无线电通信技术

随着6G对泛在连接的需求，非地面网络(Non-Terrestrial Networks,NTN)与通信感知一体化(Integrated Sensing and Communications,ISAC)的融合成为重要趋势。仿射频分复用(Affine Frequency Division Multiplexing,AFDM)凭借其在啁啾时频域的独特调制特性，被视为高动态场景的有力候选波形。采用叠加导频帧结构能显著提升频谱效率，但在双色散一体化场景下，面临数据-导频相互污染的问题，现有的AFDM研究对于多径大多基于整数倍采样间隔的传输模型展开，但在实际信道中，存在分数能量泄露，会加剧数据-导频相互污染。因此面向NTN场景，考虑了更贴近实际的分数阶采样间隔传输模型，并提出了一种AFDM通感一体自适应功控及信道估计方法，发射端的自适应导频功率分配(Adaptive Pilot Power Allocation,APPA)机制，可以改善叠加导频结构中数据-导频相互干扰，而接收端的基于牛顿化正交匹配追踪(Newtonized Orthogonal Matching Pursuit,NOMP)的信道估计算法，可获取时延-多普勒信息，并作为反馈变量逆向调节下一次的功率分配。结果表明，所提方案在感知性能损失可接受的同时，提升了高移动环境下的通信可靠性，为AFDM-ISAC技术走向空天地一体化落地提供了理论支撑。

Driven by the demand for ubiquitous connectivity in 6G, the integration of Non-Terrestrial Networks(NTN) and Integrated Sensing and Communications(ISAC) has emerged as a significant trend. Affine Frequency Division Multiplexing(AFDM), leveraging its unique modulation characteristics in the chirp time-frequency domain, is considered a promising waveform candidate for high-mobility scenarios. Although the adoption of a superimposed pilot frame structure can substantially enhance spectral efficiency, it suffers from severe data-pilot mutual contamination in doubly-selective ISAC channels. Existing research on AFDM mostly assumes transmission models with integer multiples of the sampling interval for multipath delays. In practical channels, however, fractional energy leakage inevitably occurs, which further exacerbates this data-pilot interference. To address this challenge in NTN scenarios, this paper considers a more realistic transmission model featuring fractional sampling intervals and proposes an adaptive power control and channel estimation method for AFDM-ISAC systems. Specifically, an Adaptive Pilot Power Allocation(APPA) mechanism is developed at the transmitter to mitigate the mutual interference between data and pilots in the superimposed pilot structure. At the receiver, a channel estimation algorithm based on Newtonized Orthogonal Matching Pursuit(NOMP) is designed to accurately acquire delayDoppler information, which is then fed back to inversely adjust the power allocation for the subsequent transmission. Results show that the proposed scheme enhances communication reliability in high-mobility scenarios while maintaining tolerable sensing performance loss, providing solid theoretical support for deploying AFDM-ISAC in space-air-ground integrated networks.