January 6, 2002doc.: IEEE /044r0 SubmissionRishi Mohindra, MAXIMSlide 1 Proposal for IEEE802.11g Receiver Adjacent Channel Rejection Requirement when receiving 11b or QPSK packets in presence of OFDM blocker Rishi Mohindra MAXIM Integrated Products

January 6, 2002doc.: IEEE /044r0 SubmissionRishi Mohindra, MAXIMSlide 2 Why is Adjacent Channel Rejection of OFDM jammer a concern for the receiver when receiving 11b or QPSK packets ? 11a standard allows large out-of-band transmitter power spectral density. –Pages 3 & 4 show some possible OFDM jammer spectral plots. The adjacent channel OFDM jammer spills about –32 to -39 dB relative power into the 11b receiver pass band, for a 25 MHz center frequency separation. –Graph on page 5 shows simulated OFDM Adjacent Channel Power ratio as a function of center frequency separation between the 11b pass band and the OFDM jammer. For a -70 dBm 11b received signal, the OFDM jammer (25 MHz away) should not be more than about –55 dBm in order to get about 15 dB S/Interference ratio with some margin.

January 6, 2002doc.: IEEE /044r0 SubmissionRishi Mohindra, MAXIMSlide 3

January 6, 2002doc.: IEEE /044r0 SubmissionRishi Mohindra, MAXIMSlide 4 dBm, In 1 MHz

January 6, 2002doc.: IEEE /044r0 SubmissionRishi Mohindra, MAXIMSlide 5

January 6, 2002doc.: IEEE /044r0 SubmissionRishi Mohindra, MAXIMSlide 6 Proposal for IEEE802.11g Receiver Adjacent Channel Rejection Requirement of OFDM Blocker when receiving 11b or QPSK packets: For a -70dBm 11b or QPSK received signal and a –55dBm OFDM blocker 25 MHz away, the PER should be 10% or less. It is preferable to actually state the type of modulation (e.g. 64- QAM) and data rate (e.g. 54 Mbits/s) of the OFDM blocking signal, since a higher out-of-band spectral power (spectral regrowth) can be transmitted for BPSK or 4-QAM compared to 64-QAM, when meeting the constellation error and spectral template requirements of 11a.