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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Multicarrier-UWB] Date Submitted: [10 May 2003] Source: [Ahmed H Tewfik] Company [University of Minnesota]

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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Multicarrier-UWB] Date Submitted: [10 May 2003] Source: [Ahmed H Tewfik] Company [University of Minnesota] Address [Dept. of Electrical and Computer Engineering, Room 4-174 EECS Bldg.,Minneapolis, MN 55455] Voice:[612-625-6024], FAX: [612-625-4583], E-Mail:[tewfik@ece.umn.edu] Re: [03147r0P802-15_TG3a-University-of-Minnesota-CFP-Presentation.ppt] Response to a Call for Contributions Task Group 3a Call For Intent and Proposals, November 2002, updated January 2003, 02371r0P802-15_SG3a-5_Criteria.doc Abstract: [We propose a multi-carrier UWB system for WPAN communications. We describe system design issues and proposed transmitter and receiver structures. We also provide a self-evaluation of the proposed system.] Purpose: [For consideration by 802.15.3a task group.] Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. Tewfik/Saberinia, U. of MN

  2. Fast Frequency HoppingUWB-OFDM H. Tewfik and E. Saberinia University of Minnesota Tewfik/Saberinia, U. of MN

  3. Fast Frequency HoppingUWB-OFDM • Focus of this presentation : FFH UWB-OFDM as compromise between multiband or multicarrier UWB and wideband OFDM • Full simulation results and implementation details to be presented by July meeting (PPT + full Word report) Tewfik/Saberinia, U. of MN

  4. Overview • FFH-UWB-OFDM: compromise between multi-band UWB and pure OFDM UWB • System comparisons and design trade-offs • Proposed System Transmitter and Receiver Structures • Coexistence and Multiple piconets • Complexity and Power Consumption • Conclusion Tewfik/Saberinia, U. of MN

  5. Multi-Carrier UWB • Multi-band UWB • Can exploit Multipath diversity • Usually requires Rake type receiver to do so • Needs multiple band transmitter and receiver • Pure OFDM UWB • No need for Rake receiver • Suffers from frequency selective fading • Requires heavy coding and interleaving to achieve frequency diversity • Long FFT and IFFT • FFH-UWB-OFDM (some where between!) • No need for Rake receiver • Implemented with short IFFT and FFT • Provides multipath and frequency diversity • Unified framework and architecture for trading complexity for ability to gather part or all multipath diversity Tewfik/Saberinia, U. of MN

  6. An FFH-UWB-OFDM Block • Make an OFDM block with N-IFFT of QAM symbols (N=32) • Create a base band signal with bandwidth W> 500 MHz and Duration NTu ns f(MHz) W 0 31 30 1 0 0 NTu t Tewfik/Saberinia, U. of MN

  7. 31 31 31 30 30 30 1 1 1 0 0 0 An FFH-UWB-OFDM Block • Lower the Average PDS • Provide multipath diversity • Transmit digital samples using N=32 short coded pulses separated by T f(MHz) W 0 0 Tu T T+Tu (N-1)T (N-1)T+ Tu t Tewfik/Saberinia, U. of MN

  8. An FFH-UWB-OFDM Block • Fast frequency hopping inside each pulse to provide: • multipath resolution • optimal frequency spreading • Two options that avoid UNII band • Use only 3.1-4.75 GHz (Lower Band System) • Use whole band 3.15-9.9 GHz and avoid 4.8-5.9 GHz (Whole Band System) Tewfik/Saberinia, U. of MN

  9. 31 31 31 30 30 30 1 1 1 0 0 0 Frequency Hopping for Lower Band System within Single Coded Pulse f(GHz) 4.75 4.2 3.65 3.1 0 Tu/3 2Tu/3 Tu t(ns) Tewfik/Saberinia, U. of MN

