Coded Computation Against Straggling Decoders for Network Function Virtualization

The uplink of a cloud radio access network (C-RAN) architecture is studied in which decoding at the cloud takes place via Network Function Virtualization (NFV) on commercial offthe-shelf (COTS) servers. In order to mitigate the impact of straggling decoders in the cloud computing platform, a novel coding strategy is proposed, whereby the cloud re-encodes the received frames via a linear code before distributing them to the decoding processors. Upper bounds on the resulting Frame Error Rate (FER) as a function of the decoding latency are derived by assuming a binary symmetric channel for uplink communications. The bounds leverage large deviation results for correlated variables, and depend on the properties of both the uplink linear channel code adopted at the user and the NFV linear code applied at the cloud. Numerical examples demonstrate that the bounds are useful tools for code design, and that coding is instrumental in obtaining a desirable trade-off between FER and decoding latency.