The objective of the activity is to design, develop and test a signalling and control protocol for two-way user terminals with active antenna elements to adapt dynamically the beam forming, bandwidth allocation, symbol rate adjustment as well as half-duplex transmit/receive operation particularly designed for operation with standardised DVB-S2x and DVB-RCS2 like air interfaces. The signallingoverhead shall be below 1% of the link capacity. Targeted Improvements:Enabling a dynamic, inter-operable control and signalling protocol as part of the DVBs family of standards for user terminals with active antennas (not existing today). Description: Emerging satellite networks offer a wide range of flexibility to create two-way connectivity to user terminals with dynamically configurable frequency, bandwidth and beam allocation. At the user terminal side, there are also several solutions for phase array flat antennas being developed for possible deployment in the mass market. Compared to the conventional systems, the emerging satellite networks demand more flexible and dynamic adaptation of the link attributes, such as the bandwidth, symbol rate, transmit/receiver time plan (for half-duplex operation), beam forming calibration and control signalling. Although proprietary solutions may exist today to communicate and control such features, the need for a standardised protocol for such signalling is recognised by industry, as for example reflected in DVB long term vision (LTV) dossier. Taking DVB family of standards for satellite air interface and signalling as the starting point, this activity aims to build the capability of dynamically controlling and adjusting the link characteristics, particularly the satellite beam attributes such as frequency and bandwidth allocation. There is existing and on-going research on how to maintain maximum link quality by adjusting the user terminal phase steering azimuth and elevation based on closed-loop feedback from the gateway. This activity will design, develop and test a signalling and control protocol for two-way user terminals. Starting point is to investigate possible modifications or the use of existing features of the DVB family of protocols for satellite air interface (i.e. DVB-S2X and DVB-RCS2) as well as signalling protocols such as DVB-SI to implement solutions to support the following features for user terminals with active TX/RX antenna: dynamic reconfiguration of the forward link bandwidth and frequency, closed-loop control of the user terminal beamforming parameters (to maximise the link quality), schedule the transmit and receive of the two-way half-duplex user terminal (non-overlapping transmission and reception in time), schedule and adjust beam switching plan (in case of beamhopping systems). The results of development and verification is expected to be shared with standardisation technical working group such as DVB TM-S.