Validating a LiFi communication system

Abstract

Most wireless devices use the radio frequency spectrum which is reaching its limits, as almost all frequencies are in use. Devices which communicate on the same radio frequencies are interfering with each other and this creates problems in the communication. Currently, there are around 10 billion of these devices. This number is rapidly growing and this increases the issue of interference. One of the possible solutions for future wireless communication is a communication technology called Light Fidelity (LiFi). This technology uses light waves to communicate rather than radio waves. Since light operates outside the common radio frequencies, LiFi does not introduce additional interference to today’s commonly used radio communication technologies. Signify is the first company with a commercially available LiFi system and has branded their system Trulifi. The Trulifi network can consist of multiple Access Point (AP)s and End Point (EP)s. These devices have a cone­like coverage area in which devices can communicate with each other. Outside this coverage area, communication is not possible. As with other communication technologies, devices within a LiFi system are also affected by interference. In the overlapping coverage areas between two APs two types of interference can occur. Downlink interference occurs whenever an EP receives messages from multiple APs at the same time, while uplink interference occurs whenever an AP is able to receive messages from an EP which is connected to a neighbouring AP. To overcome this issue Signify uses a so called LiFi controller (LC). The main task of the LC is to create an interference free communication schedule for all APs in the LiFi network. This schedule is based on the interference reports received from the APs and EPs. Validating large scale LiFi systems can become complicated, in terms of high costs involved and in the very large spaces needed to install such a large scale system. To ensure the LC operates as specified, a stress­test simulation model was designed by Signify. The stress­test simulation’s sole purpose is to ensure the LC keeps operating as specified in the worst case situation. E.g. all the possible APs, all the possible EPs and all the interference that can occur. This test is, however, not realistic as these worst case situations are not common in real­world deployments of the system. In this thesis, the problem of creating a realistic Trulifi simulation model is addressed. A literature study has been performed to investigate if existing models can be used. The conclusion of this literature study shows that a radio model needed to be designed which addressed the needs of the Trulifi system. This model has been designed with a high level of abstraction, while keeping the simulation as realistic as possible. To validate the new radio model, the Trulifi simulation has been compared to a real­world Trulifi system. Once this radio model was validated, the scheduling was compared based on different configuration sizes, as the main goal of the thesis is to create a realistic simulation model with which the Trulifi system can be validated. For this validation, the Trulifi simulation was compared to both the real­world Trulifi system and the stress­test simulation.