May 2003 doc IEEE 802 15 03111 r

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a Project: IEEE P 802. 15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Mitubishi Electric Proposal Time-Hopping Impulse Radio Date Submitted: May 5 th, 2003 Source: Andreas F. Molisch et al. , Mitsubishi Electric Research Laboratories Address MERL, 201 Broadway Cambridge, MA, 02139, USA Voice: +1 617 621 7558, FAX: +1 617 621 7550 , E-Mail: Andreas. Molisch@ieee. org Re: [Response to Call for Proposals] Abstract: We present a standards proposal for a high-data-rate physical layer of a Personal Area Network, using ultrawideband transmission. The air interface is based on time-hopping impulse radio, using BPSK for the modulation, and in addition polarity randomization of the pulses within the symbol. Combinations of delayed and weighted pulses allow an efficient shaping of the spectrum. This provides good suppression of interference, and guarantees fulfillment of coexistence requirements. The system is designed to have A/D conversion and digital processing only at the symbol rate, not the chip rate. Costs are comparable to Bluetooth. Purpose: [Proposing a PHY-layer interface for standardization by 802. 15. 3 a] Notice: This document has been prepared to assist the IEEE P 802. 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 P 802. 15. Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Ultra Wide. Band Mitsubishi Electric Proposal Time-Hopping Impulse Radio A. F. Molisch, Y. -P. Nakache, P. Orlik, J. Zhang Mitsubishi Electric Research Lab S. Y. Kung, Y. Wu, H. Kobayashi, S. Gezici, V. Poor Princeton University Y. G. Li Georgia Institute of Technology H. Sheng, A. Haimovich New Jersey Institute of Technology Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Contents – System overview – Physical-layer details – Performance evaluation – Signal robustness – Coexistence – Cost analysis – Summary and conclusions Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Goals and Solutions • Commonly used technology Time hopping impulse radio • Fulfillment of spectral mask, but full exploitation of allowed power. Interference suppression Linear combination of basis pulses • Cheap implementation, robustness to multipath Few Rake fingers, all A/D conversion and computation done at 200 MHz • Scalability Multi-code transmission Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Creation of Proposal • Proposal based on – Scientific experience of leading research groups (Princeton, Georgia Tech, MERL, MELCO) – Practical experience of high-quality product development team of Mitsubishi in USA and Japan – Experience in hardware (RF components, antennas, semiconductor, applications, …. . ) and applications design Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Transmitter Structure Sync. & Training Sequence Convolutional Code Data Source Central Timing Control Multiplexer Timing Logic Pulse Gen. TH Seq. -1 Polarity Scrambler Timing Logic Pulse Gen. TH Seq. -N Polarity Scrambler Power Control Demultiplexer Convolutional Code Submission Multiplexer Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Receiver Structure Synchronization Timing Control Channel Estimation Rake Receiver Finger 1 AGC Demultiplexer Rake Receiver Finger 2 Summer MMSE Equalizer Convolutional Decoder Data Sink Rake Receiver Finger Np Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Contents – System overview – Physical-layer details – – – acquisition channel estimation polarity hopping spectral shaping Rake structure – Performance evaluation – Summary and conclusions Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a Fast acquisition • template signal and received signal need to be aligned • standard method: serial search (chip by chip) • but: chip duration very short in UWB, takes long time • our solution: – Beacon provides rough timing estimation (within runtime of the piconet diameter) – new “block search” methods for actual acquisition Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Block Search Algorithms • Steps in acquisition: – Find delay region where signal is likely to exist – After finding it, search in more detail for first significant path • Block search algorithm – Sequantial block search (SBS): integrate output of detector over delay region (block), search for block with significant energy. Best for LOS – Average block search (ABS): average over absolute values of detector output. Best for NLOS Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a Sequential Block Search 1) Check the bth block using the first template signal (t). 2) If the output of the bth block is not higher than a block threshold, τb, then, go to step 6. 3) If the output of the bth block is higher than the block threshold, τb, then search the block in more detail, i. e. , cellby-cell serial search with a signal threshold τs, using the second template signal (t). 