Direct Sequence Spread Spectrum Physical Layer Specification IEEE Prepared by Jan Boer, Chair DS PRY Lucent Technologies WCND Utrecht

Transcription

1 Direct Sequence Spread Spectrum Physical Layer Specification IEEE Prepared by Jan Boer, Chair DS PRY Lucent Technologies WCND Utrecht Copyright 1996 IEEE, All rights reserved, This contains parts from an unapproved draft, subject to change What is DSSS? ) Signal symbol is spreaded with a sequence I 1 +1 Less power density 'l"';'1'1---'i Frequency Frequency Cupyright 1996 IEEE, All rights reserved. This contains parts froln an unapproved draft, subjoctto change 2 1 Jan Boer, Lucent Technologies

2 11 chip BARKER sequence Good autocorrelation properties Minimal sequence allowed by FCC Coding gain 10.4 db +1., Copyright 1996 IEEE, AlL rights reserved. This contains parts from an unapproved draft, subject to change 3 DSSS benefits 10 db coding gain: - Robust against interferers and noise (10 db suppression) Robust against time delay spread - Resolution of echoes ClpyriShl 1996 IEEE, All rights reserved. This contains parts from an unapproved draft, subject to change 4 2 Jan Boer, Lucent Technologies

3 IEEE DSSS PRY characteristics 2.4 GHz ISM band (FCC ) 1 and 2 Mb/s datarate (DBPSK and DQPSK modulation) Symbolrate IMHz Chipping rate 11 MHz with 11 chip Barker sequence Multiple channels in 2.4 to GHz band Copyright 1996 IEEE, An rights reserved. This contains pam; from an unapproved draft, subject to change 5 PLCP Frame Format SIGNAL 8 bits SERVICE 8 bits PLCP Header 48blls PPDU Preamble and Header always at IMb/s nbpsk Copyrl,ght@1996lEEE, All rights reserved. This contains parts from an unapproved draft, subject to change 6 3 Jan Boer, Lucent Technologies

4 PLCP synchronization PPDU 128 scrambled I bits needed for o.a. gain setting energy detection antenna selection frequency offset compensation Copyright 1996 IEEE, All rights reserved. This contains parts from an unapproved draft, subject to change 7 Start Frame Delimiter 16 bit field (hf3ao) used for - bit synchronization Copyright 1996 IEEE, All rights reserved. This contains parts from an unapproved draft, subject to change 4 Jan Boer, Lucent Technologies

5 Signal Field PPDU Rate indication hoa IMb/s DBPSK h14 2Mb/s DQPSK Other values reserved for future use (100 kb/s quantities) Copyright 19961EEE, All rights reserved. This contains parts from an unapproved draft, subject to change 9 Service Field Reserved for future use hoo signifies compliant CopyrigliL EEE, All rights reserved. This contains parts from an unapproved draft. subject to change 10 5 Jan Boer, Lucent Technologies

6 Length Field PPDU Indicates number of octets to be transmitted in MPDU Used for End of frame detection MPDU CRC sync Copyright 1996 IEEE, All rights reserved. This contains part<; from an unapproved draft, subject to change 11 CRC field PPDU CCITT CRC-16 Protects Signal, Service and Length Field Copyright 1996 IEEE, All rights reserved. This contains parts from an unapproved draft, subject to change 12 6 Jan Boer, Lucent Technologies

7 Data Scrambler Scrambler Polynomial; G(z)=Z" +Z lr SERIAL DATA I I I~ I Z 1 Z 2 Z.. Z ,r---+l~ ZoO Z.. Z ' I----, r ~ ~~ALDATA ALL bits transmitted by the DSSS Phy are scrambled Purpose Whithening the spectrum DC blocking (Barker sequnce is asymetric) Copyrig hl 1996 IEEE, All righ" reserved. This contains parts from an unapproved draft, subject to change 13 DBPSK Modulation Q BitInput o Phase Change (+jro) Table 1, 1 Mbls OBPSK Encoding Table. o 1t Copyright 1996lEEE, All rights reserved. This contains parts from an unapproved draft, subject to change 14 7 Jan Boer, Lucent Technologies

