Title: Delivery Latency Trade-Offs of Heterogeneous Contents in Fog Radio Access Networks,
Abstract: A Fog Radio Access Network (F-RAN) is a cellular wireless system that enables
content delivery via the caching of popular content at edge nodes (ENs) and
cloud processing. The existing information-theoretic analyses of F-RAN systems,
and special cases thereof, make the assumption that all requests should be
guaranteed the same delivery latency, which results in identical latency for
all files in the content library. In practice, however, contents may have
heterogeneous timeliness requirements depending on the applications that
operate on them. Given per-EN cache capacity constraint, there exists a
fundamental trade-off among the delivery latencies of different users'
requests, since contents that are allocated more cache space generally enjoy
lower delivery latencies. For the case with two ENs and two users, the optimal
latency trade-off is characterized in the high-SNR regime in terms of the
Normalized Delivery Time (NDT) metric. The main results are illustrated by
numerical examples.