In Orthogonal Time Frequency Space (OTFS) systems, in order to support high-speed mobility and multi-user compatibility, and to reconstruct the entire two-dimensional delay-Doppler (DD) channel response from limited observations in strong interference environments, pilot structures with extensive guard intervals are required for channel estimation. This leads to high pilot overhead and low information transmission efficiency. To address this issue, a pilot-sharing-based channel estimation method for OTFS systems is proposed. This method targets high-speed railway long-tunnel scenarios and leverages the correlation between adjacent users’ channels to enable cooperative sharing and reuse of pilot information, thereby effectively reducing the overall system pilot overhead. Firstly, a correlation-based shared pilot structure is designed, allowing the saved delay-Doppler resource grid elements under low pilot overhead to be reallocated for data transmission. Then, a decision-feedback-based channel estimation algorithm is designed, which significantly enhances the overall resource utilization and effective data transmission rate of the system while ensuring channel estimation accuracy. Simulation results demonstrate that, in a delay-Doppler domain grid of $32\times 32$ with a subcarrier spacing of 15 kHz and under Quadrature Phase Shift Keying (QPSK) modulation, the proposed method reduces the pilot overhead of the considered two-user system by 50% compared to existing approaches while keeping the bit error rate (BER) at a low level. This results in a relative increase of 19.05% in the system’s throughput. Moreover, at a mean square error (MSE) of $1.5\times 10^{-4}$ , the proposed algorithm achieves a performance gain of about 2 dB compared to conventional schemes.
Xiaotian Li, Zitian Zhao, Jiameng Pei et al.· IEEE Open Journal of the Com...· 0 citations
BACKGROUND
Evidence linking extreme temperature exposure to hypertensive disorders of pregnancy (HDP) remains inconsistent, with limited synthesis on exposure timing and climatic vulnerability.
OBJECTIVE
To quantify associations of extreme heat, cold, and season-related exposures with HDP, preeclampsia (PE), and gestational hypertension (GH), and to identify critical windows and vulnerable climate zones.
METHODS
We systematically searched five databases up to February 2026. Observational studies (≥500 participants) reporting HDP outcomes with recognized diagnostic criteria were included. Random-effects meta-analyses were performed with subgroup analyses by exposure window, climate zone, and study period.
RESULTS
Twenty-eight studies (23,268,235 participants) were included. Heat exposure was significantly associated with increased HDP risk (pooled OR = 1.58, 95% CI: 1.31-1.90; I² = 98%), particularly for PE (OR = 2.01, 95% CI: 1.42-2.84; I² = 99%). Cold exposure showed no statistically significant pooled association. Stronger associations were observed in arid climates (PE: OR = 2.09, 95% CI: 1.19-3.66; I² = 40%) and during late gestation (≥28 weeks: OR = 1.23, 95% CI: 1.05-1.45; I² = 95%). Continuous temperature modeling revealed a linear exposure-response relationship (OR per 1 °C = 1.03, 95% CI: 1.02-1.04; I² = 48%).
CONCLUSION
Maternal heat exposure is significantly associated with increased HDP risk, particularly preeclampsia, with pronounced effects in arid regions and late pregnancy. These findings support integrating climate-adaptive strategies into antenatal care.
Yue-Tong Zheng, Yi-Nan Wang, Yawei Zhu et al.· Ecotoxicology and Environmen...· 0 citations
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