Achieving full multiplexing and unbounded caching gains with bounded feedback resources

In the context of the K-user MISO broadcast channel with cache-aided receivers, recent multi-antenna coded-caching techniques have sought to complement the traditional multiplexing gains associated to multiple (L) antennas, with the (potentially unbounded) caching gains (G) associated to coded caching. To date, all known existing efforts to combine the two gains, either resulted in a maximum known DoF L+G that required though CSIT on all (L+G) users served at a time (i.e., that induced potentially unbounded CSIT costs that matched the DoF gains), or resulted in a much compromised DoF where multiplexing gains came at the expense of bounded caching gains. We present here a new multi-antenna coded caching algorithm that introduces a new XOR generation structure which completely untangles caching gains from CSIT, allowing for the same desired sum-DoF of L+G with a much reduced CSIT of only L channel vectors at a time (L times L channel matrix). This means that for the first time in multi-antenna coded caching, one can achieve full multiplexing gains and unbounded caching gains, at a much reduced and bounded CSIT cost usually associated to supporting only multiplexing gains. In the end, the result solidifies the role of coded caching as a method for reducing feedback requirements in multi-antenna environments.