A construction for binary sequence sets with low peak-to-average power ratio

This correspondence is concerned with asymptotic properties on the codeword length of a fixed-to-variable length code (FV code) for a general source {X/sup n/}/sub n=1//sup /spl infin// with a finite or countably infinite alphabet. Suppose that for each n /spl ges/ 1 X/sup n/ is encoded to a binary codeword /spl phi//sub n/(X/sup n/) of length l(/spl phi//sub n/(X/sup n/)). Letting /spl epsiv//sub n/ denote the decoding error probability, we consider the following two criteria on FV codes: i) /spl epsiv//sub n/ = 0 for all n /spl ges/ 1 and ii) lim sup/sub n/spl rarr//spl infin///spl epsiv//sub n/ /spl les/ /spl epsiv/ for an arbitrarily given /spl epsiv/ /spl isin/ [0,1). Under criterion i), we show that, if X/sup n/ is encoded by an arbitrary prefix-free FV code asymptotically achieving the entropy, 1/nl(/spl phi//sub n/(X/sup n/)) - 1/nlog/sub 2/ 1/PX/sup n/(X/sup n/) /spl rarr/ 0 in probability as n /spl rarr/ /spl infin/ under a certain condition, where P/sub X//sup n/ denotes the probability distribution of X/sup n/. Under criterion ii), we first determine the minimum rate achieved by FV codes. Next, we show that 1/nl(/spl phi//sub n/(X/sup n/)) of an arbitrary FV code achieving the minimum rate in a certain sense has a property similar to the lossless case.

Consider the control system (/spl Sigma/) given by x/spl dot/ = x(f + ug) where x /spl isin/ SO(3), |u| /spl les/ 1 and f, g /spl isin/ so(3) define two perpendicular left-invariant vector fields normalized so that ||f|| = cos(/spl alpha/) and ||g|| = sin(/spl alpha/), /spl alpha/ /spl isin/ (0, /spl pi//4). In this paper, we provide an upper bound and a lower bound for N(/spl alpha/), the maximum number of switchings for time-optimal trajectories of (/spl Sigma/). More precisely, we show that N/sub S/(/spl alpha/) /spl les/ N(/spl alpha/) /spl les/ N/sub S/(/spl alpha/) /spl les/+4, where N/sub S/(a) is a suitable integer function of /spl alpha/ such that N/sub S/(/spl alpha/) /sub /spl alpha//spl rarr/0//sup /spl sim//. The result is obtained by studying the time optimal synthesis of a projected control problem on /spl Ropf/P/sup 2/, where the projection is defined by an appropriate Hopf fibration.

Summary form only given. In the recent search for new high temperature permanent magnetic materials, research has concentrated on bulk Sm/sub 2/Co/sub 17/ type magnets. The usual approach to development of coercivity in these bulk materials is to prepare a nanophase cellular microstructure with cell walls which act as pinning sites. In this work, a systematic investigation of structural and magnetic properties is carried out on Sm/sub x/Zr/sub y/(Co/sub 1-z/Fe/sub z/)/sub 100-x-y/ nanocrystalline powders, where 13 /spl les/ x /spl les/ 15, 0 /spl les/ y /spl les/ 5, and 0 /spl les/ z /spl les/ 0.5. The samples were prepared by mechanical alloying followed by an optimized annealing procedure. X-ray diffraction patterns showed that the as-milled powders were amorphous. Substitution of Fe leads to small amounts of /spl alpha/-Fe crystallites in a few compositions. Initially, powders with y = 0 were prepared with a view to optimize the Fe content to yield the best room temperature coercivity and remanence. It was found that z = 0.1 was the best Fe content for all Sm compositions. Samples without Zr showed a mixture of Th/sub 2/Ni/sub 17/ and Th/sub 2/Zn/sub 17/-type structures and room temperature coercivity of 1.4 T. All other compositions were then prepared by varying x and y and keeping z = 0.1. These samples also showed a mixture of Sm/sub 2/Co/sub 17/ phases along with minor amounts of SmCo/sub 5/, dependent on Zr content. Maximum coercivity of 1.7 T at room temperature is obtained in the composition Sm/sub 14/Zr/sub 3/(Co/sub 09/Fe/sub 01/)/sub 83/. Enhanced remanence (/spl sigma//sub r///spl sigma//sub s/ /spl ges/ 0.65) is achieved in all compositions, indicating the intergrain exchange coupling among the fine grains. Initial magnetization curves show that the magnetization behavior in these materials is pinning controlled. A discussion of the variation of magnetic properties with alloying addition and selection of suitable alloys for further studies at high temperature are presented.

