Abstract
This paper studies the capacity of the two-user
intensity-modulation/direct-detection (IM/DD) interference channel (IC),
which is relevant in the context of multi-user optical wireless
communications. Despite some known single-letter capacity
characterizations for general discrete-memoryless ICs, a computable
capacity expression for the IM/DD IC is missing. In this paper, we
provide tight and easily computable inner and outer bounds for a general
two-user IM/DD IC under peak and average optical intensity constraints.
The bounds enable characterizing the asymptotic sum-rate capacity in the
strong and weak interference regimes, as well as the generalized degrees
of freedom (GDoF) in the symmetric case. Using the obtained bounds, the
GDoF of the IM/DD IC is shown to have a ‘W’ shape similar to the
Gaussian IC with power constraints. The obtained bounds are also
evaluated numerically in different interference regimes to show their
tightness, and used to study the performance of on-chip and indoor OWC
systems.