Dias Rodrigues, Miguel Raul;
(2002)
Modelling and performance assessment of OFDM communication systems in the presence of non-linearities.
Doctoral thesis (Ph.D.), University College London (United Kingdom).
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Abstract
This thesis is concerned with the development of analytic techniques to assess the impact of non-linearides on the performance of orthogonal frequency division multiplexing (OFDM) signals in fibre-radio based wireless networks. Volterra series are used to model both the frequency independent and the frequency dependent behaviour exhibited by fibre-radio system non-linearities. Expressions to determine the power density spectrum (PDS) of non-linearly distorted OFDM signals are derived and validated by comparing analytic to simulation results. Such expressions relate the PDS of the distorted signal to the harmonic power density spectra (HPDS) of the non-distorted signal and the transfer functions of the non-linearity. Expressions to determine the error probability of non-linearly distorted OFDM signals in additive white Gaussian noise (AWGN) are also derived and validated by comparing analytic to simulation results. Such expressions relate the error probability of the OFDM signal to the error probabilities of the OFDM sub-channels, each of which is given as the expectation with respect to the intermodulation distortion (IMD) random variable (RV) of the error probability in AWGN conditioned by a given value of the IMD RV. To calculate the error probability expectations, an investigation of appropriate approximations/estimations for the IMD distribution based on a limited number of moments of the IMD RV is carried out. Finally, the analytic techniques are applied to two different intensity modulation/direct detection (IM/DD) fibre-radio systems. One of the systems is based on the direct modulation of a laser source and exhibits frequency dependent non-linear behaviour. The other system is based on the external modulation of a laser source and exhibits frequency independent non-linear behaviour. Merits and demerits of the techniques are discussed by comparing analytic to simulation results. Overall, this thesis provides a range of analytical tools to assess the performance of fibre-radio based wireless networks employing OFDM signalling as well as further insight into the behaviour of non-linearly distorted OFDM signals.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D. |
| Title: | Modelling and performance assessment of OFDM communication systems in the presence of non-linearities |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| Keywords: | (UMI)AAIU643682; Applied sciences; Wireless networks |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10101224 |
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