  We consider the problem of downloading content from a cellular network where
content is cached at the wireless edge while achieving privacy. In particular,
we consider private information retrieval (PIR) of content from a library of
files, i.e., the user wishes to download a file and does not want the network
to learn any information about which file she is interested in. To reduce the
backhaul usage, content is cached at the wireless edge in a number of
small-cell base stations (SBSs) using maximum distance separable codes. We
propose a PIR scheme for this scenario that achieves privacy against a number
of spy SBSs that (possibly) collaborate. The proposed PIR scheme is an
extension of a recently introduced scheme by Kumar et al. to the case of
multiple code rates, suitable for the scenario where files have different
popularities. We then derive the backhaul rate and optimize the content
placement to minimize it. We prove that uniform content placement is optimal,
i.e., all files that are cached should be stored using the same code rate. This
is in contrast to the case where no PIR is required. Furthermore, we show
numerically that popular content placement is optimal for some scenarios.
