Chapter 5 Introduction to Personal Communications Systems (PCS): What’s PCS and its Principles 2018/11/29 Prof. Huei-Wen Ferng

What’s PCS 2018/11/29 Prof. Huei-Wen Ferng

What is Personal Communication? A PCS provides people with wireless access to information service e.g. Cordless, cellular, mobile data networks and etc. Mobility is the heart of PCS 2018/11/29 Prof. Huei-Wen Ferng

Characteristics of PCS 2018/11/29 Prof. Huei-Wen Ferng

Characteristics of PCS Personal Information Machine (PIM) Information device carried by the person such as PDA, Notebook, Cellular Phone Personal Address Associated with the person as he or she changes location Personal Profile Contains details of services selected by the subscriber Ubiquitous: Services will be available anywhere & anytime 2018/11/29 Prof. Huei-Wen Ferng

Dimensions of PCS 2018/11/29 Prof. Huei-Wen Ferng

Examples of Two Telephone Calls Conventional Call A pair of wires connects each telephone to the switching system Each pair of wires has its own telephone number Cellular Call Wireless: Signals travel through the air Each host associates with a telephone number regardless of location 2018/11/29 Prof. Huei-Wen Ferng

Conventional Phone Call: Network Elements Public Switched Telephone Network 2018/11/29 Prof. Huei-Wen Ferng

Conventional Phone Call: Information Flow 2018/11/29 Prof. Huei-Wen Ferng

Cellular Phone Call: Initialization 2018/11/29 Prof. Huei-Wen Ferng

Cellular Phone Call: Service Request 2018/11/29 Prof. Huei-Wen Ferng

Cellular Phone Call: Paging 2018/11/29 Prof. Huei-Wen Ferng

Cellular Phone Call: Response to Paging 2018/11/29 Prof. Huei-Wen Ferng

Cellular Phone Call: Channel Assignment 2018/11/29 Prof. Huei-Wen Ferng

Cellular Phone Call: Conversation 2018/11/29 Prof. Huei-Wen Ferng

Cellular Phone Call: Handoff (Hard and Soft) 2018/11/29 Prof. Huei-Wen Ferng

A Cellular System A cellular system includes: Telephone sets, radio channels, base stations, a switch, and connections linking to the switch Cellular systems are more complex than conventional telephone systems 2018/11/29 Prof. Huei-Wen Ferng

Network Elements 2018/11/29 Prof. Huei-Wen Ferng

Information Flow 2018/11/29 Prof. Huei-Wen Ferng

Technical Challenges Mobility: Roaming Ether: Radio signals Location management and Handoff Ether: Radio signals Access technology: FDMA, TDMA, CDMA Channel impairments: fading and noise Bandwidth: channel reuse, signal compression, an efficient modulation and coding Privacy and Security: Encryption and Authentication Energy: Power control 2018/11/29 Prof. Huei-Wen Ferng

Evolution of PCS Four stepping-stones to PCS Cellular Networks Cordless Telephones Mobile Computing Paging 2018/11/29 Prof. Huei-Wen Ferng

2018/11/29 Prof. Huei-Wen Ferng

Cellular Networks Four major trends in cellular technologies: Analog systems ® Digital systems Signaling and network control technologies ® Standard Vehicle-mounted ® Small portable units Expanding the scope of services such as caller ID, transmit text message, direct access to internet and WWW 2018/11/29 Prof. Huei-Wen Ferng

Standards AMPS (Advanced Mobile Phone System) Used in the US and Canada Frequency bands: 850 MHz Access: FDMA More than 700 service areas (two companies/each area) GSM (Global System for Mobile Communications) Used in Europe Frequency bands: 900 MHz &1800 MHz Access: TDMA 2018/11/29 Prof. Huei-Wen Ferng

GSM and its Predecessor 2018/11/29 Prof. Huei-Wen Ferng

AMPS and its Successor 2018/11/29 Prof. Huei-Wen Ferng

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) 2018/11/29 Prof. Huei-Wen Ferng

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 email Two-way paging services are supported since 1995 in USA 2018/11/29 Prof. Huei-Wen Ferng

