# Classes of Full-Duplex Channels with Capacity Achieved Without Adaptation

## TL;DR

This paper identifies two classes of full-duplex channels where simple non-adaptive transmission achieves Shannon capacity, eliminating the need for complex adaptive strategies in certain communication scenarios.

## Contribution

It introduces two classes of channels—injective semi-deterministic and Poisson two-way channels—where capacity is achieved without adaptation, simplifying full-duplex communication design.

## Key findings

- Capacity achieved without adaptation in injective semi-deterministic channels.
- Non-adaptive transmission is asymptotically optimal for Poisson channels in high dark current.
- Provides theoretical capacity results for specific full-duplex channel models.

## Abstract

Full-duplex communication allows a terminal to transmit and receive signals simultaneously, and hence, it is helpful in general to adapt transmissions to received signals. However, this often requires unaffordable complexity. This work focuses on simple non-adaptive transmission, and provides two classes of channels for which Shannon's information capacity regions are achieved without adaptation. The first is the injective semi-deterministic two-way channel that includes additive channels with various types of noises modeling wireless, coaxial cable, and other settings. The other is the Poisson two-way channel, for which we show that non-adaptive transmission is asymptotically optimal in the high dark current regime.