Differential multiple-length transmit diversity

We propose a new bandwidth-efficient differential transmit diversity scheme as an extension of differential space-time block codes from orthogonal designs. The information is coded in both the difference of successive unit-length vectors and the length difference of successive transmit vectors. We derive a simple soft-output detector which does not require knowledge of the channel coefficients or of the noise variance. The new scheme outperforms the existing unit-length approach at high bandwidth-efficiency, particularly in time-varying channels. At the same time the detection complexity is reduced.