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

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Pulsed-UWB-OFDM] Date Submitted: [14 July 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. Pulsed-UWB-OFDM H. Tewfik and E. Saberinia University of Minnesota Tewfik/Saberinia, U. of MN

3. Overview • Pulsed-UWB-OFDM • Comparison with Pure-OFDM • Proposed System Transmitter and Receiver Structures • Coexistence and Multiple piconets • Complexity and Power Consumption • Conclusion Tewfik/Saberinia, U. of MN

4. Basic Idea • Using OFDM modulation to simplify channel equalization, capturing channel energy and digital modem implementation • Using Pulsed-OFDM instead of normal OFDM to add the ability of getting the advantages of multi-path diversity and decreasing Complexity • Dividing the whole bandwidth to multiple sub-bands and hopping between these bands in order to frequency spreading and multi-piconet support Tewfik/Saberinia, U. of MN

5. What is Pulsed-OFDM? • A Pulsed OFDM symbol is frequency spreading of OFDM signal using a shaping pulse that is wider than the bandwidth of OFDM signal • This is equal to using a pulse with duty cycle less than 1 for sending every symbol out of OFDM modulation ( out of IFFT block) Tewfik/Saberinia, U. of MN

6. Normal OFDM block in Time-Frequency • symbol rate=1/Tu • W=symbol rate f(MHz) W 0 31 30 1 0 0 NTu t Tewfik/Saberinia, U. of MN

7. 31 31 31 31 31 31 31 31 31 31 31 31 30 30 30 30 30 30 30 30 30 30 30 30 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 Pulsed OFDM block in Time-Frequency • symbol rate=1/T • W=1/Tu=symbol rate*(T/Tu) ( frequency spreading ) f(MHz) W 0 0 Tu T=4Tu T+Tu (N-1)T (N-1)T+ Tu t Tewfik/Saberinia, U. of MN

8. Multi-path diversity in Pulsed-OFDM • In Pulsed OFDM we can resolve multipath for delays: t<T-Tu • Lets Spreading gain is equal K=T/Tu be an integer • Then we can resolve K multipath (get K independent virtual channel) Tewfik/Saberinia, U. of MN

9. Simulation Results • Simulation For CM4 Tewfik/Saberinia, U. of MN

10. Single-Channel To Multi-Channel A pulsed-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

11. 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

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

13. Proposed System • N=32 Subcarrier • C=8 Cyclic Prefix • 2/3 Convolutional Channel Coding • QPSK Constellation • Ts=1.8 ns • Duty Cycle • K=4 for 110Mbits/s (4 multipath diversity) • K=3 for 165Mbits/s (3 multipath diversity) • K=2 for 220Mbits/s (2 multipath diversity) • K=1 for 440Mbits/s Tewfik/Saberinia, U. of MN

14. IFFT Constellation Convolutional Input DAC Insert Pilots Interleaver Mapping Encoder Data Add CP & GI p exp ( j 2 f t ) c Frequency Hopping Transmitter Tewfik/Saberinia, U. of MN

15. p cos ( 2 f t ) c Remove CP 4x 32-point FFT One Tape equalizer and combine channels LPF VGA ADC BPF LNA LPF VGA ADC p sin ( 2 f t ) c Decoder De interleaver De mapping Receiver Tewfik/Saberinia, U. of MN

16. Transmitter Complexity • 2/3 Convolution Coder • IFFT • 32-point • QPSK only • D/A operating at 130 to 520 MHz Tewfik/Saberinia, U. of MN

17. Receiver Complexity • Simple equalization and channel estimation using cyclic prefix and FFT: • 4 x 32-Point QPSK FFT • 128 1-tap equalizer • decoder Tewfik/Saberinia, U. of MN

18. Coexistence Tewfik/Saberinia, U. of MN

19. 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

20. Conclusion • Pulsed-UWB-OFDM used OFDM modulation in order to: • Avoids Rake type receiver with reasonable size FFT-IFFT • Simple channel equalization and synchronization • Capture the channel energy • Pulsed OFDM use Pulsating normal OFDM in order to: • Frequency spreading • Providing multipath diversity • Decrease the complexity of the transceiver Tewfik/Saberinia, U. of MN