Doctoral Examination: Information-Theoretic Analysis of Optical Wireless Communication Systems with Interference

Zhenyu Charlus Zhang, supervised by Dr. Anas Chaaban, will defend their dissertation titled “Information-Theoretic Analysis of Optical Wireless Communication Systems with Interference” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Electrical Engineering.

An abstract for Zhenyu’s dissertation is included below.

Examinations are open to all members of the campus community as well as the general public.

If you would like to attend this virtual examination please contact the supervisor at anas.chaaban@ubc.ca to receive a zoom link.

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ABSTRACT

Optical wireless communications (OWC) is a technology that employs optical signals to carry information in wireless links. OWC is considered as a complement to radio-frequency (RF) communications when RF links are restricted, and as a solution for the crisis of an ever increasing demand on wireless communication given an overwhelmingly limited RF bandwidth. Due to the broadcast nature of OWC, interference is hard to avoid in OWC links. In order to instruct the design of OWC systems that communicate efficiently in the presence of interference, we investigate the fundamental limits of the OWC systems from an information-theoretical perspective in this dissertation. To this end, we model OWC link as intensity-modulation-with-direct-detection (IM/DD) channels with interference caused by concurrent transmissions/receptions, and we study the capacity of these channels.

Specifically, we study the capacity of four classes of IM/DD channels, including the point-to-point (P2P) channel whose capacity is important in the study of channels with interference, the dirty paper channel (DPC) which arises in scenarios with inter-user interference (IUI), the broadcast channel (BC) where a transmitter transmits to multiple receivers, and the interference channel (IC) where multiple transmitter-receiver pairs communicate concurrently over the same OWC medium. For the IM/DD P2P channel, we derive new closed-form capacity lower bounds based on several specified input distributions. For the IM/DD DPC which helps to model the IUI in the IM/DD BC, we derive a capacity upper bound and several capacity lower bounds, which are based on Costa’s writing-on-dirty-paper (WDP) coding and two proposed precoding schemes. We further define a class of discrete DPC whose state is less harmful. For the IM/DD BC, which suffers from IUI, we consider a scalar and a vector input, and derive new capacity inner bounds for both cases based on either new input distributions or based on the DPC. As for the IM/DD IC, we derive easily-computable capacity inner and outer bounds and characterize the generalized degrees of freedom (GDoF) of the symmetric IM/DD IC.