Information Theory for Cloud-RAN Downlink Channels

The downlink of a cloud radio access network (C-RAN) can be modeled as a diamond network. The baseband unit (BBU) is connected to remote radio heads (RRHs) via fiber links that are modeled as rate-limited bit pipes. A capacity lower bound is based on Marton’s coding, and a capacity upper bound uses Ozarow’s technique to augment the system with an auxiliary random variable. The bounds characterize the capacity of scalar Gaussian C-RANs for interesting regimes of operation. The bounds are also shown to characterize the capacity of a binary adder channel model for all ranges of bit-pipe capacities, which seems to yield a new combinatorial result on sum sets. Extensions to multiple RRHs are discussed.

The talk is based on joint work with Shirin Saeedi Bidokhti and Shlomo Shamai. This research was supported in part by DFG Grant KR 3517/9-1, and by the EU Horizon 2020 Research And Innovation Programme, grant no. 694630.