On the iterative mitigation of clipping noise for COFDM transmissions

Abstract

SUMMARYLarge peak-to-average power ratio (PAPR) of multicarrier communication systems is a widely discussed topic in the literature and remains the major drawback of the orthogonal frequency division multiplexing (OFDM) modulation. Deliberate amplitude clipping has been found as a suitable way to reduce output signal peaks at the transmitter side. Unfortunately, it also causes numerous degradations. In this paper, we propose a study of nonlinearities led by the clipping process and a comparison of iterative receivers derived from the turbo-principle and devoted to the system performance restoration under severe clipping ratio (CR) constraint.

Clipping noise mitigation with capacity approaching FEC codes for PAPR reduction of OFDM signals

“…In [23] the authors capitalize on the work of Tellado [20] and Chen [21] to propose a new version of the iterative clipping noise cancellation receiver. This version consists in: 1) applying a Maximum Likelihood (ML) demapping to the signals obtained after clipping noise cancellation in the frequency domain, 2) converting the a posteriori log likelihood ratio (LLR), provided by the channel decoder, into symbol estimatesX k , which are used to reconstruct an estimation of the clipping noise, thanks to a soft mapper.…”

“…It has been shown by simulations that for small clipping ratios, equal or lower than 1, the attenuation α must be taken into account in the ML demapping otherwise BER performance is strongly degraded. The iterative algorithm works as follows [23]: InitializeỸ (0) k = Y k , and i = 1.…”

“…Then we focus on the iterative clipping noise cancellation receiver [23] associated with capacity approaching codes, such as low density parity check codes (LDPC) or turbo codes. The BER performance of the iterative receiver is evaluated numerically and compared to the derived lower bound.…”

Transforming the distribution of OFDM signals for peak‐to‐average power ratio reduction

“…Therefore, many schemes have been proposed and analysed in the literature to reduce the PAPR in OFDM systems, such as partial transmit sequence (PTS) [2,3], selective mapping (SLM) [4,5], scrambling [6], tone reservation and injection [7,8], unitary transformation [9], clipping [10,11] and companding [12][13][14][15]. Among them, clipping may be the simplest scheme and it has been used in some communication standards.…”

Soft Decision Aided Suboptimal ML Detection Receiver for Clipped COFDM Transmissions

“…In case of clipping the complex OFDM signal envelope, the distortion noise can be reasonably modeled as Gaussian and receivers based on the turbo-principle are known to give potentially good performance in such condition. Decision aided reconstruction [8], [9], clipping noise cancellation [10], [11], [12] and clipping function inversion [13], [14] are noteworthy iterative techniques mitigating the clipping non-linearity effects by observed channel signal direct correction.…”