The main progress beyond the SoA, draws from the main novelty behind our approach which has been to use caching not as a means of reducing the volume of the communication problem, but rather as a means for changing the structure of the problem.
We have addressed the existing crippling bottlenecks of cache-aided communications.
One considerable improvement over the SoA can be found in our effort to alleviate the subpacketization bottleneck which can severely deteriorate the Coded Caching gains in practical systems. The progress here was that -- as we have shown for the first time -- pairing transmitters with Coded Caching not only does not increase the required subpacketization, but actually can severely reduce it. Our contribution beyond SoA lies in the realization that having this extra dimensionality on the transmitter side, in fact reduces rather than increases subpacketization, and does so in a very accelerated manner. This property is based on the novel principle of the virtual decomposition of the cache-aided MISO BC into parallel, single-stream coded caching channels with fewer users each. This decomposition is made possible because, as we have shown, the optimal performance can be gained without encoding across parallel channels.
The second progress beyond SoA involved our effort to alleviate the CSI Bottleneck, which saw a scaling (with the number of users) of the feedback requirements of multi-antenna systems. The effects of this bottleneck were first revealed in our work, which provided the novelty of a fundamentally different XOR design, which managed to reduce the per-transmission CSI requirements, from CSI that scaled with the number of users, to CSI equal to L, i.e. managed to completely untangled the CSI cost from the number of users.
Similar progress involved completely new ways of designing algorithms to resolve the link-asymmetry bottleneck. It was long thought that the performance of coded caching is limited by the weakest-link user. We provided a completely novel solution that bypasses information theoretic intuition by sending sequences of multi-casting messages, one on top of each other, thus showing that in fact the weakest users need not “pull down” the rest, but rather that the strongest users can “pull up” the rest, without any performance degradation for themselves.
