PAPR reduction in FBMC systems using an FBMC optimized ACE method

Abstract

The aim of this dissertation was to investigate peak-to-average power ratio (PAPR) reduction techniques for filter bank multicarrier (FBMC) modulated systems. Research into current PAPR reduction techniques in FBMC and orthogonal frequency division multiplexing (OFDM) found that the active constellation extension (ACE) method has not been exploited for use in FBMC systems. This is, in part, due to the complexities involved in signal processing inherent of FBMC systems, as well as FBMC being a relatively new subject matter in the telecommunications field. The outcomes of the dissertation were four novel PAPR reduction techniques for FBMC systems. These techniques can be split up into two namely linear programming optimization ACE-based techniques and overlapping ACE techniques. The techniques compensate for the overlapping symbols in FBMC by utilizing a frame based approach. This characteristic makes them ideal candidates to be applied in burst transmission. Furthermore, because an ACE based technique is used, they do not require the transmission of side information. The PAPR performance of the techniques are shown to match, or in some cases improve, current PAPR techniques for FBMC. The analysis of the proposed approaches also address some complexity issues with current FBMC implementations. The out-of-band (OOB) interference of the techniques under clipping scenarios is investigated. It is shown that the OOB interference can be minimized whilst still maintaining good PAPR performance. Additional results are also provided by means of a study of the PAPR reduction techniques proposed as applied to a high power amplifier based model. The corresponding power amplifier efficiency as well as bit-error rate (BER) degradation are investigated and compared to other standard techniques for PAPR reduction in FBMC systems. It was found that the proposed techniques can achieve a higher amplifier efficiency than existing techniques at a marginal trade-off in BER degradation. This BER degradation is lower than existing techniques due to the marginal increase in average transmit power. As illustrated by exhaustive simulations, the single scaling and overlapping smart gradient-project ACE-based techniques proposed, are ideal candidates for practical implementation in systems employing the low complexity polyphase implementation of FBMC modulators. The methods are shown to offer significant PAPR reduction and increase the feasibility of FBMC as a replacement modulation system for OFDM.

Die doel van hierdie verhandeling is om top-tot-gemiddelde drywingsverhouding (PAPR) verminderingstegnieke vir filterbank veelvuldige draer (FBMC) -gemoduleerde stelsels te ondersoek. Huidige PAPR verminderingstegnieke in FBMC en ortogonale frekwensie verdeling multipleksering (OFDM) is ondersoek en daar is bevind dat die aktiewe konstellasie uitbreidingsmetode (ACE) nog nie vantevore ontgin is in FBMC stelsels nie. Dit is gedeeltelik as gevolg van die inherente kompleksiteit van seinverwerking in FBMC stelsels en ook omdat FBMC n relatief nuwe onderwerp in die veld van telekommunikasie is. Die resultate van hierdie verhandeling is vier unieke PAPR verminderingstegnieke vir FBMC stelsels. Hierdie tegnieke kan opgedeel word in lineêre programeringsgeoptimiseerde tegnieke en oorvleuelende ACE tegnieke. Om vir die oorvleueling van simbole in FBMC te vergoed, word n raamgebaseerde benadering gebruik. Hierdie kenmerk maak hierdie tegnieke ideaal vir vlaaguitsending. Omdat n ACE-gebaseerde tegniek gebruik word, is transmissie van kant inligting onnodig. Die PAPR werkverrigting van dié tegnieke is op standaard met, en in sommige gevalle n verbetering op huidige PAPR tegnieke vir FBMC. Die ontleding van die voorgestelde benaderings spreek ook die kompleksiteitkwessies met die implementering van huidige tegnieke aan. Die buite band (OOB) steuring van die tegnieke onder geknipte scenarios word ondersoek. Daar word getoon dat die OOB steuring verminder kan word terwyl goeie PAPR verrigting gehandhaaf word. Addisionele studieresultate word ook voorsien deur n studie van die voorgestelde PAPR reduksietegnieke toegepas op n hoë drywing versterker (HPA)model. Die ooreenstemmende drywingsversterker doeltreffendheid asook die degradering van die bit fout waarde (BER) is ondersoek en vergelyk met ander tegnieke vir PAPR vermindering in FBMC stelsels. Daar is bevind dat die voorgestelde tegnieke n hoër drywing versterker doeltreffendheid kan bereik as bestaande tegnieke afgespeel ten koste van n marginale BER degradasie. Hierdie degradasie is laer as bestaande tegnieke as gevolg van die marginale toename in gemiddelde uitsendingskrag. Uitvoerige simulasies toon dat die voorgestelde enkel skalering en oorvleuelende slim gradiënt projek ACE gebaseerde tegnieke die ideale kandidate is vir praktiese toepassing in stelsels wat gebruik maak van die lae kompleksiteit veelfase toepassing van FBMC modulators. Dié metodes bring n beduidende PAPR vermindering te weeg en maak FBMC meer haalbaar as n vervanging modulasie stelsel vir OFDM.