Preamble-Referenced Cyclic Cross-correlation Chirp Spread Spectrum Communication Technology in Complex Multipath Environments

YE Yun; ZHANG Chengyu; PANG Haodong; MA Wenfeng; LI Xuejiao; ZHANG Xiaokai

doi:10.11999/JEIT260702

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YE Yun, ZHANG Chengyu, PANG Haodong, MA Wenfeng, LI Xuejiao, ZHANG Xiaokai. Preamble-Referenced Cyclic Cross-correlation Chirp Spread Spectrum Communication Technology in Complex Multipath Environments[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260702

Citation:

YE Yun, ZHANG Chengyu, PANG Haodong, MA Wenfeng, LI Xuejiao, ZHANG Xiaokai. Preamble-Referenced Cyclic Cross-correlation Chirp Spread Spectrum Communication Technology in Complex Multipath Environments[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260702

Citation:

YE Yun, ZHANG Chengyu, PANG Haodong, MA Wenfeng, LI Xuejiao, ZHANG Xiaokai. Preamble-Referenced Cyclic Cross-correlation Chirp Spread Spectrum Communication Technology in Complex Multipath Environments[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260702

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Preamble-Referenced Cyclic Cross-correlation Chirp Spread Spectrum Communication Technology in Complex Multipath Environments

doi: 10.11999/JEIT260702 cstr: 32379.14.JEIT260702

1.
Army Engineering of PLA, Nanjing 210007, China
2.
Unit 31605 of PLA, Nanjing 211100, China

Funds: The National Natural Science Foundation of China (6240013161, 62671615), The Natural Science Foundation of Jiangsu Province (BK20241601)

