I. Introduction
The design of energy-efficient lighting systems is important, given that electric lighting is a major constituent of electricity consumption in office buildings [1]. An approach to saving energy is by providing illumination at a prescribed level only in occupied regions and providing lower illumination levels in unoccupied regions. Control schemes have been designed with these illumination objectives [2], [3]. A key ingredient in this approach is granular presence sensing, i.e. coarsely determining spatial occupancy in a given space. While energy efficiency is an important design consideration, catering to individual user illumination needs is equally important. Thus providing occupants with the ability to control lighting to meet individual needs is necessary. Control schemes may then take specific user inputs into consideration to enhance user satisfaction with the rendered illumination [4]–[6]. In this paper, we present an ultrasonic system to provide the functionalities of granular presence sensing and user communication in a smart lighting system.