireless

Data ram Protocol

UDP

Wireless DataNetworkNon-IP IP




3131Nguyen Tuan Nam/WNC 2011Nguyen Tuan Nam/WNC 2011



•• Represents the transfer or transmission layerRepresents the transfer or transmission layer•• Adaptation layer that makes data network look Adaptation layer that makes data network look like UDP to the upper layerslike UDP to the upper layers

– – Unreliable transport of dataUnreliable transport of data – – wowo -- t port num ers or or g n an est nat ont port num ers or or g n an est nat on

•• WAP is completely independent from anyWAP is completely independent from any




Wireless Transport Layer SecurityWireless Transport Layer Security(WTLS)(WTLS)

•• A secure data pipe A secure data pipe

•• Above the transport protocol layer (WDP) Above the transport protocol layer (WDP)

•• A protocol based on TLS A protocol based on TLS – – Optimized for lowOptimized for low--bandwidth networks with relativelybandwidth networks with relatively

•• Provide (endProvide (end--toto--end)end) – – Privacy (Confidentiality)Privacy (Confidentiality)

– – Data integrityData integrity – – Authentication Authentication




•• Inc u es 2 ayersInc u es 2 ayers – – WTLS Record ProtocolWTLS Record Protocol – –

•• At each communication’s beginning At each communication’s beginning

– – 2 party need to do a handshake2 party need to do a handshake•• ego a e e parame ers an me o s or e secureego a e e parame ers an me o s or e secureconnectionconnection

– – Once the secure channel is established, each partyOnce the secure channel is established, each party

– – Multiple secure connection can take advantage of theMultiple secure connection can take advantage of thesame secure sessionsame secure session




..•• Divi e into 2 ayersDivi e into 2 ayers

– – Record protocol:Record protocol:•• Data compression (optional)Data compression (optional)•• MAC (message authentication code)MAC (message authentication code)

•• Transmission of the cryptographically protected dataTransmission of the cryptographically protected data•• May fragment data into manageable blocksMay fragment data into manageable blocks

– – WTLS Handshake Protocol layerWTLS Handshake Protocol layer•• Handshake rotocolHandshake rotocol•• Alert protocol Alert protocol•• Change Cipher Spec protocolChange Cipher Spec protocol

•• Connection StateConnection State – – Operating environment for Record ProtocolOperating environment for Record Protocol

– – Processed and negotiated in Handshake protocolProcessed and negotiated in Handshake protocol•• Processed in advanceProcessed in advance•• Allow communication peers too agree upon security parameters such as a session key, Allow communication peers too agree upon security parameters such as a session key,

peer certificates, compression method, master secret and a key refreshedpeer certificates, compression method, master secret and a key refreshed••




..

Take messages from

higher level layerDeliver to higher layer

Compress data(optional)

Decompress

Apply MAC Verify

Encrypts

Transmits the result Received data

Decrypts




•• Exc ange He o message to negotiate a gorit msExc ange He o message to negotiate a gorit ms

•• UsingUsing public key encryptionpublic key encryption techniques to exchange necessarytechniques to exchange necessarycryptographic parameters so that client and server can generate thecryptographic parameters so that client and server can generate thesamesame rere--master secret kemaster secret ke

•• Exchange certificate and cryptographic information so that eitherExchange certificate and cryptographic information so that eitherclient, server, or both can authenticate each otherclient, server, or both can authenticate each other

•• Generate master secret key from the preGenerate master secret key from the pre--master secret keymaster secret key•• Provi e security parameters to t e recor ayerProvi e security parameters to t e recor ayer•• Client and server may verify that each peer shares the sameClient and server may verify that each peer shares the same

security parameters, and the handshake didn’t compromised bysecurity parameters, and the handshake didn’t compromised byattackersattackers

Why do we need to generate the secret key from PKI?Why don’t we use PKI instead?




Wireless Transaction ProtocolWireless Transaction Protocol(WTP)(WTP)

•• Provi e transaction support re ia eProvi e transaction support re ia e

request/response)request/response) that is adapted to thethat is adapted to thewireless worldwireless world

•• Include optional userInclude optional user--toto--user reliability byuser reliability bytriggering the confirmation of each receivedtriggering the confirmation of each received

•• Delaying ACK is used to reduce the number of Delaying ACK is used to reduce the number of message sentmessage sent

•• Message orientation: basic unit of interchange isMessage orientation: basic unit of interchange isan entire message, not a stream of bytesan entire message, not a stream of bytes


Why don’t we use TCP?



messagemessage – –

“ “occasionallyoccasionally” send a datagram within the same” send a datagram within the samecontext of an existing session using WTPcontext of an existing session using WTP

