High frequency Differential MIMO: Basic theory and transceiver architectures

We propose a new multiple input multiple output (MIMO) transceiver architecture - Differential MIMO (D-MIMO) - that enables linear interference suppression between multiple spatially multiplexed and differentially encoded data streams. The D-MIMO transceiver architecture is particularly attractive in emerging high-frequency systems, such as millimeter-wave systems, in which the requirement of a phase-coherent local oscillator at the receiver can be challenging. A direct application of conventional linear interference suppression techniques is not possible with differential communication. Thus, we first develop a general model for D-MIMO systems, with a corresponding D-MIMO channel matrix, that forms the basis of the development in this paper. A surprising result is that a quasi-coherent version of the underlying channel matrix can also be estimated from the D-MIMO matrix, making conventional linear interference suppression possible as well. This leads to two D-MIMO transceiver architectures that are developed. Numerical results illustrate the promising and nearly identical performance of the proposed transceivers and the communication breakdown that can occur without interference suppression.