Communication procedure in a mobile network

A method of communications between a primary station (100) and a plurality of secondary stations (110), wherein (a) the primary station (100) forms a secondary station (110) to search a first channel at least one of a plurality of search spaces (210a to 210c) having a first structure, said first structure consisting of at least a first number of resource sets, where at least one set of resources may be used to transmit a message to a secondary station; (B) the primary station (100) sets a characteristic of the first channel to a first value; and (c) the primary station (100) changes the characteristic of the first channel to a second value upon detection (250) of an event Capacity search spaces.