1. Low PAPR Binary Preamble Design
September 2006
doc.: IEEE yy/xxxxr0
January 2007
Low PAPR Binary Preamble Design
IEEE P Wireless RANs Date:
Authors:
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Monisha Ghosh, Philips
Carlos Cordeiro, Philips

2. Advantage Of Binary Preambles
January 2007
Advantage Of Binary Preambles
Binary preambles enable very simple channel estimation, with no multiplications required.
Significant complexity advantage for large FFT sizes, e.g 2K-FFT systems.
Storage requirements are minimal: 1 bit per preamble symbol.
Generating the preambles with shift-registers eliminates the need for any storage of multiple sequences.
Monisha Ghosh, Philips

3. Method For Generating Binary Preambles.
January 2007
Method For Generating Binary Preambles.
General preamble structure in the frequency domain:
[0 p1 … pL 0 … 0 pL+1 … p2L]
Problem: Determine the sequences [p1..pL] and [pL+1 … p2L] to minimize PAPR of 4-times oversampled signal in the time domain.
Let N = smallest power of 2 > L. For example, if L = 840, choose N = 1024.
Pick a maximal length sequence of length N. For example, for N = 1024, choose x10 +x8 +x7 + x5 +1, and initialize the shift-register with all ones, to generate a sequence a(n).
Cyclically shift sequence a(n) by shift S1 and let [p1..pL] = first L values of shifted sequence.
Cyclically shift sequence a(n) by shift S2 and let [pL+1..p2L] = first L values of shifted sequence.
Form the preamble sequence [0 p1 … pL 0 … 0 pL+1 … p2L].
Take IFFT of oversampled preamble and evaluate PAPR.
Repeat for all combination of S1 and S2.
Pick the combination (S1, S2) that minimizes PAPR.
Monisha Ghosh, Philips

4. Example Assume L = 840 (1680 data+pilot carriers).
January 2007
Example
Assume L = 840 (1680 data+pilot carriers).
Superframe/frame short: training symbol on every 4th frequency.
Length 255 M-sequence: x8 + x7 +x3 + x2 + 1.
S1 = 226, S2 = 109; PAPR = dB
Frame long: training symbol on every 2nd frequency.
Length 511 M-sequence: x9 + x8 + x7 + x6 +x4 +x2 + 1
S1 = 256 S2 = 492; PAPR = dB
Superframe long: training symbol on every frequency.
Length 1023 M-sequence: x10 +x8 +x7 +x5 +1
S1 = 296, S2 = 808; PAPR = dB
If multiple preambles are required choose another generator, or another combination of (S1,S2).
Monisha Ghosh, Philips

5. PAPR Of Random QPSK Data
January 2007
PAPR Of Random QPSK Data
PAPR < 5 dB for the preamble sequences will be adequate.
Monisha Ghosh, Philips

6. January 2007
Conclusions
Binary preambles for various decimation factors can be easily generated with low PAPR.
Method presented leads to a very simple specification (generator + shifts) of sequences.
Monisha Ghosh, Philips