Abstract: Techniques are disclosed relating to synchronization of radios in a large antenna count (LAC) system. In some embodiments, a LAC system includes a plurality of slave radios, a clock and trigger distribution system, and a master device. In these embodiments, the plurality of slave radios are configured to establish a fixed relationship between a reference clock and their respective local clocks. In these embodiments, the master device and plurality of slave radios are configured to generate and align respective common periodic time reference (CPTR) signals, at a lower frequency than the local clocks. In these embodiments, the master device is configured to transmit a trigger signal based on its CPTR and the plurality of slave radios are configured to perform an action based on the trigger at a subsequent edge of their CPTRs. This may allow synchronization of sampling for antennas in a massive MIMO base station, for example.

Abstract: Techniques are disclosed relating to signaling and frame structure for massive MIMO communication systems. In some embodiments, an apparatus is configured to receive an uplink pilot symbol from a mobile device over a first channel and receive uplink data from the mobile device over the first channel, where the uplink data is included in one or more orthogonal frequency division multiplexing (OFDM) symbols at a symbol rate. In these embodiments, the apparatus is configured to, determine channel information based on the pilot symbol, precode downlink data based on the channel information, and transmit the precoded downlink data to the mobile device. In these embodiments, a transition interval between receiving the uplink pilot symbol and beginning to transmit the precoded downlink data corresponds to less than five OFDM symbols at the symbol rate. This may facilitate reciprocity-based precoding for fast-moving mobile devices, in some embodiments.