8 DQPSK Modulation Q Dibit pattern (do,dl) do is lirst in time Phase Change (+jm) f f12 (-1f12) Table 1, 2 Mbfs OQPSK Encoding Table Copyright 1996 IEEE, All rights reserved. This contains parts from an unapproved draft, subject to change 15 Transmit Spectrum Mask Transmit Spectrum Mask Unfiltered Sinxlx -50 db fc -22 MHz fc -11 MHz fc fc +11 MHz fc +22 Mhz Copyrigh.@1996IEEE,Allrightsreserved. This contains pans from an unapproved draf., subjec o change 16 8 Jan Boer, Lucent Technologies

9 DSSS Channels CHNL_ID FCC ETSI Channel Japan Channel Frequencies Frequency Frequencies MHz N/A N/A MHz N/A N/A MHz 2422 MHz N/A MHz 2427 MHz N/A MHz 2432 MHz N/A MHz 2437 MHz N/A MHz 2442 MHz N/A MHz 2447 MHz N/A MHz 2452 MHz N/A MHz 2457 MHz N/A MHz 2462 MHz N/A 12 N/A NJA 2484 MHz Table 1, DSSS PHY Frequency Channel Plan Copyright 1996 IEEE. All rights reserved. This contains parts from an unapproved draft, subject to change 17 Clear Channel Assessment Three methods: - CCA mode 1: Energy above threshold - CCA mode 2: Carrier sense only - CCA mode 3: Carrier sense with energy above threshold Energy detection function of TX power - Tx power> 100 mw: -80 dbm - Tx power> 50mW : -76 dbm - Tx power < = 50mW: -70dBm Energy detect time : 15 Jls Correct PLCP header --> CCA busy for full (intended) duration of of frame as indicated by PLCP Length field Copyright 1996 IEEE. All rights reserved. This contains parts from an unapproved draft. subject to change 18 9 Jan Boer, Lucent Technologies

10 DSSS Specification Summary Slottime TX to Rx turnaround time Rx to Tx turnaround time Operating temperature range type 1: 0-40 C type 2: C Tx Power Levels 1000mW USA 100mW Europe 10 mwimhz Japan Minimum Transmitted Power Tx power level control 20 Ils 10 Ils 5 Ils 1 m W required above 100 m W Copyright 1996 IEEE, All rights reserved. Thjs contains parts from an unapproved draft. subject to change 19 DSSS Specification Summary (cant) Tx Center Frequency Tolerance Chip Clock Frequency Tolerance Tx Power On Ramp Tx Power Down Ramp RF Carrier suppression Transmit modulation accuracy Rx sensitivity Rx max input level Rx adjacent channel rejection +/- 25 ppm +/- 25 ppm 21ls 21ls 15 db test procedure FER (1024 Bytes) -4 db >35 > 30 MHz separation Copyright 1996 IEEE, All rights reserved. This contains parts from an unapproved draft, subject to change Jan Boer, Lucent Technologies

11 PLCP Transmit Procedure MAC PHY PLCP PMD_ANTSEL, PMD_RATE, PMD_ TXPWRLVL, PMD_TXSTART PHY PMD SYNC MPDU Scramble start CRC16 CRC16 Rate change start TX Power TX Power RAMP start end RAMP off Copyngh' 1996 IEEE, AlL righ<s reserved. This cdnmins parts from an unapproved draft, subject'" change 21 PLCP Receive Procedure MAC PHY _DATA.ind(DATA) PHY _RXSTART.ind(RXVECTOR).,...""... PHY PLCP PHY PMD Descramble start CRC CRC Rate change start start end Co pyri lth~ 1996 I.~EE, All rights reserved. This contains parts from an unapproved draft, subject to change Jan Boer, Lucent Technologies

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