2001/11/30 prof. huei-wen ferng 1 chapter 5 introduction to personal communications systems (pcs):...

2001/11/30 Prof. Huei-Wen Ferng 1

Chapter 5Chapter 5

Introduction to Personal Introduction to Personal Communications Systems (PCS):Communications Systems (PCS):

What’s PCS and its PrinciplesWhat’s PCS and its Principles


What’s PCSWhat’s PCS

2001/11/302001/11/30 Prof. Huei-Wen FerngProf. Huei-Wen Ferng 33

What is Personal What is Personal Communication?Communication?

A PCS provides people with wireless A PCS provides people with wireless access to information serviceaccess to information service• e.g. Cordless, cellular, mobile data e.g. Cordless, cellular, mobile data

networks and etc.networks and etc. Mobility is the heart of PCSMobility is the heart of PCS


Characteristics of PCSCharacteristics of PCS


Characteristics of PCSCharacteristics of PCS Personal Information Machine (PIM)Personal Information Machine (PIM)

• Information device carried by the person Information device carried by the person such as PDA, Notebook, Cellular Phonesuch as PDA, Notebook, Cellular Phone

Personal AddressPersonal Address• Associated with the person as he or she Associated with the person as he or she

changes locationchanges location Personal ProfilePersonal Profile

• Contains details of services selected by the Contains details of services selected by the subscribersubscriber

Ubiquitous: Ubiquitous: • Services will be available anywhere & Services will be available anywhere &

anytimeanytime


Dimensions of PCSDimensions of PCS


Examples of Two Telephone CallsExamples of Two Telephone Calls

Conventional CallConventional Call• A pair of wires connects each telephone A pair of wires connects each telephone

to the switching systemto the switching system• Each pair of wires has its own Each pair of wires has its own

telephone numbertelephone number Cellular CallCellular Call

• Wireless: Signals travel through the airWireless: Signals travel through the air• Each host associates with a telephone Each host associates with a telephone

number regardless of locationnumber regardless of location


Conventional Phone Call:Conventional Phone Call:Network ElementsNetwork Elements

Public SwitchedTelephone Network


Conventional Phone Call: Conventional Phone Call: Information FlowInformation Flow


Cellular Phone Call:Cellular Phone Call:InitializationInitialization


Cellular Phone Call: Cellular Phone Call: Service RequestService Request


Cellular Phone Call: Cellular Phone Call: PagingPaging


Cellular Phone Call:Cellular Phone Call: Response to PagingResponse to Paging


Cellular Phone Call:Cellular Phone Call: Channel AssignmentChannel Assignment


Cellular Phone Call:Cellular Phone Call: ConversationConversation


Cellular Phone Call:Cellular Phone Call: Handoff (Hard and Soft)Handoff (Hard and Soft)


A Cellular SystemA Cellular System

A cellular system includes:A cellular system includes:• Telephone sets, radio channels, base Telephone sets, radio channels, base

stations, a switch, and connections stations, a switch, and connections linking to the switchlinking to the switch

Cellular systems are more complex Cellular systems are more complex than conventional telephone systemsthan conventional telephone systems


Network ElementsNetwork Elements


Information FlowInformation Flow


Technical ChallengesTechnical Challenges

MobilityMobility: Roaming: Roaming• Location management and HandoffLocation management and Handoff

EtherEther: Radio signals: Radio signals• Access technologyAccess technology: FDMA, TDMA, CDMA: FDMA, TDMA, CDMA• Channel impairmentsChannel impairments: fading and noise: fading and noise• BandwidthBandwidth: channel reuse, signal compression, : channel reuse, signal compression,

an efficient modulation and codingan efficient modulation and coding• Privacy and SecurityPrivacy and Security: Encryption and : Encryption and

AuthenticationAuthentication EnergyEnergy: Power control: Power control


Evolution of PCSEvolution of PCS

Four stepping-stones to PCSFour stepping-stones to PCS• Cellular NetworksCellular Networks• Cordless TelephonesCordless Telephones• Mobile ComputingMobile Computing• PagingPaging


Cellular NetworksCellular Networks

Four major trends in cellular Four major trends in cellular technologies:technologies:• Analog systems Analog systems Digital systemsDigital systems• Signaling and network control Signaling and network control

technologies technologies StandardStandard• Vehicle-mounted Vehicle-mounted Small portable unitsSmall portable units• Expanding the scope of services such as Expanding the scope of services such as

caller ID, transmit text message, direct caller ID, transmit text message, direct access to internet and WWWaccess to internet and WWW


StandardsStandards

AMPSAMPS (Advanced Mobile Phone System) (Advanced Mobile Phone System) • Used in the US and CanadaUsed in the US and Canada• Frequency bands: 850 MHzFrequency bands: 850 MHz• Access: FDMAAccess: FDMA• More than 700 service areas (two More than 700 service areas (two

companies/each area)companies/each area) GSMGSM (Global System for Mobile (Global System for Mobile

