LTE trials in the return channel over satellite

Integrating terrestrial and satellite communications promises several advantages, whereas the most evident one is that modern satellite networks achieve global coverage using a multiple spot beam architecture. In order to increase the spectral efficiency, orthogonal waveforms like single-carrier frequency-division multiple access (SC-FDMA) are investigated recently. In this paper, we verify experimentally that SC-FDMA waveforms taken from the 3GPP Long Term Evolution (LTE) standard can be transmitted reliably in the return channel over satellite using low-cost equipment. Mainly, we introduce an additional timing advance offset depending on satellite elevation and geographical location. And we ensure that precise information about the frequency offset measured in the forward channel is reused for compensation in the return channel at each terminal. We demonstrate in real-time transmission experiments over a geostationary Ku-band satellite that all modulation formats defined for the up-link in the LTE Release 8 standard can be decoded error-free. Using 16-QAM, we have realized a spectral efficiency of 3.2 bits/s/Hz.