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: TG4a Review of proposed UWB-IR Modulation schemes Date Submitted: 21 April 2005 Source: Gian Mario Maggio (STMicroelectronics), Philippe Rouzet (STMicroelectronics) Contact: Philippe rouzet. Voice: +41 22 929 58 66, E-Mail: philippe.rouzet@st.com Abstract: Review of proposed modulations/waveforms for TG4a PHY standard (UWB IR part) Purpose: To provide information for further investigation on and selection of the modulation /waveform for UWB Impulse Radio (low bit rate plus ranging) 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. Gian Mario Maggio; Philippe Rouzet (STM)

2. IEEE 802.15.4a PHY:UWB-IR Modulation UWB Technical Editing Group (initial draft Gian Mario Maggio and PhR) purpose is to initialize discussion inside the UWB PHY technical group See slides 3 to 20 on Pulse shape, modulation and waveform, Other slides are informative Gian Mario Maggio; Philippe Rouzet (STM)

3. Topics for Discussion* • Pulse shaping • Modulation formats • Waveform design • Receiver Architectures • Adaptive modulation & coding • Synchronization • Support for SOP • What else? ACTION LIST UWB PHY GROUP (*) Note: The discussion is restricted to UWB-IR only. Gian Mario Maggio; Philippe Rouzet (STM)

4. UWB-PHY: Introduction • Impulse-radio based (pulse-shape independent) • Support for different receiver architectures (coherent/non-coherent) • Flexible modulation format • Support for multiple rates • Support for SOP Gian Mario Maggio; Philippe Rouzet (STM)

5. Definitions • Coherent RX: The phase of the received carrier waveform is known, and utilized for demodulation • Differentially-coherent RX: The carrier phase of the previous signaling interval is used as phase reference for demodulation • Non-coherent RX: The phase information (e.g. pulse polarity) is unknown at the receiver -operates as an energy collector -or as an amplitude detector Gian Mario Maggio; Philippe Rouzet (STM)

6. Pulse Shaping a) Gaussian b) Raised cosine c) Chaotic d) Chirp … Optional: • Variable pulse shapes with SSA (Soft Spectrum Adaptation) • Linear pulse combination Gian Mario Maggio; Philippe Rouzet (STM)

7. Linear Pulse Combination • 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 (closed-form) • Refinement by back-propagating neural network • Matched filter at receiver  good spectrum helps coexistence and interference suppression Gian Mario Maggio; Philippe Rouzet (STM)

8. Modulation Format(s) • Simple, scalable modulation format • One mandatory mode plus one or more optional modulation modes • Modulation compatible with multiple coherent/non-coherent receiver schemes  Flexibility for system designer • Time hopping (TH) to achieve multiple access Gian Mario Maggio; Philippe Rouzet (STM)

9. Pros/Cons of RX Architectures Coherent + : Sensitivity + : Use of polarity to carry data + : Optimal processing gain achievable - : Complexity of channel estimation and RAKE receiver - : Longer acquisition time Differentially-Coherent (or using Transmitted Reference) + : Gives a reference for faster channel estimation (coherent approach) + : No channel estimation (non-coherent approach) - : Asymptotic loss of 3dB for transmitted reference (not for DPSK) Non-coherent + : Low complexity + : Acquisition speed - : Sensitivity, robustness to SOP and interferers Gian Mario Maggio; Philippe Rouzet (STM)

10. Time Hopping-IR: Basics +1 Tc Tf Ts -1 • Each symbol represented by sequence of very short pulses • Each user uses different PN sequences (for multiple access) • Bandwidth mostly determined by pulse shape Gian Mario Maggio; Philippe Rouzet (STM)

11. data Td +1 Tc Tf reference Ts -1 Transmitted Reference: Basics • First pulse serves as template for estimating channel distortions • Second pulse carries information • Drawback: Waste of 3dB energy on reference pulses Gian Mario Maggio; Philippe Rouzet (STM)

12. Waveform Design (1/2) • Combination of BPPM with BPSK • Guarantee coexistence of coherent and non-coherent architectures: • Non-coherent receivers just look for energy in the early or late slots to decode the bit (BPPM) • Coherent and differentially-coherent receivers, in addition, understand the fine structure of the signal (BPSK or DBPSK) • Principle: Non-coherent and differentially-coherent modes should not penalize coherent RX performance Gian Mario Maggio; Philippe Rouzet (STM)

