Objective

The paper aims to present a generalized modulation scheme that can improve the anti-interference performance of global navigation satellite systems (GNSS) and mitigate the ambiguity problem in BOC modulation.

Summary background data

With the exponential growth of location-based services, there is a need to improve the positioning accuracy and the capability to resist against external interference in challenging environments, such as urban canyons, forested terrains, and indoor areas, in which signal attenuation, interference, and multipath fading can seriously degrade the positioning accuracy of global navigation satellite systems (GNSS) and GNSS-like systems. The binary offset carrier (BOC) modulation has been adopted in GNSSs because of its good spectral isolation from heritage signals, high accuracy, multipath interference resistance, and flexibility in signal implementation compared with BPSK-R modulation. However, for high-order BOC modulation, the main drawback is the ambiguity in tracking due to the multiple side peaks of the autocorrelation function (ACF). The receiver may incorrectly lock onto one of these side peaks, causing intolerable measurement bias, and this undesirable behavior limits the application of this modulation scheme in navigation systems.

Methods

We present a generalized low-ambiguity anti-interference spread spectrum modulation based on frequency-hopping BOC (FH-BOC). First, we formulate the mathematical model of FH-BOC modulation and derive the analytical expressions for the normalized ACF and PSD, and we analyze the time and frequency properties of several representative FH-BOC signals. Next, we present recommended parameter selections, a generation and detection scheme for FH-BOC modulation. Finally, we analyze the characteristics of the ACF and PSD, the tracking performance, the spectral separation, and the anti-narrowband interference and multipath interference performance for several specific BOC and FH-BOC signals.

Results

The results show that FH-BOC with the largest frequency-hopping band has lower ACF ambiguity, better anti-interception performance, and better anti-intrasystem interference, narrowband interference, and multipath interference performance than BOC modulation with the same main lobe bandwidth (MLB). The tracking and anti-interference performance of FH-BOC is similar to that of BOC modulation with the same ACF main peak width.

Conclusions

FH-BOC is a generalized type of modulation that includes BOC modulation. The proposed FH-BOC signal improves the anti-interference performance and mitigates the ACF ambiguity problem of BOC modulation. The acquisition time and complexity of the receiving process for the proposed FH-BOC signal are the same for the BOC signal with the same MLB. The new modulation scheme which we proposed can serve as a new paradigm for the next-generation GNSS signal design, especially military signal design. It can also be used in the signal design for GNSS-like systems, such as systems for indoor positioning, GNSS enhancement, and pseudolite-based positioning.

中文翻译：

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FH-BOC：基于跳频二进制偏移载波的广义低歧义抗干扰扩频调制

目的

本文旨在提出一种通用的调制方案，该方案可以提高全球导航卫星系统（GNSS）的抗干扰性能，并减轻BOC调制中的歧义问题。

摘要背景数据

随着基于位置的服务呈指数级增长，需要提高定位精度和抵御挑战性环境（如城市峡谷，森林地形和室内区域）中的外部干扰的能力，在这些环境中，信号衰减，干扰，多径衰落会严重降低全球导航卫星系统（GNSS）和类似GNSS系统的定位精度。与BPSK-R调制相比，GNSS中采用了二进制偏移载波（BOC）调制，因为它与传统信号具有良好的频谱隔离性，高精度，多径抗干扰性以及信号实现的灵活性。但是，对于高阶BOC调制，主要缺点是由于自相关函数（ACF）的多个侧峰而导致跟踪不明确。

方法

我们提出了一种基于跳频BOC（FH-BOC）的广义低歧义抗干扰扩频调制。首先，我们建立了FH-BOC调制的数学模型，并导出了归一化ACF和PSD的解析表达式，并分析了几种代表性FH-BOC信号的时间和频率特性。接下来，我们介绍推荐的参数选择，FH-BOC调制的生成和检测方案。最后，我们分析了几种特定的BOC和FH-BOC信号的ACF和PSD的特性，跟踪性能，频谱分离以及抗窄带干扰和多径干扰性能。

结果

结果表明，与相同主瓣带宽（MLB）的BOC调制相比，跳频带宽最大的FH-BOC具有更低的ACF模糊度，更好的抗拦截性能以及更好的抗系统内干扰，窄带干扰和多径干扰性能）。FH-BOC的跟踪和抗干扰性能类似于具有相同ACF主峰宽的BOC调制。

结论

FH-BOC是一种通用类型的调制，其中包括BOC调制。所提出的FH-BOC信号提高了抗干扰性能并减轻了BOC调制的ACF模糊性问题。对于具有相同MLB的BOC信号，所提出的FH-BOC信号的获取时间和接收过程的复杂度是相同的。我们提出的新调制方案可以作为下一代GNSS信号设计（尤其是军事信号设计）的新范例。它还可以用于类似GNSS的系统的信号设计中，例如用于室内定位，GNSS增强和基​​于伪卫星的定位的系统。