A 
digital video broadcast network comprises a content provider and several transmitters. Each 
transmitter may transmit more than one 
signal, different signals having different frequencies, multiplexes and the like and relating to different network types. An integrated 
receiver / decoder (IRD) is mobile in the area around the transmitters. As well as transmitting 
service information as part of a network information table on a data layer, the transmitters provide in their output signals 
transmitter parameter information as TPS data on a 
physical layer. This TPS information includes information identifying whether there are other networks available, and preferably the number of other networks. Transmission parameters relating to the other networks are included in an other_network_descriptor, forming part of an NIT actual or a BAT, or alternatively in an NIT_other. This information is used by the IRD in 
signal scan. Using the described broadcast signals, 
signal scan can be made more efficient, resulting in reduced 
power consumption and scanning time. IRDs may also receive 
free field three dimensional models of signal levels created for a group of cells. The models may be in the form of bitmaps and used during 
handover procedures.