This investigation presents a modified selected mapping (SLM) scheme for reducing the peak-to-average power ratio (PAPR) of an OFDM transmitted signal using a discrete Fourier transform (DFT) and a discrete cosine transform (DCT) kernel is proposed and investigated. The coefficient array of DFT or DCT is designed to reduce the correlation among original QAM constellations. In this technique, the preprocessing in each OFDM symbol is embedded between the multiplication of the phase sequences and the IFFT process. Then, the OFDM signal with the lowest PAPR is selected for transmission. Simulation results indicate that the proposed scheme can achieve better performance than the conventional SLM method in reducing PAPR while using the half number of branches in one OFDM frame.

In this paper, we propose a new peak-to-average power ratio (PAPR) reduction technique, which is referred to as trellis-assisted constellation subset selection ( TACSS , or TAX for short), for orthogonal frequency-division multiplexing (OFDM) signals. We control the signal transition by judiciously selecting the appropriate constellation subset for PAPR reduction with the controlling bits that are subject to the trellis-based constraint imposed by a bank of memories. A novel constellation design suitable for the proposed system is also introduced. A major property offered by the proposed approach is that the controlling bits and the information bits are perfectly separable at the receiver, which leads to a simple implementation of its soft-in–soft-out (SISO) decoder for coded OFDM systems. Through the performance analysis of PAPR reduction capability, power amplifier (PA) efficiency, average mutual information (AMI), and bit error rate (BER), the achievable tradeoff relationship between the transmitter and receiver performances of the proposed system is addressed. Furthermore, performance comparisons of the proposed scheme with other major PAPR reduction schemes such as trellis shaping, discrete Fourier transform (DFT) precoding, and clipping and filtering demonstrate its practical advantage in a high-spectral-efficiency regime.

An iterative peak-to-average power ratio (PAR) reduction algorithm for discrete multi tone (DMT) based systems, such as OFDM and VDSL, is introduced. The proposed algorithm uses reserved or unused tones to minimize the l/sub /spl infin// norm of the DMT symbol vector iteratively based on a subgradient optimization technique. The resulting iterative algorithm has a very simple update rule and, therefore, a low computational complexity. Furthermore, the PSD level constraints can be easily incorporated into the algorithm. The proposed algorithm's performance is illustrated for an OFDM system with 256 carriers. It is shown that a high PAR reduction is achieved, especially for the cases where the PAR reduction tones are allowed to exceed the PSD mask level.

Orthogonal frequency division multiplexing (OFDM) signals have a generic problem of high peak to average power ratio (PAPR) which is defined as the ratio of the peak power to the average power of the OFDM signal. The drawback of the high PAPR is that the dynamic range of the power amplifiers (PA) & digital-to-analog (D/A) converters required during the transmission and reception of the signal is higher. As a result, the total cost of the transceiver increases, with reduced efficiency. This paper includes an idea of the PAPR constraint, along with the implementation and analysis of some specific algorithms for PAPR reduction of the OFDM signals. All the PAPR reduction algorithms are implemented and tested in the OFDM transceiver designed using Matlab. Analyzing some specific algorithms, we propose a novel algorithm by combining the subcarrier phase adjustment and linear combination of the time domain OFDM signals. Simulation results for a OFDM system employing Quadrature Amplitude Shift Keying (QASK) symbols and Quadrature Amplitude Modulation (QAM) can achieve a PAPR reduction of 5 dB.

