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).

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.

The growing demand for transmission capacity for mobile access has led in recent years public administrations to consider new ways of spectrum management, which include sharing between different services and operators. At the invitation of the Italian Ministry of Economic Development we have participated and contributed to a field experiment aimed at assessing the problems of interference eventually suffered by Fixed Services (Radio Links for TV contribution / distribution) by LTE services in the 3.6-3.7 GHz band.