Use this URL to cite or link to this record in EThOS:
Title: Optical wireless systems performance enhancement through an assessment of the channel impairments
Author: Sterckx, K. L.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2000
Availability of Full Text:
Access from EThOS:
This thesis describes a newly proposed algorithm that can be used to determine the transmission power needed to attain the required bit-error-rate in optical wireless communication links. The algorithm demonstrates, for the first time, the feasibility of assessing the joint influence of multipath dispersion and background noise. Since the method accounts also for the pulse shape and the receiver circuitry related noise, a comprehensive treatment for the performance of the entire optical wireless communication link can be carried out. The newly devised algorithm is subsequently used to asses the improvement in performance achieved by three novel approaches that combat the impairment incurred by background noise, multipath dispersion or both. The first approach exploits a novel three-segment pyramidal fly-eye detection antenna and offers a significant improvement in receiver sensitivity. The approach is essentially a diversity detection method of limited complexity. It will be demonstrated that, within the optical wireless environment under investigation, a sensitivity improvement of up to 2.3 dB can be achieved. The second approach combats the impairments induced by the optical wireless channel through adjustment of the detection threshold according to the incident ambient light and the shape of the received signal pulse. The method proves to be especially useful in tracked systems. Using an adaptive threshold approach, a sensitivity improvement of up to 7.5 dB can be obtained when the system is influenced by multipath dispersion. Under the influence of background noise, the adaptive threshold approach offers up to 4 dB sensitivity improvement over a fixed threshold system. The third approach involves the transmission of a distorted signal, shaped to equalise the multipath dispersion incurred by the optical wireless channel through which the signal travels. The pre-distortion equalisation pulse requires a DC offset and, as such, the technique yields an improvement provided that multipath dispersion has a significant influence on the received signal. In practice this equates to higher bit rates.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available