802.11a/g Kernel Identification
description
Transcript of 802.11a/g Kernel Identification
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802.11a/g Kernel 802.11a/g Kernel IdentificationIdentification
Saba ZiaSaba Zia
Bilal SaqibBilal Saqib
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Physical Layer Architecture and Kernel Physical Layer Architecture and Kernel Identification (802.11a)Identification (802.11a)
Ref: IEEE Std 802.11a-1999(R2003)
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Physical Layer Architecture and Kernel Physical Layer Architecture and Kernel IdentificationIdentification
Data Scrambler/ DescramblerData Scrambler/ Descrambler
Convolutional Encoder / Viterbi decoder
Convolutional Encoder / Viterbi decoder
Data interleaver/ DeinterleaverData interleaver/ Deinterleaver
Guard interval insertionGuard interval insertion
OFDM modulationOFDM modulation
Subcarrier Modulation Mapping
Subcarrier Modulation Mapping
Individual Properties of each KernelIndividual Properties of each KernelData Scrambler/DescramblerData Scrambler/Descrambler
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127 bit frame synchronous scrambler127 bit frame synchronous scrambler S(x)=xS(x)=x77 +x +x44 +1 +1
Ref: IEEE Std 802.11a-1999(R2003)
Individual Properties of each KernelIndividual Properties of each KernelConvolutional Encoder/ Viterbi DecoderConvolutional Encoder/ Viterbi Decoder
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R = ½, 2/3, ¾R = ½, 2/3, ¾ For R= 1/2, GFor R= 1/2, G00=133=13388 G G11 = 171 = 17188
Decoding by Viterbi AlgorithmDecoding by Viterbi AlgorithmRef: IEEE Std 802.11a-1999(R2003)
Individual Properties of each KernelIndividual Properties of each KernelPuncturing/De-puncturing PatternsPuncturing/De-puncturing Patterns
66Ref: IEEE Std 802.11a-1999(R2003)
Individual Properties of each KernelIndividual Properties of each KernelPuncturing/De-puncturing PatternsPuncturing/De-puncturing Patterns
77Ref: IEEE Std 802.11a-1999(R2003)
Individual Properties of each KernelIndividual Properties of each KernelData Interleaver/ DeinterleaverData Interleaver/ Deinterleaver
Block size corresponding to the number Block size corresponding to the number of bits in a single OFDM symbol, NCBPSof bits in a single OFDM symbol, NCBPS
Two-step permutationTwo-step permutation i = (Ni = (NCBPSCBPS/16) (k mod 16) + floor(k/16) where k = 0,1,/16) (k mod 16) + floor(k/16) where k = 0,1,
…,N…,NCBPS CBPS – 1– 1
j = s × floor(i/s) + (i + Nj = s × floor(i/s) + (i + NCBPSCBPS – floor(16 × i/N – floor(16 × i/NCBPSCBPS)) mod s )) mod s
where i = 0,1,… Nwhere i = 0,1,… NCBPSCBPS – 1 – 1
The value of s is determined by the number of coded bits per The value of s is determined by the number of coded bits per subcarrier, Nsubcarrier, NBPSCBPSC, according to s = max(N, according to s = max(NBPSCBPSC/2,1)/2,1)
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Individual Properties of each KernelIndividual Properties of each KernelSubcarrier Modulation MappingSubcarrier Modulation Mapping
BPSK,QPSK,16 QAM or 64 QAM BPSK,QPSK,16 QAM or 64 QAM depending on the rate requesteddepending on the rate requested
Gray coded constellation mappingsGray coded constellation mappings Resultant, d = (I + jQ) X KResultant, d = (I + jQ) X KMODMOD
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Ref: IEEE Std 802.11a-1999(R2003)
Individual Properties of each KernelIndividual Properties of each KernelOFDM modulation (IFFT)OFDM modulation (IFFT)
Divide the complex number string into groups of 48 complex Divide the complex number string into groups of 48 complex numbers. Each such group will be associated with one OFDM numbers. Each such group will be associated with one OFDM symbol.symbol.
Each complex number is mapped into OFDM subcarriers Each complex number is mapped into OFDM subcarriers numbered –26 to –22, –20 to –8, –6 to –1, 1 to 6, 8 to 20, and 22 numbered –26 to –22, –20 to –8, –6 to –1, 1 to 6, 8 to 20, and 22 to 26. to 26.
The “0” subcarrier, associated with center frequency, is omitted The “0” subcarrier, associated with center frequency, is omitted and filled with zero value. and filled with zero value.
Four subcarriers are inserted as pilots into positions –21, –7, 7, Four subcarriers are inserted as pilots into positions –21, –7, 7, and 21. The total number of the subcarriers is 52 (48 + 4). and 21. The total number of the subcarriers is 52 (48 + 4).
For each group of subcarriers –26 to 26, convert the subcarriers For each group of subcarriers –26 to 26, convert the subcarriers to time domain using inverse Fourier transformto time domain using inverse Fourier transform
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Individual Properties of each KernelIndividual Properties of each KernelOFDM modulation (IFFT)OFDM modulation (IFFT)
1111Ref: IEEE Std 802.11a-1999(R2003)
Individual Properties of each KernelIndividual Properties of each KernelGuard Interval InsertionGuard Interval Insertion
Prepend to the Fourier-transformed waveform a circular extension Prepend to the Fourier-transformed waveform a circular extension of itself thus forming a GI, and truncate the resulting periodic of itself thus forming a GI, and truncate the resulting periodic waveform to a single OFDM symbol length by applying time waveform to a single OFDM symbol length by applying time domain windowing. domain windowing. 1212
Ref: IEEE Std 802.11a-1999(R2003)
Rate Dependent ParametersRate Dependent Parameters
1313Ref: IEEE Std 802.11a-1999(R2003)
Timing Related ParametersTiming Related Parameters
1414Ref: IEEE Std 802.11a-1999(R2003)
Physical Layer Architecture and Kernel Physical Layer Architecture and Kernel Identification (802.11g)Identification (802.11g)
802.11g offers four operational modes802.11g offers four operational modesDSSS /CCK DSSS /CCK OFDM (Kernels identical to 802.11a)OFDM (Kernels identical to 802.11a)PBCC (optional)PBCC (optional)DSSS/OFDM (optional)DSSS/OFDM (optional)
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DSSS/CCK based kernelsDSSS/CCK based kernels
CRCCRC Data Scrambler/DescramblerData Scrambler/Descrambler DQPSK/DBPSKDQPSK/DBPSK
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