Abstract: Methods for controlling orthogonal frequency division multiple access (OFDMA) communications over satellite links. The methods include estimating a differential delay in a satellite spotbeam between a mean propagation delay in the spotbeam and a propagation delay between a user terminal in the spotbeam and a satellite, estimating an overlap between an OFDMA uplink frame and an OFDMA downlink frame as a result of the differential delay, and providing a guard band in the OFDMA uplink frame and/or the OFDMA downlink frame to reduce an overlap between remaining portions of the OFDMA uplink frame and the OFDMA downlink frame other than the guard band. Corresponding systems and devices are also disclosed.

Abstract: A device for processing a digital signal of an optical transmission system is described. The device comprises: a polarization beam splitter for receiving the signal, a phase shifter for shifting the phase of the signal at the orthogonal output of the polarization beam splitter, and means for combining the signal at the parallel output of the polarization beam splitter and the shifted signal.

Abstract: A method of operating an optical transmission system is described. The transmission system is provided with a bit-to-bit polarization interleaved bitstream having a given bitrate. The transmission system comprises a birefringent element and/or a decision circuit. The birefringent element and/or the decision circuit are triggered by a trigger signal having a frequency of half of the bitrate.

Abstract: The invention disclose a device an a method for compensation of polarization mode dispersion comprising following steps: Measuring the degree of polarization of a signal at the receiver, Running an algorithm to find the maximum of degree of polarization, Comparing the degree of polarization with reference values of the compensation system in a data base, Switching the new starting point to the opposite side of the Poincare Sphere, when the reference value is under a definite threshold value and Selecting the new starting point from the data base.