Coded Information Retrieval in Multi-User MIMO Systems

We introduce a novel coding design to facilitate data exchange among distributed nodes in a multiple-input multiple-output (MIMO) wireless system. Each node has limited access to data through local observation or computation, and data exchange is orchestrated by a multi-antenna access point (AP) through consecutive uplink (UL) and downlink (DL) transmission phases. During the UL transmission, various subsets of users simultaneously transmit parts of their locally available data to the AP. This phase is paired with a novel precoder design that enables the over-the-air aggregation of the transmitted data to result in specific linear combinations useful for the upcoming DL. The AP then processes its received data and sends back the resulting linear combinations of received signals to a set of users. The proposed content-aware MIMO information exchange strategy is shown to be able to boost the degree-of-freedom (DoF) gain of the underlying coding mechanism by a multiplicative factor proportional to the receiver-side spatial multiplexing gain compared to the existing multi-input single-output solution.