2018/11/29 Prof. Huei-Wen Ferng

Current PCS Europe: The term of PCS originated in 1989 in the United Kingdom Spectrum is assigned around 1800 MHz North America: Spectrum is assigned around 1900 MHz High-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 2018/11/29 Prof. Huei-Wen Ferng

Frequency Bands 2018/11/29 Prof. Huei-Wen Ferng

Other Wireless Communications Systems Four important systems to serve special needs Mobile communication satellites: low-bit-rate, global coverage area Wireless local area networks: high-bit-rate, limited coverage area Wireless local loops: higher spectrum efficiency Wireless data networks: diversity 2018/11/29 Prof. Huei-Wen Ferng

2018/11/29 Prof. Huei-Wen Ferng

Mobile Satellite Systems A major trends since 1990: Broadcast satellite TV industry Two-way communication between satellites and vehicles, ships One-way GPS 2018/11/29 Prof. Huei-Wen Ferng

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) Disadvantages: high transmission power, long propagation path delay, poor radio coverage at high latitudes MEO (Medium Earth Orbits) at 10,000 km above the earth 2018/11/29 Prof. Huei-Wen Ferng

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 2018/11/29 Prof. Huei-Wen Ferng

Principles of PCS 2018/11/29 Prof. Huei-Wen Ferng

Information Services for People Telephone Services Short Message Services (SMS) Voice-band Data and Facsimile Direct Digital Access Transparent data transmission: using FEC Non-transparent data transmission: using ARQ Closed User Groups Telemetry Wireless Local Loops Video and Other Broadband Services 2018/11/29 Prof. Huei-Wen Ferng

Voice-band Data and Facsimile 2018/11/29 Prof. Huei-Wen Ferng

Figures of Merit (Design Goals) Subscribing to a system: Terminal 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 operation Operating company: Infrastructure cost, Cell radius, Spectrum efficiency, Network security, Early deployment and adaptability 2018/11/29 Prof. Huei-Wen Ferng

System Operations User Information Transport Mobility Management Authentication and Encryption Call Management Radio Resources Management Operations, Administration and Maintenance (OA&M) 2018/11/29 Prof. Huei-Wen Ferng

Radio Resources Management Resources assigned by the system to a terminal includes: A base station A physical channel depends on the access technology The power of the signal transmitted by the terminal The power of the signal transmitted to the terminal by the base station RRM is an combination optimization problem 2018/11/29 Prof. Huei-Wen Ferng

2018/11/29 Prof. Huei-Wen Ferng

Four Separate Tasks Call Admission Base Station and Channel Assignment Determine whether the system accepts a request to set up a new communication Base Station and Channel Assignment Fixed channel allocation Dynamic channel allocation Power Control Reduce system interference Promote battery life Handoff Criteria 2018/11/29 Prof. Huei-Wen Ferng

2018/11/29 Prof. Huei-Wen Ferng

PCS Architecture: Network Elements 2018/11/29 Prof. Huei-Wen Ferng

Examples: Cellular - Centralized 2018/11/29 Prof. Huei-Wen Ferng

Cordless - Distributed 2018/11/29 Prof. Huei-Wen Ferng

Air Interfaces 2018/11/29 Prof. Huei-Wen Ferng

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 2018/11/29 Prof. Huei-Wen Ferng

How to Conquer the Obstacles Modulation Source coding Channel coding Interleaving Diversity reception Channel equalization 2018/11/29 Prof. Huei-Wen Ferng

Media Access 2018/11/29 Prof. Huei-Wen Ferng

Media Access Three frequently used access techniques: FDMA TDMA CDMA Two multiplexing methods: TDM FDM 2018/11/29 Prof. Huei-Wen Ferng

Review Exercise Why do cellular phone systems require handoff procedures? What are some advantages and disadvantages of using communications satellites to provide wireless personal communications? Why does a terminal register its location with a network? What is the advantage of frequent registration? What is the disadvantage? Compare fixed channel allocation with dynamic channel allocation. What are some advantages and disadvantages of the two approaches? 2018/11/29 Prof. Huei-Wen Ferng

References David J. Goodman, Wireless Personal Communications Systems, Chapter One and Two. 2018/11/29 Prof. Huei-Wen Ferng