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**Frequency Domain Modulators for 802.11b**

July 2000 doc.: IEEE /202 July 2000 Frequency Domain Modulators for b Mark Webster Intersil Corporation July 2000 Mark Webster, Intersil Mark Webster, Intersil

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July 2000 doc.: IEEE /202 July 2000 Overview Examine frequency domain modulator for and 2 Mbps Barker signaling. Examine frequency domain modulator for and 11 Mbps CCK signaling. Examine frequency domain modulator for and 11 Mbps PBCC signaling. Compare b frequency domain modulators to OFDM modulator. Cyclic extensions for Barker or CCK transmissions (non b variant). Mark Webster, Intersil Mark Webster, Intersil

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**1 and 2 Mbps BARKER Mode: Time Domain Modulator**

July 2000 1 and 2 Mbps BARKER Mode: Time Domain Modulator Time Domain Multiply 1 Mbps: BPSK 2 Mbps: QPSK time Wide Sinc Spectrum time Narrow Sinc Spectrum Mark Webster, Intersil

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**Barker Code Viewed in Discrete Domain**

July 2000 Barker Code Viewed in Discrete Domain DFT SPECTRUM 11 Chip BARKER Code +1 -1 Mark Webster, Intersil

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**Barker Code Spreading Detail Pulse Shape Envelop Periodically Extended**

July 2000 Pulse Shape Envelop Barker Code Spreading Detail Chip Pulse +1 time -1 convolution Periodically Extended Barker Samples Periodically Extended Barker Chips Mark Webster, Intersil

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**Barker Mode Signaling Revisited**

July 2000 Barker Mode Signaling Revisited Time Domain Multiply Equals Frequency Domain Convolution 1 Mbps: BPSK 2 Mbps: QPSK time time Composite Mark Webster, Intersil

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**Spread Spectrum: Stacked Carriers Composite**

July 2000 Spread Spectrum: Stacked Carriers Composite Constituent Stacked Carriers Pulse Shape Envelop Mark Webster, Intersil

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**Sub-Carrier Amplitude/Phase freqMHz -5 -4 -3 -2 -1 1 2 3 4 5**

July 2000 Sub-Carrier Amplitude/Phase freqMHz -5 -4 -3 -2 -1 1 2 3 4 5 ampFreqResp 1.0000 0.2887 phzFreqRespDeg Mark Webster, Intersil

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**Frequency Domain Modulator**

July 2000 doc.: IEEE /202 July 2000 1 and 2 Mbps BARKER Mode: Frequency Domain Modulator 1 Compute Amp/Phz of each Subcarrier 11 Info Bit(s) BPSK/QPSK Rotation 11 pt. IFFT P/S 11 Constellation Mapper -5 -4 -3 -2 -1 1 2 3 4 5 Freq (MHz) A1ejq1 A2ejq2 A3ejq3 A5ejq5 A4ejq4 A6ejq6 A11ejq11 A7ejq7 A8ejq8 A10ejq10 A9ejq9 Barker Spectrum Mark Webster, Intersil Mark Webster, Intersil

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**2 Mbps Subcarrier Constellations**

July 2000 doc.: IEEE /202 2 Mbps Subcarrier Constellations July 2000 Mark Webster, Intersil Mark Webster, Intersil

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**5.5 Mbps CCK Mode: Time Domain Modulator**

July 2000 5.5 Mbps CCK Mode: Time Domain Modulator Time Domain Multiply QPSK time time 4 Spreading Codes time time time Mark Webster, Intersil

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**Frequency Domain Modulator**

July 2000 5.5 Mbps CCK Mode: Frequency Domain Modulator 1 Compute Amp/Phz of each Subcarrier 8 2 Info Bits QPSK Rotation 8 pt. IFFT P/S Constellation Mapper 8 A1ejq1 A2ejq2 A3ejq3 A5ejq5 A4ejq4 A6ejq6 A7ejq7 A8ejq8 2 Info Bits 4 Codeword Spectrums Mark Webster, Intersil

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**5.5 Mbps Codeword Subcarrier Spectrums**

July 2000 Mark Webster, Intersil

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**5.5 Mbps Subcarrier Constellations**

July 2000 doc.: IEEE /202 5.5 Mbps Subcarrier Constellations July 2000 QAM Constellations Mark Webster, Intersil Mark Webster, Intersil

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**11 Mbps CCK Mode: Time Domain Modulator**

July 2000 11 Mbps CCK Mode: Time Domain Modulator Time Domain Multiply QPSK time time 64 Spreading Codes time time time Mark Webster, Intersil

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**Frequency Domain Modulator**

July 2000 11 Mbps CCK Mode: Frequency Domain Modulator 1 Compute Amp/Phz of each Subcarrier 8 2 Info Bits QPSK Rotation 8 pt. IFFT P/S Constellation Mapper 8 A1ejq1 A2ejq2 A3ejq3 A5ejq5 A4ejq4 A6ejq6 A7ejq7 A8ejq8 6 Info Bits 64 Codeword Spectrums Mark Webster, Intersil

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**11 Mbps Subcarrier Constellations**

July 2000 QAM Constellations Sub-Carriers 1, 3, 5, 7 Sub-Carriers 2, 4, 6, 8 Mark Webster, Intersil

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**Frequency Domain Modulator**

July 2000 11 Mbps PBCC Mode: Frequency Domain Modulator Compute Amp/Phz of each Subcarrier 8 8 Info Bits 8 pt. IFFT P/S A1ejq1 A2ejq2 A3ejq3 A5ejq5 A4ejq4 A6ejq6 A7ejq7 A8ejq8 Constellation Mapper Exists, but is Complicated Mark Webster, Intersil

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**OFDM DIRECTLY EMBRACES FREQUENCY DOMAIN SIGNALING**

July 2000 OFDM DIRECTLY EMBRACES FREQUENCY DOMAIN SIGNALING Used to Eliminate the Need for IBI Equalizer 802.11A OFDM MODULATOR BLOCK DIAGRAM Add Cyclic Extension Viterbi Encoder Constellation Mapper Scrambler Interleaver IFFT BPSK Pilot Subcarriers Data Sub-Carrier Constellations BPSK: 6, 9 Mbps QPSK: 12, 18 Mbps 16 QAM: 24, 36 Mbps 64 QAM: 48, 54 Mbps Cyclically Extends Sub-Carriers Mark Webster, Intersil

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**802.11a OFDM Symbol . . . Equivalent to 64 Chip Codewords July 2000**

20 MHz x 4 usecs = 80 samples 4 usecs OFDM Symbol Cyclic Extend IFFT/FFT SPAN 16 Samples 64 Samples time ~16.25 MHz 312.5 KHz Tone Spacing 52 Subcarriers . . . frequency Mark Webster, Intersil

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**Cyclic Extensions Can Be**

July 2000 Cyclic Extensions Can Be Used on Any Codeword Original Codeword Smoothly Extends Sub-Carriers in Time Cyclically- Extended Codeword Mark Webster, Intersil

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