  A key problem in the design of cloud radio access networks (CRANs) is that of
devising effective baseband compression strategies for transmission on the
fronthaul links connecting a remote radio head (RRH) to the managing central
unit (CU). Most theoretical works on the subject implicitly assume that the
RRHs, and hence the CU, are able to perfectly recover time synchronization from
the baseband signals received in the uplink, and focus on the compression of
the data fields. This paper instead dose not assume a priori synchronization of
RRHs and CU, and considers the problem of fronthaul compression design at the
RRHs with the aim of enhancing the performance of time and phase
synchronization at the CU. The problem is tackled by analyzing the impact of
the synchronization error on the performance of the link and by adopting
information and estimationtheoretic performance metrics such as the
rate-distortion function and the Cramer-Rao bound (CRB). The proposed algorithm
is based on the Charnes-Cooper transformation and on the Difference of Convex
(DC) approach, and is shown via numerical results to outperform conventional
solutions.