13. Waveform Design (2/2) • Two possible realizations: 1) The whole symbol (consisting of Nf frames) is BPPM-modulated 2) Apply 2-ary time hopping code, so that each frame has BPPM according to TH code • Coexistence coherent/non-coherent RX: - Special encoding and waveform shaping within each frame - Use of doublets with memory from previous bit (encoding of reference pulse with previous bit) - Proposed 20ns separation between pulses - Extensible to higher order TR for either reducing the penalty in transmitting the reference pulse or increasing the bit rate - Also possible the use of multi-doublets Gian Mario Maggio; Philippe Rouzet (STM)

14. Design Parameters • Pulse Repetition Period (PRP) • Proposed range between 40ns (first realization) and 125ns (second realization) • Channelization • Coherent schemes: Use of TH codes and polarity codes • Non-coherent schemes: Use of TH codes (polarity codes for spectrum smoothing only) • TH code length • Variable TH code length; proposed range: 8-16 • TH code: Binary position, bi-phase Note: For first realization, higher-order TH with shorter chip duration (multiples of 2ns) may be used Gian Mario Maggio; Philippe Rouzet (STM)

15. Tf=PPI ppV = peak-to-peak voltage M = 1 IS « EQUIVALENT » TO Tf=PPI M = 4 ppV/2 Tf=PPI M = 2 ppV/sqrt(2) Mitigation of Peak Voltage through Multi-Pulses Gian Mario Maggio; Philippe Rouzet (STM)

16. First Realization Gian Mario Maggio; Philippe Rouzet (STM)

17. b0 b2 b4 b3 b1 b5 b-1 Tx Bits 0 0 1 1 0 0 1 Reference Polarity -1 -1 +1 +1 -1 -1 +1 -1 +1 -1 +1 -1 Ts Differential Encoding: Basics Gian Mario Maggio; Philippe Rouzet (STM)

18. First Realization + Diff. Encoding Gian Mario Maggio; Philippe Rouzet (STM)

19. Ts « 11 » 2-PPM + TR base M = 2 (with two bits/symbol) One bit/symbol also Possible !!! « 01 » « 10 » « 00 » Second Realization 2-PPM + 16 chips 2-ary TH code (coherent decoding possible) • Time hopping code is (2,2) code of length 8/16, can be exploited by non-coherent RX • Effectively, 28 or 216 codes to select for channelization for non-coherent scheme Gian Mario Maggio; Philippe Rouzet (STM)

20. τdelay +τΔ D D D « 1 » Basic Mode (as seen by non-coherent) τdelay +τΔ D D D « 1 1 » Enhanced Mode « 1 0 » Pulse Shift, polarity invert τΔ + τdelay τΔ τΔ τdelay τdelay τΔ + τdelay τΔ + τdelay τΔ + τdelay Extension: Higher-Order Modulation TH Pattern TH Code 1,1 1,1 0,1 0,0 1,0 0,1 Data 1,1 1,1 1,1 1,1 1,1 0,0 Gian Mario Maggio; Philippe Rouzet (STM)

21. ANNEX • Additional slides: support for discussion Gian Mario Maggio; Philippe Rouzet (STM)

22. Coherent Receiver: RAKE Receiver Channel Estimation Rake Receiver Finger 1 Rake Receiver Finger 2 Sequence Detector Demultiplexer Convolutional Decoder Summer Data Sink Rake Receiver Finger Np • Addition of Sequence Detector – Proposed modulation may be viewed as having memory of length 2 • Main component of Rake finger: pulse generator • A/D converter: 3-bit, operating at symbol rate • No adjustable delay elements required Gian Mario Maggio; Philippe Rouzet (STM)

23. Differentially-Coherent Receiver(for Transmitted Reference) Matched Filter Convolutional Decoder Td • Note: Addition of Matched Filter prior to Delay & Correlation operations improves output SNR and reduces noise-noise cross terms Gian Mario Maggio; Philippe Rouzet (STM)

