Upper Bounding the Capacity of Binary Chip-Asynchronous Optical CDMA

The chip-asynchronous binary OCDMA network transmission with single-user demodulation and decoding at the receiver is considered. Numerical results showing significant capacity improvement in this channel have been recently presented. This paper establishes upper bounds on the symmetric sum-capacity of this channel scenario. In particular, the probability distribution of the capacity achieving non-Gaussian multi-user interference is first derived closed-form. Ihara´s inequality on the capacity of channels with non-Gaussian additive noise is then used as a tool to establish an upper bound on OCDMA channel sum-capacity. Numerical results illustrate validity of the established upper bound.