1. Lecturer: Michael O'Grady Course: MSc Ubiquitous & Multimedia Systems Unit: Context Sensitive Service Delivery Lecture: Mobile Communications Overview

2. Outline

Introduce some basic wireless concepts

Describe the evolution of cellular telecommunications networks

Reflect on the services supportd by cellular networks

Consider the issue of standardization in wireless communications

3. Recall: PSTN Public Switched Telephone Network Concatenation of the interconnected Networks operated by the various telephone companies (telcos) and public utility companies (PTTs) throughout the world Originally -human operated (plugboards), analoguesignal Later - Electromechanical switchesToday - Automated, digitalBut the so-called last mile problem 4. Recall: PLMN

Public Land Mobile Network (PLMN)

• Operated by either government agency or government appointed company.

• Objective is to deliver services to those members of the public who are mobile.

• May be considered an extension or an

• integral part of the PSTN.

• Uses Wireless technologies.

5. Advantages of Wireless

Constant connection

Access to up-to-date information

Minimum installation issues

Freedom to roam

Scalability

No cables

Extensibility e.g remote areas with satellite

6. Disadvantages of Wireless

Careful planning of network essential

Environment generally hostile

Security

Safety

spectrum licenses

poor data rates

cost (domain dependant)

7. Some Historical Developments

Origins debatable but .

• 1887 - Hertz demonstrates EM waves

• 1896 - Marconi demonstrates wireless telegraph apparatus

• 1901 - First radio signal across the Atlantic (Cornwall to Newfoundland)

• 1914 - First wireless voice transmission

• 1946 - PSTN augmented with wireless

• 1947 - Cellular Network proposed

8. Why Cellular?

Originally proposed by D. H. Ring in an unpublished paper.

Why?

• Potential for existing systems to expand was severely limited.

How?

• Reuse frequencies so as to maximize the use of the available radio spectrum thus improving scalability.

Note: This issue will be revisited when the GSM architecture is discussed.

9. Standardization

Advantages include

• • accelerates the availability of new equipment and services

• • lowers costs through increased competition

• • ensures reliability of supply

• • ensures interoperability

De Jure

• • defined by industry groups or government agencies

De Facto

• • established as the result of a product dominating the market

10. 1G - Characteristics

Analogue transmission technology

Pioneered semiconductor and microprocessor technology

Focus on voice

Data services almost non-existent

Incompatible standards

• Different frequencies and signaling

• International roaming impossible

Inefficient use of the radio spectrum

11. 1G - NTT

Nippon Telephone & Telegraph (NTT)

• Now NTT DoCoMo

1979

Tokyo

Worlds first operational cellular system

12. 1G - NMT-450

Nordic Mobile Telephone 450

1982

Sweden

First wireless communications standard deployed in Europe

Pioneered the use of light portable handsets

Supported international roaming

13. 1G - AMPS

Advanced Mobile Phone System (AMPS)

1982

USA

Mandated (FCC) as the standard to which all operators in the USA had to adhere to.

14. 1G - TACS

Total Access Coverage (TACS)

1985

UK

Adaptation of AMPS

Complies with frequency allocation in Europe

15. 1G - Network Access Technique

Frequency Division Multiple Access (FDMA)

Subdivides the available spectrum into a number of frequency slots

Each user is assigned a separate frequency.

16. 1G - Services

Standard voice

No data services

No supplementary services

• • Call barring

17. The 1G Landscape

A series of incompatible networks

Limited capacity for expansion

Limited support for roaming

Susceptible to interference

Poor security

No support for wireless data

No third party applications

18. Solution: 2G

Digital techniques rather than analogue

Increased flexibility

• error control

• compression

More efficient use of available bandwidth

Increased compatibility with the fixed component of the PSTN

Increased quality of service

Possibility of wireless data services

19. 2G - GSM

Global System for Mobile Communication (GSM)

Conceived in 1982

Deployed in 1992 in Europe

European Telecommunications Standards Institute (ETSI)

Most successful 2G system

• 863 million users in 197 countries

20. 2G - D-AMPS

Digital Advanced Mobile Phone Service (DAMPS)

• Also called IS-54 (Interim Standard 54)

1991

Dual mode terminals ensuring backward compatibility

IS-136 introduced in 1996

Telecommunications Industry Association (TIA) TR-45 Committee

21. 2G - IS-95

Interim Standard 95 (IS-95)

Also called cdmaOne

1993

USA

Qualcomm Inc.

