  In cellular systems, confidentiality of uplink transmission with respect to
eavesdropping terminals can be ensured by creating intentional inteference via
scheduling of concurrent downlink transmissions. In this paper, this basic idea
is explored from an information-theoretic standpoint by focusing on a two-cell
scenario where the involved base stations are connected via a finite-capacity
backbone link. A number of transmission strategies are considered that aim at
improving uplink confidentiality under constraints on the downlink rate that
acts as an interfering signal. The strategies differ mainly in the way the
backbone link is exploited by the cooperating downlink- to the uplink-operated
base stations. Achievable rates are derived for both the Gaussian (unfaded) and
the fading cases, under different assumptions on the channel state information
available at different nodes. Numerical results are also provided to
corroborate the analysis. Overall, the analysis reveals that a combination of
scheduling and base station cooperation is a promising means to improve
transmission confidentiality in cellular systems.
