Abstract
—In this paper we review some of the work of the’ Satellite Working Group’ in the European Technology platform NETWORLD2020 towards a strategy for satellites in 5G. We first review the 5G vision and its drivers as defined by the terrestrial mobile community via the 5GPPP Association. We then outline the areas in which satellite can contribute to an integrated system within 5G and detail the research challenges that this provides. Finally we give views on a technology roadmap to meet these challenges such that satellites are ready by 2020 to play their part in the integrated 5G roll out.
摘要—在本文中，我们回顾了欧洲技术平台NETWORLD2020中的“卫星工作组”为实现5G卫星战略所做的一些工作。 我们首先通过5GPPP协会回顾地面移动社区定义的5G愿景及其驱动因素。 然后，我们概述了卫星可以在5G内的集成系统中做出贡献的领域，并详细介绍了由此带来的研究挑战。 最后，我们提出了应对这些挑战的技术路线图，以使卫星在2020年做好准备，在集成5G推出中发挥自己的作用。
I. INTRODUCTION
Mobile cellular communication systems have evolved through a series of standards known as ‘Generations’ from Analogue(1G) through GSM (2G) via IMT 2000 (3G) to today’s LTE(4G) systems. Satellite mobile systems have developed independently of the terrestrial systems and have largely been proprietary e.g. the Inmarsat system. There has been a loose connection in that the latter have generally used the GSM network model and more recently there have been versions of GSM/GPRS and 3G adapted for satellites e.g. the ETSI GMR series of standards. The result of this separation between the communities is that it is very difficult to integrate the two networks and thus join them so as to provide seamless services over both. Very recently the community has woken up to this problem and work is on-going to enable some integration of 4G between satellite and mobile. Today we are at the start of working towards the next generation—5G, which is likely to be standardised by 2016 and be rolled out from 2020. The EU have set up a 5GPPP research programme to fund research towards this new standard which will commence in 2015. A group of companies have formed the ‘5GPPP Association’ and have worked towards a definition of this research programme[1-2]and is also included within a new European Technology Platform— NETWORLD2020. The latter ETP merges the old terrestrial Net!works and the satellite ISI, ETP’s such as to integrate these two key components of future communications. This provides the structure in which the two communities can now work together, for the first time, to develop an integrated 5G standard. Within NETWORLD2020 there is a Satellite Working Group that is producing a White Paper on the role of satellites in 5G. This paper is based on the work conducted for that paper but also contains some personal views of the author.
一，引言
移动蜂窝通信系统已经通过一系列称为“代”的标准从模拟（1G）到GSM（2G）经由IMT 2000（3G）发展到今天的LTE（4G）系统。卫星移动系统是独立于地面系统而开发的，并且在很大程度上是专有的，例如Inmarsat系统。存在松散的联系，因为后者通常使用GSM网络模型，并且最近已经有适用于卫星等的GSM / GPRS和3G版本。 ETSI GMR系列标准。社区之间的这种分离的结果是，很难整合两个网络并因此加入它们，以在两者之间提供无缝服务。最近，社区已经意识到了这个问题，并且正在进行使卫星与移动设备之间进行4G集成的工作。今天，我们正着手迈向下一代-5G，该技术很可能在2016年实现标准化，并于2020年推出。欧盟已经建立了一个5GPPP研究计划，以资助针对该新标准的研究，该研究将于2010年开始。 2015年。一组公司成立了“ 5GPPP协会”，并致力于确定该研究计划[1-2]，并且也包含在新的欧洲技术平台NETWORLD2020中。后者的ETP合并了旧的地面Net！works和ESI卫星ISI，以便将未来通信的这两个关键组件集成在一起。这提供了两个社区现在可以首次合作开发集成的5G标准的结构。 NETWORLD2020内部有一个卫星工作组，该工作组正在编写有关5G中卫星作用的白皮书。本文基于针对该论文所做的工作，但也包含了作者的一些个人观点。
IV. KEY AREAS WHERE SATELLITE CAN PLAY A PART IN 5G
The key areas in which satellites can play a part in 5G are discussed below.
· Coverage
Satellites can provide the wide coverage to complement and to extend the dense terrestrial cells, which is in line with the ubiquitous coverage targeted by 5G networks They will not be able to match the area spectral efficiency of the 5G terrestrial but they can provide larger cells in a heterogeneous arrangement which can also be used for critical and emergency services and possibly to relieve the terrestrial cells of signaling and management functions in a software defined network configuration.
