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Originally proposed by D. H. Ring in an unpublished paper.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