May 2003 doc.: IEEE 802.15-03/141r3 May, 2005 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Ultra-Wideband Peak Power Limits] Date Submitted: [15 May, 2005] Source: [Celestino A. Corral, Shahriar Emami and Gregg Rasor] Company [Freescale Semiconductor, Inc.] Address [6100 Broken Sound Pkwy., N.W., Suite 1, Boca Raton, Florida USA 33487] Voice:[561-544-4057], FAX: [ ] Re: [Recent FCC Waiver] Abstract: [This document provides analytical and theoretical comparison of MB-OFDM and DS-UWB under peak power limited applications.] Purpose: [For discussion by IEEE 802.15 TG3a.] 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. Celestino A. Corral et al., Freescale Jai Balakrishnan et al., Texas Instruments

Ultra-Wideband Peak Power Limits May, 2005 Ultra-Wideband Peak Power Limits Celestino A. Corral, Shahriar Emami and Gregg Rasor Freescale Semiconductor, Inc. 6100 Broken Sound Parkway., N.W., Suite 1 Boca Raton, Florida USA May 17, 2005 Celestino A. Corral et al., Freescale

May, 2005 Motivation Goal: To provide a comparison between DS-UWB and MB-OFDM for peak-limited applications under the recent FCC waiver. Note: Recent FCC waiver is technology-neutral. Devices can be measured under “normal” operating conditions. These conditions can include hopping or gating. Approach: Consider DS-UWB and MB-OFDM waveforms under average- and peak-power measurements. Emphasis is on peak-to-average power ratio of waveforms. Additionally: Provide peak-power headroom levels for actual implementation considerations. Celestino A. Corral et al., Freescale

Average Power Measurements May, 2005 Average Power Measurements Radiated Waveform Spectrum analyzers measure average value of the total signal power quantized within resolution bandwidth by making a fixed number of measurements and computing a corrected average figure of power density normalized to that bandwidth. Celestino A. Corral et al., Freescale

Average Power Measurements May, 2005 Average Power Measurements Resolution bandwidth filter Block Diagram of Typical Spectrum Analyzer For FCC emission measurements, the resolution bandwidth is 1 MHz with 1 msec integration time for the RMS power and resulting EIRP. Resolution bandwidth is 50 MHz for peak power measurements. Celestino A. Corral et al., Freescale

May, 2005 Gated Signals gated signal t Gating allows greater power transmissions over narrower time intervals. This power can be used to improve SNR, SIR or range. Limit is now peak power. ungated signal T Celestino A. Corral et al., Freescale

Peak Power Measurements May, 2005 Peak Power Measurements 50 MHz 1 MHz key determinant for peak-power levels Minimize PAPR to achieve more headroom in peak power levels Peak power measurements actually made with spectrum analyzer on “peak hold” capturing over a long time period (several minutes). Celestino A. Corral et al., Freescale

Direct-Sequence UWB Sinusoidal carrier, PAPR = 3 dB May 2003 doc.: IEEE 802.15-03/141r3 May, 2005 Direct-Sequence UWB Sinusoidal carrier, PAPR = 3 dB Data spread by chipping code Upconverted to desired freq. Shaped by RRC filter with a = 0.3. Spectral BW = 1.5 GHz. Waveform has 40% fractional bandwidth between 3.1 and 4.6 GHz and consequently good fading resilience. 0.26 ns code 4.1 GHz adjust RRC Filter data Celestino A. Corral et al., Freescale Jai Balakrishnan et al., Texas Instruments

What Spectrum Analyzer Measures May, 2005 What Spectrum Analyzer Measures DS-UWB Waveform Signal over air has 5.5 dB PAPR 1 MHz Filter 50 MHz Filter DS-UWB has 8.5 dB PAPR (ungated) in 50 MHz filter. Celestino A. Corral et al., Freescale

Worst-Case PAPR of MB-OFDM May, 2005 Worst-Case PAPR of MB-OFDM Subcarrier spacing is 4.125 MHz. In 50 MHz resolution bandwidth this corresponds to 12 subcarriers. Worst-case PAPR is 10log(12)=10.8 dB. Above occurs even if MB-OFDM waveform is clipped to 9 dB PAPR. If we consider that hopping contributes 5.8 dB additional PAPR for 3 hops, the total worst-case PAPR is 16.6 dB. As a result, we have about 7.7 dB headroom for MB-OFDM. 50 MHz Celestino A. Corral et al., Freescale

How Often Does This Happen? May, 2005 How Often Does This Happen? QPSK Constellation 90o 0o 180o 270o Celestino A. Corral et al., Freescale

Impact of Filtering Operation May, 2005 Impact of Filtering Operation Worst-Case OFDM Symbol 12 Subcarriers Filter Impulse Response (50 MHz) Output of Filter (Convolution) Pulse width is about 8% of the length of OFDM symbol. pulse width The filter impulse response is very narrow relative to the OFDM waveform, so convolution results in OFDM symbol and PAPR is conserved. Celestino A. Corral et al., Freescale

What Spectrum Analyzer Measures May, 2005 What Spectrum Analyzer Measures Multi-Band OFDM Waveform Signal over air has 9 dB PAPR 1 MHz Filter 50 MHz Filter On average, peak power is -11.1 dBm and PAPR is 15 dB. Worst-case PAPR is 16.6 dB and peak-power is -7.7 dBm. Celestino A. Corral et al., Freescale

May, 2005 Summary of Results Parameter DS-UWB MB-OFDM PAPR at transmit pin 3.0 dB 9.0 dB PAPR over air after pulse shaping 5.5 dB PAPR at output of 50 MHz filter 8.5 dB 16.6 dB Peak power in 50 MHz bandwidth -15.8 dBm -7.7 dBm Thus, DS-UWB has 8.1 dB more headroom than MB-OFDM. This can be employed to overcome cable losses, antenna losses, etc. DS-UWB has a net 15.8 dB headroom for exploiting gating. Celestino A. Corral et al., Freescale

May, 2005 Conclusions Multi-band OFDM (MB-OFDM), even if clipped to a 9 dB peak-to-average over the air, can still result in up to a 16.6 dB PAPR in a 50 MHz bandwidth. For MB-OFDM, the 16.6 dB PAPR in a 50 MHz bandwidth is due to 10.8 dB of signal PAPR for 12 subcarriers captured in that bandwidth and 5.8 dB of PAPR due to the 3-hop sequence. DS-UWB has a nominal 5.5 dB PAPR after pulse shaping. The PAPR of ungated DS-UWB in a 50 MHz bandwidth is 8.5 dB. DS-UWB has 15.8 dB maximum headroom for transmission which can be exploited for gated signals. This corresponds with an approximate duty cycle of 3%. Consequently, DS-UWB has 8.1 dB more headroom than MB-OFDM for overcoming cable, filter and antenna losses. Celestino A. Corral et al., Freescale