A mobile wireless communications device comprising: an antenna; and a receiver coupled to said antenna and being configured to use a modulation having memory for a received message in a block structure, the block structure including a pair of mini-probes (21a, 21b) and a body therebetween, and to demodulate the received message by at least determining a corresponding set of received signal characteristic values based upon the pair of mini-probes (21a, 21b), wherein said determining the set of characteristic values comprises determining whether a channel estimate is minimum-phase or non minimum-phase; determining a decode starting point in the body based upon the set of received signal characteristic values, from the decode starting point, decoding the body in a first time direction, and decoding the body in a second time direction based upon at least one result of the decoding in the first direction, wherein said determining the decode starting point comprises at least: determining for each mini-probe (21a, 21b) the received signal characteristic value for a respective end portion of the body; and selectively time reversing the mini-probes (21a, 21b) and body to provide the decode starting point at the end having a desired value for the received signal characteristic value, such that the channel estimate appears always as minimum-phase; and wherein said receiver is configured to determine the channel estimate across the body based upon interpolating respective channel estimates from the mini-probes (21a, 21b) constrained by a maximum expected Doppler spread tolerance. an antenna; and a receiver coupled to said antenna and being configured to use a modulation having memory for a received message in a block structure, the block structure including a pair of mini-probes (21a, 21b) and a body therebetween, and to demodulate the received message by at least determining a corresponding set of received signal characteristic values based upon the pair of mini-probes (21a, 21b), wherein said determining the set of characteristic values comprises determining whether a channel estimate is minimum-phase or non minimum-phase; determining a decode starting point in the body based upon the set of received signal characteristic values, from the decode starting point, decoding the body in a first time direction, and decoding the body in a second time direction based upon at least one result of the decoding in the first direction, wherein said determining the decode starting point comprises at least: determining for each mini-probe (21a, 21b) the received signal characteristic value for a respective end portion of the body; and selectively time reversing the mini-probes (21a, 21b) and body to provide the decode starting point at the end having a desired value for the received signal characteristic value, such that the channel estimate appears always as minimum-phase; and determining for each mini-probe (21a, 21b) the received signal characteristic value for a respective end portion of the body; and selectively time reversing the mini-probes (21a, 21b) and body to provide the decode starting point at the end having a desired value for the received signal characteristic value, such that the channel estimate appears always as minimum-phase; and wherein said receiver is configured to determine the channel estimate across the body based upon interpolating respective channel estimates from the mini-probes (21a, 21b) constrained by a maximum expected Doppler spread tolerance.