Achieving joint secrecy with cache-channel coding over erasure broadcast channels
Résumé
We derive upper and lower bounds on the secure capacity-memory tradeoff of the K-user (K > 2) wiretap erasure broadcast channel where Kw receivers are weak and have cache memories of equal size, and Ks receivers are strong and have no cache. The bounds coincide for small and large cache memories. The lower bound also exhibits that cache memories provide larger gains under a secrecy constraint than without such a constraint. The lower bound is based on a joint cache-channel coding scheme that simultaneously exploits the cache contents and the channel statistics. Moreover, we show for the two-user scenario that in the regime of small cache memories, the capacity-memory tradeoff is larger when only the weaker receiver has cache memory than when this cache memory is split equally among the two receivers.