In a DVB-T network, a single channel is shared between transmitters associated with adjacent cells on a time-division basis. Timing allocation information signals are received at each transmitter, where it is determined therefrom and from a common time reference, such as a GPS receiver or atomic clock, when transmission is and is not allowed. Each of the transmitters then transmits on the channel at different times. The channel may carry Internet Protocol Data Cast Services. The timing allocation may be varied so that transmitters have unequal shares. The allocation may be dynamically controllable depending on demand. Using the invention, a saving of frequency spectrum is obtained without requiring channel rasterisation.