2001/11/30 Prof. Huei-Wen Ferng 1 Chapter 5 Introduction to Personal Communications Systems (PCS): What ’ s PCS and its Principles

2001/11/30 Prof. Huei-Wen Ferng 2 What’s PCS

2001/11/30 Prof. Huei-Wen Ferng 3 What is Personal Communication?  A PCS provides people with wireless access to information service e.g. Cordless, cellular, mobile data networks and etc.e.g. Cordless, cellular, mobile data networks and etc.  Mobility is the heart of PCS

2001/11/30 Prof. Huei-Wen Ferng 4 Characteristics of PCS

2001/11/30 Prof. Huei-Wen Ferng 5 Characteristics of PCS  Personal Information Machine (PIM) Information device carried by the person such as PDA, Notebook, Cellular PhoneInformation device carried by the person such as PDA, Notebook, Cellular Phone  Personal Address Associated with the person as he or she changes locationAssociated with the person as he or she changes location  Personal Profile Contains details of services selected by the subscriberContains details of services selected by the subscriber  Ubiquitous: Services will be available anywhere & anytimeServices will be available anywhere & anytime

2001/11/30 Prof. Huei-Wen Ferng 6 Dimensions of PCS

2001/11/30 Prof. Huei-Wen Ferng 7 Examples of Two Telephone Calls  Conventional Call A pair of wires connects each telephone to the switching systemA pair of wires connects each telephone to the switching system Each pair of wires has its own telephone numberEach pair of wires has its own telephone number  Cellular Call Wireless: Signals travel through the airWireless: Signals travel through the air Each host associates with a telephone number regardless of locationEach host associates with a telephone number regardless of location

2001/11/30 Prof. Huei-Wen Ferng 8 Conventional Phone Call: Network Elements Public Switched Telephone Network

2001/11/30 Prof. Huei-Wen Ferng 9 Conventional Phone Call: Information Flow

2001/11/30 Prof. Huei-Wen Ferng 10 Cellular Phone Call: Initialization

2001/11/30 Prof. Huei-Wen Ferng 11 Cellular Phone Call: Service Request

2001/11/30 Prof. Huei-Wen Ferng 12 Cellular Phone Call: Paging

2001/11/30 Prof. Huei-Wen Ferng 13 Cellular Phone Call: Response to Paging

2001/11/30 Prof. Huei-Wen Ferng 14 Cellular Phone Call: Channel Assignment

2001/11/30 Prof. Huei-Wen Ferng 15 Cellular Phone Call: Conversation

2001/11/30 Prof. Huei-Wen Ferng 16 Cellular Phone Call: Handoff (Hard and Soft)

2001/11/30 Prof. Huei-Wen Ferng 17 A Cellular System  A cellular system includes: Telephone sets, radio channels, base stations, a switch, and connections linking to the switchTelephone sets, radio channels, base stations, a switch, and connections linking to the switch  Cellular systems are more complex than conventional telephone systems

2001/11/30 Prof. Huei-Wen Ferng 18 Network Elements

2001/11/30 Prof. Huei-Wen Ferng 19 Information Flow

2001/11/30 Prof. Huei-Wen Ferng 20 Technical Challenges  Mobility: Roaming Location management and HandoffLocation management and Handoff  Ether: Radio signals Access technology: FDMA, TDMA, CDMAAccess technology: FDMA, TDMA, CDMA Channel impairments: fading and noiseChannel impairments: fading and noise Bandwidth: channel reuse, signal compression, an efficient modulation and codingBandwidth: channel reuse, signal compression, an efficient modulation and coding Privacy and Security: Encryption and AuthenticationPrivacy and Security: Encryption and Authentication  Energy: Power control

2001/11/30 Prof. Huei-Wen Ferng 21 Evolution of PCS  Four stepping-stones to PCS Cellular NetworksCellular Networks Cordless TelephonesCordless Telephones Mobile ComputingMobile Computing PagingPaging

