September 1998 doc.: IEEE 802.11-98/315 September, 1998 doc.: IEEE 802.11-98/315 September, 1998 doc.: IEEE 802.11-98/315 Summary • CCK modulation will enable 11 MBps operation in the 2.4 GHz ISM band The CCK 11 MBps Modulation for • An interoperable preamble and a short preamble IEEE 802.11 2.4 GHz WLANs will allow both interoperability and co-existence with low rate LANs Mark Webster and Carl Andren Harris Semiconductor With support from: Jan Boer and Richard van Nee Lucent Technologies Submission Submission Slide 1 Slide 2 Carl Andren, Harris Semiconductor Carl Andren, Harris Semiconductor September, 1998 doc.: IEEE 802.11-98/315 September, 1998 doc.: IEEE 802.11-98/315 Preamble Length PACKET WITH LONG PREAMBLE • Our basic approach is to include the standard DS or FH 802.11 preamble and header SCRAMBLED ONES • This length includes ample time to do diversity 1 MBPS DBPSK SYNC SFD SIGNAL SERVICE LENGTH CRC and equalization 128bits 16 bits 8 bits 8 bits BARKER 16 bits 16 bits • For the cases where interoperability is not an PLCP Preamble PLCP Header MPDU issue, a short, high rate header can be used. 144 bits 48 bits 192 us • Antenna diversity, WEP initialization and PPDU 1 DBPSK BARKER equalizer training require a somewhat longer 2 DQPSK BARKER 5.5 or 11 Mbps CCK short preamble than the shortest possible. Submission Submission Slide 3 Slide 4 Carl Andren, Harris Semiconductor Carl Andren, Harris Semiconductor September, 1998 doc.: IEEE 802.11-98/315 September, 1998 doc.: IEEE 802.11-98/315 SHORT PREAMBLE TIME LINE PACKET WITH SHORT PREAMBLE ANTENNA DIVERSITY: SIGNAL PRESENT AT BOTH ANTENNAS SCRAMBLED CCA CCA CCA BACKWARDS ZEROS SLOT k SLOT k+1 SLOT k+2 SFD µ SEC: µ shortSYNC shortSFD 0 5 10 15 20 25 30 35 40 45 50 55 60 56 bits 16 bits DBPSK BARKER SIGNAL SERVICE LENGTH CRC MPDU SYNC SFD 8 bits 8 bits 16 bits 16 bits TAIL 5.5 Mbps CCK 56 µ µ Sec PLCP Header MPDU shortPLCP Preamble 72 bits @ 1 Mbit/s 48 bits @ 5.5 Mbit/s variable @ 5.5 or 11 Mbit/s Hit No No Hit Hit AGC CIR & Freq AGC CIR & Freq Switch Ant. Hit Hit Estimate Estimate & 80.7 us Ant A Ant B Ant A Ant B Ant A Ant B Ant B Ant A Ant A SFD Search PPDU AGC LOCK AGC LOCK ANTENNA SWITCH DUE TO TRANSPORT ON ANT B ON ANT A SELECT LAG Submission Slide 5 Submission Slide 6 Carl Andren, Harris Semiconductor Carl Andren, Harris Semiconductor Submission
September 1998 doc.: IEEE 802.11-98/315 September, 1998 doc.: IEEE 802.11-98/315 September, 1998 doc.: IEEE 802.11-98/315 SHORT PREAMBLE TIME LINE SHORT PREAMBLE PERFORMANCE ANTENNA DIVERSITY: SIGNAL FADED ON ANTENNA B JAM CIR ESTIMATE AGC AND FREQ OFFSET CCA CCA CCA LOCK SLOT k SLOT k+1 SLOT k+2 AGC PREAMBLE PACKET-ERROR-RATE SIMULATION SIMULATION SIMULATION µ µ SEC: 0 5 10 15 20 25 30 35 40 45 50 55 60 SYNC SYNC MPDU 10 µ µ Sec 10 µ µ Sec MPDU SFD SYNC TAIL 56 µ µ Sec SIMULATION PARAMETERS FREQ OFFSET: 50 PPM 64 BYTE PACKETS (Equalized RAKE) Hit No No No Hit No AGC CIR & Freq SFD Search STATE: Linear (AGC locked) DELAY SPREAD @ 10% PER: 350 nsec Hit Hit Hit Hit Estimate TIME SPAN: 10 µ µ sec of Sync Ant A Ant B Ant A Ant B Ant A Ant B Ant A Ant A Eb/No @ 20% PER with 350 nsec: 15.5 dB SAMPLE RATE: 2 per Chip CIR ESTIMATES: 11 Chip SWITCH DUE AGC LOCK CMF: Used CIR estimate TO TRANSPORT ON ANT A LAG Submission Submission Slide 7 Slide 8 Carl Andren, Harris Semiconductor Carl Andren, Harris Semiconductor September, 1998 doc.: IEEE 802.11-98/315 September, 1998 doc.: IEEE 802.11-98/315 Throughput Comparison Acknowledged Packets FH Interoperability Preamble 10.00 9.00 8.00 PLW PSF CRC FH SYNC FH SFD 80 bits 16 bits 12 bits 4 bits 16 bits 7.00 6.00 Short Preamble Mbps 5.00 Long Preamble FH PLCP Preamble FH PLCP Header Short PLCP 2 Mbps 96 bits MPDU 32 bits 120 BITS 4.00 GAP 128 us 3.00 PPDU 2.00 1.00 0.00 64 128 192 256 320 384 448 512 576 640 704 768 832 896 960 1024 1088 1152 1216 1280 1344 1408 1472 1536 1600 Bytes/Packet Submission Submission Slide 9 Slide 10 Carl Andren, Harris Semiconductor Carl Andren, Harris Semiconductor September, 1998 doc.: IEEE 802.11-98/315 September, 1998 doc.: IEEE 802.11-98/315 Signal Field Length Field • The 8 bit 802.11 Signal Field indicates to the PHY the modulation • Since there is an ambiguity in the number of octets that will be described by a length in microseconds for any data rate over 8 Mbit/s, an extra bit will be placed in the service which shall be used for transmission (and reception) of the MPDU. field to indicate when the smaller potential number is correct. The data rate shall be equal to the Signal Field value multiplied by • 5.5Mbit/s CCK Length = #octets * 8/5.5, rounded up to the next integer. 100kbit/s. The extended DSSS PHY supports four mandatory modulation services given by the following 8 bit words, where the • 11Mbit/s CCK Length = #octets * 8/11 , rounded up to the next integer LSB shall be transmitted first in time: and the service field LSB bit shall indicate a ‘0’ if the rounding took less than 8/11 or a ‘1’ if the rounding took more than 8/11. – 0Ah (MSB to LSB) for 1 Mbit/s DBPSK • At the receiver, the number of octets in the MPDU is calculated as follows: – 14h (MSB to LSB) for 2 Mbit/s DQPSK • 5.5Mbit/s CCK #octets = Length * 5.5/8, rounded down to the next integer – 37h (MSB to LSB) for 5.5 Mbit/s CCK • 11Mbit/s CCK #octets = Length * 11/8 , rounded down to the next integer, – 6Eh (MSB to LSB) for 11 Mbit/s CCK minus 1 if the service field LSB bit is a ‘1’. Submission Slide 11 Submission Slide 12 Carl Andren, Harris Semiconductor Carl Andren, Harris Semiconductor Submission
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