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Doc.: IEEE 802.11-00/202r1 Submission July 2000 Mark Webster, IntersilSlide 1 of 22 Frequency Domain Modulators for 802.11b Mark Webster Intersil Corporation.

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Presentation on theme: "Doc.: IEEE 802.11-00/202r1 Submission July 2000 Mark Webster, IntersilSlide 1 of 22 Frequency Domain Modulators for 802.11b Mark Webster Intersil Corporation."— Presentation transcript:

1 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 1 of 22 Frequency Domain Modulators for b Mark Webster Intersil Corporation July 2000 This Microsoft Powerpoint presentation has notes attached. Please expand to Notes Page View mode.

2 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 2 of 22 Overview Examine frequency domain modulator for and 2 Mbps Barker signaling. Examine frequency domain modulator for 5.5 and 11 Mbps CCK signaling. Examine frequency domain modulator for 5.5 and 11 Mbps PBCC signaling. Compare b frequency domain modulators to OFDM modulator. Cyclic extensions for Barker or CCK transmissions (non b variant). This Microsoft Powerpoint presentation has notes attached. Please expand to Notes Page View mode.

3 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 3 of 22 1 and 2 Mbps BARKER Mode: Time Domain Modulator 1 Mbps: BPSK 2 Mbps: QPSK time Time Domain Multiply Narrow Sinc Spectrum Wide Sinc Spectrum

4 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 4 of Barker Code Viewed in Discrete Domain 11 Chip BARKER Code DFT SPECTRUM

5 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 5 of Chip Pulse time Periodically Extended Barker Samples Periodically Extended Barker Chips convolution Barker Code Spreading Detail Pulse Shape Envelop

6 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 6 of 22 Barker Mode Signaling Revisited 1 Mbps: BPSK 2 Mbps: QPSK time Time Domain Multiply Equals Frequency Domain Convolution time Composite

7 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 7 of 22 Pulse Shape Envelop Constituent Stacked Carriers Spread Spectrum: Stacked Carriers Composite

8 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 8 of 22 phzFreqRespDeg ampFreqResp freqMHz Sub-Carrier Amplitude/Phase

9 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 9 of pt. IFFT Compute Amp/Phz of each Subcarrier P/S Barker Spectrum BPSK/QPSK Rotation Info Bit(s) 1 and 2 Mbps BARKER Mode: Frequency Domain Modulator Constellation Mapper Freq (MHz) A 1 e j 1 A 2 e j 2 A 3 e j 3 A 5 e j 5 A 4 e j 4 A 6 e j 6 A 11 e j 11 A 7 e j 7 A 8 e j 8 A 10 e j 10 A 9 e j

10 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 10 of 22 2 Mbps Subcarrier Constellations All Subcarriers carry QPSK at their respective phase tilt.

11 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 11 of Mbps CCK Mode: Time Domain Modulator QPSK time Time Domain Multiply time 4 Spreading Codes

12 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 12 of Mbps Codeword Subcarrier Spectrums

13 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 13 of 22 8 pt. IFFT Compute Amp/Phz of each Subcarrier P/S 4 Codeword Spectrums QPSK Rotation 2 Info Bits 5.5 Mbps CCK Mode: Frequency Domain Modulator Constellation Mapper Info Bits A 1 e j 1 A 2 e j 2 A 3 e j 3 A 5 e j 5 A 4 e j 4 A 6 e j 6 A 7 e j 7 A 8 e j

14 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 14 of Mbps Subcarrier Constellations 3 unique QAM constellations to within a phase tilt. QPSK8 QAM QPSK 5 QAM 8 QAM

15 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 15 of Mbps CCK Mode: Time Domain Modulator QPSK time Time Domain Multiply time 64 Spreading Codes

16 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 16 of 22 8 pt. IFFT Compute Amp/Phz of each Subcarrier P/S 64 Codeword Spectrums QPSK Rotation 2 Info Bits 11 Mbps CCK Mode: Frequency Domain Modulator Constellation Mapper Info Bits A 1 e j 1 A 2 e j 2 A 3 e j 3 A 5 e j 5 A 4 e j 4 A 6 e j 6 A 7 e j 7 A 8 e j

17 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 17 of Mbps Subcarrier Constellations Sub-Carriers 1, 3, 5, 7 Sub-Carriers 2, 4, 6, 8 QAM Constellations 9 QAM24 QAM

18 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 18 of 22 8 pt. IFFT Compute Amp/Phz of each Subcarrier P/S 8 Info Bits 11 Mbps PBCC Mode: Frequency Domain Modulator Constellation Mapper Exists, but is Complicated 8 A 1 e j 1 A 2 e j 2 A 3 e j 3 A 5 e j 5 A 4 e j 4 A 6 e j 6 A 7 e j 7 A 8 e j

19 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 19 of 22 Scrambler Viterbi Encoder Interleaver Constellation Mapper IFFT Add Cyclic Extension A OFDM MODULATOR BLOCK DIAGRAM Data Sub-Carrier Constellations BPSK: 6, 9 Mbps QPSK: 12, 18 Mbps 16 QAM: 24, 36 Mbps 64 QAM: 48, 54 Mbps OFDM DIRECTLY EMBRACES FREQUENCY DOMAIN SIGNALING Used to Eliminate the Need for IBI Equalizer BPSK Pilot Subcarriers Cyclically Extends Sub-Carriers

20 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 20 of Samples 64 Samples IFFT/FFT SPAN Cyclic Extend 4 usecs OFDM Symbol KHz Tone Spacing 52 Subcarriers... frequency time a OFDM Symbol 20 MHz x 4 usecs = 80 samples ~16.25 MHz Equivalent to 64 Chip Codewords

21 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 21 of 22 Cyclic Extensions Can Be Used on Any Codeword Original Codeword Cyclically- Extended Codeword Smoothly Extends Sub-Carriers in Time

22 doc.: IEEE /202r1 Submission July 2000 Mark Webster, IntersilSlide 22 of 22 Summary 1 and 2 DSSS Barker code modulation is actually OFDM with 11 sub-carriers. Each sub-carrier uses phase-tilted QPSK. All sub-carriers are equal amplitude, but the center b 5.5 Mbps CCK is actually OFDM with 8 sub- carriers. Two sub-carriers carry QPSK. Two sub-carriers carry 5 QAM. Four sub-carriers carry 8 QAM b 11 Mbps CCK is actually OFDM with 8 sub- carriers. Four sub-carriers carry 9 QAM. Four sub-carriers carry 24 QAM. Cyclic extensions can be added to all these signals to eliminate the need for inter-block interference (IBI) equalization.


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