TG4a Frequency Proposal

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [TG4a Frequency Band Proposal] Date Submitted: [May 2004] Source: [Matt Welborn] Company [Freescale Semiconductor, Inc] Address [8133 Leesburg Pike, Vienna VA 22182] Voice:[703-269-3000], FAX: [], E-Mail:[matt.welborn @ freescale.com] Re: [Response to Call for Proposals] Abstract: [This document describes a frequency band proposal for the TG4a baseline draft standard.] Purpose: [Proposal Presentation for the IEEE802.15.4a standard.] 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. Welborn (Freescale)

2. Design Consideration • TG4a is committed to support both coherent and non-coherent receiver architectures • Supports a wide range of applications that require different balances of complexity and performance • Provides flexibility to address evolving applications • Areas of tension • PRF • Peak power – NC benefits from higher peak power • Higher peak power leads to higher complexity/cost • Ranging – precisely resolve details of multipath response (“leading edge” detection) • Processing gain – Impulse radio Welborn (Freescale)

3. Advantages • Meets requirements of TG4a baseline draft • Uses non-uniform bandwidths for mandatory and two optional narrow bands • Allows same pass-band pulse shape to be used in each band (simplifies pulse generation) • Provides more uniform performance for each of three narrow bands • PRF would also scale with changing center frequency to allow fixed (integer) relationship between center frequency, BW and chip rate Welborn (Freescale)

4. Details of proposed system • Proposed waveform is similar to others proposed by Samsung, Mitsubishi, Time Domain and I2R • Should make it easier to get group support • Data symbols are transmitted using short sequences of pulses with “silent” periods • Allows coherent reception and also “energy collector” or “energy detector” architecture as well • Should support implementing low-power, low-complexity devices and still provide good performance in multipath Welborn (Freescale)

5. Signals already proposed by Others (Mitsubishi, TDC, I2R, etc) One Bit Optionally Empty Always Empty Always Empty 32 32 32 Next potential active time 32 chip sequence The Other Bit Optionally Empty Always Empty Always Empty 32 32 32 Only 160 ns of channel multipath tolerance in this case. Next potential active time 32 chip times We transmit one or the other of these patterns to carry data. Welborn (Freescale)

6. Use a Systematic Code to Compute a Redundant Bit x1=bk • Rate-½ convolutional encoder • Produce multiple coded bits from each data bit • Encoder itself is very low complexity • Special case of convolutional code is a “systematic” code • First coded bit is same as input data bit • Second coded bit is computed by encoder • Code can be chosen to have desired constraint length (TBD) & code gain (not limited to a specific constraint length) • Mapping coded bits to waveform • Map first coded bit (systematic bit) into position for BPPM • Map second coded bit into phase • Can be extended to more general (non-systematic) codes very easily Convolutional Encoder bk x2 Welborn (Freescale)

7. Non-Coherent and Coherent Demodulation X1 = 0, X2 = 0 X1 = 1, X2 = 0 X1 = 1, X2 = 1 X1 = 0, X2 = 1 • Non-coherent receiver only sees position • Demodulates only x1 • No Viterbi decoding required (easy since x1=bk) • Achieves no coding gain, assumes bk = x1  Done. • Coherent receiver demodulates position and phase • Decodes x1 & x2 • Viterbi decoding used to estimate original bit, bk • Achieves coding gain of original rate ½ code Welborn (Freescale)

8. Another way to look at this Mapping 4-BOK (coherent) constellation 2-PPM constellation 2-PPM constellation OOK constellation Non-coherent receiver cannot see these • Encoding two coded bits requires a 4-point signal constellation • Each axis represents one of two possible positions (orthogonal axes) • Phase of pulse determines sign of constellation point on axis  4-BOK • Non-coherent receiver is insensitive to phase – see only two points in constellation  2-PPM • Support for OOK receiver is possible by demodulating only one of the two dimensions (i.e. just look at first position: pulse or not?) Welborn (Freescale)

9. Multipath can Degrade the Symbol Orthogonality 2-PPM Constellation in AWGN 2-PPM Constellation In multipath Welborn (Freescale)

