Abstract: A method of spatial modulation to identify a transmitter within a transmission array, wherein the transmitter has a unique bit sequence and defines a spatial component indicative of relative location is disclosed, comprising the following steps: receiving transmitted bits from the transmission array and identifying the unique bit sequence, the spatial component and a signal components; encoding the unique bit sequence and the spatial component by grouping the transmitters into transmitter groups such that the transmitters in each group have a maximum spatial separation relative to one another to thereby form an encoded signal; decoding the encoded signal to identify the transmitter from which the transmitted bits were transmitted by determining the transmitter location from the or each group. The method preferably comprises trellis coded spatial modulation.