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May 2000

Summary of activities at ICSI Oct/99 to May/00. May 2000. José M. Páez. Introduction. Myself. José M Páez-Borrallo, Professor of Signal Theory and Communications in the Technical University of Madrid On leave at ICSI in the period Oct/99-Jun/00. Research interests.

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May 2000

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  1. Summary of activities at ICSI Oct/99 to May/00 May 2000 José M. Páez

  2. Introduction Myself • José M Páez-Borrallo, Professor of Signal Theory and Communications in • the Technical University of Madrid • On leave at ICSI in the period Oct/99-Jun/00 Research interests • Signal and Array Processing for Communications • Wireless Communications (WLL, WLAN, …) • Physical Layer: Modulations, Equalizers, Smart antennas … • Access Techniques: CDMA, OFDMA, Hybrid, …. • Mobile Digital Systems (DECT, GSM, UMTS, TD-UTRA ...) My original project at ICSI • Design and analysis of MUD receiver architecturesfor CDMA. Exploiting • dynamic Space-Time diversity to improve the radio link

  3. Activities carried out during my stay at ICSI Research • Design and analysis of MUD receiver architecturesfor CDMA with direct • application to UTRA-TDD • Design of new waveforms for CDMA. Something intermediate between • DS-CDMA and MC-CDMA • Prospective analysis and information gathering on Ultra Wide Band Radios Definition of future infrastructure for Research • Design and viability study of a Research Institute on Communications • with partnership of Industry, Telecom Operators and University

  4. Contacts in Berkeley during my stay at ICSI Cooperation with BWRC • Berkeley Wireless Research Center (BWRC). http://bwrc.eecs.berkeley.edu/ • Involved in technologies for new generations of radio systems • Cooperation in new CDMA techniques (October-February) • Continued assistance to internal BWRC seminars and tech discussions • Invited tutorial on MC Modulation in BWRC Winter’s Retreat in Monterey, CA • Poster on new waveforms for CDMA in BWRC Winter’s Retreat • Contact at BWRC: Scientific Director, Robert Brodersen

  5. Multiple Access: Sharing the medium Fix services Mobile services Multiple Access Defined • A scheme that enables many users to share a common access point • Requires “orthogonalization” of users so that they can be distinguished • Orthogonalization can be done in in time, frequency, space, or any • combination (e.g. using “codes”)

  6. TDMA Note: colors represent different users FDMA Time Time Diff. Time slots Common band Freq. Diff. Frequency channels Common time Freq. TIME separation FREQ separation DS-CDMA • Codes (waveforms) need to be orthogonal • Increase in capacity (graceful degradation) • Greater reuse factor in cellular systems • Channel impairments affect orthogonality • It appears Multiple Access Interference (MAI) Time Freq. CODE separation Multiple Access: CDMA vs. TDMA and CDMA

  7. MUD Receiver Architectures for CDMA systems

  8. MUD receiver architectures for CDMA (1) • Definition of an extended multisensor signal model for Multiple Access • Interference MAI including multipath • Design and analysis of new front-ends with MAI cancellation • Design and analysis of Decorrelation and Optimal (MMSE) vector receivers • Performance evaluation of previous receivers (mono and multisensor) • MATLAB implementation of a radio-link simulatorwith channel impairments • Adaptive implementation of receivers. Reduced-rank versions of it • Analysis of simulated results versus receivers’ complexity

  9. Intra F= Intra+Inter MUD receiver architectures for CDMA (2) MUD efficiency: It quantifies the amount of Intracell Interference removal performed by the specific MUD receiver : Cancelable Total Interference ratio

  10. K users . . . P MUD receiver architectures for CDMA (3) A feasible vector MUD Decorrelation receiver architecture Front-End Decorrelation User 1, L paths 1 User 1 Signature space-time Decorrelation Space-time filtering . . . P User K User K, L paths KL KL KL KLP 1 Multipath amplitude estimation DOA estimation To downlink in TDD systems KL P Channel estimation branch Front-end: Capture the incoming active users Channel branch: Estimate space-time info from the incoming signals Space-time filters: Isolate different users and paths Decorrelation: Remove the residual MAI from others users (eff. Signature)

