In this paper, we investigate the reduction of the shadowing fading margin that can be achieved with interburst upper layer forward error correction (UL-FEC) in terrestrial mobile broadcast systems with time slicing (i.e., discontinuous transmission). A theoretical framework is derived, for both streaming and file delivery services, as a function of the number of bursts jointly encoded, the UL-FEC code rate, the shadowing standard deviation, and the ratio between the moved distance by the user during the cycle time between bursts and the shadowing correlation distance. Results are validated with Digital Video Broadcasting-Handheld (DVB-H) and DVB-Satellite to Handhelds (DVB-SH) laboratory measurements.