The Future of Mobile CommunicationsThe Future of Mobile Communications

Professor Rolando Carrasco

BSc(Hons), PhD, CEng, FIEE

R.Carrasco@newcastle.ac.uk

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School of Electrical, Electronic and Computing Engineering

Research Project 1Research Project 1

• The Capacity and Throughput Improvement of Fixed Broadband Wireless Access Systems

Dr. Pei Xiao, Research Fellow (three years)

Mr. M. K. Khan BEng, MSc, Research Student (21/2 years)

EPSRC Grant in collaboration with Dr. I. Wassell, Cambridge University and Cambridge Broadband Ltd

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Network Interface

Subscriber Unit Standard 4 Sector Base Station

AP AP AP AP

AP beam patterns

0

30

60

90

120

150

180

210

240

270

300

330

15

12

9

6

3

0

AP

APAP

AP

256 x CPE

256 x CPE256 x CPE

256 x CPE

90° x 8°antenna

23° x 23°antenna

3 options for user interfaces100 BaseT100 BaseT & E1100 BaseT & 2x POTS

SDH / ATM

Network

VectaStar System ConfigurationVectaStar System Configuration

Copyright Cambridge University 3

Research Project 2Research Project 2

• Space-Time Diversity Coding Combined with Equalisation for MIMO Wireless Channels.Mr. Cameron B Shaw BEng(Hons), MEng (PhD Student), 15 months remaining

EPSRC grant in collaboration with Lancaster University (Professor Honary) and MOD (Ministry Of Defence)

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The world of mobile communications

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•Have you ever heard the phrase “the future is here today”? Well, in the case of mobile communication technologies, this phrase is true.

•However, it is not yet fully realized.

ContentsContents

• Introduction

• Challenges in the Migration to Future Mobile Systems

• 2G, 3G and 4G wireless systems

• Research Challenges:– Mobile Stations, Systems, Services

• Conclusion

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Introduction (2)Introduction (2)

• 2G Mobile Systems– GSM, IS-95 and CDMA one carry speech and low bit rate

data

• 3G Mobile Systems– Higher data rate– Multi-media systems– GPRS– IMT 2000– Bluetooth– WLAN and HiperLAN– Developing new standards and hardware

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4G Mobile Systems (2006)4G Mobile Systems (2006)

• Access, handoff

• Location coordination

• Resource coordination to add new users

• Support for multicasting and Quality of Service

• Wireless security and authentication

• Network failure and backup

• Pricing and billing8

The world of mobile communications

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•Out of a world population of 6.32 billion people, approximately 1.12 billion, or 1 in 6, have a mobile phone and 71.6% are GSM customers

•Total Operator revenues for 2006 have been estimated to be over $100 billion for Western Europe

•China Mobile with over 100 million customers are connecting 2 million new customers each month

•About 2 billion people in the world have yet to make a phone call and it is likely that when it happens it will be on a mobile phone rather than a fixed line

What is Wireless Data?What is Wireless Data?

• Paging/short messaging• Vehicle tracking and dispatch• Transaction processing• Warehouse inventory• Subscriber information services• Wireless remote access to host• File transfer to/from laptop,J2ME• Wireless Internet access and Video Teleconferencing• Browsing on Laptops, PDAs ,Phones• Messaging,E-mail,SMS,Fax,Voice,Pager

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Mobile Computing SystemsMobile Computing Systems

• Future Mobile Systems– Personalised Services providing stable system

performance and Quality of Service (QoS)– Challenges:

• Mobile Station• System(Networks) • Service and standards

Mobile VCE (www.mobilevce.com), MIRAI and DocoMo

VCE = Virtual Centre of Excellence in Mobile and Personal Communication 11

Mobile Computing SystemsMobile Computing Systems

• Some key features of Future Mobile Systems– High usability:

• Anytime, anywhere and with any technology (all-IP based heterogeneous networks)

– Support for Multi-media Services at low transmission cost

– Personalisation(having human characteristics)– Integrated Services

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Everything is IP

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Research ChallengesResearch Challenges

• Mobile Station– Multimode user terminals(multi-functional,software upgrades)– Wireless system discovery(searching for wireless system)– Wireless system selection(suitable technology)

• System– Terminal Mobility(to locate and update the locations)– Network infrastructure and QoS support– Security, performance and complexity– Fault tolerance and Survivability

• Service– Multi-operators and billing system– Personal mobility– New Applications

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Mobile StationsMobile Stations

