July 2005 France Telecom doc.: IEEE a Submission Slide 1 Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Simulation results of non-coherent reception based system proposed for the Low Rate alt-PHY ( a) Date Submitted: 15th July 2005 Source: Patricia Martigne Company: France Telecom R&D Address: 28 Chemin du Vieux Chêne – BP98 – Meylan Cedex - France Voice: Abstract: Simulation results related to low rate and ranging applications Purpose: This document shows some simulation results obtained for non-coherent receivers using UWB-IR technology as proposed by FT R&D fellows Notice:This document has been prepared to assist the IEEE P 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

July 2005 France Telecom doc.: IEEE a Submission Slide 2 UWB-Impulse Radio (IR) with Time-Hopping coding non-coherent reception Simulations performed by Patricia MARTIGNE, Benoit MISCOPEIN, Jean SCHWOERER

July 2005 France Telecom doc.: IEEE a Submission Slide 3 CONTENT 1.General description of the system 2.Focus on the synchronization process, including simulation results 3.Specificities for ranging applications, including first simulation results 4.Conclusion

July 2005 France Telecom doc.: IEEE a Submission Slide 4 UWB-IR based system Impulse-radio (IR) based: –Very short pulses  Reduced ISI –Robustness against fading –Episodic transmission (for LDR) allowing long sleep-mode periods and energy saving Time Hopping coding: –Multiple access management –Timing approach used for efficient synchronization –Smoothing the spectrum Low-complexity implementation (OOK modulation, pulse repetition for robustness of the transmitted symbol) 1.General description 2.Synchronization process 3.Ranging applications 4.Conclusion

July 2005 France Telecom doc.: IEEE a Submission Slide 5 UWB-IR based system 8 pulses per symbol Use of an 8-ary Time Hopping code of length 8 – Use of such a TH code combined with the band plan may allow to handle the SOP issue – Code order and length are scalable to meet different requirements Tp = 1ns, Tc = 20 ns, Tf = 160 ns, Tsymbol = 1080 ns Tp Tf PRP ± TH Tc 1- General description

July 2005 France Telecom doc.: IEEE a Submission Slide 6 UWB-IR Transmitter Pulse Generator Clock F < 100 MHz Control Logic BaseBand signal RF Signal PSDU Data Pulse shaper PA (option) Main Goal : "Low cost & low consumption". – Pulses are generated in baseband. – No mixer, no VCO but pulse shaping. – Simple control logic and "reasonable" clock frequency (Crystal) 1- General description

July 2005 France Telecom doc.: IEEE a Submission Slide 7 UWB-IR Receiver Energy detection technique rather than coherent receiver, for relaxed synchronization constraints. Threshold detection (no A/D conversion). – The threshold is set by the demodulation block at each symbol time, if needed. Synchronization fully re-acquired for each new packet received (=> no very accurate timebase needed). 1- General description

July 2005 France Telecom doc.: IEEE a Submission Slide 8 BPF UWB-IR non-coherent Receiver Time base 1- 2ns accuracy Analog comparator LPF / 2-4ns integrator ( ) 2 Time stamps 1st path detection Synchro / demodulation : Communication applications Ranging applications Reception performs an energy detection and creates a {thresholder, timebase} couple, in order to timestamp the threshold crossings. 1- General description

July 2005 France Telecom doc.: IEEE a Submission Slide 9 Each time the signal amplitude exceeds a given threshold, a timestamp is associated to this event and can be exploited by the digital part. Analog signal conditioning Digital signal processing Time base 1- General description UWB-IR non-coherent Receiver

July 2005 France Telecom doc.: IEEE a Submission Slide 10 UWB-IR non-coherent Receiver Symbol detection 1- General description

July 2005 France Telecom doc.: IEEE a Submission Slide 11 Synchronization algorithm for non-coherent receivers During a synchronization preamble of unmodulated symbols, the algorithm used consists in parsing the received timestamps, so as to identify a known Time Hopping sequence. Simulations have been performed to validate the performances of such an algorithm, in terms of accuracy, and of mean elapsed time in acquisition. 1.General description 2.Synchronization process 3.Ranging applications 4.Conclusion

July 2005 France Telecom doc.: IEEE a Submission Slide 12 Packet Acquisition & Synchronization The synchronization algorithm detects the threshold crossings, and updates an assumption matrix, which can also be viewed as a tree exploration i Detected edge for t_pos(i) i No edge detection for t_pos(i) ? Δ1,2 Δ2,3 Δ3,4 Δ2,3 Δ3,4 = ? Time base origin determination Δi,j = Known time offset between the pulses appearance, with respect to the TH code. 2- Synchronization process

