Capacity of Frequency-based Channels: Encoding Information in Molecular Concentrations

TL;DR

This paper analyzes the capacity of a molecular communication channel where information is encoded in molecule concentrations or frequencies, providing bounds and implications for DNA storage despite zero channel capacity.

Contribution

It offers a tight characterization of the channel capacity with object constraints and applies findings to DNA storage, revealing potential for high information density.

Findings

Capacity bounds for frequency-based molecular channels

Application to DNA storage with high information density

Channel capacity is zero but still allows large information density

Abstract

We consider a molecular channel, in which messages are encoded to the frequency of objects (or concentration of molecules) in a pool, and whose output during reading time is a noisy version of the input frequencies, as obtained by sampling with replacement from the pool. We tightly characterize the capacity of this channel using upper and lower bounds, when the number of objects in the pool of objects is constrained. We apply this result to the DNA storage channel in the short-molecule regime, and show that even though the capacity of this channel is technically zero, it can still achieve a large information density.