Agents, Mobility, Ubiquity & Virtuality

Gregory O’HareDepartment of Computer Science,University College Dublin

Mobile Communications Development

COMP40300 Context-Sensitive Service Delivery

Lecture 5 & 6

Professor Gregory O’HareSchool of Computer Science & Informatics,University College Dublin (UCD)

Outline

Introduce some basic wireless concepts

Describe the evolution of cellular telecommunications networks

Reflect on the services supported by cellular networks

Consider the issue of standardization in wireless communications

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), analogue signal

Later - Electromechanical switches Today - Automated, digital

But …… the so-called “last mile problem”

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.

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

Disadvantages of Wireless

Careful planning of network essential

Environment generally hostile

Security

Safety

spectrum licenses

poor data rates

cost (domain dependant)

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

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Originally proposed by D. H. Ring in an unpublished paper.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

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

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

1G - NTT

Nippon Telephone & Telegraph (NTT)

Now NTT DoCoMo

1979

Tokyo

World’s first operational cellular system

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

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.

1G - TACS

Total Access Coverage (TACS)

1985

UK

Adaptation of AMPS

Complies with frequency allocation in Europe

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.

1G - Services

Standard voice

No data services

No supplementary services Call barring

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

Solution: 2G

Digital techniques rather than analogue

Increased flexibility –error control & Compresssion

More efficient use of available bandwidth

Increased compatibility with the fixed component of the PSTN

Increased quality of service

Possibility of wireless data services

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

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

2G - IS-95

Interim Standard 95 (IS-95)

Also called cdmaOne

1993

USA

Qualcomm Inc.

Pioneered the use of the network access technique CDMA

2G - PDC

Personal Digital Cellular (PDC)

1991

Japan

Two modes

Full-rate

Half-rate

12% of global digital subscriptions in 1999.

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

2G - Services

Depends on

Network standard

Operator policies

Improved standard telephony (speech)

Basic wireless data

Additional services

Call barring

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

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

Recall: Circuit v Packet Switching

Circuit Switched ..

A dedicated channel is established for the duration 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.

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

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

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.

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)

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

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

2.5G - Services

Standard services that can use packet switching:

WWW browsing

email

file downloading e.g. mp3

Multimedia Messaging Service (MMS)

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!

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

3G - Interface Standards II

Radio-Interface Standard Cellular Network Standards Organisation

IMT-DS GSM, PDC 3GPP

IMT-TC D-AMPS 3GPP

IMT-MC IS-95, PDC 3GPP2

IMT-SC Any TDMA Network UWCC

Table 1: 3G interface standards for the predominant 2G networks.

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;

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!

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

3G Networks

2G Network 3G SuccessorGSM UMTSPDC CDMA2000IS-95 CDMA2000DAMPS IS-136HS or UMTS

Example: 3G Services (UMTS)

Universal Mobile Telephone System (UMTS)

Four QoS classes of services

Conversational Class (real time) Voice, video telephony,video gaming

Streaming Class (real time) multimedia, video on demand, webcast

Interactive Class (best effort) WWW browsing, database access, online gaming

Background Class (best effort) email, SMS, file downloading

Quality of Service (QoS)

“the collective effect of service performances which determine the degree of satisfaction of a user of a service”… ITU 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

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

3.5G

UMTS

High Speed Downlink Packet Access (HSDPA)

14 Mbps (but 1 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

4G- Some Speculations

Global Mobility

Increased data rates..100Mbps?

All IP network

When?

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!

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

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!

3GPP - Organizational Partners

Organisation Region URL

Association of Radio Industries and

Businesses (ARIB)

Japan http://www.arib.or.jp

China Wireless Telecommunications

Standard Group (CWTS)

China http://www.cwts.org

European Telecommunications Standards

Institute (ETSI)

Europe http://www.etsi.org

Committee T1 (T1) USA http://www.t1.org

Telecommunications Technology Association

(TTA)

Korea http://www.tta.or.kr

Telecommunications Technology Committee

(TTC)

Japan http://www.ttc.or.jp

3GPP2 - Organizational Partners

Organisation Region URL

Association of Radio Industries and

Businesses (ARIB)

Japan http://www.arib.or.jp

China Wireless Telecommunications

Standard Group (CWTS)

China http://www.cwts.org

Telecommunications Industry Association

(TIA)

USA http://www.tiaonline.org

Telecommunications Technology Association

(TTA)

Korea http://www.tta.or.kr

Telecommunications Technology Committee

(TTC)

Japan http://www.ttc.or.jp

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

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?