We study the transmission over a cloud radio access network in which multiple
base stations (BS) are connected to a central processor (CP) via
finite-capacity backhaul links. We propose two lattice-based coding schemes. In
the first scheme, the base stations decode linear combinations of the
transmitted messages, in the spirit of compute-and-forward (CoF), but differs
from it essentially in that the decoded equations are remapped to linear
combinations of the channel input symbols, sent compressed in a lossy manner to
the central processor, and are not required to be linearly independent. Also,
by opposition to the standard CoF, an appropriate multi-user decoder is
utilized to recover the sent messages. The second coding scheme generalizes the
first one by also allowing, at each relay node, a joint compression of the
decoded equation and the received signal. Both schemes apply in general, but
are more suited for situations in which there are more users than base
stations. We show that both schemes can outperform standard CoF and successive
Wyner-Ziv schemes in certain regimes, and illustrate the gains through some
numerical examples.Comment: Submitted to IEEE Transactions on Communication