  This work focuses on quality adaptation as a means to counter the effects of
channel degradation in wireless, cache-aided channels. We design a delivery
scheme which combines coded caching, superposition coding, and scalable source
coding, while keeping the caching scheme oblivious to channel qualities. By
properly adjusting the quality at the degraded users we are able to satisfy all
demands in a time-efficient manner. In addition, superposition coding allows us
to serve high-rate users with high content quality without subjecting them to a
delay penalty caused by users with lower rate channels. We design a
communication framework that covers all possible channel rate and quality
configurations and we further provide algorithms that can optimise the served
quality. An interesting outcome of this work is that a modest quality reduction
at the degraded users can counter the effects of significant channel
degradation. For example, in a 100-user system with normalized cache size 1/10
at each user, if 10 users experience channel degradation of 60% compared to the
rate of the non-degraded users, we show that our transmission strategy leads to
a 85% quality at the degraded users and perfect quality at the non-degraded
users.