· Integration
Integrating satellites with the terrestrial system is perhaps the key area that enables many advantages. Improving QoE by intelligently routing traffic between the delivery systems and caching high capacity video for onward transmission terrestrially. This can be empowered by the inherent multicast/broadcast capabilities of satellite systems, while propagation latency is no longer an issue thanks to intelligent caching. Off loading traffic from the terrestrial system to save on valuable terrestrial spectrum opens up the possibility of improving resilience and security using the two networks.
· Backhaul
One of the major issues in 5G is seen to be the increased demands on the backhaul with very large numbers of small cells. High throughput satellites can be used here to compliment terrestrial provision and provide backhaul in areas where it is difficult to do so terrestrially. In a virtualised and SDN it might also be possible to include some of the network node functions on board the satellite and thus save on physical sites on the ground.
· Resilience, security and availability
We have seen that this is a key feature in 5G and satellites can be used to provide an overlay network that can take over and keep alive the network in case of man-made or natural disasters. They will not be able to provide the full set of services but they are key to retention of critical and life-saving services. As 5G becomes not just a nice to have facility but an essential part of national infrastructures, it will be used more for strategic services.
· IoT
The inclusion of billions of sensors in the IoT all transmitting low date rate M2M and being scattered over wide areas makes it well suited to satellite collection and distribution. Here again integrated systems are forseen with new network architectures collecting from clusters of sensors and satellite being used to backhaul them to fusion POP’s. Based on the wide satellite coverage, IoT economies of scale can be achieved and promote viable business models for a large number of bursty-low rate transmissions.
· Spectrum
The lack of spectrum was seen as one of the key drivers to the 5G network architecture. The demands on the design of the network could be relaxed if more spectrum could be made available. Frequency sharing on a dynamic basis between mobile and satellite systems can deliver major increases in the spectrum provided both sectors accept the sharing principles. Here techniques of data bases and cognitive radio can be built into future systems to allow such frequency sharing. This can be a win-win situation to both sectors and would be enhanced by an integrated approach。
IV。卫星可以在5G中发挥作用的关键领域
下文讨论了卫星可以在5G中发挥作用的关键领域。
·覆盖范围
卫星可以提供广泛的覆盖范围，以补充和扩展密集的地面蜂窝网络，这与5G网络所针对的普遍覆盖范围是一致的。它们将无法与5G地面频谱效率相匹配，但是它们可以在5G网络中提供更大的小区。一种异构安排，也可以用于紧急和紧急服务，并可能减轻软件定义的网络配置中地面小区的信令和管理功能。
·融合
将卫星与地面系统整合可能是实现许多优势的关键领域。通过在传送系统之间智能路由流量并缓存高容量视频以进行地面传输来改善QoE。卫星系统固有的多播/广播功能可以实现这一点，而由于智能缓存，传播延迟不再成为问题。从地面系统卸载流量以节省宝贵的地面频谱，为使用这两个网络提高弹性和安全性提供了可能性。
·回传
5G的主要问题之一是大量小蜂窝对回程的需求增加。高吞吐量卫星可用于补充地面资源，并在难以进行地面传输的区域提供回程。在虚拟化和SDN中，还可能在卫星上包含一些网络节点功能，从而节省地面上的物理站点。
·弹性，安全性和可用性
我们已经看到，这是5G的一项关键功能，人造卫星可用于提供覆盖网络，在人为或自然灾害的情况下，该网络可以接管并保持该网络的生命。他们将无法提供全套服务，但对于保留关键且可挽救生命的服务至关重要。随着5G不仅成为拥有设施的好地方，而且成为国家基础设施的重要组成部分，它将更多地用于战略服务。
·物联网
物联网中包含数十亿个传感器，它们全部传输低日期速率M2M，并且散布在广阔的区域，因此非常适合卫星收集和分配。在这里，集成系统将通过新的网络架构进行预见，这些架构将从传感器和卫星集群中收集，这些传感器和卫星用于回传它们以融合POP。基于广泛的卫星覆盖范围，可以实现物联网的规模经济并促进适用于大量突发性低速率传输的可行业务模型。
·频谱
频谱的缺乏被视为5G网络架构的关键驱动因素之一。如果可以提供更多频谱，则可以放宽对网络设计的要求。如果两个部门都接受共享原则，则在移动和卫星系统之间动态地进行频率共享可以大大提高频谱。在这里，数据库和认知无线电的技术可以内置到未来的系统中，以允许这种频率共享。这对双方来说都是双赢的局面，如果采取综合措施，这种局面将会得到改善。
V. ADDRESSING THE 5G KEY AREAS
The NETWORLD2020 experts group have brigaded topics for consideration into four areas; services&requirements, software
defined networks and virtualisation, connectivity and networks
and air interface.
