HARQ Soft Combining Using Bidirectional LSTMs

*Adithya S. Ubaradka     *Hemang J Jamadagni     *Rohit Sunil     B. R. Chandavarkar^📧
National Institute of Technology Karnataka, Surathkal

(*) equal contribution, (^📧) corresponding author.

SSWC 2024    Springer Conference Proceedings

Abstract

Hybrid Automatic Repeat reQuest is used in modern wireless data communica- tion to integrate both Automatic Repeat reQuest and high-rate Forward Error Correction mechanisms to enhance the reliability of data transmission. Unlike traditional ARQ, where an error-ridden frame is discarded upon reception, HARQ temporarily stores the erroneous frame in a buffer. When the re-transmission of the same frame occurs, these two frames are com- bined to generate a new frame, trying to minimize errors. This is HARQ with Soft Combining. Existing methods like Chase Combining (Type-I) and Incremental Redundancy (Type-II and Type-III) implement Log-Likelihood Ratio and Maximum Ratio Combining to combine two erroneous frames. This paper uses a Bidirectional Long Short-Term Memory model to com- bine two frames with high channel noise errors. This paper introduces the BiLSTM model, which aims to reduce Bit Error Rate and provides an approach for integrating this model into the existing HARQ structure.

Overview

Usage

Set up the environment

conda create -n harq_soft_combining_using_bilstms -f environment.yaml
conda activate harq_soft_combining_using_bilstms

Run Main

Modulation Schemes

Quadrature Amplitude Modulation(QAM) - "qam" 
Pulse amplitude modulation(PAM) - "pam" 
Phase-shift keying(PSK) - "psk" 
Amplitude shift keying(ASK) - "ask" 

python3 main.py -m "<modulation-scheme>" 

The plots are saved in their respective folders.

Run Demo Notebook

Change the "MOD" macro to any of the modulation techniques used.

Citation

If you find HARQ Soft Combining Using Bidirectional LSTMs useful in your research or applications, please consider giving us a star 🌟 and citing it using the following:

@InProceedings{10.1007/978-981-96-1348-9_9,
    author    ="Ubaradka, Adithya S.and Jamadagni, Hemang J. and Sunil, Rohit and Chandavarkar, B. R.",
    editor    ="Chaki, Rituparna and Cortesi, Agostino and DasGupta, Suparna and Saha, Soumyabrata",
    title     ="HARQ Soft Combining Using Bidirectional LSTMs",
    booktitle ="Smart Systems and Wireless Communication",
    year      ="2025",
    publisher ="Springer Nature Singapore",
    address   ="Singapore",
    pages     ="109--122",
}