10. Choosing the Chip Rate and Symbol Rate Tchip • Resulting waveform has “uniformly” spaced pulses (underlying chip-rate clock is constant), but exactly one-half of pulses have non-zero amplitude • PSD should be same as pulse spectrum (flat), since pulse phase is i.i.d. (TBD) • Chip rate can be chosen to allow effective non-coherent demodulation in multipath • Choose Tchip = (1/Fchip) > ~delay spread • Above waveform shown with (one symbol) = (two chips) [not to scale] • In general, (one symbol) = N x (2 chips) in order to spread symbol • N is chosen to achieve desired lower data rates • Allows fully coherent BPSK receiver, with NO LOSS in performance • Also allows non-coherent receiver using PPM or OOK demodulation Tsymbol Welborn (Freescale)

11. Expanded View of 24-chip Burst Sequence Similar signal using 24-pulse sequence Can use coherent or non-coherent receiver Can use PPM/OOK by sending pulse burst in Either first or second bit location Ts = 109 ns Tm = ~218 ns One BPPM symbol 24-chip codes sent at 221 MHz rate (~4.5 ns per pulse) The “burst” rate is an average 2.3 MHz for the 2-PPM mode Welborn (Freescale)

12. Proposed Signal uses 24-chip pulse sequence, similar to original “Chaotic” noise signals and can support Non-coherent Receivers Original signal proposed by Samsung for non-coherent receiver Ts = 100 ns Tm = 400 ns Similar signal using 24-pulse sequence Can use coherent or non-coherent receiver Can use PPM/OOK by sending pulse burst in Either first or second bit location Ts = 109 ns Tm = ~218 ns Welborn (Freescale)

13. Frequency Plan Band No. 4 1 2 3 3 4 5 GHz 3.25 3.5 3.75 4.25 4.5 4.75 Welborn (Freescale)

14. Frequency Factorization Welborn (Freescale)

15. PLL Reference Diagram fX fComp Oscillator Reference Divider (R) output XTAL Phase Det. LPF VCO Divider, N Welborn (Freescale)

16. Higher Band Frequency Plan Band No. 8 5 6 7 6 8 10 GHz 6.5 7 7.5 8.5 9 9.5 Welborn (Freescale)

17. One possible mapping of pulses to bits: Use 31-chip Codes • Can support both coherent and non-coherent pulse compression • Add 33 zero chips to get baseline mode for non-coherent receivers • However, these codes have poor spectral properties (see following slides) Welborn (Freescale)

18. Signal structure using a 31-chip Burst Sequence Hypothetical signal using 31-pulse sequence Can use coherent or non-coherent receiver Can use PPM/OOK by sending pulse burst in Either first or second bit location Ts = 140 ns Tm = ~290 ns Based on same 31-chip sequences proposed by Francois Chin of I2R at ~4.5 ns Tc spacing These codes need to be further analyzed to make sure spectral properties are acceptable Welborn (Freescale)

19. Code number 1 Back-off = -5.1601 dB Code number 2 Back-off = -4.7141 dB -40 -40 -50 -50 -60 -60 -70 -70 2 3 4 5 6 2 3 4 5 6 Code number 3 Back-off = -4.4672 dB Code number 4 Back-off = -5.9843 dB 9 9 x 10 x 10 -40 -40 -50 -50 -60 -60 -70 -70 2 3 4 5 6 2 3 4 5 6 Code number 5 Back-off = -5.2357 dB Code number 6 Back-off = -4.4672 dB 9 9 x 10 x 10 -40 -40 -50 -50 -60 -60 -70 -70 2 3 4 5 6 2 3 4 5 6 9 9 x 10 x 10 PSD plots for Proposed 31-chip codes – These codes cost 5 dB or more in Tx power Welborn (Freescale)

20. The Impact of a PSD • As we see, the PSD using the 31-chip codes results in about 5 dB Tx power reduction • Result is reduced range and/or robustness • An alternative is to consider similar length codes that have better spectral properties • One example would be length-24 ternary codes with two “zeros” per code • Codes exist that could provide only a 2 dB penalty on Tx power (see next page) • Other codes exist, including “hierarchical codes”, analysis is ongoing Welborn (Freescale)

