| 1 | function [rc, phiests] = phaseNoiseCorr(r, M, phoffset, blocksize) |
| 2 | %% Phase noise correction. |
| 3 | %% Inputs: |
| 4 | %% - r: Received symbols |
| 5 | %% - M: Order of constellation, M=4 for QPSK |
| 6 | %% - phoffset: Phase of the 0th symbol in the constellation |
| 7 | %% - blocksize: Viterbi-Viterbi algorithm block size |
| 8 | %% Outputs: |
| 9 | %% - rc: Symbols with corrected phase |
| 10 | %% - phiests: Estimates of the phase noise |
| 11 | |
| 12 | n = length(r); |
| 13 | phiests = zeros(1, n); |
| 14 | rc = zeros(1, n); |
| 15 | |
| 16 | for l = 1 : blocksize : n |
| 17 | block = r(l : min(l + blocksize - 1, n)); |
| 18 | |
| 19 | sum_M = sum(block .^ M); |
| 20 | phi_est = angle(sum_M .* exp(1j * M * phoffset)) / M; |
| 21 | |
| 22 | if l > 1 |
| 23 | %% Phase unwrapping |
| 24 | phi_prev = phiests(l - 1); |
| 25 | m = floor(0.5 + (phi_prev - phi_est) * M / (2 * pi)); |
| 26 | phi_est = phi_est + m * 2 * pi / M; |
| 27 | end |
| 28 | |
| 29 | block = block .* exp(1j * -phi_est); |
| 30 | rc(l : min(l + blocksize - 1, n)) = block; |
| 31 | phiests(l : min(l + blocksize - 1, n)) = phi_est; |
| 32 | end |
| 33 | end |