doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 1 Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Multi-Band OFDM Interference on In-Band QPSK Receivers] Date Submitted: [13 July, 2004] Source: [Celestino A. Corral, Shahriar Emami, Gregg Rasor] Company [Motorola] Address [8000 W. Sunrise Blvd., Plantation, Florida, USA 33322] Voice:[ ], FAX: [ ] Re: [] Abstract:[This document provides simulation and theoretical results that demonstrate MB-OFDM is an extremely harmful type of interference to wideband in-band QPSK systems such as TVRO receivers. A MB-OFDM interference model is derived based on simulation and analytical results.] Purpose:[For discussion by IEEE TG3a.] 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 P

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 2 Multi-band OFDM Interference on In-Band QPSK Receivers Celestino A. Corral, Shahriar Emami and Gregg Rasor Motorola 8000 W. Sunrise Blvd. Plantation, Florida July 13, 2004

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 3 Motivation  Goal: To characterize the impact of Multi-band OFDM UWB interference on in-band broadband wireless system like C-band satellite receivers.  Note: Multi-band OFDM (MB-OFDM) and Multi-band UWB (MB- UWB) requires power scaling of the waveform to compare competing technologies based on interpretation of FCC rules.  Model of MB-OFDM interference derived. This model is bounded by periodically gated AWGN and impulsive MB-OFDM interference.  Reconcile observed test results of MB-OFDM interference on satellite receivers as presented in ABQ meeting.

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 4 Multi-band UWB Power  FCC states power spectral density for UWB devices must be dBm/MHz in band between 3.1 and 10.6 GHz  Since multi-band signals hop over a selected band of frequencies, the power spectrum is scaled by the hop and averaged over the band.  The resulting power spectral density is made equal to a system over any arbitrary band. PSD level Multi-band spectrum Integrate the spectrum over band and average by band To implement equal PSD over hop bandwidth, we need requiring a power scaling. f1f1 f2f2 fxfx

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 5 Multi-band UWB Power Equate power Both systems transmit with equal power at a given range. Assuming DS-UWB bandwith is 2 GHz and MB-OFDM bandwidth is 528 MHz. Actual MB-OFDM PSD over its transmission bandwidth.

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 6 In-band Receiver Filters f c > 3 GHz BW < 40 MHz Q > 50 typical Band-pass Filter Frequency Response High-Q band-pass filter can be approximated by [1]: complex frequency of band-pass filter complex frequency of low-pass prototype filter Step response of band-pass filter has low-pass impulse response envelope: [1] A. Papoulis, The Fourier Integral and its Application, Chap. 7, New York: McGraw-Hill, [2] G. E. Valley, Jr., and H. Wallman, Vacuum Tube Amplifiers, New York: McGraw-Hill, Temporal characteristics of high-Q band-pass filter determined by low-pass prototype. This includes rise time, which obeys the following relation [2]: Rise time of band-pass filter determined by 3dB bandwidth of low-pass prototype. Not a function of filter approximation or order

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 7 In-band Receiver Filters Band-pass filter rise time for 40 MHz bandwidth. Received power: Filter responds quite fast and observes virtually full power of filtered MB- OFDM signal. Portion due to filter bandwidthPortion due to temporal response Filter with slower response. in dB

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 8 Coherent Detection QPSK Simulation Detector Window Matched Filter Block Diagram of Simulator Assume perfect synchronization Assume perfect phase estimation Input filter bandwidth wide enough so rise time not a factor Interference bandwidth is very large relative to filter bandwidth and approaches thermal noise as in [3]. [3] J. Brandao, “Interference effect on the performance of PSK and QAM systems,” IEE Proceedings I, vol. 138, pp. 331—337, Aug QPSK system at Msym/sec, similar to Dubai EDTV at 4020 MHz. 0 < Eb/No < 30 dB symbols, 500 packets per E b /N o set. Sample rate: 120 samples/QPSK symbol. Multi-band OFDM and all gated noise is 896 samples long. Noise Source

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 9 Simulation Results: Gated Noise 3 dB

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 10 Simplified Theoretical Reason Probability of symbol error for QPSK [4] Q-function for communication Gated noise duty cycle: N p is time interference is present, N s is time interference is silent. Probability of error is due only to when the noise is present P ep ; for the case it is silent P es = 0: Q is very sensitive to  under high signal-to-noise (SNR), meaning small changes in duty cycle will impact probability of error when minor changes in bit energy is most significant. equivalent “quasi-fading” of bit energy relative to fixed noise power N o Actual error must be scaled by duty cycle as this is time interference is present [4] J. G. Proakis, Digital Communications, 4 th Ed., Boston, MA: McGraw-Hill, 2001.

