Non-Orthogonal HARQ-CC over SDR: A GNU Radio-Based Implementation

Fuente: arXiv
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Auteurs principaux: Huang, Hongling, Wang, Jintao, Shi, Zheng, Wang, Xu, Yang, Guanghua, Ma, Shaodan, Ding, Haichuan
Format: Preprint
Publié: 2026
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author Huang, Hongling
Wang, Jintao
Shi, Zheng
Wang, Xu
Yang, Guanghua
Ma, Shaodan
Ding, Haichuan
author_facet Huang, Hongling
Wang, Jintao
Shi, Zheng
Wang, Xu
Yang, Guanghua
Ma, Shaodan
Ding, Haichuan
contents Hybrid Automatic Repeat Request (HARQ) schemes typically allocate all available resources to retransmit failed packets to ensure reliability. However, under stringent delay constraints, these schemes often exhibit low spectral efficiency and increased transmission latency. To address these challenges, this paper proposes an efficient Non-Orthogonal HARQ with Chase Combining (N-HARQ-CC) transmission strategy. Specifically, the proposed approach allocates a larger portion of retransmission resources to new data packets, reserving only a small fraction for retransmitting previously erroneous packets. This is based on the observation that only a small number of information bits are typically incorrect, enabling surplus communication resources to be utilized for transmitting new messages. The N-HARQ-CC scheme retransmits the same redundant version of a failed packet and employs Maximum Ratio Combining (MRC) for decoding. To minimize complex packet scheduling and decoding complexity, the proposed scheme limits superposition to at most two messages per transmission round. At the receiver, Successive Interference Cancellation (SIC) is used to decouple the superimposed messages. The proposed N-HARQ-CC system was implemented using GNU Radio and USRP platforms for validation. Compared to conventional Type-I HARQ and HARQ-CC schemes, the proposed scheme achieves a significant improvement in spectral efficiency of approximately 0.5 bps/Hz, aligning with the low-latency requirements of 6G networks.
format Preprint
id arxiv_https___arxiv_org_abs_2603_03746
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Non-Orthogonal HARQ-CC over SDR: A GNU Radio-Based Implementation
Huang, Hongling
Wang, Jintao
Shi, Zheng
Wang, Xu
Yang, Guanghua
Ma, Shaodan
Ding, Haichuan
Signal Processing
Hybrid Automatic Repeat Request (HARQ) schemes typically allocate all available resources to retransmit failed packets to ensure reliability. However, under stringent delay constraints, these schemes often exhibit low spectral efficiency and increased transmission latency. To address these challenges, this paper proposes an efficient Non-Orthogonal HARQ with Chase Combining (N-HARQ-CC) transmission strategy. Specifically, the proposed approach allocates a larger portion of retransmission resources to new data packets, reserving only a small fraction for retransmitting previously erroneous packets. This is based on the observation that only a small number of information bits are typically incorrect, enabling surplus communication resources to be utilized for transmitting new messages. The N-HARQ-CC scheme retransmits the same redundant version of a failed packet and employs Maximum Ratio Combining (MRC) for decoding. To minimize complex packet scheduling and decoding complexity, the proposed scheme limits superposition to at most two messages per transmission round. At the receiver, Successive Interference Cancellation (SIC) is used to decouple the superimposed messages. The proposed N-HARQ-CC system was implemented using GNU Radio and USRP platforms for validation. Compared to conventional Type-I HARQ and HARQ-CC schemes, the proposed scheme achieves a significant improvement in spectral efficiency of approximately 0.5 bps/Hz, aligning with the low-latency requirements of 6G networks.
title Non-Orthogonal HARQ-CC over SDR: A GNU Radio-Based Implementation
topic Signal Processing
url https://arxiv.org/abs/2603.03746