An ideal software radio system

• New coding/interleaving/diversity/equalisation/SISO channel/MIMO channels• Multicarrier, spread spectrum and antenna solutions• Adaptive coding modulation, detection, synchronisation and automatic repeat request• Multimedia protocols, new access,timing control and QoS• New applications• A software radio approach can be used so that the user terminal adapts itself to the wireless • interface

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Multimode user Terminals: To design a single user terminal that can operate in differentwireless networks

Technical ChallengesTechnical Challenges

• Low-Power/Low-Cost Implementations• Scarce Radio Spectrum• Radio Channel Characteristics

- Limits on Signal Coverage

- Limits on Data Rates• Efficient Network Architectures and Protocols• Seamless Internetworking• Authentication and Security

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Radio EnvironmentRadio Environment

• Path Loss

• Shadow Fading

• Multipath

• Interference

• Infrared Versus Radio

• Doppler Spread

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Link Performance Measures EfficiencyLink Performance Measures Efficiency

• Spectral Efficiency- a measure of the data rate per unit bandwidth for a given bit error probability and transmitted power

• Power Efficiency- a measure of the required received power to achieve a given data rate for a given error probability and bandwidth

• Throughput/Delay

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HOW DO WE OVERCOME THE LIMITATIONS HOW DO WE OVERCOME THE LIMITATIONS IMPOSED BY THE RADIO CHANNEL?IMPOSED BY THE RADIO CHANNEL?

• Flat Fading Counter measures - Fade Margin

- Diversity

- Coding and Interleaving

- Adaptive Techniques

• Delay Spread Counter measures - Equalization

- Multicarrier

- Spread Spectrum

- Antenna Solutions 19

EQUALIZER TYPES AND STRUCTURESEQUALIZER TYPES AND STRUCTURES

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Convolutional ‘outer’ code I ISI Channel

I

I-1 SISO EqualiserSISO ‘outer’ decoder

data

Estimated data

Turbo Equaliser

AWGN

Turbo EqualisationTurbo Equalisation

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MIMO Turbo EqualisationMIMO Turbo Equalisation

Data Model: 2-User, 2-Path, 2-Antenna (Example)

h11(1)

h11(0)

h12(1)h12(0)

h21(0)h21(1)

h22(0)h22(1)

User 1

User 2

b1(n)

b2(n) )()1()1(

)1()(

)0(

)0(

)1()1(

)1()(

)0(

)0()(

122

212

22

21

112

111

12

11

nnbh

hnb

h

h

nbh

hnb

h

hn

n

r

r1(n)

r2(n)

)()1().1()().0(

)1().1()().0(

2222

1111

nnbnb

nbnb

nhh

hh

Space Domain Sampling

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Algebraic-Geometric CodesAlgebraic-Geometric Codes

• Algebraic geometry is a powerful tool for constructing codes with good parameters e.g. Hamming distance, code rate and large code length.

• Very long codes can be constructed by choosing curves containing many points. Reed Solomon codes are constructed from a line, which has less points, and hence they are much shorter than AG codes

• There is almost no limit to the number of AG codes that can be constructed from a variety of different classes of curve. There are not many Reed Solomon codes.

• AG codes perform better than Reed Solomon codes for high code rates over smaller finite fields and are suitable for application in mobile communications and storage devices

• Further investigation is needed into constructing new codes from different classes of curves and the development of low complexity decoding algorithms for future hardware implementation.

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Algebraic-Geometric CodesAlgebraic-Geometric Codes

• Hermitian curves can be used to construct very long codes:

Example: C(x,y) = x5 + y4 + y, defined over GF(16) gives codes 64 symbols long. A Reed Solomon code over GF(16) is only 15 symbols long

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

-4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Eb/N0 , dB

BE

R

(64,39)AG, R=0.61

(15,9)RS, R=0.6

Uncoded BPSK

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Construction of LDPC codes for Application with Construction of LDPC codes for Application with Broadband Communication SystemsBroadband Communication Systems

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• LPDC codes are a class of Block codes that perform very close to Shannon limit.

• Uses efficient encoding and iterative decoding schemes to achieve low latency .

• Highly parallel nature and low complexity of decoding algorithm results in fast iterative decoding and less complex Hardware architecture.

• Better performance using equalisation techniques in dispersive MIMO/SISO ISI fading channels.

•Performance is drastically improved by concatenating with Space time Codes

•Suitable for high data rate applications.

SUI-3 LDPC-QPSK With SRK Equalisation

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Broadband Fixed Wireless Access (BFWA) Broadband Fixed Wireless Access (BFWA) systemssystems

• Aim of BFWA is to deliver broadband data services to homes and businesses in a flexible and efficient manner.

