对《与<降低OFDM系统峰均功率比的载波干涉技术>作者商榷》的回应

指出了<与<降低OFDM系统峰均功率比的载波干涉技术>作者商榷>文中对载波干涉(CI)技术存在的理解上的错误,强调了CI信号和CI/OFDM系统的主要特点.     

降低OFDM系统峰均功率比的载波干涉技术

介绍了应用载波干涉技术的OFDM系统,即CU/OFDM系统,说明了通过CI技术降低OFDM系统峰均功率比的基本原理和特点,并通过计算机仿真展示了系统峰均功率比改善的具体效果.仿真表明,载波干涉技术应用灵活,实施复杂度较低,能有效地解决OFDM系统的高峰均功率比问题.     

对《与<降低OFDM系统峰均功率比的载波干涉技术>作者商榷》的回应

指出了<与<降低OFDM系统峰均功率比的载波干涉技术>作者商榷>文中对载波干涉(CI)技术存在的理解上的错误,强调了CI信号和CI/OFDM系统的主要特点.     

基于载波干涉和压扩技术的OFDM系统PAPR降低算法

提出一种新的基于联合使用载波干涉技术和μ-law压缩扩张技术的正交频分复用(OFDM)系统峰均比(PAPR)降低算法.该方案通过载波干涉扩展在一定程度上降低了系统的峰均比,并获得了较大的频率分集增益.此外,更为显著的峰均比降低在压缩扩张单元获得.仿真结果表明,通过合理选取压扩参数,该方案以较低的计算复杂度有效地降低了OFDM系统的峰均比,同时获得可靠的系统误码率性能.     

降低OFDM系统峰均功率比的研究

对载波干涉技术降低OFDM的峰均功率比方法进行改进。先对输入信号进行分组,使系统峰值功率得到明显降低,之后再对分组后的信号进行载波干涉。理论分析及仿真结果表明,提出的方法能使系统峰值功率有明显降低,进而达到了进一步的降低峰均功率比的目的。该方法算法简单、不产生失真,不用传送边带信息,易于与其他降低PAPR的技术相结合使用,具有较好的实用性。     

一种降低空时分组码OFDM信号峰均功率比的方法

正交频分复用(OFDM)信号包含许多独立调制的子载波,当子载波相干地叠加时会产生一个很大的峰均功率比。空时分组码OFDM系统是在OFDM系统中引入空时分组编码,通过选择映射的方法来降低空时分组码OFDM信号的峰值功率,从而降低峰均功率比(PAPR),并通过仿真对系统性能进行比较。     

基于不同载波干涉编码OFDM性能分析

在载波干涉编码正交频分复用（CI/OFDM）系统中采用了几种CDMA扩频序列作为载波干涉码。并比较了用不同载波干涉编码的正交频分复用（OFDM）系统性能。从理论分析和Matlab实验仿真得出CI/OFDM系统的比特误码率（BER）随着子载波数目增加而变低,BER与采用不同的载波干涉（CI）编码无关。并证明CI/OFDM系统的峰均比（PAPR）主要取决于子载波数的大小以及CI码的性质。     

载波干涉 OFDM 系统峰均功率比特性分析

通过分析正交频分码分复用(OFDM-CDM)系统的信号包络，提出一种定性地分析不同 OFDM-CDM 系统峰均功率比(PAPR)特性的方法。根据这一方法对比分析了分别采用载波干涉(CI)扩 频码和 Wlash 扩频码的 OFDM-CDM 系统，在不同子载波数情况下的 PAPR 特性。理论分析和计算机仿 真结果表明，无论系统所采用子载波数量的大小，采用载波干涉(CI)扩频码的 OFDM-CDM 系统，即载 波干涉 OFDM 系统的 PAPR 状况，相对传统的 OFDM 系统都得到了显著的改善。     

基于CI的Turbo编码V-BLAST OFDM系统PAPR降低算法

MIMO-OFDM已成为4G宽带无线通信系统极具前景的备选方案,但与OFDM系统一样,系统仍然存在高峰均比（PAPR）问题。针对Turbo编码V-BLAST OFDM系统,提出了基于载波干涉（CI）技术的降低系统PAPR方案,说明了通过CI技术降低系统峰均比的基本原理。仿真结果表明,该方案不仅有效降低了系统的峰均比,还使得整个系统的BER性能得到进一步提高。     

一种基于信号分组平均降低OFDM系统PAPR的方法

介绍了OFDM是一多载波调制技术,具有抗多径信道干扰和频谱利用率高等特点根据OFDM信号的统计特性提出一种降低OFDM系统PAPR(峰均功率比)值的方法,即将IFFT变换后的个信号按一定的规律分成V组,计算分组平均值,用分组平均值代替相应的原信号值。仿真结果表明信号分组平均方法可非常有效地降低系统的峰均功率比值。     

An Overview: Peak-to-Average Power Ratio Reduction Techniques for OFDM Signals

One of the challenging issues for Orthogonal Frequency Division Multiplexing (OFDM) system is its high Peak-to-Average Power Ratio (PAPR). In this paper, we review and analysis different OFDM PAPR reduction techniques, based on computational complexity, bandwidth expansion, spectral spillage and performance. We also discuss some methods of PAPR reduction for multiuser OFDM broadband communication systems.     