Communications)Communications)• Used in EuropeUsed in Europe• Frequency bands: 900 MHz &1800 MHzFrequency bands: 900 MHz &1800 MHz• Access: TDMAAccess: TDMA


GSM and its PredecessorGSM and its Predecessor


AMPS and its SuccessorAMPS and its Successor


Cordless PhonesCordless Phones

Limited distance from a single residential Limited distance from a single residential BSBS

Standards: CT2 (Cordless Telephone, Standards: CT2 (Cordless Telephone, Second Generation), DECT (Digital Second Generation), DECT (Digital European Cordless Telecommunications) European Cordless Telecommunications) and CT2Plusand CT2Plus• To interconnect many different base stations To interconnect many different base stations

such as residential BSs, BSs connected to such as residential BSs, BSs connected to business telephone systems (PBX), and business telephone systems (PBX), and telepoint BSs (BS in public area)telepoint BSs (BS in public area)


Mobile Computing and PagingMobile Computing and Paging

Mobile Computing = Portable Mobile Computing = Portable Computers + InternetComputers + Internet

Paging is the oldest of PCS and the Paging is the oldest of PCS and the cheapest onecheapest one

The most advanced pagers also The most advanced pagers also receive voice email receive voice email

Two-way paging services are Two-way paging services are supported since 1995 in USAsupported since 1995 in USA


Current PCSCurrent PCS EuropeEurope: The term of PCS originated in 1989 in t: The term of PCS originated in 1989 in t

he United Kingdomhe United Kingdom• Spectrum is assigned around 1800 MHzSpectrum is assigned around 1800 MHz

North AmericaNorth America::• Spectrum is assigned around 1900 MHzSpectrum is assigned around 1900 MHz • High-tier systems: High transmission power serving High-tier systems: High transmission power serving

at vehicle speed such as NA-TDMA, NA-CDMA, GSMat vehicle speed such as NA-TDMA, NA-CDMA, GSM Low-tier systemsLow-tier systems: PACS (Personal Access Com: PACS (Personal Access Com

munications system), DECTmunications system), DECT JapanJapan: A low-tier system PHS (Personal Handy: A low-tier system PHS (Personal Handy

phone System) operated in 1995phone System) operated in 1995


Frequency BandsFrequency Bands


Other Wireless Other Wireless Communications SystemsCommunications Systems

Four important systems to serve Four important systems to serve special needsspecial needs• Mobile communication satellitesMobile communication satellites: low-: low-

bit-rate, global coverage areabit-rate, global coverage area• Wireless local area networksWireless local area networks: high-bit-: high-bit-

rate, limited coverage arearate, limited coverage area• Wireless local loopsWireless local loops: higher spectrum : higher spectrum

efficiencyefficiency• Wireless data networksWireless data networks: diversity: diversity


Mobile Satellite SystemsMobile Satellite Systems

A major trends since 1990:A major trends since 1990:• Broadcast satellite TV industryBroadcast satellite TV industry• Two-way communication between Two-way communication between

satellites and vehicles, shipssatellites and vehicles, ships• One-way GPSOne-way GPS


Categories of Satellite Categories of Satellite SystemsSystems

GEOGEO (geosynchronous orbits) at 35,800 (geosynchronous orbits) at 35,800 km above the equatorkm above the equator• Advantage: simple network configuration (3 Advantage: simple network configuration (3

satellites are enough to cover the earth)satellites are enough to cover the earth)• Disadvantages: high transmission power, Disadvantages: high transmission power,

long propagation path delay, poor radio long propagation path delay, poor radio coverage at high latitudescoverage at high latitudes

MEOMEO (Medium Earth Orbits) at 10,000 (Medium Earth Orbits) at 10,000 km above the earthkm above the earth


Categories of Satellite Categories of Satellite SystemsSystems

LEOLEO (Low Earth Orbits) on the order (Low Earth Orbits) on the order of 500 to 2,000 km above the earthof 500 to 2,000 km above the earth

Both the MEO and LEO satellite Both the MEO and LEO satellite systems required handoff in satellitessystems required handoff in satellites

Channel Transmission rates: Channel Transmission rates:

2.4Kbps ~ 2 Mbps2.4Kbps ~ 2 Mbps


Principles of PCSPrinciples of PCS


Information Services for PeopleInformation Services for People Telephone ServicesTelephone Services Short Message Services (SMS)Short Message Services (SMS) Voice-band Data and FacsimileVoice-band Data and Facsimile Direct Digital AccessDirect Digital Access