4) If no signal cell is detected in the block, go to step 6. 5) If the signal cell is detected in the block, DONE. 6) Set b = (b mod B) + 1 and go to step 1. Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a Average Block Search 1) Check difference between successive averages wi mod B - w(i 1) mod B. 2) If the difference is not higher than a first threshold go to step 6. 3) If the difference is higher than, check z(i mod B)K+1, …, z(i mod B)+1)K serially, comparing to a second threshold, . 4) If no signal cells detected, go to step 6. 5) If signal cell(s) are detected, DONE. 6) Set i = (i + 1) mod B, and go to step 1. Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a Channel Estimation • Swept delay correlator • Principle: estimating only one channel sample per symbol. Similar concept as STDCC channel sounder of Cox (1973). • Sampler, AD converter operating at SYMBOL frequency • Requires longer training sequence • Three-step procedure for estimating coefficients: – With lower accuracy: estimate at which taps energy is significant – With higher accuracy: determine tap weights – Determine effective channel seen by equalizer • “Silence periods”: for estimation of interference Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Channel Estimator – Block Diagram Multiplier & Low-Pass Filter Programmable Training Waveform Gen. Adj. Weight Rake Finger 1 Multiplier & Low-Pass Filter Receiver Front End Programmable Training Waveform Gen. Adj. Weight Timing Controller MMSE EQ Output Equalizer Σ Rake Finger 2 Coefficients Multiplier & Low-Pass Filter Programmable Training Waveform GEN. Rake receiver Output Adj. Weight Equalizer Estimator Rake Finger N Channel Estimator EQ Training Sequence Channel Estimation Output Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a Estimator algorithm evaluation of one sample per 5 ns interval, offset by Tc Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Estimator • Multi-step procedure 1. estimate which taps have significant weights 2. estimate tap weights for L significant taps 3. determine Rake receiver weights via minimum mean square error criterion 4. determine equivalent (symbol-spaced) channel from transmitter to output Rake receiver 5. find equalizer for this equivalent channel (MMSE) Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Modulation and Multiple Access • Multiple access: – Combination of pulse-position-hopping and polarity hopping for multiple access – More degrees of freedom for design of good hopping sequence than pure pulse-position-hopping – Short hopping sequences, to make equalizer implementation easier • Modulation: BPSK • Channel coding: – rate ½ convolutional code; – requires 4 d. B SNR for 10^-5 BER – Improvement by 3 d. B possible by turbo codes Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Spectral Shaping & Interference Suppression • Basis pulse: fifth derivative of Gaussian pulse • Drawbacks: Power spectral density of the monocycle 10 log 10|P(f)|2 d. B Magnitude of p(t) Monocycle, 5 th derivative of gaussian pulse Time (s) frequency (Hz) – Loses 3 d. B compared to FCC-allowed power – Strong radiation at 2. 45 and 5. 2 GHz Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Linear Pulse Combination • Solution: linear combination of delayed, weighted pulses – Adaptive determination of weight and delay – Number of pulses and delay range restricted – Can adjust to interferers at different distances (required nulldepth) and frequencies • Weight/delay adaptation in two-step procedure • Initialization as solution to quadratic optimization problem (closedform) • Refinement by back-propagating neural network • Matched filter at receiver good spectrum helps coexistence and interference suppression Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Initialization • find “modified” mask that follows FCC and required interference suppression (e. g. , 20 d. B for 802. 11 a • approximate “optimum filling of mask” as • solution of this in closed form (eigenvector belonging to largest eigenvalue) Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a Iterative Refinement • backpropagating neural network Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a Rake Receiver • Main component of Rake finger: pulse generator • A/D converter: 3 -bit, operating at 220 Msamples/s • No adjustable delay elements required Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Contents – System overview – Physical-layer details – Performance evaluation – Signal robustness – Coexistence – Cost analysis – Summary and conclusions Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Link Budget Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a 110 Mbps: PER as Function of Distance Sensitivity: AWGN 13 m cm 1 6. 8 cm 2 6. 2 cm 3 5. 3 cm 4 5. 