  10. 31 31 31 31 30 30 30 30 1 1 1 1 0 0 0 0 Frequency Hopping for Lower Band System within Single Coded Pulse f(GHz) 4.75 3.1 0 Tu/4 Tu/2 3Tu/4 Tu t(ns) Tewfik/Saberinia, U. of MN

  11. 23 23 23 23 23 23 22 22 22 22 22 22 1 1 1 1 1 1 0 0 0 0 0 0 An FFH-UWB-OFDM Block f(GHz) 4.75 4.2 3.65 3.1 • Repeat this block every T=12.8ns N=32 times 0 Tu T t(ns) Tewfik/Saberinia, U. of MN

  12. 31 31 31 31 31 31 31 31 31 31 30 30 30 30 30 30 30 30 30 30 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 Frequency Hopping for Whole Band System f(GHz) 9.75 5.9 4.8 3.15 0 Tu t(ns) Tewfik/Saberinia, U. of MN

  13. Spectrum • Bandwidth=1.65GHz • Multipath resolution=0.6ns • Bandwidth=7.5GHz • Multipath resolution=0.13ns Tewfik/Saberinia, U. of MN

  14. Single-Channel To Multi-Channel A FFH-UWB-OFDM over a channel with L tap Pure-OFDM over K independent channel with L/K tap K=T/Tr Tewfik/Saberinia, U. of MN

  15. Single-Channel To Multi-Channel • Provides K multipath diversity • Captures all the channel energy • K=1 is pure OFDM • K=channel length is Multi-band system Tewfik/Saberinia, U. of MN

  16. Proposed System • N=32 Subcarrier • C=10 Cyclic Prefix • ¾ Convolutional Channel Coding • QPSK Constellation: • T=10.3ns: 110 Mbits/s (Collect K=17 multipath) • T=5.45ns: 210 Mbits/s (Collect K=9 multipath) • 16-QAM for 480 Mbits/s Tewfik/Saberinia, U. of MN

  17. Transmitter I FFT ¾ Convolution Code QAM Mapping D/A Interleaving X Frequency Hopping Input rate= 1/T M samples/s (100 or 200 M samples/s) Tewfik/Saberinia, U. of MN

  18. Receiver 1.65 G samples/s  capture 17 paths 825 M samples/s  capture 8 paths Combine Channels K 1-tap Equalizers Matched Filter FFT X Frequency Hopping De Interleaving Decoding De-mapping Tewfik/Saberinia, U. of MN

  19. Tradeoff between Complexity and Performance • Transmitter provides full multipath and frequency diversity • Flexible receiver structures that trade complexity for degree of diversity exploitation, e.g. : • Sampling rate=1.65 GHZ 17 multipath diversity • Sampling rate=825 MHZ 8 multipath diversity • Sampling rate=550 MHZ 6 multipath diversity • Always capture the whole channel energy Tewfik/Saberinia, U. of MN

  20. Transmitter Complexity • ¾ Convolution Coder • IFFT • 32-point • QPSK only • D/A operating at 100 to 200 MHz Tewfik/Saberinia, U. of MN

  21. Receiver Complexity • Possible to choose different A/D sampling rates • multibit vs 1 bit • Simple equalization and channel estimation using cyclic prefix and FFT: • 32-Point QPSK FFT • K 1-tap equalizer (K=17 or K=9) • Can capture more diversity or use larger bands as technology improves Tewfik/Saberinia, U. of MN

  22. Coexistence Tewfik/Saberinia, U. of MN

  23. Multiple Piconets • Simultaneous operation achieved by proper selection of: • FH code • Use of pilots • Add pseudo-random codes on top of modulation • Combination Tewfik/Saberinia, U. of MN

  24. Conclusion • FFH-UWB-OFDM provides a compromise between pure OFDM and Multi-band UWB • Provides full frequency diversity • Provides multipath diversity while capturing all channel energy • Avoids Rake type receiver with reasonable size FFT-IFFT • Unified structures and architectures that offer trade-offs between complexity and extent of multipath diversity exploitation Tewfik/Saberinia, U. of MN

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