  A fog-radio access network (F-RAN) architecture is studied for an
Internet-of-Things (IoT) system in which wireless sensors monitor a number of
multi-valued events and transmit in the uplink using grant-free random access
to multiple edge nodes (ENs). Each EN is connected to a central processor (CP)
via a finite-capacity fronthaul link. In contrast to conventional
information-agnostic protocols based on separate source-channel (SSC) coding,
where each device uses a separate codebook, this paper considers an
information-centric approach based on joint source-channel (JSC) coding via a
non-orthogonal generalization of type-based multiple access (TBMA). By
leveraging the semantics of the observed signals, all sensors measuring the
same event share the same codebook (with non-orthogonal codewords), and all
such sensors making the same local estimate of the event transmit the same
codeword. The F-RAN architecture directly detects the events values without
first performing individual decoding for each device. Cloud and edge detection
schemes based on Bayesian message passing are designed and trade-offs between
cloud and edge processing are assessed.