In this section we present the inputs from the satellite WG to these four areas. The latter will eventually be combined into a single White Paper and then form the strategic research agenda for the ETP. It is noted that the 5G call (Nov 14) of the EU considers groupings of, Radio Network architectures and technologies, convergence beyond the last mile, network virtualisation and software defined networks and network management. There is clear commonality in these areas and in the following they are addressed as far as satellites are concerned.
V.解决5G关键领域
NETWORLD2020专家组将各个主题分为四个领域： 服务与需求，软件
定义的网络以及虚拟化，连接性和网络
和空中接口。在本节中，我们介绍了卫星工作组对这四个领域的投入。 后者最终将合并为一份白皮书，然后形成ETP的战略研究议程。 值得注意的是，欧盟的5G呼叫（11月14日）考虑了以下方面的分组：无线电网络架构和技术，超越最后一英里的融合，网络虚拟化以及软件定义的网络和网络管理。 在这些领域有明显的共性，下面就卫星问题着手解决。
Services and user requirements:
Satellites will play an important role in the extension of 5G cellular networks to sea, air and remote land areas that are not covered by the small cell networks. With many more people expecting to have the same coverage when travelling (on cruise liners, passenger aircraft, high speed trains and in holiday villas) it is key that satellite allows seamless extension of 5G services.
IoT coverage to wide areas involving sensors and M2M connections are ideal services to make use of satellite wide area coverage. The challenge is to design efficient low data rate communications in large numbers via the satellite.
Transport services including V2V are again ideal for satellite with its wide coverage. In the safety market all new vehicles are likely to be mandated to include safety packages and given the need for ubiquitous coverage, systems that follow on from the EU SAFETRIP demonstration for example could play a key role.
Localisation and positioning is key to many different 5G services. The integration of cellular and satellite positioning systems is a key challenge to enabling this vast range of services.
Satellites are already used for earth resource data which is in itself used as an input to many new services. Coupling this with integrated satellite and cellular communications will provide a powerful new fusion enabling the innovation of such services.
Security services require high resilience and thus the use of satellite together with cellular delivery will help provide the applications engaged by the user. The aim is that whenever the user’s location database moves during a location handoff, a service handoff also ensues collocation of the service proxy with the location database. This allows the proxy to know the location of the mobile user and reduce the network communication cost for service delivery. Different users with vastly different mobility and service patterns can adopt different integrated location and service management methods to optimize system performance.
服务和用户要求：
卫星将在将5G蜂窝网络扩展到小型蜂窝网络未覆盖的海洋，空中和偏远陆地区域中发挥重要作用。随着越来越多的人期望在旅行时（在邮轮，客机，高速火车和度假别墅中）具有相同的覆盖范围，卫星允许5G服务无缝扩展的关键是关键。
物联网覆盖范围广，涉及传感器和M2M连接是利用卫星广域覆盖的理想服务。挑战是通过卫星设计大量有效的低数据速率通信。
包括V2V在内的运输服务再次凭借其广泛的覆盖范围而成为卫星的理想选择。在安全市场上，所有新车都可能被要求包括安全套件，并且由于需要无处不在的覆盖范围，因此，以欧盟SAFETRIP示范为基础的系统可以发挥关键作用。
本地化和定位是许多不同5G服务的关键。蜂窝和卫星定位系统的集成是实现如此广泛的服务的关键挑战。
卫星已经用于地球资源数据，其本身已用作许多新服务的输入。将其与集成的卫星和蜂窝通信相结合将提供强大的新融合，从而实现此类服务的创新。
安全服务需要很高的弹性，因此将卫星与蜂窝传输一起使用将有助于提供用户参与的应用程序。目的是在位置移交期间每当用户的位置数据库移动时，服务移交也会确保服务代理与位置数据库的并置。这允许代理知道移动用户的位置，并减少用于服务交付的网络通信成本。具有极大不同的移动性和服务模式的不同用户可以采用不同的集成位置和服务管理方法来优化系统性能。
Security services require high resilience and thus the use of satellite together with cellular delivery will help provide the several nines availability required. Most countries have fall back disaster and emergency networks which can benefit from an integrated satellite and cellular approach. There is increased use of surveillance using UAV’s and the necessity for real time high definition video which is best delivered by satellite. Satellites have traditionally been used for broadcast purposes but as we move into the domain of CDN’s the ability of satellites to download high data that can be cached for onward delivery becomes an attractive feature for multicast in satellite and cellular integration .QoE is becoming the byword for service provision but it is little understood at the moment. It is clear that peak and average bit rates are not the determining factor but sustainable bit rate links and QoE.
