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 of good codes for Gaussian channel

Consider a problem of forward error-correction for the additive white Gaussian noise (AWGN) channel. For finite blocklength codes the backoff from the channel capacity is inversely proportional to the square root of the blocklength. In this paper it is shown that codes achieving this tradeoff must necessarily have peak-to-average power ratio (PAPR) proportional to logarithm of the blocklength. This is extended to codes approaching capacity slower, and to PAPR measured at the output of an OFDM modulator. As a by-product the convergence of (Smith's) amplitude-constrained AWGN capacity to Shannon's classical formula is characterized in the regime of large amplitudes. This converse-type result builds upon recent contributions in the study of empirical output distributions of good channel codes