Rai CRIT, in cooperation with RaiWay, launched in 2015 an experimental trial in Aosta Valley where two data streams share the same UHF channel in time-division: one conveys conventional HDTV programs targeting domestic DVB-T2 receiver, and a second one conveys a flow intended for 4G LTE-A+ devices such as smart-phones and tablets.

This brief note describes the context in which we operated, introduces the concept of Tower Overlay over LTE-A + (TOoL +) and shows the results of the trial carried out in the Aosta Valley.

In October 2016, at the Laboratory of Rai CRIT, it was carried out a series of tests on the demonstrator for time synchronization and frequency alternative to GNSS (Global Navigation Satellite System), developed by Antares S.c.ar.l under the European Demeter project, in collaboration with INRIM.
The tests have allowed us to evaluate the behavior of the developed system, especially in reference to the specific needs for synchronization of a network of DTT transmitters in single frequency (SFN).

Rai CRIT, in cooperation with Production Engineering, carried out theoretical evaluation and laboratory tests on the equipment currently used for the transmission of the signals coming from motorcycles shooting between aircraft (or helicopter) and OB Van. The objective was to evaluate the efficiency and the operating limits of the system currently in use in Rai, and try to analyze and propose the necessary improvements. In three laboratory sessions were measured performance of the equipment and the antennas available. We analyzed various modulation schemes and the effect of vibration of the aircraft on the antennas. Problems and issues have been identified and solutions were proposed.

The  Research Center in co-operation with Rai Way has launched in Aosta Valley on UHF channel 53 a second  DVB-T2 transmitter located in Salirod-Saint Vincent that, along with the transmitter Gerdaz-Aosta, installed in 2012, allowed to set up a DVB-T2 a small regional single frequency network test bed. This field trial has allowed us to experience the typical issues associated with a SFN: synchronization of transmitters, assessment of the areas of overlapping coverage, delays inserted to avoid static interference zones etc

The Research Center, after experimenting in the laboratory the first prototypes of DVB-T2 lite, activated in Aosta Valley a single frequency network  on UHF channel 53 in order to test the potential offered by the new system . The scheme chosen for the testing involves the use of “mixed” system: the T2 signal is split into two sub frames, one compatible with the standard T2 base, the other T2 lite, optimized respectively for fixed and mobile reception . The four transmitters of Gerdaz, Salirod, Arpy and Courtil radiate a bouquet consists of three HD programs for the T2 base and from one to three services oriented to mobile reception for the T2 lite.