Full metadata record
DC FieldValueLanguage
dc.contributorDepartment of Electronic and Information Engineeringen_US
dc.creatorZheng, Yijie-
dc.publisherHong Kong Polytechnic University-
dc.rightsAll rights reserveden_US
dc.titlePartial transmit sequence based reduction of OFDM peak-to-average power ratio using simulated annealingen_US
dcterms.abstractOrthogonal frequency-division multiplexing (OFDM) is a modulation for many current and future wireless communication systems. OFDM wins its reputation for saving bandwidth, avoiding frequency selective fading and improving transmission efficiency. This technique has already been applied to video broadcasting, wireless local area networks and many other regions. OFDM adopts multi-carrier system, which divides one original carrier into several independent subcarriers, and these subcarriers are ensured to be orthogonal with each other. As a proverb says: "One coin has two sides" . Though the technique obtains these wonderful advantages, one side-effect can not be neglected, which is the production of high peak power. People use peak-te-average power ratio (PAPR) to express the extent of this situation. Negative effect of signal power value comes out in the time domain after adding all the subcarriers together. Assume the number of subcarriers is N, in a most unfortunate situation, which means all subcarriers are in the same phases in an instant time, then the combined signal will have a highest signal power value which will be N times larger than the average. In this condition, a tough problem will happen in the part of power amplifier (PA). Generally, PA has a saturation limit, it works in a linear state normally when signal value is smaller than the limit, but if the signal value becomes larger than the limit, the operation of PA won't be well and signals will be distorted and finally the communication leads to a failure. This is the most important reason that we care about high PAPR value. PTS is an efficient approach for mitigating PAPR, it uses a certain number of scramble sequences to combine with the input data and try to change the waveform of the signals. Here scramble sequences can be phase factors, which are in the range of [0,2pi]. Optimal PTS uses a full (exhaustive) enumeration method to calculate all the possible results, then selects one group of the phase factors which can minimize PAPR as the ideal answer. Though PTS actually provides a useful solution, huge calculation task turns to be time-consuming, if the number of subcarriers increases largely, this problem is thus highlighted. In order to improve searching efficiency, a heuristic technique which is called "Simulated Annealing(SA)" is applied. SA is a scientific algorithm which combines PTS as a combinatorial problem. In the process of searching the smallest PAPR, this algorithm tries to compare a new produced solution with the current solution, monitor the changed state and select the better one, i.e. do a downhill movement to accept smaller value. What's more, it allows some uphill action when a predefined relation is met. With this step running on and on, simulation results show that this measure really saves large calculation tasks and approximates the PTS method, which eventually proves it is a great improvement to achieve good PAPR reduction.en_US
dcterms.extentvii, 84 leaves : ill. ; 31 cm.en_US
dcterms.isPartOfPolyU Electronic Thesesen_US
dcterms.educationalLevelAll Masteren_US
dcterms.LCSHHong Kong Polytechnic University -- Dissertationsen_US
dcterms.LCSHOrthogonal frequency division multiplexing.en_US
dcterms.LCSHSignal processing -- Digital techniquesen_US
dcterms.LCSHSequences (Mathematics)en_US
dcterms.accessRightsrestricted accessen_US

Files in This Item:
File Description SizeFormat 
b23568136.pdfFor All Users (off-campus access for PolyU Staff & Students only)11.15 MBAdobe PDFView/Open

Copyright Undertaking

As a bona fide Library user, I declare that:

  1. I will abide by the rules and legal ordinances governing copyright regarding the use of the Database.
  2. I will use the Database for the purpose of my research or private study only and not for circulation or further reproduction or any other purpose.
  3. I agree to indemnify and hold the University harmless from and against any loss, damage, cost, liability or expenses arising from copyright infringement or unauthorized usage.

By downloading any item(s) listed above, you acknowledge that you have read and understood the copyright undertaking as stated above, and agree to be bound by all of its terms.

Show simple item record

Please use this identifier to cite or link to this item: https://theses.lib.polyu.edu.hk/handle/200/5837