Pioneered the use of the network access technique CDMA

22. 2G - PDC

Personal Digital Cellular (PDC)

1991

Japan

Two modes

• Full-rate

• Half-rate

12% of global digital subscriptions in 1999.

23. 2G - Network Access Technique

Time Division Multiple Access (TDMA)

• Users share a frequency band by multiplexing their transmissions in time

In practice ..

• Available spectrum is divided into frequency channels (recall FDMA!)

• Each frequency channel is further subdivided into cyclic timeslots (1,2,3,1,2,3,1,2,3 )

• A call is assigned a time slot

24. 2G - Services

Depends on

• Network standard

• Operator policies

Improved standard telephony (speech)

Basic wireless data

Additional services

• Call barring

25. Example: GSM Services

Teleservices

• • Speech

• • Emergency calls

• • Short Message Service (SMS)

Bearer Services

• • Telefax

• • Basic data (9.6kb/s)

Supplementary Services

• • Call forwarding

• • Call barring

26. 2G - 3G Transition Driver?

Higher data bandwidth requirement

• • anticipated subscriber demand for

• • • audio/Video streaming

• • • other multimedia services

• • • collaborative services

• • • location services

Possibility of third party applications being developed

27. Recall: Circuit v Packet Switching

Circuit Switched ..

• A dedicated channel is established for theduration of a call

Packet Switched

• A message is subdivided into packets which are sent individually and may follow different routes to their destination. The packets are then used to reassemble the original message.

28. 3G - Migration Strategies

Migrate straight to 3G

• This approach is being take by some operators in Japan (PDC) and the USA (IS-95)

Migrate incrementally to 3G

• Operators progressively and incrementally incorporate a number of technologies into their networks

• This approach is taken by operators in both Europe and the USA

• This strategy is sometimes referred to as 2.5G

29. 2.5G - HSCSD (GSM)

High Speed Circuit Switched Data (HSCSD)

Uses existing GSM infrastructure and interface

Data rates of up to 57.6 kb/s (4 channels @ 14.4 kb/s)

Inefficient for certain types of application

30. 2.5G - GPRS (GSM)

General Packet Radio Service (GPRS)

Introduces packet switching to GSM

Always-on

Uses multiple timeslots (channels)

• 14.4 kb/s per channel

• Maximum of 115.2 kb/s

Dynamic resource allocation

Supports IP

Billing per KB, NOT per sec.

31. 2.5G - EDGE (GSM)

Enhanced Data rates for GSM Evolution (EDGE)

Maximum 384 kb/s

8 Phase Shift Keying (8PSK)

• Send more bits down the line

• 3 fold increase over GSM

Two classes of handset:

• Class A (EDGE only on downlink)

• Class B ( EDGE on uplink and downlink)

32. 2.5G - D-AMPS (IS-136+)

Two phase migration path

• IS-136+

• • Integrate GPRS

• • Note: packet switching already supported by Cellular Digital Packet Data (CDPD)!

• IS-136 High Speed Outdoor

• • Integrate EDGE

Subscribers can roam between IS-136HS and GSM networks supporting EDGE

33. 2.5G - IS-95B (IS-95)

Enhanced version of IS-95

Already supports packet switching (CDPD)

Maximum of 115.2 (8 channels @ 14.4kb/s)

Realistically

• 28.8 kb/s to 57.6 kb/s on downlink

• 14.4 kb/s on uplink

34. 2.5G - Services

Standard services that can use packet switching:

• WWW browsing

• email

• file downloading e.g. mp3

• Multimedia Messaging Service (MMS)

35. 3G - The IMT2000 Initiative

Conceived in 1986

Sought to define a single world-wide standard for accessing the global telecommunications infrastructure from both terrestrial and satellite mobile systems

Problem: backward compatibility

So five standards approved for the air interface!

36. 3G -Air Interface Standards I

• IMT-DS (Direct Spread), also known as Wideband CDMA Frequency Division Duplex (W-CDMA-FDD).