0 Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a 110 Mbps: Probability of Link Success Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a 110 Mbps: Outage vs. SNR Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a 110 Mbps: Single co-channel interferer separation distance In AWGN: PER < 8% at less than 1 m Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a 110 Mbps: Single co-channel interferer separation distance Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a 110 Mbps: Single co-channel interferer separation distance Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a 110 Mbps: Single co-channel interferer separation distance Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a 200 Mbps: PER as Function of Distance Sensitivity: AWGN 9. 2 m cm 1 4. 5 cm 2 3. 2 Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a 200 Mbps: Probability of Link Success Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a 200 Mbps: Outage vs. SNR Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a 200 Mbps: Single co-channel interferer separation distance In AWGN: PER < 8% at less than 1 m Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a 200 Mbps: Single co-channel interferer separation distance Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a 200 Mbps: Single co-channel interferer separation distance Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 200 Mbps: Single co-channel interferer separation distance Test link AWGN 20 first realizations of cm 1 20 first realizations of cm 2 Submission uncoordinated piconet AWGN st 21 realization of cm 1 21 st realization of cm 3 21 st realization of cm 4 dint <1 m 1. 5 m 1. 3 m 1. 6 m 1. 7 m 1. 4 m Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Susceptibility to Interference • Piconets – 20 first realizations of the 4 channel model and AWGN – Desired user: 6 d. B above sensitivity • admissible distance of interferer: less than 2 m for 110 and 200 Mbps • 802. 11 a: influence only when interferer less than 2 m distance, in CM 2 for test link and interferer at 200 Mbps • 802. 11 b: no noticeable influence (even at less than 1 m distance of interferers) in all cases Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 At 110 Mbps: Susceptibility to Interference Channel of test link : AWGN and cm 1 channel of Interferer microwave oven 802. 11 a bluetooth 802. 11 b and 802. 15. 3 802. 15. 4 in-band modulated in-band tone AWGN < 1 m < 1 m cm 1 < 1 m < 1 m cm 2 < 1 m < 1 m Channel of test link: cm 2 channel of Interferer microwave oven 802. 11 a bluetooth 802. 11 b and 802. 15. 3 802. 15. 4 in-band modulated in-band tone AWGN < 1 m < 1 m cm 1 < 1 m < 1 m cm 2 < 1 m < 1 m Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 At 200 Mbps: Susceptibility to Interference Channel of test link : AWGN and cm 1 channel of Interferer microwave oven 802. 11 a bluetooth 802. 11 b and 802. 15. 3 802. 15. 4 in-band modulated in-band tone AWGN < 1 m < 1 m cm 1 < 1 m < 1 m cm 2 < 1 m < 1 m Channel of test link: cm 2 channel of Interferer microwave oven 802. 11 a bluetooth 802. 11 b and 802. 15. 3 802. 15. 4 in-band modulated in-band tone AWGN < 1 m < 1 m cm 1 < 1 m < 1 m cm 2 < 1 m < 2 m < 1 m < 1 m Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a Coexistence (at 1 m) Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a Cost Estimates (for 110 Mbit/s mode) • TX – Digital: • Coders 100 k gates • timing logic <100 k gates – RF • Pulse generators (4): • Polarity scramblers • Summers Submission 0. 6 mm 2 0. 04 mm 2 Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a Cost Estimates (for 110 Mbit/s mode) • RX – Digital: • Viterbi Decoder 100 k gates • timing logic <100 k gates • MMSE equalizer 50 k gates • Rake finger weighting and summing <50 k gates – RF • LNA (11 d. B SNR) 0. 05 mm 2 • Pulse generators (2*10): 3. 2 mm 2 • Polarity descramblers 0. 04 mm 2 • Low-pass filters 0. 48 mm 2 • Summers 0. 04 mm 2 Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Cost Estimates - Summary • RF part: – total die size <10 mm 2 – less than Bluetooth – 0. 18 mu CMOS technology sufficient • Digital part: – Less than 500 k gates – Operation at 220 Mbit/s • Antenna: cavity-backed spiral antenna • Total costs comparable to Bluetooth Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a Self-Evaluation (I) Submission Molisch et al. , Time Hopping Impulse Radio

May 2003 doc. : IEEE 802. 15 03111 r 1_TG 3 a Self-Evaluation (II) Submission Molisch et al. , Time Hopping Impulse Radio

doc. : IEEE 802. 15 03111 r 1_TG 3 a May 2003 Summary and Conclusions • TH-IR based standards proposal – Meets targets of 802. 15. 3 a for LOS • Innovative way to manage spectrum – Meet FCC requirements – Improve performance in interference environment – Decrease interference to other systems • Allows cheap implementation – All digital operations at symbol rate, not chip rate • Scaleable – Multicode / multirate system. Submission Molisch et al. , Time Hopping Impulse Radio