dc.contributor |
Universitat Politècnica de Catalunya. Departament de Teoria del Senyal i Comunicacions |
dc.contributor |
Ruiz Boqué, Sílvia |
dc.contributor.author |
Revuelto Lorda, Natalia |
dc.date |
2008-09-18 |
dc.identifier.uri |
http://hdl.handle.net/2099.1/6135 |
dc.language.iso |
eng |
dc.publisher |
Universitat Politècnica de Catalunya |
dc.rights |
Attribution-NonCommercial-ShareAlike 3.0 Spain |
dc.rights |
info:eu-repo/semantics/openAccess |
dc.rights |
http://creativecommons.org/licenses/by-nc-sa/3.0/es/ |
dc.subject |
Àrees temàtiques de la UPC::Enginyeria de la telecomunicació::Telemàtica i xarxes d'ordinadors |
dc.subject |
Àrees temàtiques de la UPC::Enginyeria de la telecomunicació::Radiocomunicació i exploració electromagnètica::Comunicacions mòbils |
dc.subject |
Wireless communication systems |
dc.subject |
Orthogonal frequency division multiplexing |
dc.subject |
Wireless communications |
dc.subject |
OFDM |
dc.subject |
PAPR |
dc.subject |
Clipping |
dc.subject |
Xarxes d'àrea local sense fils (Xarxes d'ordinadors) |
dc.subject |
Comunicacions mòbils, Sistemes de |
dc.title |
PAPR reduction in OFDM systems |
dc.type |
info:eu-repo/semantics/masterThesis |
dc.description.abstract |
In the last years wireless communications have experienced a fast growth due to the high
mobility that they allow. However, wireless channels have some disadvantages, like multipath
fading, that make them difficult to deal with. A modulation that efficiently deals with
selective fading channels is OFDM. The advancements in digital signal processing and
very large scale integrated circuits allow efficient and cost-effective implementation of the
FFT operations making OFDM an attractive solution for wireless channels. An important
disadvantage of OFDM systems is their high peak-to-average power ratio (PAPR). High
PAPR degrades OFDM signals by forcing the analog amplifier to work in the nonlinear
region, distorting this way the signal and making the amplifier to consume more power.
There are several ways to reduce the PAPR of OFDM signals which can be divided in two
groups: the techniques that non-linearly distort the signal and the ones that reduce the
PAPR without distorting the signal. A simple technique, belonging to the first group, is to
clip the signal to a maximumallowed value, at the cost of BER degradation and out-of-band
radiation. Clipping does not add extra information to the signal and high peaks occur with
low probability so the signal is seldom distorted. Out-of-band radiation can be reduced by
filtering at the transmitter, the filter used in this project consists on a FFT-IFFT pair which
is easier to implement than traditional FIR filters and allows the implementation of the
clip&filter set several times in order to reduce the peak regrowth that filtering introduces.
The BER degradation can be mitigated by reconstructing the signal at the receiver. We
analyzed the performance of some commonly used techniques that iteratively try to guess
the original symbols and proposed an improvement for one of those techniques. The
methods have been tested with Matlab and from the simulation results some conclusions
are extracted. |