1. The Future of Mobile Communications
Professor Rolando Carrasco
BSc(Hons), PhD, CEng, FIEE
School of Electrical, Electronic
and Computing Engineering 1

2. Research 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

3. VectaStar System Configuration
Standard 4 Sector Base Station
Subscriber Unit
90° x 8°
antenna
23° x 23°
antenna AP
256 x CPE AP AP AP AP
Network Interface
3 options for user interfaces
100 BaseT
100 BaseT & E1
100 BaseT & 2x POTS
SDH / ATM
Network 3
Copyright Cambridge University

4. Research 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

5. The world of mobile communications
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.
Well, in the case of mobile communication technologies, this phrase is true. Our society currently has in place technology that will allow you to communicate with anyone anytime in most major metropolitan areas. Think about it: if you have the need for people to be able to reach you at anytime, then you either buy a cellular phone with service or a beeper with coverage for the entire U.S. You can even receive on your beeper. Additionally, if you have a notebook computer or a personal data assistant (PDA), you can receive or communicate over networks using built-in modems with cellular capability.
however, it is not yet fully realized. While a person can receive on their beeper or voice data on their cellular phone, they can’t yet send or receive pictures or video. These are the limitations of today’s communication conduits. The limitation isn’t so much about technology as it is about standardization and integration. The transmission of voice and requires agreement among many parties, including the cellular provider, the phone or beeper manufacturer, the FCC, and probably several others. Since pictures and video are much more resource intensive than or voice, it is somewhat more difficult to settle on standards for this type of communication. Because of the tremendous profit potential, you can bet that standards will be agreed upon in the near future. 5

6. Contents Introduction
Challenges in the Migration to Future Mobile Systems
2G, 3G and 4G wireless systems
Research Challenges:
Mobile Stations, Systems, Services
Conclusion 6

7. Introduction (2) 2G Mobile Systems 3G 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

8. 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 billing 8

9. The world of mobile communications
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 9

10. 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, ,SMS,Fax,Voice,Pager 10

11. Mobile 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 ( MIRAI and DocoMo
VCE = Virtual Centre of Excellence in Mobile and Personal Communication 11

12. Mobile 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

13. Everything is IP 13

14. Research Challenges Mobile Station System Service
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

15. Mobile Stations An ideal software radio system
Multimode user Terminals: To design a single user terminal that can operate in different
wireless networks
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

16. Technical 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

17. Radio Environment Path Loss Shadow Fading Multipath Interference
Infrared Versus Radio
Doppler Spread 17

18. Link 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

19. HOW DO WE OVERCOME THE LIMITATIONS 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

20. EQUALIZER TYPES AND STRUCTURES20

21. Convolutional ‘outer’ code
Turbo Equalisation
AWGN
data
Convolutional ‘outer’ code I
ISI Channel I
Estimated data
SISO ‘outer’ decoder
I-1
SISO Equaliser
Turbo Equaliser 21

22. MIMO Turbo Equalisation
Data Model: 2-User, 2-Path, 2-Antenna (Example)
Space Domain Sampling
h11(1)
h11(0)
h12(0)
h12(1)
b1(n)
r1(n)
User 1
h21(0)
h21(1)
b2(n)
h22(0)
r2(n)
h22(1)
User 2 22

23. Algebraic-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

24. Algebraic-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 24

25. Construction of LDPC codes for Application with Broadband Communication Systems
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. 25

26. SUI-3 LDPC-QPSK With SRK Equalisation26

27. Broadband Fixed Wireless Access (BFWA) systems
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 , 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

28. Comparison of different equalisation schemes in BFWA systems28

29. MIMO 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

30. Space-Time Ring Trellis Coded Modulation
Tx1
Tx2
r1(x)
r2(x)
g11(x)
g22(x)
g12(x)
g21(x)
ST-Ring TCM Decoder
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

31. Maximum a-posteriori 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. 5 10 15 20 25 30
-60
-50
-40
-30
-20
-10 31

32. Way to download Software
Mobile Station
Wireless system discovery
GSM
GPRS
Via PC server
CDMA
Via PDA
Scanning…
Via smart card
UMTS
OTA
Via Memory card
WLAN
Available Systems
Way to download Software
To discover available wireless systems by processing the signals sent from different wireless
systems (different access protocols) 32

33. Mobile Station
Wireless System Selection: Selection of the most suitable technology for a particular service
We can choose any available wireless device for each particular
communication session (fit to user QoS requirements)
Right network selection can ensure the QoS required by each Session Initiation
Protocol (SIP) messages.
Adequate knowledge of each network is required before a selection is made
Location information of the source mobile nodes, available networks of both
mobile nodes and user preference are all taken into account in the selection
when a mobile node makes a call to another mobile node 33

34. System Terminal Mobility The system tracks and locates a
Location Management
Terminal Mobility
The system tracks and locates a
mobile terminal for possible
connection
Terminal moves between
subnets
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

35. System Enhanced Mobile IPv6 Schemes
Figure shows an example of horizontal and vertical handoff
UMTS coverage
GSM coverage
Vertical handoff
Horizontal handoff
WLAN coverage
Main problems: - handover performance
- handover failure due to lack of resources
- authentication of redirection 35

36. System
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

37. System Network Infrastructure and QoS Support
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 WLAN and
HiperLAN, /802.20
Problems: Integration, QoS guarantee for end-to-end
time-sensitive (3GPP) 37

38. System
Security
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 38

39. Mobile Station – GSM Functional Architecture
Radio Subsystem
Points of reference
Base Station Subsystem (BSS)
Network and Switching Subsystem (NSS)
Operation Subsystem (OSS) MS
VLR
BTS
BSC
AuC
HLR
BTS MS
OMC
BSC MS
BTS
MSC
EIR
Interface to other networks
Transition to ISDN, PDN, PSTN 39
Radio Interface
BTS-BSC Interface

40. System Fault Tolerance and Survivability: To minimise the failures and
Their potential impacts in any level of tree-like topology
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 40

41. Services 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

42. Services Personal Mobility: different terminals, same address
The movement of users instead of users’ terminals and involves the provision of
personal communication and personalised operating environments 42

43. Services Personal Mobility (Agent Support for Personal Mobility)
Mobile-agent based infrastructure is one widely studied
(Agent Support for Personal Mobility)
Agents act as intermediaries between the user and the
Internet 43

44. Application
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

45. Improving the way we work
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 45

46. Conclusions
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

47. Conclusions
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