LED Backhaul Project Engineer Blog

LED Backhaul In-house experimental environment

Last Update: Aug 24th, 2021

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Introduction

In order to conduct a field test of the effects of last mile communication through a window as described in the paper introduced in the first issue of the Engineering Blog, we installed an LED backhaul in the premises of our Yokohama headquarters and have been operating it 24 hours a day to measure changes due to weather and aging.
This time, we will introduce the state of the field test, focusing on the installation situation in particular.

Main experimental equipment

・LED Backhaul x2
It is used as a line connecting the roof of the building and the office of the LED communication business project. One side is installed outdoors and the other side is installed indoors, with a piece of glass sandwiched between the devices.

・Raspberry Pi 3 x1
In order to record the LED Backhaul device status (signal-to-noise ratio, physical layer communication speed) at one-minute intervals, we used a Raspberry Pi, which is inexpensive and can be expected to operate stably for a long time, instead of an expensive Windows PC.

・IP Camera x1
The field test can be carried out using only the equipment listed above, but since we have prepared a line that connects to the outdoors, we will connect the camera as a disaster countermeasure camera to remotely monitor the headquarters premises in preparation for recent disasters such as typhoons and heavy rain.

Installation of equipment

・Building roof
A commercially available general-purpose two-stage outdoor air conditioner mount was suitable in terms of size and load capacity, so we installed the LED Backhaul and IP camera in the upper section and the waterproof box in the lower section to accommodate the power connection and NW equipment inside. To adjust the direction of the LED Backhaul, we used a general-purpose head for surveillance cameras that is also available as an option, and to connect the head to the outdoor air conditioner mount, we made our own 3mm thick aluminum plate to align the bolt holes. As a countermeasure for storefronts, a concrete pedestal is fastened to the legs of the mount, and a rope is used to tie the mount to the rooftop fence.
As a result of past installations, it is important to use a board that has less deflection and deformation due to the environment to stabilize the communication environment. Wooden boards will inevitably deform due to rainfall and drying, and thin iron boards will deflect and change over time due to the load, so it would be helpful if you could avoid them when considering the installation method.

・In the office The LED Backhaul is installed using a commercially available metal rack/metal shelf. As in the case of the building's rooftop, a general-purpose head is used for directional adjustment, and a mounting plate manufactured with a 3D printer is used to align the bolt holes and fix it to the top of the metal rack.
The installation method using metal racks is easy to deploy and has excellent strength, making it a strong ally for building various experimental environments and attending exhibitions. When using commercially available metal racks, it is important to note that lightweight shelves that have been made by changing the diameter of the bars to a thinner one or reducing the number of bars to reduce the overall weight of the shelves may be deflected by the weight of the LED Backhaul. Although the burden of transportation will increase, using traditional heavy-weight shelves will lead to a more stable communication environment.

As you can see, depending on the installation environment, it is easy to build a communication environment between buildings by combining general-purpose fittings generally available in the market and making some dedicated products by yourself.

NW構成

The following NW configuration was built by combining various equipment.

Since the LED Backhaul in the office is connected to the company's internal NW, the devices connected to it can also be connected via the company's internal NW. As a result, it is possible to check the video and images from the IP cameras from within the head office, from each location, or from home via remote access while connected to the internal NW.
We plan to write a separate article on the measurement data of this environment after we have measured the effects of typhoons. We are aware of the effects of guerrilla rain and typhoons in the past, but we have not been able to obtain actual measurements of the effects of typhoons since we built this environment. Since the natural environment is uncontrollable, it may take some time to write about it, but we would appreciate it if you could wait a little while.