Received Date: 2026-05-29
Accepted Date: 2026-08-24
Rev Recd Date: 2026-08-19

Available Online: 2026-08-28

Abstract

Abstract

Objective Ground unmanned platforms operating in urban streets, industrial parks, and underground passages require reliable short-burst command-and-control communication. In these complex near-ground environments, reception is affected by strong multipath fading, large Carrier Frequency Offset (CFO), residual Timing Offset (TO), Sampling Frequency Offset (SFO), and in-band interference from coexisting wireless systems. Conventional Chirp Spread Spectrum (CSS) receivers based on single-peak decisions in the dechirp-Discrete Fourier Transform (DFT) domain are vulnerable to multipath-induced spectral splitting and interference-induced bin masking. Direct-Sequence Spread Spectrum (DSSS) receivers can also be sensitive to synchronization errors under combined offsets and show reduced energy efficiency under multipath. Robust handling of these impairments is therefore required for low-latency control links and for the coexistence of unmanned ground platforms with legacy wireless infrastructure in dense deployments. Methods A Preamble-Referenced Cyclic Cross-correlation CSS (PRCC-CSS) scheme is proposed in which frame structure, synchronization estimation, and payload detection are jointly designed. Each frame consists of multiple identical up-chirp preamble symbols, a down-chirp Start-of-Frame Delimiter (SFD), and CSS-modulated payload symbols. Integer CFO and TO are jointly estimated from closed-form linear combinations of the complementary frequency-domain indices at the dechirp-DFT outputs of the up-chirp preamble and down-chirp SFD. Fractional CFO is estimated from inter-symbol phase differences between adjacent preamble symbols, whereas fractional TO is estimated by interpolation around the main peak of the averaged preamble spectrum. Under a common oscillator-reference assumption, SFO-induced bin drift is compensated using the clock-offset relation derived from CFO. After offset compensation, the averaged preamble spectrum is used to construct a frame-specific reference spectrum that represents the current multipath frequency-domain structure. Each payload symbol is then detected by cyclically cross-correlating its spectrum with the reference spectrum over candidate cyclic shifts. The shift corresponding to the maximum cyclic cross-correlation is selected as the demodulated symbol index. In this way, the multipath-induced frequency-domain structure is converted from an adverse perturbation into a matchable intra-frame reference feature. Multipath-robust structure-matched payload detection is therefore achieved without explicit path-by-path channel estimation. Results and Discussions PRCC-CSS is evaluated under identical bandwidth, sampling rate, and processing gain at a target Bit Error Rate (BER) of 10^–4. First, it is compared with three DSSS baselines using Binary Phase-Shift Keying (BPSK), Quadrature Phase-Shift Keying (QPSK), and 16-ary Quadrature Amplitude Modulation (16QAM) under three channel conditions. Under Additive White Gaussian Noise (AWGN, Fig. 1), PRCC-CSS reaches the target BER at approximately 4.9 dB E_b/N₀, compared with 8.5～9.0 dB for the best DSSS baseline. This result indicates that chirp index modulation combined with preamble-referenced correlation provides frequency-domain energy aggregation independent of a specific multipath profile. Under the Extended Typical Urban (ETU) channel without interference (Fig. 2), PRCC-CSS requires approximately 6.5 dB E_b/N₀, compared with approximately 10.0 dB for the best DSSS baseline. The reference spectrum captures and reuses the per-frame multipath frequency-domain structure, whereas finite-finger DSSS-RAKE is more strongly affected by path-capture and code-synchronization errors. Under ETU with in-band interference at a Jamming-to-Signal Ratio (JSR) of 5 dB (Fig. 3), PRCC-CSS requires approximately 7.8～8.0 dB E_b/N₀, compared with 10.8～11.0 dB for the best DSSS baseline. The reference and payload spectra experience nearly the same multipath frequency-domain structure within a frame, which helps preserve decision separability during cyclic cross-correlation. By contrast, DSSS-RAKE accumulates residual interference across its combining fingers. Second, PRCC-CSS is compared with Dechirp Non-Coherent (DNC) and coherent peak detection at Spreading Factor (SF)=7 and SF=9 under ETU with interference (Fig. 4). At SF=7, DNC does not reach the target BER within the tested Signal-to-Interference-plus-Noise Ratio (SINR) range. At SF=9, DNC requires approximately 4 dB SINR. PRCC-CSS reaches the same target at approximately –5 dB SINR at SF=7 and –11 dB at SF=9, corresponding to an SINR threshold improvement of approximately 9～15 dB. These results show that the gain is mainly attributable to frame-wide cyclic matching rather than phase compensation alone. Third, a Software-Defined Radio (SDR) prototype is evaluated on an ETU-emulated channel at JSR = 5 dB (Figs. 5 and 6). Of the 332 received frames, 300 are retained as reliable, corresponding to a frame retention rate of 90.4%. Among the retained frames, no symbol errors are observed in 6 000 payload symbols, and no bit errors are observed in 54 000 payload bits. The retained-frame conditional BER therefore has a one-sided 95% upper confidence bound of 5.56 × 10^-5. Conclusions The proposed PRCC-CSS scheme jointly integrates integer and fractional CFO and TO estimation, SFO estimation, and cyclic cross-correlation payload detection. At BER=10^–4, PRCC-CSS reduces the required E_b/N₀ by approximately 2.8～4.1 dB relative to the best DSSS baseline using BPSK, QPSK, or 16QAM across AWGN, ETU, and ETU with JSR=5 dB. Under ETU with interference, PRCC-CSS reduces the required SINR by approximately 9～15 dB relative to DNC at SF=7 and SF=9 and maintains a further consistent margin over coherent peak detection. In the SDR prototype, 90.4% of the received frames are retained, and the retained-frame conditional BER has a one-sided 95% upper confidence bound of 5.56×10^–5. By using the multipath-induced frequency-domain structure as a matchable intra-frame reference feature rather than as a perturbation, PRCC-CSS provides a candidate physical-layer solution for reliable short-burst communication in complex near-ground environments. Future work will extend the scheme to higher-order CSS modulation, multi-antenna diversity reception, and adaptive reference-spectrum updating for time-varying channels.
- Chirp Spread Spectrum (CSS),
- Short-burst communication,
- Synchronization estimation,
- Cyclic cross-correlation,
- Multipath-robust detection,
- Unmanned ground platform

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References(18)

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