An interleaver (11b) for filling an interleaver matrix (51) used in interleaving a packet of bits for transmission as symbols via a wireless communication channel in a wireless communication system (11 12) including a modulator (11c), the interleaver (11b) having a number of rows (or columns, depending on whether bits are pulled column-wise or row-wise for encoding as symbols by the modulator) that is not divisible by the number of bits in a symbol, but having at least as many bits as in a packet, and so having, unavoidably, more elements than there are bits in a packet.