Abstract :
[en] Network coding is an efficient means to improve
the spectrum efficiency of satellite communications. However, its
resilience to eavesdropping attacks is not well understood. This
paper studies the confidentiality issue in a bidirectional satellite
network consisting of two mobile users who want to exchange
message via a multibeam satellite using the XOR network coding
protocol. We aim to maximize the sum secrecy rate by designing
the optimal beamforming vector along with optimizing the return
and forward link time allocation. The problem is non-convex,
and we find its optimal solution using semidefinite programming
together with a 1-D search. For comparison, we also solve
the sum secrecy rate maximization problem for a conventional
reference scheme without using network coding. Simulation
results using realistic system parameters demonstrate that the
bidirectional scheme using network coding provides considerably
higher secrecy rate compared to that of the conventional scheme.
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