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

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Presentation on theme: "The Future of Mobile Communications Professor Rolando Carrasco BSc(Hons), PhD, CEng, FIEE 1 School of Electrical, Electronic."— Presentation transcript:

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

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 (2 1/2 years) EPSRC Grant in collaboration with Dr. I. Wassell, Cambridge University and Cambridge Broadband Ltd 2

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

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 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.

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 –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 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

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 (www.mobilevce.com), 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 –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 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 different wireless networks

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 STRUCTURES 20

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

22 MIMO Turbo Equalisation Data Model: 2-User, 2-Path, 2-Antenna (Example) h 11 (1) h 11 (0) h 12 (1) h 12 (0) h 21 (0) h 21 (1) h 22 (0) h 22 (1) User 1 User 2 b1(n)b1(n) b2(n)b2(n) r1(n)r1(n) r2(n)r2(n) Space Domain Sampling 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) = x 5 + y 4 + 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 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.

26 SUI-3 LDPC-QPSK With SRK Equalisation 26

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 systems 28

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 r 1 (x) r 2 (x) g 11 (x) g 22 (x) g 12 (x) g 21 (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 channels 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

32 Mobile Station Via Memory card Via PC server Via smart card WLAN OTA UMTSCDMAGPRS 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)

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 Location Management The system tracks and locates a mobile 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 between subnets

35 System 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

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

38 System 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

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

40 System 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: To minimise the failures and Their potential impacts in any level of tree-like topology 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 The movement of users instead of users terminals and involves the provision of personal communication and personalised operating environments Personal Mobility: different terminals, same address 42

43 Services 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

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 45 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

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


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