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 11 Theoretical vs. Simulated Results: Gated Noise Simulated

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 12 Simulation Results: MB-OFDM 9 dB 3 hops AWGN

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 13 Simulation Results: Impulsive MB- OFDM Theory Worst-case peak-to-average power assumed for each MB-OFDM symbol ?? dB

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 14 Simulation Results: 3 hops Gated AWGN lower bound Impulsive MB-OFDM upper bound MB-OFDM

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 15 MB-OFDM Interference Model Amplitude distribution of AWGNAmplitude distribution of MB-OFDMAmplitude distribution of Impulsive MB-OFDM Multi-band OFDM transmissions can be long or bursty: Long transmissions have amplitude distribution that approaches AWGN Bursty transmissions can be potentially impulsive We need to combine the Gaussian and impulsive characteristics

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 16 MB-OFDM Interference Model Class A Model [5]: Interference has “gaps” in time; i.e., non-zero probability of time during which there is no interference in the receiver. Interference timeReceiver bandwidth Model Incorporates Gaussian and Impulsive Factors: impulse index Peak factor (PAP) Carrier-to-noise ratio for M-ary QAM std. dev. mean power ratio Average symbol error rate: [5] D. Middleton, “Non-Gaussian noise models in signal processing for telecommunications: New methods and results for class A and class B noise models,” IEEE Trans. Inform. Theory, vol. 45, pp. 1129—1149, May 1999.

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 17 MB-OFDM Model Simulated Model

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 18 Filtered MB-OFDM 40 MHz 9 subcarriers The filtered waveform is generated and then scaled to obtain same power as AWGN over the packet. The waveform is then scaled by a factor of 9/128 (in number of subcarriers) to reduce the level to a filtered amount. This is almost the same amount as 40/528 (in MHz), which corresponds to the desired power reduction relative to the full bandwidth of the 128-subcarrier symbol: Received power: Assumed 0 dB 9/128 factor (40/528 factor)

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 19 Simulation Results: Filtered MB-OFDM

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 20 Conclusions  Multi-band OFDM and Multi-band UWB equate power spectral density by scaling power in the hop and averaging over the entire hop bandwidth. This equates the transmitted power of a Multi- band system with DS-UWB over a fixed bandwidth.  Probability of symbol error shows gated noise is akin to quasi- fading of bit energy relative to fixed AWGN level.  The gated and scaled interference is more harmful than AWGN depending on the hop depth. Gated noise interference produces performance 3 dB from theory; MB-OFDM produces performance 8 dB from theory.  Multi-band OFDM can be impulsive. Under worst-case peak-to- average power Multi-band OFDM is a significant interferer to in- band coherent detection QPSK receivers.  MB-OFDM model was derived based on combination of Gaussian and impulsive characteristics of MB-OFDM.

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 21 Narrowband Filter Response Wideband Filter Response Only upper portion of response captured Narrowband Filter Response Fast rise time Delay applies across entire response Full level of interference reached within response time of the filter, and present for most of the interference time. Total power captured Slow rise time Delay applies across entire response Full level of interference not reached within response time of the filter. Total power can be captured if rise time and interference time are about equal. Narrowband filters “favor” narrow pulsed interference; full level of interference is not captured.

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 22 Backup: Gated Noise Results for Other Hops Increasing hop depth results in more degradation at high SNR

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 23 Backup: MB-OFDM Results for Other Hops Increasing hop depth results in more degradation at high SNR

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 24 Backup: Impulsive MB-OFDM Results for Other Hops Increasing hop depth results in more degradation at high SNR

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 25 Backup: Gated Noise Theoretical Results for Other Hops 37 13

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 26 Backup: MB-OFDM Class A Model Results for Other Hops

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 27 Properties of Q and Quasi-Fading Working with Q(x) directly is difficult. We use approximation [4] P. L. Borjesson and C-E. W. Sundberg, “Simple approximations of the error function Q(x) for communication applications,” IEEE Trans. Commun., vol. COM-27, pp. 639—643, March where [4]: as then so decays more rapidly Decay factor: Value

doc.: IEEE /315r0 Submission July 2004 Celestino A. Corral et al., MotorolaSlide 28 Peak-to-Average Power “Tracking” Peak-to-average of AWGN and MB-OFDM “track” over different hop depths.