• Main driver is to provide Internet access for applications such as E-mail, web-browsing, file downloading and transfer, audio and video services over Internet.

• In BFWA systems, radio signal travels via multipath from transmitter to receiver antennas. Multipath propagation causes intersymbol interference and degrade the system performance.

• Turbo equalization is a powerful technique to remove the effect of intersymbol interference.

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Comparison of different equalisation schemes in BFWA Comparison of different equalisation schemes in BFWA systemssystems

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MIMO Channels for BFWA SystemsMIMO Channels for BFWA Systems

• Use MIMO space-time coding to increase the capacity of BFWA system.

• Signals from different antennas can be separated through orthogonal design, such as Alamouti algorithm.

• When used over frequency selective channels, a channel equalizer has to be used at the receiver along with the space-time decoder.

• STBC can be applied in conjunction with OFDM which converts the frequency selective channel into a set of independent parallel frequency-flat subchannels. The Alamouti scheme is then applied to each subcarrier.

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Space-Time Ring Trellis Coded ModulationSpace-Time Ring Trellis Coded Modulation

Tx1

Tx2

r1(x)

r2(x)

g11(x)

g22(x)

g12(x)

g21(x)QPSK

Demodulator

QPSKDemodulator

00

32

20

12

33

21

13

01

22

10

02

30

11

03

31

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State = 0

State = 1

State = 2

State = 3

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22

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ST-Ring TCM Decoder

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

-4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

SNR (dB)

BE

R

Indoor (21/3)

Indoor (Delay diversity)

Indoor (212/31)

Pedestrian (21/3)

Pedestrian (Delay diversity)

Pedestrian (212/31)

Vehicular (21/3)

Vehicular (Delay diversity)

Vehicular (212/31)

Indoor (2103/132)

Pedestrian (2103/132)

Vehicular (2103/132)

The uncorrelated fading channels are used to provide diversity

Very good results can be obtained with just 2 tx & 2 rx antennas.

Higher coding gains achieved and error floors removed by using higher state codes.

Higher coding gains are achieved and error floors removed by using higher state codes.

Cannot fully recover vehicular channel data. Equalisation is needed.

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Maximum Maximum a-posterioria-posteriori Turbo Equalisation Turbo Equalisation

Realistic channel models are created to properly test the mobile communication systems.

Indoor, pedestrian and vehicular scenarios are simulated based on actual measured results from urban mobile radio channels.

Over realistic channels (such as the urban mobile channel) the intersymbol interference produced needs mitigation to improve performance.

The goal of equalisation is the cancellation of the Inter-Symbol Interference (ISI), or equivalently the flattening of the radio channel’s frequency response

Turbo equalisation combines decoding and equalisation by converting the channel into a type of ‘code’ which can then be iteratively decoded with a symbol-by-symbol decoder.

MAPEqualiser

MAPDecoder

+-

+

-

a prioriinformation

a posterioriinformation

a prioriinformation

a posterioriinformation

extrinsic information

extrinsic information

recievedmessage ( y )

L (c t|y )

L (c t)L ext (c t|y )

L ext (c t|y )

L ext (c t)

L ext (c t)

5 10 15 20 25 30-60

-50

-40

-30

-20

-10

0

5 10 15 20 25 30-60

-50

-40

-30

-20

-10

0

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Mobile StationMobile Station

Via Memory card

Via PC server

Via smart card

WLAN

OTAUMTS

CDMA

GPRS

GSM

Scanning…

Available Systems

Way to download Software

Wireless system discovery

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Via PDA

• To discover available wireless systems by processing the signals sent from different wireless systems (different access protocols)

Mobile StationMobile Station

Wireless System Selection: Selection of the most suitable technology for a particular service

• We can choose any available wireless device for each particularcommunication session (fit to user QoS requirements)

• Right network selection can ensure the QoS required by each Session InitiationProtocol (SIP) messages.

• Adequate knowledge of each network is required before a selection is madeLocation information of the source mobile nodes, available networks of bothmobile nodes and user preference are all taken into account in the selectionwhen a mobile node makes a call to another mobile node

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System

Terminal Mobility

Location Management

The system tracks and locates amobile terminal for possible connection

• To locate and update the locations of the terminals in various systems• Location Management: Information about the roaming terminals such as original and current located cells, authentication information and QoS• Service Mobility: Keep same service while mobile

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Terminal moves betweensubnets

SystemSystem

• Enhanced Mobile IPv6 Schemes

Figure shows an example of horizontal and vertical handoff

UMTS coverage

GSM coverage

WLAN coverage

Vertical handoff

Horizontal handoff

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• Main problems: - handover performance - handover failure due to lack of resources - authentication of redirection

SystemSystem

Problems

• Real-Time Multimedia Services that are highly time-sensitive• It is unacceptable if the MIPv6 handoff process significantly degrades system performance. • New handoff decision policies and new handoff algorithms. The terminal moves from one cell to another (two different wireless systems e.g. WLAN and GSM).

