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The Future of Mobile CommunicationsThe Future of Mobile Communications
Professor Rolando Carrasco
BSc(Hons), PhD, CEng, FIEE
1
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
2
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)
4
The world of mobile communications
5
•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
6
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
7
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
9
•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
10
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
12
Everything is IP
13
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
14
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
15
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
16
Radio EnvironmentRadio Environment
• Path Loss
• Shadow Fading
• Multipath
• Interference
• Infrared Versus Radio
• Doppler Spread
17
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
18
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
20
Convolutional ‘outer’ code I ISI Channel
I
I-1 SISO EqualiserSISO ‘outer’ decoder
data
Estimated data
Turbo Equaliser
AWGN
Turbo EqualisationTurbo Equalisation
21
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
22
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.
23
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
24
Construction of LDPC codes for Application with Construction of LDPC codes for Application with Broadband Communication SystemsBroadband Communication Systems
25
• 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
26
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.
27
Comparison of different equalisation schemes in BFWA Comparison of different equalisation schemes in BFWA systemssystems
28
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.
29
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
23
00
32
20
12
33
21
13
01
22
10
02
30
11
03
31
23
State = 0
State = 1
State = 2
State = 3
00
33
22
11
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.
30
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
32
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
33
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
34
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
35
• 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).
36
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
37
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
38
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
39
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
40
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
41
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
42
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
43
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
44
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
46
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
47