Peak-to-Average Ratio Reduction for MIMO and Multi-user OFDM Systems

  • A major drawback of MIMO-OFDM systems is its high Peak-to-Average Ratio (PAR). The signal is clipped when the peak values are higher than the linear operation range of non-linear devices. In order to avoid clipping the signal above a certain threshold, measure must be taken to limit all peaks crossing the threshold value. In this thesis, we therefore investigate and address the PAR problem of different MIMO-OFDM scenarios and provide countermeasures to limit the peak excursions in MIMO-OFDM systems. First, we extend the Tone-Reservation algorithm for PAR reduction of MIMO-OFDM systems. For a point-to-point scenario, a spiky function is generated on the weakest eigenchannel not suited for data transmission. This spiky function is then iteratively used for PAR reduction of the transmit signal. For a multi-user broadcast scenario, the spiky function is generated on a small percent of tones reserved on all spatial dimensions, in the conventional manner. This spiky function is then used to limit the peak excursions of the transmit signal. Second, we introduce a novel Least-Squares iterative PAR reduction algorithm for MIMO-OFDM scenarios. For a P2P scenario, the weakest eigenchannel is used to approximate the peak excursions on the remaining spatial dimensions in a least-squares fashion. This model function is then added to the transmit signal for PAR reduction. The algorithm is thoroughly investigated in terms of the capacity loss and the mean power increase due to the modeled function. Moreover, for a broadcast scenario, we consider that one user is inactive and the channel associated to it is not used. This inactive channel is then used to approximate and model the peak excursions on the remaining spatial dimensions in the similar fashion. In a further part of this thesis, we consider PAR reduction using Trellis Shaping for single antenna systems. We concatenate an optimized irregular LDPC code with Trellis Shaping for PAR reduction.

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Publishing Institution:IRC-Library, Information Resource Center der Jacobs University Bremen
Granting Institution:Jacobs Univ.
Author:Abdul Wakeel
Referee:Werner Henkel, Hideki Ochiai, Mathias Bode
Advisor:Werner Henkel
Persistent Identifier (URN):urn:nbn:de:gbv:579-opus-1004575
Document Type:PhD Thesis
Date of Successful Oral Defense:2016/08/01
Date of First Publication:2016/02/11
Academic Department:Computer Science & Electrical Engineering
PhD Degree:Electrical Engineering
Focus Area:Mobility
Other Countries Involved:Japan
Library of Congress Classification:T Technology / TK Electrical engineering. Electronics. Nuclear engineering / TK5101-6720 Telecommunication. Including telegraphy, telephone, radio, radar, television [and positioning technology] / TK5101-5105.8887 Telecommunication / TK5103.2-5103.4885 Wireless communication systems. Mobile communication systems / TK5103.484 Orthogonal frequency division multiplexing (OFDM)
Call No:Thesis 2016/01

$Rev: 13581 $