Upgrade of trigger and data acquisition systems for the LHC experiments

The Large Hadron Collider (LHC) and its experiments demonstrated high performance over the first two years of operations, producing many physics results. However, the actual beam conditions are far from the nominal ones, which will be reached in the next years after following shutdown periods, mandatory to upgrade and maintain the accelerator complex. Further, there is a plan of increasing the delivered instantaneous luminosity beyond the design value up to 5 times of it, i.e. 5x10(34) cm(-2s-1), which will allow the experiments to collect much higher integrated luminosity than initially anticipated, opening many new physics programs. New requirements on the read-out and trigger systems of the LHC experiments are required, thus an upgrade plan is on the way to be established. Moreover, technology improves and more performing detectors can be adopted and some components need to be replaced since they have been damaged by the radiation. This talk presents, after a brief introduction to the present status of the read-out system of the LHC experiments, an overview of the various R&D upgrade possibilities at various phases from now to the highest luminosity LHC period. In particular, we will focus on the evolution of the DAQ systems to cope with the new trigger requirements and the integration of sub-detectors with new back-end electronics.