Galileo系统中MBOC调制信号及性能分析

MBOC(Multiplexed Binary Offset Carrier)调制是GalileoE1频段以及GPS L1C频段推荐使用的一种优化调制方式。与BOC调制相比,MBOC调制方式的功率谱密度函数提供了更为丰富的高频分量,因此具有更高的伪码跟踪精度和抗多径性能。Galileo E1 OS采用了CBOC(6,1,1/11)(Composite Binary Offset Carrier)的方式实现MBOC调制。通过MATLAB仿真,对该信号的自相关函数、频谱特性进行了研究,并且通过与BOC调制信号的比对,证明了MBOC在码跟踪特性和抗多径性能方面的优越性。     

混合二进制偏移载波调制技术

针对即将在全球卫星导航定位系统GPS的L1民用信号和伽利略卫星导航定位系统的L1开放服务信号中使用的BOC调制技术的优化问题,对MBOC调制技术的基本概念作了重点介绍.并在此基础上用仿真方法验证MBOC(6,1,1/11)信号的多径误差和Gabor带宽,给出仿真结果,同时与BOC信号作比较.仿真结果表明:在采用正弦副载波时,MBOC(6,1,1/11)信号的抗多径性能相对于BOC(1,1)信号和BOC(2,2)信号有明显改善;但在采用余弦副载波时,MBOC(6,1,1/11)信号的抗多径性能相对于BOC(2,2)信号没有明显改善,并且BOC(2,2)信号在Gabor带宽方面还要优于MBOC(6,1,1/11),而BOC信号接收机结构的实现却更加容易.因此,余弦副载波类型的BOC(2,2)相对于MBOC(6,1,1/11)更有优势.     

MBOC信号模拟及其性能评估

在全球卫星导航系统的现代化框架中,MBOC调制信号是新近提出的一种调制方式,将成为GalileoE1OS和GPSL1C的候选信号,因而MBOC数字中频信号的产生对于新的导航信号结构的研究和新一代接收机的研制具有极其重要的意义。对MBOC信号的时域和频域特性进行了理论分析、对其产生方式进行了仿真验证。设计开发了相应的数字中频信号模拟器,生成了CBOC和TMBOC两种实现方式下的MBOC信号,并采用软件接收机进行了闭环测试,得到了预期的结果。     

BOC、MBOC和CBCS三种子载波调制方式的性能分析

根据自相关函数、功率谱密度、多径误差包络和Cramer Rao跟踪误差下边界等性能指标,分析和评估了BOC、MBOC和CBCS的性能.结果表明,MBOC和CBCS的功率谱密度的两个分裂主瓣在±1.023MHz附近,保证了与BOC(1,1)的互操作性,但它们的高频分量幅度都明显高于BOC(1,1);MBOC和CBCS的自相关函数比BOC(1,1)窄;从抗多径误差能力和Cramer Rao跟踪误差下边界这两方面来比较,MBOC和CBCS的性能比BOC(1,1)好.     

MBOC调制及Matlab仿真

MBOC(Mulitplexed Binary Offset Carrier)调制信号具跟踪精度好和抗多径等性能,目前GPS、伽利略、北斗均有计划采用这种调制信号。文章首先介绍了MBOC的基本原理,然后分别具体阐释了TMBOC和CBOC调制方法相关特点,最后在Matlab中对这两种调制MBOC调制进行了仿真。     

Performance of the Proposed Galileo CBOC Modulation in Heavy Multipath Environment

In the framework of the modernization plans of Global Navigation Satellite Systems (GNSS) a new Multiplexed Binary Offset Carrier (MBOC) modulation has been proposed as a possible Signal-In-Space (SIS) with improved performance with respect to the robustness against external sources of degradation. Discussion around such signal format are still on-going at the time of writing, anyway it is the most probable candidate signal that will be adopted by both GPS L1C and the Galileo E1 Open Service (OS) signals [(, 2004)] as modernization of the present BOC(1,1). In the context of the integration between wireless communication and satellite navigation, one of the major problems is that usually the GNSS receiver has to work in a critical environment characterized by a heavy presence of multipath or interference sources. Some examples are urban canyons or light indoor spaces. These are also typical situations for the usage of personal communications systems. The new MBOC modulation have been studied with the specific goal to create a signal more robust with respect to multipath, bringing the high performance of Galileo in situations in which the present BOC(1,1) shows limitations. In this sense, future Location Based Services (LBS) provided on the basis of the GNSS OS will benefits from this intrinsic robustness of the signal. Throughout the paper a review of the MBOC structure will be presented, specifying that in the Galileo framework such a structure has been proposed in a version named Composite BOC (CBOC). In particular, the paper presents the simulation of the CBOC behavior in presence of multipath showing the extreme improvement with respect to other BOC solutions.

基于MBOC调制的北斗导航信号的多径误差分析

为了定量地分析MBOC(Multiplexed binary offset carrier)调制的北斗导航信号的多径误差,在分析MBOC调制信号原理的基础上,建立了相应的多径信号模型,利用超前减滞后功率鉴相器和反正切函数鉴相器,推导了多径效应导致码相位跟踪误差和载波相位误差的表达式.对不同的多径直达幅度比(Multipath todirect ratio,MDR)、相关器间隔、前端带宽时MBOC调制信号的多径性能进行了仿真,并针对存在噪声干扰时的码跟踪误差进行了仿真分析.仿真结果表明,多径直达幅度比由-3 dB减小到-6 dB时,所产生的多径误差包络也相应地减小.在多径直达信号幅度比(MDR)一定时,采用窄相关技术和较宽的接收机前端带宽均能很好地抑制多径误差.存在噪声干扰时,码跟踪误差随着载噪比(Carrier to Noise Ratio,CNR)的增加逐渐减小为0.     

基于自相关副峰消除的多径抑制技术改进

为消除Sine-BOC(1,1)信号自相关函数的旁瓣所引起的跟踪模糊问题,Oliver Julien提出了自相关副峰消除技术。在此研究的基础上,将其与传统的窄相关和Strobe多径抑制技术相结合,并针对Sine-BOC(1,1)和CBOC(6,1,1/11)信号进行多径抑制性能分析。通过分析EML鉴别曲线过零点偏移情况和多径抑制能力可知,ASPeCT技术不仅消除跟踪模糊,而且能够有效地提升窄相关和Strobe技术的多径抑制能力。