a/g Kernel Identification Saba Zia Bilal Saqib

2 Physical Layer Architecture and Kernel Identification (802.11a) Ref: IEEE Std a-1999(R2003)

3 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 4  127 bit frame synchronous scrambler  S(x)=x 7 +x 4 +1 Ref: IEEE Std a-1999(R2003)

Individual Properties of each Kernel Convolutional Encoder/ Viterbi Decoder 5  R = ½, 2/3, ¾  For R= 1/2, G 0 =133 8 G 1 =  Decoding by Viterbi Algorithm Ref: IEEE Std a-1999(R2003)

Individual Properties of each Kernel Puncturing/De-puncturing Patterns 6 Ref: IEEE Std a-1999(R2003)

Individual Properties of each Kernel Puncturing/De-puncturing Patterns 7 Ref: IEEE Std a-1999(R2003)

Individual Properties of each Kernel Data Interleaver/ Deinterleaver  Block size corresponding to the number of bits in a single OFDM symbol, NCBPS  Two-step permutation  i = (N CBPS /16) (k mod 16) + floor(k/16) where k = 0,1,…,N CBPS – 1  j = s × floor(i/s) + (i + N CBPS – floor(16 × i/N CBPS )) mod s where i = 0,1,… N CBPS – 1  The value of s is determined by the number of coded bits per subcarrier, N BPSC, according to s = max(N BPSC /2,1) 8

Individual Properties of each Kernel Subcarrier Modulation Mapping  BPSK,QPSK,16 QAM or 64 QAM depending on the rate requested  Gray coded constellation mappings  Resultant, d = (I + jQ) X K MOD 9 Ref: IEEE Std a-1999(R2003)

Individual Properties of each Kernel OFDM 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 10

Individual Properties of each Kernel OFDM modulation (IFFT) 11 Ref: IEEE Std a-1999(R2003)

Individual Properties of each Kernel Guard 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. 12 Ref: IEEE Std a-1999(R2003)

Rate Dependent Parameters 13 Ref: IEEE Std a-1999(R2003)

Timing Related Parameters 14 Ref: IEEE Std a-1999(R2003)

Physical Layer Architecture and Kernel Identification (802.11g)  g offers four operational modes DSSS /CCK DSSS /CCK OFDM (Kernels identical to a) OFDM (Kernels identical to a) PBCC (optional) PBCC (optional) DSSS/OFDM (optional) DSSS/OFDM (optional) 15

DSSS/CCK based kernels  CRC  Data Scrambler/Descrambler  DQPSK/DBPSK 16