A Comparative Analysis of Retrieval-Augmented Generation Techniques for Bengali Standard-to-Dialect Machine Translation Using LLMs

K. M. Jubair Sami, Dipto Sumit, Ariyan Hossain, Farig Sadeque


Abstract
Translating from a standard language to its regional dialects is a significant NLP challenge due to scarce data and linguistic variation, a problem prominent in the Bengali language. This paper proposes and compares two novel RAG pipelines for standard-to-dialectal Bengali translation. The first, a Transcript-Based Pipeline, uses large dialect sentence contexts from audio transcripts. The second, a more effective Standardized Sentence-Pairs Pipeline, utilizes structured local_dialect:standard_bengali sentence pairs. We evaluated both pipelines across six Bengali dialects and multiple LLMs using BLEU, ChrF, WER, and BERTScore. Our findings show that the sentence-pair pipeline consistently outperforms the transcript-based one, reducing Word Error Rate (WER) from 76% to 55% for the Chittagong dialect. Critically, this RAG approach enables smaller models (e.g., Llama-3.1-8B) to outperform much larger models (e.g., GPT-OSS-120B), demonstrating that a well-designed retrieval strategy can be more crucial than model size. This work contributes an effective, fine-tuning-free solution for low-resource dialect translation, offering a practical blueprint for preserving linguistic diversity.
Anthology ID:
2025.banglalp-1.22
Volume:
Proceedings of the Second Workshop on Bangla Language Processing (BLP-2025)
Month:
December
Year:
2025
Address:
Mumbai, India
Editors:
Firoj Alam, Sudipta Kar, Shammur Absar Chowdhury, Naeemul Hassan, Enamul Hoque Prince, Mohiuddin Tasnim, Md Rashad Al Hasan Rony, Md Tahmid Rahman Rahman
Venues:
BanglaLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
266–279
Language:
URL:
https://preview.aclanthology.org/ingest-ijcnlp-aacl/2025.banglalp-1.22/
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Bibkey:
Cite (ACL):
K. M. Jubair Sami, Dipto Sumit, Ariyan Hossain, and Farig Sadeque. 2025. A Comparative Analysis of Retrieval-Augmented Generation Techniques for Bengali Standard-to-Dialect Machine Translation Using LLMs. In Proceedings of the Second Workshop on Bangla Language Processing (BLP-2025), pages 266–279, Mumbai, India. Association for Computational Linguistics.
Cite (Informal):
A Comparative Analysis of Retrieval-Augmented Generation Techniques for Bengali Standard-to-Dialect Machine Translation Using LLMs (Sami et al., BanglaLP 2025)
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https://preview.aclanthology.org/ingest-ijcnlp-aacl/2025.banglalp-1.22.pdf