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SystemSystem

• To integrate the existing non-IP-based and IP-based systems

• Non-IP-based systems (voice delivery) e.g. GSM, CDMA2000 and UMTS

• IP-based systems (data services) e.g. 802.11 WLAN and HiperLAN, 802.16/802.20

Problems: Integration, QoS guarantee for end-to-end time-sensitive (3GPP)

Network Infrastructure and QoS Support

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SystemSystem

• The heterogeneity of wireless networks complicates the security issues

• 2G/3G have been widely studied

• The key concern in security designs for 4G networks is flexibility. The key sizes and encryption and decryption algorithms of existing schemes are also fixed.

• Reconfigurable security mechanisms are needed (Tiny SESAME)

• Modifications in existing security schemes may be applicable to heterogeneous systems

Security

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Mobile Station – Mobile Station – GSM Functional ArchitectureGSM Functional Architecture

BTS

BTS

BTS

BSC

BSC

HLR

VLR

AuC

OMC

MSC EIR

Interface to other networks

Transition to ISDN, PDN, PSTNRadio Interface

MS

MS

MS

BTS-BSC Interface

Base Station Subsystem (BSS) Network and Switching Subsystem (NSS)

Operation Subsystem (OSS)Points of reference

Radio Subsystem

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SystemSystem

Reliability, availability and survivability of the network

• A cellular wireless access network is typically designed as a tree-like topology that has several levels (device, cell, switch and network levels)

Problems: Any level fails (hardware/software), all levels below will be affected

• Consideration, power consumption, user mobility, QoS management, security, system capacity and link error rates of many different wireless networks.

• The first is to use hierarchical cellular network systems The second is to use collocated or overlapping heterogeneous wireless network

Fault Tolerance and Survivability: Fault Tolerance and Survivability: To minimise the failures andTo minimise the failures andTheir potential impacts in any level of tree-like topologyTheir potential impacts in any level of tree-like topology

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ServicesServices

Multiple Operators and Billing System

• More comprehensive billing and accounting systems are needed (different types of services)

• Multiple service providers

• Operators need to design new business architecture, accounting processes and accounting data maintenance.

• Future Wireless Networks support multimedia communications, which consists of different media components with possibly different charging units

• This adds difficulty to the task of designing a good charging scheme for all customers

• Scalability, flexibility, stability, accuracy and usability

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ServicesServices

• The movement of users instead of users’ terminals and involves the provision of personal communication and personalised operating environments

Personal Mobility: different terminals, same addressPersonal Mobility: different terminals, same address

Laptop computer

Pen computer

At 10.00am a video message is sentto Mary. She reads the message usingher PC in her office

At 6.00pm another videomessage is sent to Mary.She reads the message using her PDA whendriving her car.

At 8.30pm a video messageis sent to Mary again. She reads the message usingher laptop PC at home

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ServicesServices

• Mobile-agent based infrastructure is one widely studied (Agent Support for Personal Mobility)

• Agents act as intermediaries between the user and the Internet

Personal Mobility

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ApplicationApplication

• Mobile computing in a Fieldwork Environment Ecologists, archaeologists, computer scientists and engineers

• Communication and Ad Hoc Networking in the field, prevent disaster, reduce crime and terrorism

• Health and Education• E-Commerce, E-Business, E-Government• Partnership Universities• Entertainment, games, smart home

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Improving the way we work

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•The way and means that people use to communicate is changing

•People need the ability to work anywhere, anytime, anyplace

•Best Value, being effective and efficient

•Work is an activity not a building or place

ConclusionsConclusions

• In this presentation research challenges in the emigration to future networks are studied and described

• The challenges are grouped into three aspects: Mobile Station, System and Service

• Wireless technologies used to decrease crime and prevent emergency disasters and terrorism

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ConclusionsConclusions

• The challenges were identified, such as multicarrier user terminals, wireless system discovery, terminal mobility, QoS support and business opportunities

• Mobile communication impact in urban/rural areas

• Project of Innovation for job creation using wireless technologies

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