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

鉴于除了射频频谱之外对移动容量的空前需求，考虑未来地面无线系统的红外和可见光频谱是很自然的。使用这些部分电磁频谱的无线系统可以被归类为与毫米波无线电系统相关的nmWave无线通信系统，并且两者都在当前的5G系统中被标准化。因此，TOWS将提供一条技术逻辑路径，以确保无线系统是面向未来的，并确保它们能够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将不会与射频通信竞争，相反，这些系统遵循过去30年来蜂窝通信的趋势。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和Beyond承诺增加无线容量，以适应日益拥挤的频谱中的流量增长，但现在需要采取行动，以确保英国在快速移动的6G领域处于领先地位。无线光网络(OW)使用简单的信号源和探测器开辟了带宽超过540 THz的新频段，并且可以比蜂窝和WiFi更简单，具有显著更大的频谱。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避免了复杂的信号源和探测器，并具有良好的室内信道条件。当在室内使用光信号时，光信号被限制在其产生的环境中，这在物理层提供了更高的安全性，并能够重复使用相邻房间中的波长，从而从根本上增加了容量。我们的愿景是开发和实验演示多用户太比特/S光无线系统，其容量至少比当前规划的5G光纤和无线电系统高两个数量级，并制定了无线系统的路线图，可以提供高达四个数量级的容量。拟议系统的四个功能使这种前所未有的容量成为可能，从而实现这一颠覆性的进步。首先，与可见光通信(VLC)不同，我们将利用红外光谱，这为与VLC相关的光线变暗问题提供了解决方案，消除了上行链路VLC的眩光，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、多单元运行，我们将引入一种新型的类LED可控激光二极管阵列，该阵列在确保超高速性能的同时，不受传统激光二极管的散斑损伤的影响。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，这些系统具有自适应的方向性，以实现全面覆盖，减少用户和小区间干扰，并最终纳入射频系统，以实现无缝过渡和促进整体网络控制，实质上是将软件定义的无线电引入光无线。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进行控制。我们将为我们的光纤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无缝切换，例如为了恢复能力。我们相信，这项工作虽然具有挑战性，但是可行的，因为它将利用财团内部的现有技能和研究，包括OW链路设计方面的卓越、先进的编码和调制、用于前程和回程网络的优化算法、表面发射激光器设计方面的专业知识以及用于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.