24. BPPM Demodulation branch Controlled Integrator Band Matched r(t) LNA Dump Latch x2 RAZ ADC RAZ DUMP BPF Tracking Thresholds setting Non-Coherent Receiver (Energy Collector) Gian Mario Maggio; Philippe Rouzet (STM)

25. Band Matched Band Matched ADC ADC BPF BPF De-Spreading TH Codes TH Sequence Matched Filter r(t) Bit Demodulation LNA Case I - Coherent TH de-spreading TH Sequence Matched Filter b(t) soft info Bit Demodulation r(t) LNA Case II – Non-coherent / differential TH despreading Gian Mario Maggio; Philippe Rouzet (STM)

26. TR-BPPM Schemes Comparison (1/2) Notes: • Results are theoretical calculations • Assumes ideal ”impulse” UWB pulses in AWGN channel • Different TR-BBPM options are considered with different number of pulses per pulse train • Multipath fading simulations can be performed to back up theory Gian Mario Maggio; Philippe Rouzet (STM)

27. TR-BPPM Schemes Comparison (2/2) • Parameters: • PPI slot - slot inside each TH chip containing a burst of pulses including reference pulses • Np represents the number of pulses in each PPI slot • The energy E per PPI slot is kept constant • The pulse energy Ep = E/Np • TW represent the time-bandwidth product Gian Mario Maggio; Philippe Rouzet (STM)

28. Pulse Repetition Structures- Scheme 1TR-BPPM with doublets Gian Mario Maggio; Philippe Rouzet (STM)

29. Pulse Repetition Structures - Scheme 2TR-BPPM single reference Gian Mario Maggio; Philippe Rouzet (STM)

30. Pulse Repetition Structures - Scheme 3Auto Correlation BPPM with doublets Gian Mario Maggio; Philippe Rouzet (STM)

31. Pulse Repetition Structures - Scheme 4Auto Correlation BPPM single reference Gian Mario Maggio; Philippe Rouzet (STM)

32. Pulse Repetition Structures - Scheme 5Auto Correlation BPPM alternate • Scheme 5: “AC Alternate” performs better then all the other pulse repetition structures • AC generally performs better than TR • “AC alternate” and “AC with doublets” require a single delay Gian Mario Maggio; Philippe Rouzet (STM)

33. Adaptive Modulation & Coding • Adaptive modulation (enhanced modes, available for coherent receiver) • Adaptive frame duration (Tf) • Adaptive processing gain (variable number of pulses/bit) • Adaptive coding rate (e.g. by acting on the puncturing associated with a convolutional code) Gian Mario Maggio; Philippe Rouzet (STM)

34. Decision/ FEC decoder LPF GA ADC Comm.data GA LPF ADC Ranging data I Local oscillator Peak detection Sync. Q Time base Calculation Overall Block Diagram (with Optional CSS) Transmitter Comm.data BW = 500MHz to 2GHz FEC & Modulation Spreading Pulse shaping CHIRP GA & BPF Ranging data Local oscillator Receiver Pre-Select Filter De- CHIRP LNA Ranging processing Additional circuits to DS-UWB as an option Ranging and communication can be done simultaneously. Gian Mario Maggio; Philippe Rouzet (STM)

35. In this calculation, (24,12) Golay code is assumed. There will be several dB change if different codes are used. • Coherent detection is assumed. There is a maximum of 3dB loss if differential detection is used. DS-UWB Link Budget (BW=500MHz) Gian Mario Maggio; Philippe Rouzet (STM)

36. Scalability With DS Lengths (Examples) Gian Mario Maggio; Philippe Rouzet (STM)

37. PRI VPeak TC Minimum PRF Requirements • Assumptions: • IR-UWB • Modulation: BPSK • Fc = 4056 MHz (26x156) • Chip rate = Fc/3 = 1352 Mcps • CMOS 90 nm technology voltage swing is: • 1 V internal (0.5 peak) • 2.5 V I/O (1.25 peak) • Note: Gian Mario Maggio; Philippe Rouzet (STM)

38. Maximum Available Preamble bits for Synchronization • * Assuming IR-UWB, PRF = 13 Mcps, and time slip of ¼ of a chip Gian Mario Maggio; Philippe Rouzet (STM)