doc.: IEEE /0034r0 Submission September 2005 Jim Lansford, AlereonSlide 1 Detect and Avoid for MB-OFDM Notice: This document has been prepared to assist IEEE 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 grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEEs name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEEs sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the TAG of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE TAG. If you have questions, contact the IEEE Patent Committee Administrator at. Date: Authors:

doc.: IEEE /0034r0 Submission September 2005 Jim Lansford, AlereonSlide 2 Abstract Detect and Avoid (DAA) is under discussion by both Japanese and European regulatory agencies as a non- collaborative coexistence technique. DAA requires the receiver to detect the presence of interference and suppress energy in that portion of the band. MB- OFDM is particularly well suited to implement DAA, because the FFT can be used as a channelized radiometer, and the IFFT can be used to sculpt the transmit spectrum.

doc.: IEEE /0034r0 Submission September 2005 Jim Lansford, AlereonSlide 3 Background UWB was developed as an underlay –FCC bought into the concept –Most of the rest of the world has been sceptical –Its a coexistence problem What are the issues? –Detecting the presence of an incumbent signal (FWA) –Dropping emissions in the shared band so that interference on the incumbent is minimized This is a form of cognitive radio –Similar to waterfilling TBD: Detection level/confidence and suppression level

doc.: IEEE /0034r0 Submission September 2005 Jim Lansford, AlereonSlide 4 How does MB-OFDM implement DAA? Detect: Channelized radiometer –128 channel FFT inherent in the design –Integrate spectra to achieve desired P d Avoid: Bandstop filter (frequency domain) –128 point IFFT –Additional signal processing techniques can increase notch depth, subject to RF linearity ADC DAC FFT/ IFFT Filter/ Decimate Interp. /Filter AGC Detect Despread Demap Deinterleave Depuncture Viterbi Spreading Mapping Interleave Puncture Convo- lutional Coder MAC/PHY Interface ChanEst CFO Equalize ADC DAC FFT/ IFFT Filter/ Decimate Interp. /Filter AGC Detect Despread Demap Deinterleave Depuncture Viterbi Spreading Mapping Interleave Puncture Convo- lutional Coder MAC/PHY Interface ChanEst CFO Equalize Mixer & Filter Mixer & Filter 90°

doc.: IEEE /0034r0 Submission September 2005 Jim Lansford, AlereonSlide 5 Detect (1) Channelized radiometers have been used for decades –Narrowband detection in a wideband channel –Used in Radar and communication intercept receivers –Theory well developed If FFT bins contain noise alone, distribution is Rayleigh If narrowband signal + noise, distribution is Rician FFT ()2()2 <><> P(N) P(S+N)

doc.: IEEE /0034r0 Submission September 2005 Jim Lansford, AlereonSlide 6 Detect (2) Averaging spectra reduces the variance of the distribution For ensemble average of N spectra, variance within a bin decreases by 1/N, standard deviation by 1/sqrt(N) Thus, detection probability can be made arbitrarily close to 1 but integration time can become large There is a considerable body of research for fluctuating signals (such as pulsed beacons)

doc.: IEEE /0034r0 Submission September 2005 Jim Lansford, AlereonSlide 7 Detect (3) For MB-OFDM system, FFT resolution is 528/128=4.125MHz kTB for a single tone is = -108dBm Assume 6.6dB NF in RF => N 0 = -101dBm FWA characteristics –5 or 10MHz BW –4W uplink, Downlink power <-90dBm at UWB system For FWA downlink, detection probability at -90dBm should be more than adequate – unless DL is in a fade –Uplink can always be easily detected –Uplink confirms local activity after downlink detected

doc.: IEEE /0034r0 Submission September 2005 Jim Lansford, AlereonSlide 8 Detect (4) Detection test setup –This is a demo –Fading channel tests will be done later UWB transmitter UWB Receiver FWA signal Generator Rhode & Schwartz Spectrum Analyzer +

doc.: IEEE /0034r0 Submission September 2005 Jim Lansford, AlereonSlide 9 Detect (5) Spectrum analyzer Noise floor MB-OFDM signal (zoomed: 200MHz)

doc.: IEEE /0034r0 Submission September 2005 Jim Lansford, AlereonSlide 10 Detect (6) FWA -90dBm FWA Signal + OFDM Signal (10ms averaging, -81dBm)

doc.: IEEE /0034r0 Submission September 2005 Jim Lansford, AlereonSlide 11 Avoid (1) Spectral notches have been discussed widely in a in reference to MB-OFDM Generally, can be considered frequency domain bandstop filters (FIR) –Like any FIR filter, intentional ISI can be introduced to control notch depth and width –EVM of RF chain must be consistent with desired depth Typically, these notches can be 15-20dB in depth More advanced techniques are under evaluation to achieve deeper notches

doc.: IEEE /0034r0 Submission September 2005 Jim Lansford, AlereonSlide 12 Avoid (2) MB-OFDM signal with 20MHz notch (5 tones) MB-OFDM signal plus FWA inside 20MHz notch 20MHz

doc.: IEEE /0034r0 Submission September 2005 Jim Lansford, AlereonSlide 13 Summary These measurements were made on an actual MB- OFDM system BER/PER increase from removal of five tones is insignificant –Erasure performance has been well documented Detection algorithm works, but needs further study –Fluctuating FWA signal –Strategies for downlink+uplink detection Collaborative coexistence (in a laptop, for example) would work even better Spectral sculpting really works…

doc.: IEEE /0034r0 Submission September 2005 Jim Lansford, AlereonSlide 14 References M.Skolnik, Introduction to Radar Systems, McGraw Hill, 1980 Johanna Vartiainen, Concentrated Signal Extraction using Consecutive Mean Excision Algorithms, Proceedings of the 2005 Finnish Signal Processing Symposium - FINSIG'05, August, 2005, Kuopio, Finland, pp S. M. Kay, Fundamentals of Statistical Signal Processing: Detection Theory., Prentice Hall, 1998.