  11. K users . . . P User 1 MUD receiver architectures for CDMA (4) A feasible vector MUD MSE receiver architecture Minimize MSE Front-End Filtering GOAL User 1, L paths KLP K Rank reduction . . . User filters User K User K, L paths K K KLP Training sequence Computing matrix transformation Further refinement Channel estimation branch Front-end: Capture the incoming active users Channel branch: Estimate rank-reduction matrix from space-time info Space-time filters: Isolate different users and recover the desired signals Training: Provides the info sequence to form the goal function

  12. MUD receiver architectures for CDMA (5) Some simulated results Spreading gain: 15 1000 QPSK symbols 5 active users 2 paths per user (span 1/4 symbol) Linear array of 8 sensors 4 different architectures

  13. New TF waveforms for CDMA

  14. New TF waveforms for CDMA: CDMA concept (1) • Any symbol is carried by a set of waveforms (basis) • This set of “carriers” is needed to provide “virtual” separation among users • Can choose anyorthogonal basis -- each user is not limited to one time or frequency slot • This generalization results in a “code” space where users may overlap in frequency/time • Much research has been done and many different flavors exist: DS-CDMA, MC-CDMA, etc. continuous: where symbol chips basis (waveforms) discrete: where

  15. Channel effect on the signals Note:colors represent different chips for 1 user and 1 symbol. Tc channel t T Tc An unique wide-band spectrum means resistance to time-varying channel and frequency noise/jitter 1/Tc f Time dispersive channel causes signal distortion and Inter-Chip-Interference (breaks orthogonality) Waveform set: Short pulses Signal basis: Identity matrix 1 Code & Chips -1 User i: si=Yci User j: sj=Ycj 1 siTsj =ciTYTYcj=dij 1 -1 -1 1 1 T=MTc Symbol Two diff. users share the same Signal basis and have diff. codes Chips are time located New TF waveforms for CDMA: Standard DS-CDMA (2)

  16. Channel effect on the signals Note: colors represent different chips for 1 user and 1 symbol. Df = 1/T T Narrower bands meansmore sensitive to channel variation and frequency noise/jitter t channel Longer symbol duration minimizes ISI effect due to channel dispersion Waveform set: sinusoids T=Tc Signal basis: DFT matrix User i: si=Yci User j: sj=Ycj Symbol siTsj =ciTFTFcj=dij 1 -1 -1 1 Code & chips Two diff. users share the same Signal basis and have diff. codes Chips are frequency located New TF waveforms for CDMA: Multicarrier CDMA (3)

  17. 1D-Symbol T-F spreading of 2D-Symbols Symbol duration 1D-Symbol Tc DS-CDMA M T-chips, 1 carrier, B=1/Tc T ... Same spread gain: M M/2 T-chips, 2 carriers, B=1/2Tc+1/2Tc 2D-Symbol 2Tc M/K T-chips, K carriers, B=K/KTc=1/Tc ... Better spectral efficiency (lower side lobes) More resistance to channel time dispersion It allows to exploit spectral knowledge of channel Research 2D orthogonal or pseudorandom codes Increasing no. of carriers Increasing no. of T-chips KTc MTc=T 1 T-chip, M carriers, B=M/MTc=1/Tc MC-CDMA New TF waveforms for CDMA: Time-frequency chips (4)

  18. Spectra Wide-band spectra Frequency New TF waveforms for CDMA: Example (5) DS-CDMA is tiled in time and is susceptible to distortion caused by time-dispersive channel MC-CDMA is tiled in frequency is susceptible to channel variations and frequency noise/jitter Discrete chirps Waveform set: discrete chirps Long waveforms -1 -1 1 1 2D Code & chips -1 -1 1 1 -1 1 1 1 T=4Tc Time Symbol Chips are time-frequency located Provides intermediate level of resistance to time and frequency impairments

