Bio

Hyeji Kim is a Ph.D. candidate in the Department of Electrical Engineering at Stanford University advised by Prof. Abbas El Gamal. She received the B.S. degree with honors in Electrical Engineering from the Korea Advanced Institute of Science and Technology (KAIST) in 2011 and the M.S. degree in Electrical Engineering from Stanford University in 2013. Her research interest include information theory, communication systems, and statistical learning. She is a recipient of the Stanford Graduate Fellowship.

Superposition coding is almost always optimal for the Poisson broadcast channel

Superposition coding is almost always optimal for the Poisson broadcast channel

The two fundamental building blocks of wireless networks is the multiple access channel (multiple transmitters and one receiver) and the broadcast channel (one transmitter and multiple receivers). While the capacity region for multiple access channel is known, the capacity region for broadcast channels has been an open problem for 40 years.

A continuous-time Poisson channel is a canonical model for optical communications that is widely used to transmit telephone signals, internet communication, and cable television signals. The 2-receiver continuous-time Poisson broadcast channel is a 2-receiver broadcast channel for which the channel to each receiver is a continuous-time Poisson channel. 
We show that superposition coding is optimal for this channel for almost all channel parameter values. Interestingly, the channel in some subset of these parameter values does not belong to any of the existing classes of broadcast channels for which superposition coding is known to be optimal. For the rest of the channel parameter values, we show that there is a gap between the best known inner bound and the best known outer bound – Marton’s inner bound and the UV outer bound.