21. 24-bit Code number 1 Back-off = -1.9077 dB 24-bit Code number 2 Back-off = -1.9445 dB -40 -40 -50 -50 -60 -60 -70 -70 2 3 4 5 6 2 3 4 5 6 24-bit Code number 3 Back-off = -2.0199 dB 24-bit Code number 4 Back-off = -2.0419 dB 9 9 x 10 x 10 -40 -40 -50 -50 -60 -60 -70 -70 2 3 4 5 6 2 3 4 5 6 24-bit Code number 5 Back-off = -1.9027 dB 24-bit Code number 6 Back-off = -2.1993 dB 9 9 x 10 x 10 -40 -40 -50 -50 -60 -60 -70 -70 2 3 4 5 6 2 3 4 5 6 9 9 x 10 x 10 PSD plots for Proposed 24-chip codesMultiple codes are available with only ~2 dB backoff Welborn (Freescale)

22. PSD plots for Barker 11 & 13 codes (for reference) Barker-11 Back-off = -1.1789 dB Barker-13 Back-off = -2.8395 dB -35 -35 -40 -40 -45 -45 -50 -50 -55 -55 -60 -60 -65 -65 -70 -70 2 3 4 5 6 2 3 4 5 6 9 9 x 10 x 10 Welborn (Freescale)

23. Expanded View of 24-chip Burst Sequence Similar signal using 24-pulse sequence Can use coherent or non-coherent receiver Can use PPM/OOK by sending pulse burst in Either first or second bit location Ts = 109 ns Tm = ~218 ns One BPPM symbol 24-chip codes sent at 221 MHz rate (~4.5 ns per pulse) The “burst” rate is an average 2.3 MHz for the 2-PPM mode Welborn (Freescale)

24. Proposed System Parameters (Mandatory Center Band) • Bandwidth: Optional bands #1 & 3 are slightly different BW and frequency as noted on previous slides • Wide band #4 uses narrower pulses to achieve higher bandwidth Welborn (Freescale)

25. PRF and Data Rate Details Welborn (Freescale)

26. TG4 Standard contains the concept of Reduced Functionality and Full-functionality devices (RFD & FFD) Proposal is to allow RFD to have only non-coherent receiver Will have reduced operating range, but also potentially lower complexity RFD may have slightly lower ranging capabilities TOA ranging (when SNR is adequate) Maybe only Tx for TDOA-2 ranging FFD can form and coordinate piconet for low cost/low complexity RFD radios RFD-only piconets at short range? RFD and FFD Class Devices Coherent Receiver= FFD RFD can use simple non-coherent receiver for OOK or PPM FFD Welborn (Freescale)

27. Possible Techniques to Optimize Radio Operations for Dynamic Conditions • Every link will connect a transmitter and a receiver – these may be a different mix of capability for each link • Applications that are sensitive to power and/or cost may want to match their operation to dynamic conditions such as • Capabilities of the intended receiver (coherent vs. non-coherent) • Dynamic channel, noise, interference or path loss conditions • Example: a small homogeneous cluster of low-complexity (non-coherent) radios want to operate at short range – can they operate in a lower complexity • Dynamically changing • Transmit power • Non-coherent vs. coherent pulses Example: • Preamble length • PRF • Spectral shape Welborn (Freescale)

28. Positioning from TOA 3 anchors with known positions (at least) are required to retrieve a 2D-position from 3 TOAs Anchor 2 (xA2,yA2) Anchor 1 (xA1,yA1) Mobile (xm,ym) Anchor 3 (xA3,yA3) Estimated Position Measurements Specific Positioning Algorithms TOA Ranging for both FFD and RFD Welborn (Freescale)

29. TDOA Ranging Requires FFDs to Act as “Reference Nodes” reference node= FFD SOI = RFD – only needs to transmit signal when TDOA ranging FFD FFD Key: Sync Pulse Location Pulse TDOA backhaul • Controller: • Can be wired or wireless connection to FFDs • Needs protocol to allow synchronizing clocks Mode 2 - Active Welborn (Freescale)