  19. Research Institute on Communications

  20. Research Institute on Communications (1) Foundation statements • Provide an environment for research into the issues necessary to support Technology, Networks and Applications for future mobile communication systems. • Center for education of new engineers in the field of Wireless Technologies and Services • Mixed participation of Industry, Telecom operators and University • Promote start-up companies from the Institute on own results • The Institute will pursue an active policy of placing research results in the public domain as determined by the Scientific Board Center lifetime of at least 7 years with yearly reviews and 4+3 year informal commitments

  21. Research Institute on Communications (2) Medium and long term R&D Specific Projects & Consortia Ph D Theses Master Theses Specific needs Multidisciplinary projects Institute Utilization of known R&D Continuous Analysis of extern R&D Prediction of tech needs Product Focalization Own development in the CI Prospective & Innovation Creation of start-ups

  22. Radio Access & Technologies Low power RF design Audio & Video coding Mobile multimedia communications Fix-mobile convergent services Universal spectrum sharing Mobile IP, WLL and WLANs Multicast over IP networks Bandwidth-on-demand management Interconnectivity and networks transparency Digital TV & Radio, WebTV, etc Multimedia content production Research Institute on Communications (3) Research issues at the Institute Prospective & Innovation Office 3 research areas This is a 1st proposal. It has to be determined within the Advisory Board

  23. Research Institute on Communications (4) • 2 Workshops per year: • Research staff is committed to present their results publicly • Monographic sessions, Poster presentations and Tech discussions • Open assistance to externpublic (other companies, institutes, etc) • 2 montly Seminars: • Given by CI staff, company partners and invited speakers • Semester calendar of seminars (as continuing education for some companies) • Non-partners assistance by invitation or payment • 2 montly technical meetings per research area • Development of research agenda and summary of work done • Paper Reading and discussion sessions • Restricted assistance to associated partners

  24. Research Institute on Communications (5) Initial Participation (commitment for 4 years) Associated Affiliated Funding 150 Keuro/year 50 Keuro/year Fix lab seats up to 2 engineers Only for Seminars Human resources Types of Company Partnership

  25. Research Institute on Communications (6) University Head Telecom Faculty Head Dpt. Radiotech Head Dept. Electronics Head Dept. Networks Head Dept. Basic Sci Industry 10-12 Associated Companies Institute Head of Institute Vicehead of Institute Technology Responsible Network Responsible Application Responsible Individual 4 known professionals Institute Advisory Board

  26. Research Institute on Communications (7) Benefits of being an Institute partner Affi. Asso. • Memberof theAdvisory board • Memberof theScientific board (Impact on the research agenda) • Participation in large pre-competitive, interdisciplinary research effort with relatively modest investment • Free Assistance to workshops and seminars • Free assistance to periodic technical meetings • In-situ involvement with a large number of outstanding students and staff (1-2 engineers per year) • Co-utilization of lab installations and tech resources • First hand knowledge of Center results and free development of them • Unlimited explotation rights of developed technologies and prototypes • Direct access to a number of graduates who have expertise in the area of mobile communications

  27. Personal University: 0.77 (22%) Hired: 0.91 (26%) 1.68(46%) Infrastructure Material Lab: 50 (9%) Computers: 20 (3%) Software: 12 (2%) 82(14%) Research Institute on Communications (8) University & hired personal and infrastructure funding 3.5 Meuros Others Univ: 0.89 (25%) Taxes: 0.27 (8%) Misc.: 0.19 (5%) 1.35(38%)

  28. Research Institute on Communications (9) Institute permanent staff (estimation) From University Hired Personal 4 Faculty staff 1 MBA Exec. team (5%) 13 Faculty staff (4 per area +1) 12 PhD students (4 per area) 24 Master students (8 por área) 14 Doctors (4 per area+2) 12+ Industry engineers Resarch staff (82%) 4 engineers 5 Administrative staff Administr. & support staff (13%) 3 Grad. students Total: 56 (61%) Total: 36 (39%) Employment creation: 24/80 (30%)

  29. Research Institute on Communications (10) Feasible funding sources 3.5 Meuros

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