The widespread adoption of wireless communication devices has led to increasingly congested wireless networks, creating a need for alternative communication technologies. A promising alternative is Visible Light Communication (VLC), which, instead of using radio frequencies, leve
...
The widespread adoption of wireless communication devices has led to increasingly congested wireless networks, creating a need for alternative communication technologies. A promising alternative is Visible Light Communication (VLC), which, instead of using radio frequencies, leverages the visible light spectrum to enable data transmission. Unfortunately, using visible light to communicate comes with its own set of limitations, such as the relatively high power consumption of sustaining a light source. In pursuit of lower power consumption, passive VLC has recently been gaining attention. Passive VLC is a form of VLC that uses ambient light to transmit data. Typically, it does so by modulating sunlight or artificial lights using Liquid Crystals (LCs). However, LCs, amongst other things, have very limited modulation speeds. This limitation has prompted the search for transmitters capable of achieving higher modulation speeds. Recent works have investigated the use of Digital Micromirror Devices (DMDs), which can achieve significantly higher modulation speeds. Unfortunately, DMDs require precise alignment for both incoming and outgoing light, imposing strict alignment constraints. To avoid these constraints, we investigate alternative transmitter designs using mechanical actuators. This has led to the design of two novel passive VLC systems dubbed DiscoLink and SpeakerLink. The DiscoLink transmitter, which makes use of a stepper motor to oscillate a multitude of small mirrors, achieves a throughput speed of 66 bits per second. Meanwhile, SpeakerLink, which makes use of a voice coil to oscillate a DVD, achieves a throughput speed of 20 bits per second. Their unique designs are enabled by using an event camera as a receiver, leveraging its high spatial and temporal resolution. Both systems operate on the principle of oscillating a reflective surface to alternate between different origins of ambient light reflected toward the receiver. Therefore, unlike other passive VLC systems, these transmitters do not have traditional ”on” and ”off” states between which they can alternate. The designs also necessitate the development of a novel modulation scheme, for which we propose two distinct methods. Although both DiscoLink and SpeakerLink do not face the alignment constraints of DMDs, they do face other challenges, such as low throughput speeds, reduced range, and noise. Whilst the practical use of these systems is limited due to these challenges, they highlight a new potential design space for passive VLC.