– – pp ca on requ r ng a agram serv ce as e rpp ca on requ r ng a agram serv ce as e rprimary meansprimary means of data delivery should use WDPof data delivery should use WDP

– –

•• Initiator sends the invoke message to the ResponderInitiator sends the invoke message to the Responder

•• Responder does not ACK Responder does not ACK


•• n a or oes no per orm re ransm ss onn a or oes no per orm re ransm ss on



•• Reliable invoke message with no resultReliable invoke message with no resultmessagemessage

– – Reliable datagram service (reliable push)Reliable datagram service (reliable push)

– – TransactionTransaction•• Initiator sends the invoke messageInitiator sends the invoke message

•• Responder ACKsResponder ACKs

•• If User ACK function is enabled, the WTP user atIf User ACK function is enabled, the WTP user atthe Responder confirms the invoke messagethe Responder confirms the invoke message




•• Re ia e invo e message wit one re ia e resu tRe ia e invo e message wit one re ia e resu t

messagemessage – – Invoke message is sent from Initiator to ResponderInvoke message is sent from Initiator to Responder – – espon er rep es w exac y one resu message mp c yespon er rep es w exac y one resu message mp c y

ACKs the invoke message) ACKs the invoke message) – – If Responder takes longer to service the invoke thanIf Responder takes longer to service the invoke than

Res onder’s ACK timer intervalRes onder’s ACK timer interval Res onder ma re l with aRes onder ma re l with a “hold “hold--on” message (prevent Initiator from unnecessarilyon” message (prevent Initiator from unnecessarilyretransmit the invoke message)retransmit the invoke message)

– – The result message is ACKed by the InitiatorThe result message is ACKed by the Initiator – –

•• WTP user at the Responder confirms the invoke message before theWTP user at the Responder confirms the invoke message before theresult is generatedresult is generated

•• WTP user at the Initiator confirms the result message before ACK isWTP user at the Initiator confirms the result message before ACK is




•• Provide the Wireless Application Environment aProvide the Wireless Application Environment aconsistent interface with 2 servicesconsistent interface with 2 services – – --

Transaction Layer Protocol (WTP)Transaction Layer Protocol (WTP)

– – Connectionless service to operate above either secureConnectionless service to operate above either secureor nonor non--secure a agram serv cesecure a agram serv ce

•• Currently provide HTTP functionality andCurrently provide HTTP functionality and,,

session state with session suspend and resumesession state with session suspend and resumecapabilitiescapabilities




Wireless Application EnvironmentWireless Application Environment(WAE)(WAE)

•• Two languagesTwo languages – – WML Wireless Marku Lan ua eWML Wireless Marku Lan ua e

•• A WML document is known as a deck A WML document is known as a deck

•• Data in the deck is structured into one or moreData in the deck is structured into one or morecar s, eac o w c represent a s ng e nteract oncar s, eac o w c represent a s ng e nteract onwith userwith user

••

into a deck?into a deck?

– – XHTML Mobile ProfileXHTML Mobile Profile




•• Down oa No ia Mo i e Browser 4. 4.1Down oa No ia Mo i e Browser 4. 4.1

•• Creating a HelloWorld.wml, with 2 cards (pages)Creating a HelloWorld.wml, with 2 cards (pages)

– – Card 1: Show a “Hello world” text, with a link to cardCard 1: Show a “Hello world” text, with a link to card22

•• Show a “You got it” textShow a “You got it” text•• Show the name of FIT and its telephone number with a link Show the name of FIT and its telephone number with a link

to callto call

•• A link back to card 1 A link back to card 1•• Project description will be postedProject description will be posted













•• Rapi y growing roa an wire ess access tec no ogy 802.16 802.16eRapi y growing roa an wire ess access tec no ogy 802.16 802.16e

•• One base station and a group of subscriber station form a cell with a pointOne base station and a group of subscriber station form a cell with a point--toto--multipoint structuremultipoint structure•• Use OFDMA (Orthogonal Frequency Division Multiple Access)Use OFDMA (Orthogonal Frequency Division Multiple Access)•• Provide a connectionProvide a connection--oriented to upperoriented to upper--layers of the protocol stack layers of the protocol stack •• High data ratesHigh data rates•• Quality of ServiceQuality of Service

– – – – The QoS parameters for a connection can be varied by the subscribers makingThe QoS parameters for a connection can be varied by the subscribers making

requests to the base station to change them while a connection is in progressrequests to the base station to change them while a connection is in progress – – Four forms: constant bit rate grant, real time polling, nonFour forms: constant bit rate grant, real time polling, non--realreal--time polling, andtime polling, and

best effortbest effort

••Can operate at either higher bitrates or over longer distance but not both.Can operate at either higher bitrates or over longer distance but not both.Why?Why?


Documents

Lecture 05 Cellular Satellite Network WAP