# Spatial Coding Techniques for Molecular MIMO

## TL;DR

This paper explores spatial coding methods for molecular MIMO communication, demonstrating that repetition MIMO coding enhances performance more effectively than Alamouti-type coding, with neural networks used for channel analysis.

## Contribution

It introduces and analyzes two spatial coding techniques for molecular MIMO systems, highlighting the effectiveness of repetition MIMO coding over Alamouti-type coding.

## Key findings

- Repetition MIMO coding outperforms Alamouti-type coding.
- Neural networks accurately model channel impulse responses.
- Spatial diversity improves molecular MIMO system performance.

## Abstract

This paper studies spatial diversity techniques applied to multiple-input multiple-output (MIMO) diffusion-based molecular communications (DBMC). Two types of spatial coding techniques, namely Alamouti-type coding and repetition MIMO coding are suggested and analyzed. In addition, we consider receiver-side equal-gain combining, which is equivalent to maximum-ratio combining in symmetrical scenarios. For numerical analysis, the channel impulse responses of a symmetrical $2 \times 2$ MIMO-DBMC system are acquired by a trained artificial neural network. It is demonstrated that spatial diversity has the potential to improve the system performance and that repetition MIMO coding outperforms Alamouti-type coding.