Synchronization process in optical frequency division multiplexing transmission systems

摘要

The present invention discloses a synchronization method suitable for increasing the receiving speed in the receiving part of an orthogonal optical frequency division multiplexing (OOFDM) transceiver.

主权项

1. A symbol synchronization method in a receiving part of an optical orthogonal frequency division multiplexing (OOFDM) transceiver that comprises the steps of:
a) converting incoming real-valued samples from serial to parallel into two orthogonal frequency division multiplexing (OFDM) symbol groups wherein one group contains an original copy of the symbols and the other group contains a time-delayed copy of the symbols; b) performing a first subtraction operation between sample at position x of the original symbol copy and sample at position x+N−L of the time-delayed copy wherein N is the total number of samples and L is a length of a cyclic prefix; c) storing a first absolute value of the first subtraction in position x of a synchronization register; d) performing a next subtraction operation between sample at position x+1 x of the original symbol copy and sample at position x+1+N−L of its time-delayed copy counterpart; e) storing a next absolute value of the next subtraction in position x+1 of the synchronization register; f) repeating the subtraction operation until x=N and selecting a subsequent sample as x=1; g) when the synchronization register is full, reallocating each slot of the synchronization register with subsequent round of subtractions wherein random noise and inter-symbol interference is minimized by averaging each new value with the value stored previously using equation y(n)=α·x(n)+(1−α)·y(n−1) wherein α is a coefficient controlling the growth of the calculated value, y(n−1) is a synchronization vector previously stored in the synchronization register and x(n) is a new synchronization vector; h) repeating the operation over at most 500 blocks of symbols as needed to generate a synchronization profile; i) inverting the synchronization profile in order to generate a window; j) calculating a centre of gravity of the window in order to determine a synchronization signal position; k) convolving the window of step j) with a Gaussian window having its centre positioned at the position of the synchronization signal.