OFDM has been adopted as a standard for various high data rate wireless communication systems due to several benefits. One of the major drawbacks in OFDM system is its high Peak-to-Average Power Ratio (PAPR) of its transmitted signals thereby making transmitter amplifier to operate beyond its linear range of operation resulting in signal distortion. In this research work a simple method for reducing Peak-to-Average Power Ratio in OFDM is presented. The method is based on Discrete Cosine Transform (DCT) aided successive addition and subtraction (SAS) of data symbols within a single OFDM frame. Performance of the proposed method is evaluated and compared with the existing techniques. Joint reduction in PAPR by combining SAS preprocessed DCT technique and companding is also presented where system utilizes companding technique to further reduce the PAPR of the OFDM signal. Keywords: OFDM; PAPR; DCT; SAS; CompandingOFDM has been adopted as a standard for various high data rate wireless communication systems due to several benefits. One of the major drawbacks in OFDM system is its high Peak-to-Average Power Ratio (PAPR) of its transmitted signals thereby making transmitter amplifier to operate beyond its linear range of operation resulting in signal distortion. In this research work a simple method for reducing Peak-to-Average Power Ratio in OFDM is presented. The method is based on Discrete Cosine Transform (DCT) aided successive addition and subtraction (SAS) of data symbols within a single OFDM frame. Performance of the proposed method is evaluated and compared with the existing techniques. Joint reduction in PAPR by combining SAS preprocessed DCT technique and companding is also presented where system utilizes companding technique to further reduce the PAPR of the OFDM signal. Keywords: OFDM; PAPR; DCT; SAS; Companding

Channel capacity and Peak Average to Power Ratio (PAPR) are essential elements in offering dependable communication through wireless medium in wireless communication system. The rating of an amplifier in an Orthogonal Frequency Division Multiplexing (OFDM) system, as well as prospective future candidates of 5G systems such as Filter Bank Multicarrier (FBMC) and Universal Filtered Multicarrier (UFMC), affected by a high peak to average power ratio. The demand for channel capacity fluctuates due to the growing number of wireless network users. This paper recommended a low PAPR FBMC method, showing excellent performance in terms of PAPR reduction gain, overhead computation complexity and overhead SI compared to the current PAPR reduction scheme. In order to further increase the reduction in PAPR we have developed four variants of FBMC waveforms for DFT expansion, ITSM and the selected with the smallest peak capacity. In order to further reduce the PAPR rate of DFT expansion we have produced four different versions. After implementation of the proposed algorithm, the PAPR of the FBMC method has been considerably reduced. Following use of DFT propagation and ITSM conditioning, PAPR was decreased by 25 percent. The side data, which is persistent with traditional PAPR reduction techniques like cutting, partial transmission series, and selective mapping, is also disabled. The proposed device improves the transmitters' lifetime and efficiency through waveform accuracy. The study begun was planned to reduce the limitations of contending waveforms in order to create a resourceful communication system.

High Peak-to-Average Power Ratio (PAPR) of the Orthogonal Frequency Division Multiplexing (OFDM) signal is one of the limitations to the transmission performance of optical OFDM system. In this paper, we propose a novel hybrid PAPR reduction technique called Hadamard Transform Combined with Partial transmit sequence (HTCP). The proposed HTCP scheme combines the merits of two complementary techniques, i.e., Hadamard transform and Partial Transmit Sequence (PTS), to improve the performance of the optical OFDM system in terms of PAPR and Bit Error Rate (BER). Simulation results show that the HTCP scheme has better performance with regard to PAPR and BER compared with the case of applying only the Hadamard transform or PTS technique.

Orthogonal frequency-division multiplexing (OFDM) is an orthogonal waveform technique for encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for wide band digital communication, used in applications such as wireless networks and 4G mobile communications such as LTE, WIMAX and Wifi. It still exists with some of the drawbacks, out of which, high peak to average power ratio (PAPR) gives rise to non-linear distortion, inter-symbol interference and out-of-band radiation. There has been various ways developed and implemented to reduce PAPR. we will describe all of these techniques to reduce PAPR, then focus on technique called Partial Transmit Sequence technique(PTS) which comes under Signal scrambling techniques. In this technique, the symbol in the frequency domain is partitioned into smaller disjoint sub-blocks. The objective is to design an optimal phase for the sub-block set that minimizes the PAPR. In this paper, an efficient Universal Software Radio Peripheral (USRP) implementation of PTS scheme for PAPR reduction OFDM signals using LABVIEW has been carried out.