July 2005 France Telecom doc.: IEEE a Submission Slide 13 Packet acquisition & Synchronization The threshold level is set to detect a number of crossings consistent with the expectations (known time hopping sequence) For any tested Channel Model, the synchronization is properly acquired (during the Synch preamble) Measured accuracy is around several 100s of ps. 2- Synchronization process

July 2005 France Telecom doc.: IEEE a Submission Slide 14 Time needed for synchronization 2- Synchronization process

July 2005 France Telecom doc.: IEEE a Submission Slide 15 Time needed for synchronization  The synchronization is quickly acquired :  in CM1 condition it is acquired in less than 2 symbol times for a range of 50 meters  in CM2, CM3 or CM5 condition it is acquired in less than 5 symbol times for a range of 30 meters The synchronization is achievable within the 32 bytes synchronization preamble. Simulation results 2- Synchronization process

July 2005 France Telecom doc.: IEEE a Submission Slide 16 Time accuracy during synchronization  Timing retrieval accuracy : the tolerance window, set up for the timestamps validation, is centered around the theoretical position and is set to a width of 1.25ns mean synchronization accuracy obtained in this simulation is 625ps This value is precise enough to ensure a correct data demodulation Considering that 625 ps represents a distance of 19 cm, this accuracy is fully consistent with the UWB-IR ranging capabilities. Simulation results 2- Synchronization process

July 2005 France Telecom doc.: IEEE a Submission Slide 17 Accuracy vs. tolerance width (for CM2) 2- Synchronization process

July 2005 France Telecom doc.: IEEE a Submission Slide 18 Accuracy vs. tolerance width (for CM2) Simulation results CM2 model, 30 meter range, several widths have been tested for the tolerance window: wt = 16, 20, 32, 40  For each width, a standard deviation has been computed.  Mean elapsed time to acquire the synchronization (tsynch) as well as the related standard deviation for each window width are gathered in the table.  To illustrate the tolerance window width dependance of the synchronization accuracy, each case is represented by a centered normal distribution on the figure. When setting the window width from 2.5 ns to 1 ns, the standard deviation of the synchronization error is divided by 2 but the required time for acquisition encounters a 40 % increase. Tslot/32 = 1.25 ns appears as an acceptable value in this case. 2- Synchronization process

July 2005 France Telecom doc.: IEEE a Submission Slide 19 Ranging applications Once the synchronization is acquired, the system may be used either for communication applications or for ranging applications (slide 8). The latter one is particularly challenging for non- coherent receivers when accurate ranging measurements (less than 1 meter accuracy) are aimed at. The ranging technique is based on the synchronization acquisition algorithm, aiming at detecting the direct path. 1.General description 2.Synchronization process 3.Ranging applications 4.Conclusion

July 2005 France Telecom doc.: IEEE a Submission Slide 20 BPF UWB-IR non-coherent receiver for ranging "Path-arrival dates" table 1D to 2D Conversion Assumption path synchronization Matrix Filtering + Assumption/path selection Time base 1- 2ns accuracy Time stamping Analog comparator LPF / 2-4ns integrator ( ) 2 3- Ranging applications

July 2005 France Telecom doc.: IEEE a Submission Slide 21 Leading edge detection Simulations have been performed for CM1 model, over a 50µs preamble (40 symbols) They provide the accuracy in 1st path detection obtained for a given Signal to Noise Ratio at the receiver antenna (input to the band pass filter) Graphs are given for a (SNR) ANT between -9,5dB and -1dB (corresponding to a E symbol /E 0 ranging from around 20dB to 28dB) Simulation results 3- Ranging applications

July 2005 France Telecom doc.: IEEE a Submission Slide 22 Leading edge detection Simulation results 3- Ranging applications

July 2005 France Telecom doc.: IEEE a Submission Slide 23 Leading edge detection Simulation results 3- Ranging applications Some more simulations are on going  to obtain results with other channel models  to have a look at the accuracy obtained with longer preambles (500µs, 4ms)

July 2005 France Telecom doc.: IEEE a Submission Slide 24 UWB-IR non-coherent schemes for IEEE a targeted applications The proposed non-coherent reception concept has an efficient behaviour in synchronization, using a time-stamping process with less than 700ps accuracy (accuracy for the detection of the strongest path) provides 1st path-detection for ranging applications with an accuracy of typ. some hundreds of ps is still simple-designed, meeting a PAR goals of low complexity and low cost. 1.General description 2.Synchronization process 3.Ranging applications 4.Conclusion 4- Conclusion

July 2005 France Telecom doc.: IEEE a Submission Slide 25 UWB-IR non-coherent schemes for IEEE a targeted applications 1.General description 2.Synchronization process 3.Ranging applications 4.Conclusion 4- Conclusion This first set of simulations is showing the relevance of considering this kind of UWB-IR non-coherent receivers, using Time Hopping coding, when drafting the 15.4a standard.