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

2. What’s PCS
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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.
Mobility is the heart of PCS
2018/11/29
Prof. Huei-Wen Ferng

4. Characteristics of PCS
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Prof. Huei-Wen Ferng

5. 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

6. Dimensions of PCS
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Prof. Huei-Wen Ferng

7. 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

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

9. Conventional Phone Call: Information Flow
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10. Cellular Phone Call: Initialization
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11. Cellular Phone Call: Service Request
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12. Cellular Phone Call: Paging
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13. Cellular Phone Call: Response to Paging
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14. Cellular Phone Call: Channel Assignment
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Prof. Huei-Wen Ferng

15. Cellular Phone Call: Conversation
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16. Cellular Phone Call: Handoff (Hard and Soft)
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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 switch
Cellular systems are more complex than conventional telephone systems
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Prof. Huei-Wen Ferng

18. Network Elements
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19. Information Flow
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Prof. Huei-Wen Ferng

20. 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

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

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23. 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

24. 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
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Prof. Huei-Wen Ferng

25. GSM and its Predecessor
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Prof. Huei-Wen Ferng

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

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30. 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
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Prof. Huei-Wen Ferng

31. Frequency Bands
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Prof. Huei-Wen Ferng

32. 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

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

37. Principles of PCS
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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 FEC
Non-transparent data transmission: using ARQ
Closed User Groups
Telemetry
Wireless Local Loops
Video and Other Broadband Services
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Prof. Huei-Wen Ferng

39. Voice-band Data and Facsimile
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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, 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

41. 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

42. 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

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44. 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

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46. PCS Architecture: Network Elements
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Prof. Huei-Wen Ferng

47. Examples: Cellular - Centralized
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Prof. Huei-Wen Ferng

48. Cordless - Distributed
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Prof. Huei-Wen Ferng

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

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

52. Media Access
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Prof. Huei-Wen Ferng

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

54. 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

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