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Phase turbo-synchronization scheme

Phase turbo-synchronization scheme. NewCom dept 1 (CNRS 19) Lab. SATIE Benoit Geller, Jean-Pierre Barbot, Christophe Vanstraceele, Stéphanie Bay. a k. φ k. y k. Synchronization. Problem presentation. Transmitted Symbols. Received symbols. Noise b. phase rotation φ. ( chanel).

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Phase turbo-synchronization scheme

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  1. Phase turbo-synchronization scheme NewCom dept 1 (CNRS 19) Lab. SATIE Benoit Geller, Jean-Pierre Barbot, Christophe Vanstraceele, Stéphanie Bay

  2. ak φk yk Synchronization Problem presentation Transmitted Symbols Received symbols Noise b phase rotation φ (chanel) (receiver) 1024-QAM 00 01 10 11

  3. Synchronization • Data Aided estimator: pilot symbols, • Blind estimator : use properties of the signal, • Semi-blind Here : hight coding rate => use the properties of the turbo-decoder

  4. n1 2. the k2 rows are coded C1(n1,k1,d1), redundancy on the rows 3. the n1 columns are coded by C2(n2,k2,d2). n2 redundancy on redondancies redundancy on the columns Block Turbo-Codes Product code 1. k1×k2 information bits in a matrix, k1 Informative bits k2 • The otained code C = C1 × C2 parameters are : • n = n1 × n2 • k = k1 × k2 • d = d1 × d2

  5. Turbo codes blocs half an iteration of the R. Pyndiah’s Turbo decoder : SISO decoder (row or column)

  6. Block Turbo codes Computation of the soft output : Log-likelihood Evaluatation of the reliability of the Chase decision : where : with the concurrent code words of Ci such that with the concurrent code words of Ci such that

  7. Block Turbo codes Computation of the soft output : R. Pyndiah’s decoder with : = word of the code at minimal distance from R with its j ième bit at +1. = word of the code at minimal distance from R with its j ième bit at -1. Extrinsic Information Soft decision with : and

  8. Synchro : LLR Log_likelihood Distribution Constant phase offset on a code word demapping turbo decoder LLR

  9. Synchro : LLR Mean of the LLR absolute value R(l) = reliability of the l th code word. Absolute value Sort (growing order) Rtri(l )

  10. Synchro : LLR Linear drift Phase error due to linear drift demapping turbo decoder M(l)

  11. Synchro : LLR Estimator definition Received symboles Transmitted symbols k = 1 … K Built the sequence demapping turbo decoder Estimator :

  12. Synchro : Maximisation des LLR Algorithme du gradient Soft demapper Turbo decoder Estimator

  13. Synchro : LLR Dependancy on mf

  14. Synchro : LLR Mean Square Errors

  15. Synchro : Maximisation des LLR Mean Square Errors • large constellations, low SNR, • no pilot symbols, • No Phase ambiguity, • easy to implement. Brevet n°04O6290

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