安全服务需要很高的弹性，因此将卫星与蜂窝传输一起使用将有助于提供所需的可用性。 大多数国家都有后备的灾难和应急网络，这些网络可以从集成的卫星和蜂窝方法中受益。 越来越多地使用无人机进行监视，并且有必要提供最好由卫星提供的实时高清视频。 卫星传统上一直用于广播目的，但是随着我们进入CDN领域，卫星下载可缓存的高数据以继续传输的能力已成为卫星和蜂窝集成中多播的一个吸引人的功能。QoE成为了代名词。 服务提供，但目前尚不甚了解。 显然，峰值和平均比特率不是决定因素，而是可持续的比特率链接和QoE。
Air interface:
The 5G air interface has the challenge of incorporating a range of different traffic types from high rate video down to the low rate IoT applications and serving applications with a range of latency requirements, while providing ubiquitous coverage. We see that the integration of satellite and cellular 5G is essential to extract the combined benefits of both sectors. The drivers in the satellite channel are however different from those in the cellular—signal to noise ratio is much lower, multipath is not so important but the channel is non-linear and suffers from more latency inhibiting adaption—depending on the satellite orbit. In this respect we need to adopt as far as possible flexible waveforms and air interfaces, which can be easily tuned depending on the channel they have to face. Hierarchical modulations are also an interesting tool for this reconciliation of the terrestrial and satellite air interfaces.
空中接口：
5G空中接口面临的挑战是要整合各种不同的流量类型，从高速率视频到低速率IoT应用程序，并为具有各种延迟要求的应用程序提供服务，同时提供无处不在的覆盖范围。我们看到，卫星和蜂窝5G的集成对于提取两个行业的综合利益至关重要。但是，卫星信道中的驱动器不同于蜂窝信道中的驱动器-信噪比要低得多，多径并不是那么重要，但是信道是非线性的，并且受制于更多的延迟抑制适应性-取决于卫星轨道。在这方面，我们需要尽可能采用灵活的波形和空中接口，可以根据它们所面对的通道轻松进行调整。分层调制也是用于协调地面和卫星空中接口的有趣工具。
Concerning the MAC, there is much to gain from an integrated terminal which uses as much commonality as possible with terrestrial, e.g. by implementing software MAC for example. This needs to be coupled to the energy reduction that can be achieved in the terminal design
关于MAC，从集成终端获得许多好处，该集成终端与地面（例如，地面）使用尽可能多的通用性。例如通过实现软件MAC。这需要与终端设计中可以实现的节能相结合。
Multi-polarization MIMO as a scheme that requires reduced channel state information suitable for satellite and context aware multi-user detection, either centralized or decentralized, as a means to introduce QoE requirements. Aggressive frequency reuse combined with multiuser MIMO techniques can provide improved and flexible system
throughput. For these techniques a feedback channel is important, it can be terrestrial; thus further fostering some integration. Receivers for bursty communications are an area of research that will benefit the role of satellites in IoT.Multicarrier schemes such as filter bank systems or other enhanced OFDM schemes with appropriate modulations that offer optimal spectral efficiency and frequency granularity are being investigated in terrestrial wireless but also have
commonality to satellite systems
多极化MIMO作为一种方案，要求减少的信道状态信息适合于集中式或分散式的卫星和上下文感知多用户检测，以此作为引入QoE要求的手段。 积极的频率重用与多用户MIMO技术相结合可提供改进且灵活的系统
吞吐量。 对于这些技术，反馈渠道很重要，它可能是地面的。 从而进一步促进了整合。 突发通信的接收器是一个研究领域，将有利于卫星在物联网中的作用。正在研究陆地无线中的多载波方案，例如滤波器组系统或具有适当调制的其他增强OFDM方案，这些调制可提供最佳频谱效率和频率粒度，但是 与卫星系统有共同点
It is quite clear that there is a spectrum crunch looming for
cellular and a need to use spectrum more efficiently. Thus
frequency sharing between cellular and satellite is one
component that can contribute to solving this problem. At the
moment frequency bands are segmented but this is wasteful and
we need to allocate them more dynamically on the basis of
demand. Techniques such as intelligent data bases and
Cognitive Radio as well as smart antenna beamforming can be
used to facilitate frequency sharing to the benefit of both
sectors.
很明显，蜂窝网络迫在眉睫，需要更有效地利用频谱。 因此，蜂窝与卫星之间的频率共享是有助于解决这一问题的一个组件。 目前频段已分段，但这很浪费，我们需要根据需求更动态地分配它们。 可以使用诸如智能数据库和认知无线电以及智能天线波束成形之类的技术来促进频率共享，从而使两个部门受益。