Modified Adjacent Frequency Coding For Increased Notch Depth under DAA/Spectral Sculpting Kevin A. Shelby, Johann Chiang, Dr. Jim Lansford Alereon Inc. CrownCom Mykonos June 2006

WiMedia Confidential 2 Outline -Objectives -Regulatory Outlook -System Overview -System Design Considerations -Simulation Results -Closing Remarks

WiMedia Confidential 3 Objectives -Extend adjacent frequency coding to include some form of multi-carrier modulation: -Reuse antipodal signaling aimed at canceling sidelobe contributions in adjacent carriers; -Introduce multi-carrier modulation to minimize the impact on the existing WiMedia PHY Specification: -Preserve the existing time/frequency spreading characteristics in order to maintain system performance in the presence of a variety of channel impairments, SOP interference most notably; -Preserve the existing tone mapping to minimize the impact on the interleave and cyclic shift structures.

WiMedia Confidential 4 Current Regulatory Outlook Band Group 1 Band Group 2 Band Group 3 Band Group 4 Band Group 5 DAA Required DAA Required DAA Requirement Postponed in Europe until June 30, 2010 Increased Rolloff

WiMedia Confidential 5 Adjacent Sidelobe Contributions -AFC leverages the observation that sidelobe contributions in adjacent tones are similar in amplitude:

WiMedia Confidential 6 Sidelobe Cancellation -The achievable notch depth can be increased by canceling adjacent sidelobe contributions:

WiMedia Confidential 7 Existing DCM Mechanism -Dual Carrier Modulation as originally conceived can be described in terms of a linear transformation, M, as follows: -Where the indices {a,b,c,d} represent a mapping from the interleaved transmit bitstream, -and M={m ij }; i,j=[1:2] constitutes a linear mapping of tones in the transmit OFDM symbol.

WiMedia Confidential 8 Modified AFC -Building directly on the original AFC proposal, a linear mapping resembling that employed by DCM can be identified, aimed at canceling mutual interference in adjacent subcarriers: -Where c k = x k +j y k corresponds to the output of the symbol mapper, QPSK or DCM encoded, depending on the selected data rate.* *The extent to which M-AFC can be applied at rates above 200Mb/s is still under investigation.

WiMedia Confidential 9 Baseband Transmitter IFFT Symbol Mapper Coding/ Puncturing ScramblerInterleaver Pilots Zero DC DACs P/S (  )* 2X Preamble Add Zero Suffix Analog Filters Tone Nulling Guard

WiMedia Confidential 10 System Design Considerations Notch Depth Notch depth varies as a function of the scaling factor, , with the benefit of antipodal signaling maximized as  approaches unity.   1 Invertible Matrix The principal objective in introducing the scaling factor was to permit an invertible matrix at the receiver. Det(M) = 1-  2   ≠ 1 Tone Erasure The potential for symbol erasure occurs whenever the data content in adjacent tones is the same, i.e. c 2n = c 2n+1. y 2n = c 2n (1-  )   < 1 RX SNRSNR in the RX constellation is maximized when the TX mapping results in evenly distributed constellation points.  = 1/2

WiMedia Confidential 11 Achievable Notch Depth

WiMedia Confidential 12 TX Constellation(  =8/16 )

WiMedia Confidential 13 RX Constellation Equalizer Output DeMapper Output DeSpread Output

WiMedia Confidential 14 System Simulation Simulation results were compiled using the following system configuration: -WiMedia compliant 1.0 PHY -Mandatory rates ( Mb/s)[1][1] -M-AFC,  = 0.5 -~20MHz tone notching ( GHz) -Incumbent service passive during link tests [1][1] The applicability of M-AFC to higher data rates is still under investigation

WiMedia Confidential 15 DAA Spectral Scultping Simple Tone NotchingModified AFC

WiMedia Confidential 16 Link Performance

WiMedia Confidential 17 Closing Remarks -M-AFC applies a linear transformation at the symbol mapper output leaving tone assignment and existing interleaver structure unchanged; -Resembling DCM, M-AFC achieves antipodal signaling without sacrificing the time/frequency spreading present in the existing spec; -The resulting notch depth approaches that demonstrated with the original AFC, less ~5dB once considerations affecting link performance are taken into account; -The rate of OOB rolloff also increases similarly to the original AFC proposal over that without antipodal signaling.

WiMedia Confidential 18 Backup - Decoding A practical decoder can be derived similar to that employed for DCM. With received symbols z 1 and z 2 : The soft-demapper computes: