Phase turbosynchronization scheme New Com dept 1 CNRS

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

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

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

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

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

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

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

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

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

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

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

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

Synchro : LLR Dependancy on mf

Synchro : LLR Mean Square Errors

Synchro : Maximisation des LLR Mean Square Errors Ø large constellations, low SNR, Ø No Phase ambiguity, Ø no pilot symbols, Ø easy to implement. Brevet n° 04 O 6290