Light emitting diodes (LEDs) are considered to become the dominant source of illumination in the future,
offering long life times, energy efficiency and flexible tunability. The flexibility of adapting LED parameters
offers multiple degrees of freedom in designing LED based lighting systems. In this paper, we consider
energy-efficient illumination control design of LED based lighting systems in office spaces. Our goal is to
determine the optimum dimming levels of the LED sources so as to minimize the power consumption
while rendering (1) uniform illumination at a given illumination level in workspace regions that are
occupied, and (2) a minimum illumination level of lower value in unoccupied regions, while taking
daylight distribution over the workspace plane into account. In order to determine occupant locations,
we present an ultrasound array sensor solution with enhanced presence detection capability. We further
propose a method to estimate and disaggregate illumination contributions of daylight and the different
LED sources at the workspace plane. The performance of our proposed control solution is evaluated under
different occupancy scenarios.