A computationally efficient selected mapping technique for reducing PAPR of OFDM

In orthogonal frequency division multiplexing (OFDM) system, high value of peak-to-average power ratio (PAPR) is an operational problem that may cause non-linear distortion resulting in high bit error rate. Selected mapping (SLM) is a well known technique that shows good PAPR reduction capability but inflicts added computational overhead. In this paper, using Riemann sequence based SLM method, we applied reverse searching technique to find out low PAPR yielding phase sequences with significant reduction in computational complexity. Additionally, we explored side-information free transmission that achieves higher throughput but sacrifices PAPR reduction. Finally, to overcome this loss in PAPR reduction, we proposed application of Square-rooting companding technique over the output OFDM transmitted signal. Simulation results show that the proposed method is able to compensate the sacrifice in PAPR and achieved PAPR reduction of 8.9 dB with very low computational overhead.     

On the Use of Hexagonal Constellation for Peak-to-Average Power Ratio Reduction of an ODFM Signal

One of the main drawbacks of orthogonal frequency division multiplexing (OFDM) is the high peak-to-average power ratio (PAPR) of the OFDM signal. In this paper, we propose the use of hexagonal constellation for PAPR reduction of an OFDM signal. Because hexagonal constellation is the densest packing of regularly spaced points in two dimensions, we can have more signal points in a given area with hexagonal constellation than with quadrature amplitude modulation (QAM) constellation. We can exploit these extra degrees of freedom provided by the hexagonal constellation for PAPR reduction of an OFDM signal. We will apply the proposed technique to eliminate data rate loss due to the side information in partial transmit sequence (PTS) technique and selected mapping (SLM) technique.     

Modified selected mapping technique for PAPR reduction of coded OFDM signal

High peak-to-average power ratio (PAPR) of the transmitted signal is a major drawback of orthogonal frequency division multiplexing (OFDM). In this paper, we propose a modified selective mapping (SLM) technique for PAPR reduction of coded OFDM signal. In this technique, we embed the phase sequence, which is used to lower the PAPR of the data block, in the check symbols of the coded OFDM data block. It is shown that we can achieve both PAPR reduction from the SLM technique as well as error performance improvement from the channel coding with no loss in data rate from the transmission of side information. In addition, approximate expression for the complementary cumulative distribution function (CCDF) of the PAPR of the modified SLM technique is derived and compared with the simulation results.     

Optimization of Peak to Average Power Reduction in OFDM

Orthogonal frequency division multiplexing (OFDM) a multicarrier system [1, 2] provides base for all advanced wireless communication system. The performance of OFDM is degraded by peak-to-averagepower ratio (PAPR). High PAPR requires high power amplifiers (HPAs). The nonlinearity of the HPA exhibits amplitude and section distortions, that cause loss of orthogonality among the subcarriers, and hence, intercarrier interference (ICI) is introduced inside the transmitted signal. Not only that, high PAPR put together lands up in in-band distortion and out-of-band radiation. Rather than using HPA’s, the only way to improve performance of OFDM system is to reduce PAPR. The PAPR reduction of OFDM system gives fair reduction in PAPR under partial transmits sequence (PTS) and DCT-SLM techniques. Here in this paper we proposed a combination of PTS and DCT-SLM and an algorithm to cut back the PAPR. This hybrid combined technique reduces PAPR effectively and minimizes the complexity of PTS technique.     

A Modified SLM Scheme With Low Complexity for PAPR Reduction of OFDM Systems

In this paper, we propose a new peak-to-average power ratio (PAPR) reduction scheme of orthogonal frequency division multiplexing (OFDM) system, called a modified selected mapping (SLM) scheme, which considerably reduces the computational complexity with keeping the similar PAPR reduction performance compared with the conventional SLM scheme. The proposed scheme is analytically and numerically evaluated for the OFDM system specified in the IEEE 802.16 standard. For the OFDM system with 2048 subcarriers, the proposed scheme with 4 binary phase sequences can reduce the complex multiplications by 63.5% with the similar PAPR reduction compared with the SLM scheme with 16 binary phase sequences.     

Combined Selective Mapping and Binary Cyclic Codes for PAPR Reduction in OFDM Systems

In this paper, we consider reduction of PAPR in OFDM systems with BPSK subcarriers by combining SLM and binary cyclic codes. This combining strategy can be used for both error correction and PAPR reduction. We decompose a binary cyclic code into direct sum of two cyclic subcodes: the correction subcode used for error correction and the scrambling subcode for PAPR reduction. The transmitted OFDM signal is selected that achieves minimum PAPR, from the set of binary cyclic codewords. The received signal can be easily decoded without the need of any side information. Simulations show that the proposed scheme with simplex code as scrambling subcode achieves good PAPR reduction.     

A Low Complexity Partition Dummy Sequence Insertion PAPR Reduction Method for the OFDM System

Orthogonal Frequency Division Multiplexing (OFDM) technique has been widely adopted in many wireless communication systems because it can divide a wideband channel into several narrowband ones to avoid the frequency selective fading. However, one major drawback of the OFDM signal is the high peak-to-average power ratio (PAPR) problem. The high PAPR results in the in-band distortion and out-of-band radiation when the OFDM signal is fed into a nonlinear power amplifier. In this paper, we propose a Low Complexity Partition Dummy Sequence Insertion method to reduce the PAPR and computational complexity of the Partition Dummy Sequence method. Simulation results of the PAPR, Bit Error Rate and complexity reduction for the proposed method are evaluated to demonstrate its capabilities.