• IMT-TC (Time Code) or W-CDMA Time Division Duplex (W-CDMA-TDD).

• IMT-MC (Multi-Carrier) or CDMA2000.

• IMT-SC (Single Carrier), also known as EDGE or UWC-136.

• IMT-FT (Frequency Time), for cordless sytems e.g. DECT

37. 3G - Interface Standards II 38. 3G - Principal Requirements - I

Support for voice quality comparable with fixed line networks;

Support for both circuit-switched and packet-switched data services;

Support for roaming between different IMT-2000 operators;

Support for greater capacity and improved spectrum efficiency;

39. 3G - Principal Requirements - II

A data rate of 144 kb/s for users moving quickly e.g. moving vehicles;

A data rate of 384 kb/s for pedestrians;

A data rate of 2 Mb/s in a low mobility or office environment.

Note how a network using GPRS and EDGE meets most of these criteria!

40. 3G - Network Access Technique

Code Division Multiple Access (CDMA)

• Signal is modulated with high bandwidth spreading waveforms called signature waveforms or codes. Subscribers may submit at the same frequency and time but signal separation is facilitated via the signature waveform

In contrast with TDMA

• More robust

• Less susceptible to fading & interference

41. 3G Networks 42. Example: 3G Services (UMTS)

Universal Mobile Telephone System (UMTS)

• Four QoS classes of services

• • Conversational Class

• • • Voice, video telephony,video gaming

• • Streaming Class

• • • multimedia, video on demand, webcast

• • Interactive Class

• • • WWW browsing, database access, online gaming

• • Background Class

• • • email, SMS, file downloading

43. Quality of Service (QoS)

the collective effect of service performances which determine the degree of satisfaction of a user of a serviceITU G1000 specification

Telecommunications World

• QoS encapsulates all aspects of a service that determine the degree of satisfaction with that service.

IP World

• QoS implies guaranteed bandwidth

Pronunciation check:QoS == kwoz

44. QoS: Network v Customer

Network performance

• Packet loss, transmission delay, bit error rates, call set-up times, etc

But customer interpretation?

• Thus Q.800 suggests:

• • • Focus on effects as perceived by customer

• • • No assumptions about network design

• • • All aspects of the service considered (from customer perspective)

• • • Network independent terms used

• • • Can be assured to a user by a service provider

45. 3.5G

UMTS

• High Speed Downlink Packet Access (HSDPA)

• • 14 Mbps (but1 Mbps per subscriber!)

• • Incremental upgrade

• • More functionality in Node B

• • Backward compatible with W-CDMA

• High Speed Uplink Packet Access (HSUPA)

• Other Technologies

• • OFDN, WiMAX, etc, etc

46. 4G- Some Speculations

Global Mobility

Increased data rates..100Mbps?

All IP network

When?

47. Standardisation - ITU

Founded in 1865 in Paris by 20 European countries

• • interconnection issues

• • equipment standardization

• • uniform instructions for operating equipment

• • accounting procedures and rules

Today, affiliated with the UN

500 new or revised recommendations every year!

48. Structure of the ITU

Telecommunications Standardization (ITU-T)

• • specifications for systems networks and services

Radiocommunications (ITU-R)

• • specifies technical characteristics of terrestrial and space based wireless services and systems

Telecommunications Development (ITU-D)

• • reports, guidelines and recommendations for developing countries

49. Wireless Standardization

Recall IMT2000 vision

Two global partnerships comprising a number of traditional standardization bodies

• Third Generation Partnership Project (3GPP)

• • Concerned with EDGE & UMTS advancement

• Third Generation Partnership Project 2 (3GPP2)

• • Concerned with CDMA advancement

Note that membership not mutually exclusive!

50. 3GPP - Organizational Partners 51. 3GPP2 - Organizational Partners 52. Summary

Introduced wireless communications

Described the evolution of the various generations of cellular networks

Described the services supported by the various networks and the issues effecting their deployment

Briefly introduced the issue of standardization

53. Review Questions

Compare and contrast the three generations of mobile networks.

Trace the evolution of services from 1G to 3G.

Identify the advantages and disadvantages of circuit switched and packet switched data services from both an operator and subscriber perspective.

What benefits do standardization bring to network operators? Subscribers?

54. The End