  We consider cache-aided wireless communication scenarios where each user
requests both a file from an a-priori generated cacheable library (referred to
as 'content'), and an uncacheable 'non-content' message generated at the start
of the wireless transmission session. This scenario is easily found in
real-world wireless networks, where the two types of traffic coexist and share
limited radio resources. We focus on single-transmitter, single-antenna
wireless networks with cache-aided receivers, where the wireless channel is
modelled by a degraded Gaussian broadcast channel (GBC). For this setting, we
study the delay-rate trade-off, which characterizes the content delivery time
and non-content communication rates that can be achieved simultaneously. We
propose a scheme based on the separation principle, which isolates the coded
caching and multicasting problem from the physical layer transmission problem.
We show that this separation-based scheme is sufficient for achieving an
information-theoretically order optimal performance, up to a multiplicative
factor of 2.01 for the content delivery time, when working in the generalized
degrees of freedom (GDoF) limit. We further show that the achievable
performance is near-optimal after relaxing the GDoF limit, up to an additional
additive factor of 2 bits per dimension for the non-content rates. A key
insight emerging from our scheme is that in some scenarios considerable amounts
of non-content traffic can be communicated while maintaining the minimum
content delivery time, achieved in the absence of non-content messages;
compliments of 'topological holes' arising from asymmetries in wireless channel
gains.