The authors propose a novel localised discrete Fourier transform (DFT) spread M-ary amplitude shift keying (M-ASK) orthogonal frequency division multiplexing (OFDM) system with the Hermitian symmetry (DFT-spread M-ASK HS OFDM) to reduce the peak-to-average power ratio (PAPR). Compared with the conventional OFDM and localised DFT-spread OFDM, the proposed system has lower PAPR not only because of the DFT-spread scheme but also its lower modulation order than other OFDM systems. The lower modulation order of the proposed system can be achieved by using the Hermitian symmetry of DFT. The simulation result shows that the localised DFT-spread M-ASK HS OFDM provides a significant improvement in bit-error-rate and reduced PAPR.

Optical orthogonal-frequency-division-multiplexing (O-OFDM) has been widely explored for visible light communication (VLC) to achieve high data rates. However, O-OFDM suffers from high peak-to-average power ratio (PAPR), which causes clipping distortion, reduces illumination to communication conversion efficiency and affects the lifetime of the light-emitting diode (LED). This paper proposes a novel modulation technique, an amalgamation of discrete Fourier transform (DFT) precoding and Gaussian minimum shift keying (GMSK) pulse shaping to reduce the PAPR of OFDM based VLC system. Furthermore, the concept of group precoding is also introduced to deal with the increased complexity of the DFT precoding system. The results show that different variants of the proposed scheme provide improved PAPR, symbol-error-rate (SER), and power-saving performance as compared to the corresponding DFT precoded O-OFDM and O-OFDM counterpart. Moreover, the analytical study of PAPR, computational complexity and spectral efficiency for the proposed system have also been investigated and reported in this paper.

Wavelet Packet Modulation (WPM) is a new scheme of choosing modulation scheme for transmission of multicarrier signal on wireless channel which helps in orthogonal wavelet base in place of sine functions. Though this modulation is over all similar to that of multi carrier code division multiple accesses (MC-CDMA), it provides interesting additional features. High Peak to Average Power Ratio (PAPR) of transmitted signal is the main obstacles of the wavelet packet modulation scheme. Make use of the advantage of concentrating the energy to confirmed subspaces of the discrete wavelet transform (DWT), the performance of two methods to reduce PAPR in wavelet Packet Modulation is investigated. In general, the selective mapping (SLM) technique is used for reducing the PAPR. In our work, we use the artificial bee colony algorithm to reduce the PAPR value of the SLM for wavelet Packet modulation signals. The achievement of the (ABC) algorithm for Daubechies wavelets was compared with the classic WPM for reducing Daubechies wavelets, random search SLM for Daubechies wavelets and optimum SLM and from the results show that can get throw the algorithm proposed on good PAPR reduction by computer simulations.

In this paper, we propose a new PAPR reduction by using a partial transmit sequences (PTS) method with coded side information (SI) technique. These methods are used in an orthogonal frequency division multiplexing (OFDM) system. The OFDM employs orthogonal sub-carriers for data modulation. These sub-carriers unexpectedly present a large peak to average power ratio (PAPR) in some cases. In order to reduce PAPR, the sequence of input data is partitioned into disjoint sub-block of PTS. If number of sub-block increases, high efficiency of PAPR reduction can be obtained. However, a quite large calculation cost must be demanded and thus it is impossible to obtain the optimum PTS. In the proposed method, we introduce a coded side information technique assuming the pseudo-optimum condition into the PTS. The total calculation cost becomes drastically reduced and side information bits for recovering original data in demodulation. In simulation results, the proposed method demonstrated the improvement of PAPR and bit error rate (BER) performance.