2001/11/30 Prof. Huei-Wen Ferng 22

2001/11/30 Prof. Huei-Wen Ferng 23 Cellular Networks  Four major trends in cellular technologies: Analog systems Digital systemsAnalog systems Digital systems Signaling and network control technologies StandardSignaling and network control technologies Standard Vehicle-mounted Small portable unitsVehicle-mounted Small portable units Expanding the scope of services such as caller ID, transmit text message, direct access to internet and WWWExpanding the scope of services such as caller ID, transmit text message, direct access to internet and WWW

2001/11/30 Prof. Huei-Wen Ferng 24 Standards  AMPS (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 companies/each area)More than 700 service areas (two companies/each area)  GSM (Global System for Mobile Communications) Used in EuropeUsed in Europe Frequency bands: 900 MHz &1800 MHzFrequency bands: 900 MHz &1800 MHz Access: TDMAAccess: TDMA

2001/11/30 Prof. Huei-Wen Ferng 25 GSM and its Predecessor

2001/11/30 Prof. Huei-Wen Ferng 26 AMPS and its Successor

2001/11/30 Prof. Huei-Wen Ferng 27 Cordless Phones  Limited distance from a single residential BS  Standards: CT2 (Cordless Telephone, Second Generation), DECT (Digital European Cordless Telecommunications) and CT2Plus To interconnect many different base stations such as residential BSs, BSs connected to business telephone systems (PBX), and telepoint BSs (BS in public area)To interconnect many different base stations such as residential BSs, BSs connected to business telephone systems (PBX), and telepoint BSs (BS in public area)

2001/11/30 Prof. Huei-Wen Ferng 28 Mobile Computing and Paging  Mobile Computing = Portable Computers + Internet  Paging is the oldest of PCS and the cheapest one  The most advanced pagers also receive voice  Two-way paging services are supported since 1995 in USA

2001/11/30 Prof. Huei-Wen Ferng 29

2001/11/30 Prof. Huei-Wen Ferng 30 Current PCS  Europe: The term of PCS originated in 1989 in the United Kingdom Spectrum is assigned around 1800 MHzSpectrum is assigned around 1800 MHz  North America: Spectrum is assigned around 1900 MHzSpectrum is assigned around 1900 MHz High-tier systems: High transmission power serving at vehicle speed such as NA-TDMA, NA-CDMA, GSMHigh-tier systems: High transmission power serving at vehicle speed such as NA-TDMA, NA-CDMA, GSM  Low-tier systems: PACS (Personal Access Communications system), DECT  Japan: A low-tier system PHS (Personal Handyphone System) operated in 1995

2001/11/30 Prof. Huei-Wen Ferng 31 Frequency Bands

2001/11/30 Prof. Huei-Wen Ferng 32 Other Wireless Communications Systems  Four important systems to serve special needs Mobile communication satellites: low- bit-rate, global coverage areaMobile communication satellites: low- bit-rate, global coverage area Wireless local area networks: high- bit-rate, limited coverage areaWireless local area networks: high- bit-rate, limited coverage area Wireless local loops: higher spectrum efficiencyWireless local loops: higher spectrum efficiency Wireless data networks: diversityWireless data networks: diversity

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

2001/11/30 Prof. Huei-Wen Ferng 34 Mobile Satellite Systems  A major trends since 1990: Broadcast satellite TV industryBroadcast satellite TV industry Two-way communication between satellites and vehicles, shipsTwo-way communication between satellites and vehicles, ships One-way GPSOne-way GPS

2001/11/30 Prof. Huei-Wen Ferng 35 Categories of Satellite Systems  GEO (geosynchronous orbits) at 35,800 km above the equator Advantage: simple network configuration (3 satellites are enough to cover the earth)Advantage: simple network configuration (3 satellites are enough to cover the earth) Disadvantages: high transmission power, long propagation path delay, poor radio coverage at high latitudesDisadvantages: high transmission power, long propagation path delay, poor radio coverage at high latitudes  MEO (Medium Earth Orbits) at 10,000 km above the earth

2001/11/30 Prof. Huei-Wen Ferng 36 Categories of Satellite Systems  LEO (Low Earth Orbits) on the order of 500 to 2,000 km above the earth  Both the MEO and LEO satellite systems required handoff in satellites  Channel Transmission rates: 2.4Kbps ~ 2 Mbps

