Terabit Bidirectional Multi-user Optical Wireless System (TOWS) for 6G LiFi

鉴于对射频频谱之外的移动容量的空前需求，很自然地会考虑在未来的地面无线系统中使用红外和可见光光谱。与毫米波无线电系统相比，使用这些电磁频谱部分的无线系统可以被归类为毫米波无线通信系统，两者都正在当前的5G系统中进行标准化。因此，TOWS将提供一种技术上的逻辑途径，以确保无线系统是面向未来的，并且它们可以提供未来数据密集型服务（如高清视频流、增强现实、虚拟现实和混合现实）所需的容量。基于光的无线通信系统不会与射频通信竞争，相反，这些系统遵循了过去30年来在蜂窝通信中所见证的趋势。基于光的无线通信只是增加了新的容量——可用的频谱是射频频谱的2600倍。6G及以上承诺增加无线容量，以适应日益拥挤的频谱中流量的增长，但现在需要采取行动确保英国在快速发展的6G领域的领导地位。光学无线（OW）使用简单的源和探测器打开了带宽超过540太赫兹的新频谱带，比具有更大频谱的蜂窝和WiFi更简单。它是毫米波以外频谱的最佳选择，与太赫兹频谱（另一种可能的选择）不同，OW避免了复杂的源和探测器，并且具有良好的室内信道条件。光信号在室内使用时，被限制在其发出的环境中，这在物理层提供了额外的安全性，并且能够在相邻的房间中重复使用波长，从而从根本上增加了容量。我们的愿景是开发并实验演示多用户太比特/秒光无线系统，该系统提供的容量至少比目前计划的5G光和无线电无线系统高两个数量级，无线系统的路线图可提供高达四个数量级的容量。拟议的系统有四个特点，使这种前所未有的能力成为可能，使这种破坏性的进步成为可能。首先，与可见光通信（VLC）不同，我们将利用红外光谱，这为VLC相关的调光问题提供了解决方案，消除了上行VLC眩光，从而支持双向通信。其次，为了实现更大的传输容量和多用户、多小区操作，我们将引入一种新型的类似led的可操纵激光二极管阵列，它不会受到传统激光二极管的散斑损伤，同时确保超高速性能。第三，随着容量的增加，我们将开发本地OW多用户系统来共享资源，这些系统是自适应定向的，可以在减少用户和小区间干扰的情况下实现全覆盖，并最终合并RF系统，以实现无缝过渡和促进整体网络控制，本质上是将软件定义无线电引入光学无线。这意味着OW多用户系统可以很容易地设计成允许非常高的聚合容量，因为波束可以以紧凑的方式控制。我们将为我们的光学多用户系统开发先进的小区间编码和切换，这也允许在需要时与无线电系统进行无缝切换，例如弹性。我们相信这项工作，虽然具有挑战性，但是可行的，因为它将利用联盟现有的技术和研究，包括卓越的OW链路设计，先进的编码和调制，前端和回程网络的优化算法，表面发射激光设计的专业知识和超灵敏探测的单光子雪崩探测器。

Given the unprecedented demand for mobile capacity beyond that available from the RF spectrum, it is natural to consider the infrared and visible light spectrum for future terrestrial wireless systems. Wireless systems using these parts of the electromagnetic spectrum could be classified as nmWave wireless communications system in relation to mmWave radio systems and both are being standardised in current 5G systems. TOWS, therefore, will provide a technically logical pathway to ensure that wireless systems are future-proof and that they can deliver the capacities that future data intensive services such as high definition (HD) video streaming, augmented reality, virtual reality and mixed reality will demand. Light based wireless communication systems will not be in competition with RF communications, but instead these systems follow a trend that has been witnessed in cellular communications over the last 30 years. Light based wireless communications simply adds new capacity - the available spectrum is 2600 times the RF spectrum.6G and beyond promise increased wireless capacity to accommodate this growth in traffic in an increasingly congested spectrum, however action is required now to ensure UK leadership of the fast moving 6G field. Optical wireless (OW) opens new spectral bands with a bandwidth exceeding 540 THz using simple sources and detectors and can be simpler than cellular and WiFi with a significantly larger spectrum. It is the best choice of spectrum beyond millimetre waves, where unlike the THz spectrum (the other possible choice), OW avoids complex sources and detectors and has good indoor channel conditions. Optical signals, when used indoors, are confined to the environment in which they originate, which offers added security at the physical layer and the ability to re-use wavelengths in adjacent rooms, thus radically increasing capacity. Our vision is to develop and experimentally demonstrate multiuser Terabit/s optical wireless systems that offer capacities at least two orders of magnitude higher than the current planned 5G optical and radio wireless systems, with a roadmap to wireless systems that can offer up to four orders of magnitude higher capacity.There are four features of the proposed system which make possible such unprecedented capacities to enable this disruptive advance. Firstly, unlike visible light communications (VLC), we will exploit the infrared spectrum, this providing a solution to the light dimming problem associated with VLC, eliminating uplink VLC glare and thus supporting bidirectional communications. Secondly, to make possible much greater transmission capacities and multi-user, multi-cell operation, we will introduce a new type of LED-like steerable laser diode array, which does not suffer from the speckle impairments of conventional laser diodes while ensuring ultrahigh speed performance. Thirdly, with the added capacity, we will develop native OW multi-user systems to share the resources, these being adaptively directional to allow full coverage with reduced user and inter-cell interference and finally incorporate RF systems to allow seamless transition and facilitate overall network control, in essence to introduce software defined radio to optical wireless. This means that OW multi-user systems can readily be designed to allow very high aggregate capacities as beams can be controlled in a compact manner. We will develop advanced inter-cell coding and handover for our optical multi-user systems, this also allowing seamless handover with radio systems when required such as for resilience. We believe that this work, though challenging, is feasible as it will leverage existing skills and research within the consortium, which includes excellence in OW link design, advanced coding and modulation, optimised algorithms for front-haul and back-haul networking, expertise in surface emitting laser design and single photon avalanche detectors for ultra-sensitive detection.