# Wireless Key Generation from Imperfect Channel State Information: Performance Analysis and Improvements

## TL;DR

This paper analyzes the impact of imperfect channel state information on wireless key generation, deriving key disagreement rate formulas, optimizing energy use, and proposing a neural network prediction method to enhance key consistency, especially under low SNR and high delay.

## Contribution

It provides a closed-form KDR expression for imperfect CSI, introduces an energy-efficient power allocation scheme, and proposes a neural network based prediction algorithm for improved key agreement.

## Key findings

- NNBP significantly improves key consistency.
- Performance gain is higher in low SNR and high delay scenarios.
- Theoretical analysis aligns with simulation results.

## Abstract

The basis of generating secret key from the common wireless channel at two communication parties is reciprocity. However, due to non-simultaneous measurements and unavoidable estimation error, bias always exists and key disagreement occurs. In this paper, performance analysis and improvements for key generation exploiting imperfect channel statement information (CSI) is studied. Firstly, the closed-form expression for key disagreement rate (KDR) is derived to evaluate the key mismatch caused by time delay and estimation error. Secondly, the energy efficiency involving power allocation between key generation and private data transmission is presented. After that, a neural network based prediction (NNBP) algorithm is proposed to improve the key consistency. Simulation results verify the theoretical analysis and show that NNBP achieves significant improvements. And it's interesting to find that NNBP algorithm achieves a higher performance gain in low signal-to-noise ration (SNR) and high delay condition, which is different from other methods, like guard band based quantizer (GBBQ).