Adding Transmitters Dramatically Boosts Coded-Caching Gains for Finite File Sizes

Abstract

In the context of coded caching in the K-user BC, our work reveals the surprising fact that having multiple (L) transmitting antennas, dramatically ameliorates the long-standing subpacketization bottleneck of coded caching by reducing the required subpacketization to approximately its Lth root, thus boosting the actual DoF by a multiplicative factor of up to L. In asymptotic terms, this reveals that as long as L scales with the theoretical caching gain, then the full cumulative (multiplexing + full caching) gains are achieved with constant subpacketization. This is the first time, in any known setting, that unbounded caching gains appear under finite file-size constraints. The achieved caching gains here are up to L times higher than any caching gains previously experienced in any single-or multiantenna fully-connected setting, thus offering a multiplicative mitigation to a subpacketization problem that was previously known to hard-bound caching gains to small constants.The proposed scheme is practical and it works for all values of K, L and all cache sizes. The scheme's gains show in practice: e.g. for K = 100, when L = 1 the theoretical caching gain of G = 10, under the original coded caching algorithm, would have needed subpacketization S 1 = K G = 100 10 > 10 13 , while if extra transmitting antennas were added, the subpacketization was previously known to match or exceed S 1 . Now for L = 5, our scheme offers the theoretical (unconstrained) cumulative DoF d L = L + G = 5 + 10 = 15, with subpacketization S L = K/L G/L = 100/5 10/5 = 190. The work extends to the multi-server and cache-aided IC settings, while the scheme's performance, given subpacketization S L = K/L G/L , is within a factor of 2 from the optimal linear sum-DoF.

Optimal coded caching in heterogeneous networks with uncoded prefetching

“…Recently some progress has also been made in ameliorating the well known subpacketization bottleneck; for this see for example [22]- [28].…”

Subpacketization-Rate Trade-Off in Multi-Antenna Coded Caching

“…Interestingly, multi-antenna setups enable huge reductions in P to be achieved, without any loss in DoF. In [7] a structure for elevating single-antenna CC schemes for multi-antenna setups is introduced. The resulting CC scheme would then require…”

“…319059 (Coded Collaborative Caching for Wireless Energy Efficiency) and 318927 (6Genesis Flagship). and is shown to be nicely achievable in cache-enabled multiantenna networks [7], [8]. However, these studies consider error-free, same-capacity communication links for all users.…”

Asynchronous coded caching

“…Extensions of the basic model to general networks have been examined in [7]- [9]. Issues related to subpacketization (i.e., the number of subfiles F ) have been considered in [10]- [12]. A high subpacketization level can cause several issues in practical implementations.…”