On the selection of the best companding technique for PAPR reduction in OFDM systems

Abstract

Orthogonal frequency division multiplexing (OFDM) is used in high data rate applications due to its ability to cope with frequencyselective channels. However, OFDM suffers from the high peak-toaverage power ratio (PAPR) problem, which reduces the power amplifier (PA) efficiency or otherwise degrades bit error rate (BER) and increases out-of-band (OOB) radiation. In the literature, there are various PAPR reduction techniques. Among them companding techniques have small computational complexity, which make them attractive to be used in mobile stations (MS). Generally, companding techniques expand small signals while compressing large signals or compress large signals without affecting small signals. In this paper, different PAPR reduction companding transforms are compared. Results showed that companding transforms that compress large signals without affecting small signals (such as, Log companding and Tanh companding) are better than the others from a BER point of view. Results also showed that the Log companding transform is better than the Tanh transform, in terms of PAPR reduction gain and OOB radiation reduction. So the Log companding transform can be considered as the best practical companding transform among others. ARTICLE HISTORY

An optimal nonlinear companding transform with clipping scheme for universal filtered multicarrier systems

“…The proposed optimal hybrid transforms are compared with various companding schemes in the literature, such as DFT‐ARCT and DFT‐ μ ‐law 19 of UFMC system, ICF‐ENC (iterative clipping and filtering‐enhanced nonlinear companding) and ENC 29 of OFDM system, and μ ‐law 30 of OFDM system, as illustrated in Table 5. It is evident that from Table 5, the proposed hybrid scheme with CR = 1.3 offers improved PAPR reduction of 8.4 dB at CCDF = 10 −3 when compared with other companding schemes.…”

A Novel Hybrid Precoding-Companding Technique for Peak-to-Average Power Ratio Reduction in 5G and beyond

“…Several PAPR reduction methods are introduced, such as clipping [ 4 ], Partial Transmit Sequence (PTS) [ 5 ], Selective Mapping (SLM) [ 6 ], Interleaving [ 7 ], Active Constellation Extension (ACE) [ 8 ], Tone Reservation (TR) [ 9 ], Tone Injection (TI) [ 9 ], companding techniques [ 10 ], and precoding techniques [ 11 ]. There are mainly three categories for PAPR reduction techniques: (i) coding techniques, (ii) Multiple Signal Representation (MSR) techniques, and (iii) adding-signal techniques [ 12 ].…”

“…However, they require excessive computational complexity in addition to rate loss [ 15 ]. On the other hand, companding techniques have small PAPR reduction gain with trivial computational complexity [ 10 ]. Also, precoding techniques have moderate PAPR reduction gain with small computational complexity [ 11 ].…”

“…However, PLC is impractical. It requires many side information bits to inform the receiver with the position of data samples above or below the inflection point [ 10 ]. Recently, DHT-A introduced in [ 26 ] without comparison to any previous precoding-companding technique.…”

“… Some works hybridized A-law companding [ 26 , 31 ] and companding [ 23 ] with different precoding matrices. Although A-law and companding techniques have PAPR reduction gain and BER performance worse than the -law companding, as shown in [ 10 ]. The authors in [ 25 , 29 ] hybridized piecewise based companding techniques with different precoding matrices.…”