Augmenting WiFi Infrastructure with Visible Light Communications

利用可见光通信增强 WiFi 基础设施

• 批准号: 2284103
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2284103
• 关键词: Augmenting; WiFi; Infrastructure; Visible; Light

This proposed project concerns Visible Light Communications (VLC), and in particular the combination of Polymer Optical Fibre (POF) and free space low power VLC to create inexpensive communication links to augment existing WiFi infrastructure. This project falls within the EPSRC Optical Communications research area.There is a growing issue of high-density traffic saturation on WiFi. While an Access Point (AP) mayhave a high capacity of 900 Mbit/s under normal operation, due to concurrency effects 18 connectedusers will each experience a rate of 6 Mbit/s. This is an overall throughput far less than the capacity of the Radio Frequency (RF) channels available. This effect worsens with more connecteddevices. As a solution, manufacturers are including more RF channels on their new APs, which will eventually become saturated, only pushing the problem further down the road. A longer term solution is required, so as an alternative to RF a VLC channel could be used to augment RF systemsand remove RF congestion. The suggested augmentation is using a VLC channel to serve a data link, allowing for ensured quality of service.The Silicon Photomultiplier (SiPM) has been identified as the world's most sensitive optical reciever, and has been demonstrated to be an ideal candidate for VLC systems. This reciever can bepaired with low-power indicator LEDs to create inexpensive, practical links. The combination of indicator LEDs and SiPMs is something which hasn't been achieved before, and has the potential toperform strongly. Further characterisation of SiPM recievers must be undertaken, as well as understanding the impacts of ambient light, output pulse width, equalisation methods and more on VLC links.A suggestion for practical VLC systems is to use optical fibre to transport the optical channels throughout the serviced area from a central hub, rather than use distributed transmitters. POF has been identified as a suitible fibre, which offers mechanical benefits along with being inexpensive. Each POF fibre will carry a separate VLC channel dividing space so multiple users can be serived simultaneously without interference, other benefits which arise include increases in security, and decreases in average transmission rate. This optical fibre could inexpensively be placed in an office's suspended ceiling, and protruded through at a desired transmit location in a minimally invasive fashion. The separate optical channels would need to be distributed throughout the space covered by the WiFi, filling the space with (not necessarily separate) regions of VLC coverage. Although POF usually works in the red, it can work in the blue region and therefore emit light that can be detected by SiPMs. The 405nm wavelength is interesting as it is far less prevalent in the target home and office environments, and SiPMs are more sensitive to it. Exploration of the impacts of using POF to transport optical wireless links is also research which must be undertaken.For down-links, I aim to exploit the high sensitivity, and large area of Silicon Photomultipliers, to detect a link from POF at a range of > 3m. It would be feasible to use another POF as an up-link from a client back to the AP. Coupling the up-link light emitted from a client back into a POF wouldbe a challenge here, as POF typically has a diameter of 1mm. The low power of the emitted light inconjunction with the small area of the POF may require a solution involving a fluorophore coating on the end of a POF, or fluorophore-doped fibres connected to a POF to collect and couple more light. Since up-links are a lower rate by nature, it is crucial to explore what allows the up-link to be robust and achieve a high rate in order to guarantee quality of service.

该拟议项目涉及可见光通信（VLC），特别是聚合物光纤（POF）和自由空间低功率VLC的组合，以创建廉价的通信链路，以增强现有的WiFi基础设施。该项目福尔斯EPSRC光通信研究领域。WiFi上的高密度流量饱和问题日益严重。虽然接入点（AP）在正常操作下可能具有900 Mbit/s的高容量，但由于并发效应，18个连接的用户将各自体验6 Mbit/s的速率。这是远小于可用射频（RF）信道的容量的总吞吐量。这种影响与更多的连接设备有关。作为一种解决方案，制造商正在其新AP上包含更多的RF通道，这些通道最终将变得饱和，这只会进一步推动问题的发展。需要一个长期的解决方案，因此作为RF的替代方案，VLC通道可以用于增强RF系统并消除RF拥塞。建议的增强是使用VLC信道为数据链路服务，从而确保服务质量。硅光电倍增管（SiPM）已被确定为世界上最灵敏的光学接收器，并已被证明是VLC系统的理想候选者。这种接收器可以与低功耗LED指示灯配对，以创建廉价，实用的链接。LED指示灯和SiPM的组合是以前从未实现过的，并且具有强大的潜力。必须对SiPM接收器进行进一步的表征，并了解环境光、输出脉冲宽度、均衡方法等对VLC链路的影响。对实际VLC系统的建议是使用光纤从中央集线器在整个服务区域传输光信道，而不是使用分布式发射器。POF被认为是一种合适的纤维，它提供了沿着的机械优点，而且价格便宜。每个POF光纤将携带一个单独的VLC信道划分空间，因此多个用户可以同时提供服务而不受干扰，其他好处包括增加安全性和降低平均传输速率。这种光纤可以廉价地放置在办公室的吊顶中，并以微创方式突出到所需的传输位置。单独的光学信道将需要分布在由WiFi覆盖的整个空间中，用VLC覆盖的（不一定是单独的）区域填充空间。虽然POF通常在红色区域工作，但它可以在蓝色区域工作，因此发出的光可以被SiPM检测到。405 nm波长在家庭和办公环境中的应用相对较少，而SiPM对它的敏感性更高。探索使用POF传输光无线链路的影响也是必须进行的研究。对于下行链路，我的目标是利用硅光电倍增管的高灵敏度和大面积，在> 3 m的范围内检测POF的链路。使用另一个POF作为从客户端回到AP的上行链路是可行的。将客户端发出的上行链路光耦合回POF将是一个挑战，因为POF通常直径为1 mm。与POF的小面积结合的发射光的低功率可能需要涉及在POF的端部上的荧光团涂层或连接到POF的荧光团掺杂的纤维的解决方案，以收集和耦合更多的光。由于上行链路本质上是较低的速率，因此探索什么允许上行链路是鲁棒的并实现高速率以保证服务质量是至关重要的。