Space data and information transfer systems — Flexible advanced coding and modulation scheme for high rate telemetry applications
空间数据和信息传输系统——用于高速遥测应用的灵活高级编码和调制方案
发布日期:
2013-05-29
ISO 17854:2013定义了一种高效、全面的编码和调制解决方案,能够支持广泛的频谱效率值和数据速率。主要目标是高数据率遥测应用,即地球探索卫星服务(EESS)遥测有效载荷,在这种应用中,通过先进的自适应技术提高系统吞吐量被认为是满足未来任务要求的关键。
ISO 17854:2013基于串行级联卷积码(SCCC)的一种可能实现,提出了一种类似turbo的编码/调制方案。该方案利用了多种调制技术(包括QPSK、8PSK、16APSK、32APSK和64APSK)和广泛的编码速率。
可用的不同调制方案的数量,加上适当选择的编码率,使得整个系统能够有效地利用可用带宽,使其自身适应链路的可变条件。所提出的方案可以实现可变编码和调制(VCM)模式,该模式按照预定的时间表(例如,作为仰角的函数)根据信道条件改变传输方案。当信道可用于提供反馈(例如通过遥控)时,可以使用自适应编码和调制(ACM)模式动态调整传输方案。由于采用了实用的方法,所提出的编码方案很容易适应任何可用的调制格式:
二进制编码器的输出在交织后映射到所考虑的调制方案。换句话说,提出了一种比特交织编码调制方案。
SCCC主要用于高数据速率应用。前向纠错(FEC)方案基于两个简单的四态编码器结构的级联。SCCC方案意味着恒定长度的物理层帧,在固定位置插入导频。这种架构简化了同步过程,从而进一步允许接收机以极高的速率进行快速高效的捕获。
ISO 17854:2013描述了一种将多种调制格式与灵活的编码和同步方法紧密结合在一起的技术。
特别是,ISO 17854:2013提供了一系列推荐格式,其中每种格式都将调制技术与编码和同步方法的定制实现配对。然而,如果其他CCSDS文件中建议使用这些调制和/或代码,ISO 17854:2013不限制与这些建议一致的调制和/或代码的选择。
ISO 17854:2013 defines an efficient and comprehensive coding and modulation solution able to support a wide range of spectral efficiency values and data rates. The main target is given by high data rate telemetry applications, i.e. Earth Exploration Satellite Service (EESS) telemetry payload, where the increase of the system throughput by means of advanced adaptive techniques is deemed essential in order to fulfil the requirements imposed by future missions.
ISO 17854:2013 presents a turbo-like coding/modulation scheme based on one possible realization of a Serial Concatenated Convolutional Code (SCCC). This scheme makes use of a set of a large variety of modulation techniques (including QPSK, 8PSK, 16APSK, 32APSK, and 64APSK) and a wide range of coding rates. The number of different modulation schemes available, combined with a properly selected coding rate, allows the overall system to make efficient use of the available bandwidth, adapting itself to the variable conditions of the link. The proposed scheme can implement Variable Coding and Modulation (VCM) mode, which varies the transmission scheme to the channel conditions following a predetermined schedule (for example, as a function of the elevation angle). When a channel is available to provide feedback (e.g. via Telecommand), the transmission scheme can be dynamically adjusted using the Adaptive Coding and Modulation (ACM) mode. The proposed coding scheme is easily adapted to any of the available modulation formats thanks to the pragmatic approach adopted: the outputs of the binary encoders are mapped to the considered modulation scheme, after being interleaved. In other words, a bit-interleaved coded modulation scheme is proposed.
The use of SCCC is intended mainly for high data rate applications. The Forward Error Correction (FEC) scheme is based on the concatenation of two simple four-state encoder structures. The SCCC scheme implies a Physical Layer frame of constant length, with pilots inserted in fixed positions. This architecture simplifies the synchronization procedure, thus further allowing fast and efficient acquisition at very high rates for the receiver.
ISO 17854:2013 describes a technique incorporating multiple modulation formats paired with a flexible coding and synchronization method in a tightly integrated fashion. In particular, ISO 17854:2013 provides a series of recommended formats where each format pairs a modulation technique with a tailored implementation of the coding and synchronization method. However, where these modulations and/or codes are recommended in other CCSDS documents, ISO 17854:2013 does not limit the choice of modulations and/or codes consistent with those recommendations.