Abstract
In this thesis a low complexity and high accuracy indoor positioning system (IPS) is developed. To achieve this, optical wireless communication (OWC) between a light emitting diode (LED) based transmitter and a photodiode-based receiver is used to implement a proximity-based positioning technique. The proximity-based technique has a low complexity but its low accuracy is a major drawback of the technique. A novel overlap-based strategy which estimates position using the location of multiple LEDs (MLEM) is developed and shown to increase the accuracy of the proximity based system while maintaining its low complexity.Although overlap increases positioning accuracy, it also creates a possibility for collision of positional information carrying packets from LEDs that are in the region of overlap. Packet collisions corrupt the packet information thereby increasing the time (positioning time) for the correct positional information to reach the receiver.A novel packet duration multiplexing (PDM) algorithm is developed to reduce the probability of collisions and an improved positioning protocol is designed to reduce the positioning time.
The design and mathematical analysis of PDM algorithm is presented considering four lighting scenarios which are synchronized systems, semi-synchronized systems,slotted unsynchronized systems and unslotted unsynchronized systems. The probabilities of collisions of the systems are computed analytically and validated by numerical simulations. In addition, the average positioning time is computed analytically and this is validated by experimental measurements.
Since the optical power from an LED follows a Lambertian distribution, the low signal to noise ratio (SNR) at the edges of the LED beam, called the optical boundary, causes packet loss which increases the positioning time. To keep the system usable for human positioning, a threshold angle boundary is defined. The use of the threshold angle reduces positioning time and keeps the receiver robust enough to maintain its positioning performance when angular tilts of up to 12° are considered.
In terms of positioning error, the use of multiple receivers is investigated. For afour LED system in a room of dimensions 5m x 5m x 3.5m. an additional receiver is shown to reduce MLEM positioning error by 11.5 %. Novel optical pixeled LED luminaires (OPLL) are also investigated for further reduction of positioning error while maintaining the number of LED luminaries in a room. For 2 luminaires with 4 LEDs each, the OPLL system reduces the positioning error by 55.1 % and is 1.3 times faster than the MLEM system.
| Date of Award | 2018 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Sinan Sinanovic (Supervisor) & Roberto Ramirez-Iniguez (Supervisor) |