2001/11/30 Prof. Huei-Wen Ferng 37 Principles of PCS

2001/11/30 Prof. Huei-Wen Ferng 38 Information Services for People  Telephone Services  Short Message Services (SMS)  Voice-band Data and Facsimile  Direct Digital Access Transparent data transmission: using FECTransparent data transmission: using FEC Non-transparent data transmission: using ARQNon-transparent data transmission: using ARQ  Closed User Groups  Telemetry  Wireless Local Loops  Video and Other Broadband Services

2001/11/30 Prof. Huei-Wen Ferng 39 Voice-band Data and Facsimile

2001/11/30 Prof. Huei-Wen Ferng 40 Figures of Merit (Design Goals)  Subscribing to a system: Terminal price,Terminal size and weight, Service price, Range of services, Coverage area, RoamingTerminal price,Terminal size and weight, Service price, Range of services, Coverage area, Roaming  Using a system: User interface, Call blocking, Setup time, Transmission quality, Privacy,Mobility, Call dropping, Battery life, Modes of operationUser interface, Call blocking, Setup time, Transmission quality, Privacy,Mobility, Call dropping, Battery life, Modes of operation  Operating company: Infrastructure cost, Cell radius, Spectrum efficiency, Network security, Early deployment and adaptabilityInfrastructure cost, Cell radius, Spectrum efficiency, Network security, Early deployment and adaptability

2001/11/30 Prof. Huei-Wen Ferng 41 System Operations  User Information Transport  Mobility Management  Authentication and Encryption  Call Management  Radio Resources Management  Operations, Administration and Maintenance (OA&M)

2001/11/30 Prof. Huei-Wen Ferng 42 Radio Resources Management  Resources assigned by the system to a terminal includes: A base stationA base station A physical channel depends on the access technologyA physical channel depends on the access technology The power of the signal transmitted by the terminalThe power of the signal transmitted by the terminal The power of the signal transmitted to the terminal by the base stationThe power of the signal transmitted to the terminal by the base station  RRM is an combination optimization problem

2001/11/30 Prof. Huei-Wen Ferng 43

2001/11/30 Prof. Huei-Wen Ferng 44 Four Separate Tasks  Call Admission Determine whether the system accepts a request to set up a new communicationDetermine whether the system accepts a request to set up a new communication  Base Station and Channel Assignment Fixed channel allocationFixed channel allocation Dynamic channel allocationDynamic channel allocation  Power Control Reduce system interferenceReduce system interference Promote battery lifePromote battery life  Handoff Criteria

2001/11/30 Prof. Huei-Wen Ferng 45

2001/11/30 Prof. Huei-Wen Ferng 46 PCS Architecture: Network Elements

2001/11/30 Prof. Huei-Wen Ferng 47 Examples: Cellular - Centralized

2001/11/30 Prof. Huei-Wen Ferng 48 Cordless - Distributed

2001/11/30 Prof. Huei-Wen Ferng 49 Air Interfaces

2001/11/30 Prof. Huei-Wen Ferng 50 Obstacles of Radio Transmission  Limited spectrum that must be shared efficiently  Transmission impairments that can change abruptly with time, location and frequency band  Interrupted connections associated with handoff procedures  Limited power available to portable terminals

2001/11/30 Prof. Huei-Wen Ferng 51 How to Conquer the Obstacles  Modulation  Source coding  Channel coding  Interleaving  Diversity reception  Channel equalization

2001/11/30 Prof. Huei-Wen Ferng 52 Media Access

2001/11/30 Prof. Huei-Wen Ferng 53 Media Access  Three frequently used access techniques: FDMAFDMA TDMATDMA CDMACDMA  Two multiplexing methods: TDMTDM FDMFDM

2001/11/30 Prof. Huei-Wen Ferng 54 Review Exercise 1. Why do cellular phone systems require handoff procedures? 2. What are some advantages and disadvantages of using communications satellites to provide wireless personal communications? 3. Why does a terminal register its location with a network? What is the advantage of frequent registration? What is the disadvantage? 4. Compare fixed channel allocation with dynamic channel allocation. What are some advantages and disadvantages of the two approaches?

2001/11/30 Prof. Huei-Wen Ferng 55 References  David J. Goodman, Wireless Personal Communications Systems, Chapter One and Two.