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.

This Bachelor graduation project has the goal to create a device which is able of automatic volume control, to be used for enhancing speech intelligibility. To tackle the intelligibility of speech through Public Address Systems (PA Systems), an Intelligibility-Enhancing Automatic Volume Control system was proposed. The total system to be made must be able to alter a clean speech signal according to a noise estimation. Then the altered, enhanced, signal should be amplified before being sent to an existing Public Address System. A subsystem is added in order to dampen the outside noise in a car-like environment. The whole project is divided into three parts: Noise Statistics Estimation, Intelligibility Enhancement and Amplifier and Noise Cancellation. These parts have been performed by three different subgroups. In this report, the Amplifier and Noise Cancellation is discussed. The other parts are explained in the respective reports [1,2]. The Amplifier and Noise Cancellation group will amplify the enhanced audio signal with the use of a pre-amplifier. This group also introduces an additional noise cancellation subsystem for usage in enclosed spaces, like a car. It does so by inverting the recorded environment noise below 500 Hz, and adding this to the to be amplified signal before sending it to the PA System. This thesis is divided in two main design sections: the design of the pre-amplifier and the design of the active noise cancellation circuit. At the heart of both circuits lies a LM386 Audio Operational Amplifier (Op-Amp) but they both have different objectives. The pre-amplifier is designed to have a flat transfer function in audio range, 20 Hz to 20 kHz. The output level of the pre-amplifier is a standard level for consumer electronics, being 447 mVpp. The pre-amplifier inverts the signal from the microphone and the audio signal to achieve noise cancellation. The noise cancellation circuit features a microphone amplifier and a Low Pass Filter (LPF). The microphone amplifier amplifies the signal so that the microphone circuit’s output level is at the same level of the audio input of the pre-amplifier (200 mVpp). The filter makes sure only sounds below 500 Hz are passed to the pre-amplifier. With the inverting capabilities of the pre-amplifier and both signals being completely out of phase, a theoretical cancellation of sound signals is possible. Because of the LPF used in the microphone amplifier this cancellation is done for signals below 500 Hz. At the end of the project, a system was built which met most of the requirements. Some of the requirements can not be satisfied due to incapability of the test equipment available. The system does amplify the signal to the desired amplitude and is capable of slightly cancelling noise in a car. However, improvements of the product are needed to function more optimally.