• Transparent data transmission: using FECTransparent data transmission: using FEC• Non-transparent data transmission: using Non-transparent data transmission: using

ARQARQ Closed User GroupsClosed User Groups TelemetryTelemetry Wireless Local LoopsWireless Local Loops Video and Other Broadband ServicesVideo and Other Broadband Services


Voice-band Data and FacsimileVoice-band Data and Facsimile


Figures of Merit (Design Goals)Figures of Merit (Design Goals) Subscribing to a system: Subscribing to a system:

• Terminal price,Terminal size and weight, Terminal price,Terminal size and weight, Service price, Range of services, Coverage Service price, Range of services, Coverage area, Roamingarea, Roaming

Using a system: Using a system: • User interface, Call blocking, Setup time, User interface, Call blocking, Setup time,

Transmission quality, Privacy,Mobility, Call Transmission quality, Privacy,Mobility, Call dropping, Battery life, Modes of operationdropping, Battery life, Modes of operation

Operating company: Operating company: • Infrastructure cost, Cell radius, Spectrum Infrastructure cost, Cell radius, Spectrum

efficiency, Network security, Early deployment efficiency, Network security, Early deployment and adaptabilityand adaptability


System OperationsSystem Operations

User Information TransportUser Information Transport Mobility ManagementMobility Management Authentication and EncryptionAuthentication and Encryption Call ManagementCall Management Radio Resources ManagementRadio Resources Management OOperations, perations, AAdministration and dministration and

MMaintenance (OA&M)aintenance (OA&M)


Radio Resources Radio Resources ManagementManagement

Resources assigned by the system to a Resources assigned by the system to a terminal includes:terminal includes:• A base stationA base station• A physical channel depends on the access A physical channel depends on the access

technologytechnology• The power of the signal transmitted by the The power of the signal transmitted by the

terminalterminal• The power of the signal transmitted to the The power of the signal transmitted to the

terminal by the base stationterminal by the base station RRM is an combination optimization problemRRM is an combination optimization problem


Four Separate TasksFour Separate Tasks

Call AdmissionCall Admission• Determine whether the system accepts a Determine whether the system accepts a

request to set up a new communicationrequest to set up a new communication Base Station and Channel AssignmentBase Station and Channel Assignment

• Fixed channel allocationFixed channel allocation• Dynamic channel allocationDynamic channel allocation

Power ControlPower Control• Reduce system interferenceReduce system interference• Promote battery lifePromote battery life

Handoff CriteriaHandoff Criteria


PCS Architecture: PCS Architecture: Network ElementsNetwork Elements


Examples: Cellular - CentralizedExamples: Cellular - Centralized


Cordless - DistributedCordless - Distributed


Air InterfacesAir Interfaces


Obstacles of Radio Obstacles of Radio TransmissionTransmission

Limited spectrum that must be shared Limited spectrum that must be shared efficientlyefficiently

Transmission impairments that can Transmission impairments that can change abruptly with time, location and change abruptly with time, location and frequency bandfrequency band

Interrupted connections associated with Interrupted connections associated with handoff procedureshandoff procedures

Limited power available to portable Limited power available to portable terminalsterminals


How to Conquer the ObstaclesHow to Conquer the Obstacles

ModulationModulation Source codingSource coding Channel codingChannel coding InterleavingInterleaving Diversity receptionDiversity reception Channel equalizationChannel equalization


Media AccessMedia Access


Media AccessMedia Access

Three frequently used access Three frequently used access techniques: techniques: • FDMAFDMA• TDMATDMA• CDMACDMA

Two multiplexing methods:Two multiplexing methods:• TDMTDM• FDMFDM


Review ExerciseReview Exercise

1.1. Why do cellular phone systems require handoff Why do cellular phone systems require handoff procedures?procedures?

2.2. What are some advantages and disadvantages What are some advantages and disadvantages of using communications satellites to provide of using communications satellites to provide wireless personal communications?wireless personal communications?

3.3. Why does a terminal register its location with a Why does a terminal register its location with a network? What is the advantage of frequent network? What is the advantage of frequent registration? What is the disadvantage?registration? What is the disadvantage?

4.4. Compare fixed channel allocation with dynamic Compare fixed channel allocation with dynamic channel allocation. What are some advantages channel allocation. What are some advantages and disadvantages of the two approaches? and disadvantages of the two approaches?


ReferencesReferences

David J. Goodman, Wireless Personal David J. Goodman, Wireless Personal Communications Systems, Chapter Communications Systems, Chapter One and Two.One and Two.

2001/11/30 prof. huei-wen ferng 1 chapter 5 introduction to personal communications systems (pcs):...

Documents

hueiwen ferng

location slide

paging slide

soft slide

initialization slide

conversation slide

characteristics of pcs

whats pcs slide