A Systematic Study of the Behaviour of PMEPR in Relation to OFDM Design Parameters

The design of systems with enhanced quality of service (QoS) and improved power efficiency has evolved into an intensive research area in wired and wireless communications engineering. Orthogonal frequency division multiplexing (OFDM) has been proven to have the potential to achieve high data rates, adapt to severe channel conditions and exhibit spectral efficiency; this has gained its popular support in the design industry, especially for fourth generation (4G) systems. However, the high peak to mean envelope power ratio (PMEPR) exhibited by OFDM signals require linear operation of analog devices, with the associated trade-off of poor power efficiency. Several methods to reduce this PMEPR problem have been effectively researched while revealing the shortcomings. In this study we recognize the need to present the effect of OFDM system parameters on the behaviour of the PMEPR. In order to provide a basis for systematic selection of OFDM design parameters for PMEPR mitigation, we first study the reaction of the PMEPR to OFDM design parameters, we then analyse the effect of OFDM design parameters on the shortcomings of the PMEPR-limiting clipping technique.Peer reviewe

PEAK-TO-AVERAGE POWER RATIO REDUCTION IN AN FDM BROADCAST SYSTEM

Digital predistortion is a technique used to reduce the signal Various methods have been formulated to achievePAR dynamic range in a multichannel system in order to improve reduction in multicarrierOFDM systems. The simplest mepower amplifier (PA) efficiency. These techniques have thods are based on the observation that a high signal peak is been developed for orthogonal frequency-division multi- created when signals in multiple channels add construcplexing (OFDM) systems, but are not directly applicable to tively in phase. Such methods attempt to systematically general frequency-division multiplexing (FDM) systems insert phase shifts to subcarriers to reduce their in-phase such as those used in broadcast. A modification to the tone probability. Various algorithms have been proposed in deinjection approach allows constellation translations to be termining the optimal phase selections [2-5]. Coding is directly applied at the digital intermediate frequency (IF) another promising approach that systematically adds redundomain and provides redundancy in lowering peak-to- dancy to avoid certain symbol combinations that cause high average ratio (PAR). Simulation ofa 24-channel 256-QAM signal peaks [6-1 1]. Coding also enhances error tolerance FDM cable television transmission system shows a 3.3 dB of the system. Recent efforts explore the possibility of PAR reduction at 10-6 clipping probability. varying signal constellation in order to mitigate high PAR