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802.11a/g Kernel Identification. Saba Zia Bilal Saqib. Physical Layer Architecture and Kernel Identification (802.11a). Ref: IEEE Std 802.11a-1999(R2003). Physical Layer Architecture and Kernel Identification. Data Scrambler/ Descrambler. Convolutional Encoder / Viterbi decoder.

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802 11a g kernel identification

802.11a/g Kernel Identification

Saba Zia

BilalSaqib


Physical layer architecture and kernel identification 802 11a
Physical Layer Architecture and Kernel Identification (802.11a)

Ref: IEEE Std 802.11a-1999(R2003)


Physical layer architecture and kernel identification
Physical Layer Architecture and Kernel Identification

Data Scrambler/ Descrambler

Convolutional Encoder / Viterbi decoder

Data interleaver/ Deinterleaver

Guard interval insertion

OFDM modulation

Subcarrier Modulation Mapping


Individual properties of each kernel data scrambler descrambler
Individual Properties of each KernelData Scrambler/Descrambler

127 bit frame synchronous scrambler

S(x)=x7 +x4 +1

Ref: IEEE Std 802.11a-1999(R2003)


Individual properties of each kernel convolutional encoder viterbi decoder
Individual Properties of each KernelConvolutional Encoder/ Viterbi Decoder

  • R = ½, 2/3, ¾

  • For R= 1/2, G0=1338 G1 = 1718

  • Decoding by Viterbi Algorithm

Ref: IEEE Std 802.11a-1999(R2003)


Individual properties of each kernel puncturing de puncturing patterns
Individual Properties of each KernelPuncturing/De-puncturing Patterns

Ref: IEEE Std 802.11a-1999(R2003)


Individual properties of each kernel puncturing de puncturing patterns1
Individual Properties of each KernelPuncturing/De-puncturing Patterns

Ref: IEEE Std 802.11a-1999(R2003)


Individual properties of each kernel data interleaver deinterleaver
Individual Properties of each KernelData Interleaver/ Deinterleaver

  • Block size corresponding to the number of bits in a single OFDM symbol, NCBPS

  • Two-step permutation

    • i = (NCBPS/16) (k mod 16) + floor(k/16) where k = 0,1,…,NCBPS – 1

    • j = s × floor(i/s) + (i + NCBPS – floor(16 × i/NCBPS)) mod s where i = 0,1,… NCBPS – 1

  • The value of s is determined by the number of coded bits per subcarrier, NBPSC, according to s = max(NBPSC/2,1)


Individual properties of each kernel subcarrier modulation mapping
Individual Properties of each KernelSubcarrier Modulation Mapping

BPSK,QPSK,16 QAM or 64 QAM depending on the rate requested

Gray coded constellation mappings

Resultant, d = (I + jQ) X KMOD

Ref: IEEE Std 802.11a-1999(R2003)


Individual properties of each kernel ofdm modulation ifft
Individual Properties of each KernelOFDM modulation (IFFT)

Divide the complex number string into groups of 48 complex numbers. Each such group will be associated with one OFDM symbol.

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 to 26.

The “0” subcarrier, associated with center frequency, is omitted and filled with zero value.

Four subcarriers are inserted as pilots into positions –21, –7, 7, and 21. The total number of the subcarriers is 52 (48 + 4).

For each group of subcarriers –26 to 26, convert the subcarriers to time domain using inverse Fourier transform


Individual properties of each kernel ofdm modulation ifft1
Individual Properties of each KernelOFDM modulation (IFFT)

Ref: IEEE Std 802.11a-1999(R2003)


Individual properties of each kernel guard interval insertion
Individual Properties of each KernelGuard Interval Insertion

Prepend to the Fourier-transformed waveform a circular extension of itself thus forming a GI, and truncate the resulting periodic waveform to a single OFDM symbol length by applying time domain windowing.

Ref: IEEE Std 802.11a-1999(R2003)


Rate dependent parameters
Rate Dependent Parameters

Ref: IEEE Std 802.11a-1999(R2003)


Timing related parameters
Timing Related Parameters

Ref: IEEE Std 802.11a-1999(R2003)


Physical layer architecture and kernel identification 802 11g
Physical Layer Architecture and Kernel Identification (802.11g)

  • 802.11g offers four operational modes

    • DSSS /CCK

    • OFDM (Kernels identical to 802.11a)

    • PBCC (optional)

    • DSSS/OFDM (optional)


Dsss cck based kernels
DSSS/CCK based kernels (802.11g)

CRC

Data Scrambler/Descrambler

DQPSK/DBPSK


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