一种降低OFDM峰均比的PTS技术

为有效降低正交频分复用系统峰均功率比,以最大效率开发利用电力线通信资源,提出了一种低复杂度的基于部分传输序列的改进技术。该技术在已调信号实部和虚部分别与相位因子相乘来降低峰均功率比的基础上,采用迭代算法优化相位因子,减小计算复杂度。仿真结果表明,算法以较快的收敛速度取得较优的相位序列,显著地降低了正交频分复用系统的峰均比,提高了低压电力线通信系统的性能。     

降低基于PSWF的非正弦调制信号PAR方法

针对基于椭圆球面波的非正弦调制信号峰均功率比大的问题,提出了降低峰均功率比方法。该方法根据基于椭圆球面波的非正弦调制符号时域特性,通过选择峰均功率比小于期望值的调制符号进行传输,从而达到降低调制信号峰均功率比的目的。理论分析和仿真结果表明,该方法不仅有效降低了调制信号的峰均功率比,而且不会降低通信系统的误码性能,也不会导致调制信号功率谱展宽和功率谱集中度变差。     

降低OFDM系统峰均功率比的方法

针对正交频分复用系统,提出了一种复杂度较低的降低峰均功率比的方法.该方法首先实施时域过采样,再采用功率归一化和限幅,最后对限幅后的信号进行低通滤波.此外,从信噪比和信号噪声失真比等角度分析了限幅对过采样OFDM信号的影响.仿真结果表明,与传统的限幅滤波方法对比,该方法能有效抑制滤波后系统峰均功率比的回升.     

人工噪声辅助的物理层安全信号峰均功率比减低算法

人工噪声辅助的物理层安全通信系统采用人工噪声破坏窃听信道的方式提升系统安全信道容量是近年来物理层安全通信领域研究的经典系统模型之一。该文针对这一模型中发射信号存在高峰均功率比问题,利用噪声子空间提供的冗余度提出一种基于噪声子空间功率分配的峰均功率比降低算法。该算法通过分式规划、DC规划以及二次非凸等式约束松弛将非凸的峰均功率比优化问题转化为一系列的凸问题迭代求解。仿真结果表明在系统放大器存在一定线性范围的约束下,该文提出的算法能够有效降低人工噪声辅助的物理层安全通信系统发射信号的峰均功率比问题,达到提高系统中合法用户的通信性能的目的。     

降低峰均比对通信系统性能收益研究

频谱效率和功率效率的大幅提升是新型通信系统得以持续发展和进步的核心驱动力。降低通信系统功耗最直接的途径是提高射频前端功放的功率效率,降低发射信号的峰均比可以有效降低信号的动态范围,从而降低功率放大器的非线性失真,进而带来通信系统能量效率、频谱效率和功率效率性能的综合提升。通过公式推导,定性地描述了峰均比与能量效率、频谱效率和功率效率的关系,并定量分析了降低峰均比给功率节约带来的性能收益,定量分析结果表明,典型算法中降低峰均比节省的功率与系统功率消耗比约为27.8%。     

降低OFDM信号峰均功率比的压扩方法研究

本文通过理论推导和分析,确定了基于误差函数降低正交频分复用(OFDM)系统峰均功率比的非线性压扩方法中两个关键参数的取值,修正了以前的结果,并在此基础上提出了一种新的压扩函数来降低OFDM系统的峰均功率比.理论分析和仿真结果表明,新的压扩方法能够在保持原信号平均功率不变的情况下使峰均功率比降低到7.8dB以下,并且系统具有较好的误比特率性能.     

基于混沌码的PPM-TH超宽带信号功率谱分析

为了减小超宽带通信对其它通信系统造成干扰,依据混沌码元丰富、良好的相关特性和白噪声统计特性,将混沌码引入TH-UWB系统,推导了TH-PPM超宽带信号的功率谱密度,采用matlab仿真工具分析了基于logistic混沌映射跳时码的PPM-TH超宽带信号功率谱密度.结果表明混沌跳时码可以有效平滑功率谱且增长码周期、增大码...     

利用格雷互补序列降低OFDM信号峰平比及其DSP实现

正交频分复用(OFDM)系统具有有效抗码间串扰、频谱效率高、可以提供高速率数据传输等优点,在第三代移动通信系统(3G)中具有良好的发展前景.但是,OFDM信号峰平比比较高,影响到功放的效率,这已经成为正交频分复用系统实用化的一大障碍.本文提出了一种有效降低正交频分复用信号峰平比的方法.它基于将格雷互补序列应用于正交频分复用通信系统,以降低信号的峰平比,对于任意载波数OFDM多载波信号,其峰平比可降至不大于6dB.本文还提供了一种用DSP实现的方法.     

混沌脉位调制UWB系统及信号分析

针对高通信速率下跳时脉位调制(TH-PPM)的超宽带(UWB)系统多址能力有限、信号离散功率谱分量高的缺点,引入了基于TENT映射的混沌脉位调制(CPPM)UWB系统,得到了其信号的功率谱密度表达式.分析和仿真表明高速UWB系统CPPM比TH-PPM的信号具有更强的多址能力和更平滑的连续功率谱分量,而且离散谱分量比TH-PPM方式低三个数量级.从而能减少对其它通信系统的干扰、具有更低截获概率和高保密性.     

多带OFDM-UWB系统峰均功率比降低方法研究

针对多带OFDM—UWB信号存在高峰均功率比的问题，提出了利用扩展与交织降低系统信号峰均功率比的方法。该方法通过对传输数据进行正交扩展与交织，使得进入多载波调制的数据趋于高斯分布，减小了传输数据自相关函数的旁瓣峰值，降低了OFDM-UWB信号的峰均功率比。由于采用正交矩阵进行扩展，扩展前后的数据传输速率保持不变。仿真结果表明，扩展与交织可以有效地降低信号峰均功率比2-5dB左右。同时该方法还具有抗窄带干扰的鲁棒性。     

A New Transceiver Scheme for OFDMA System Based on Discrete Cosine Transform and Phase Modulation

A high peak-to-average power ratio of the transmit signal is a major drawback of multicarrier transmissions, such as orthogonal frequency division multiplexing (OFDM) and orthogonal frequency division multiple access (OFDMA). An alternative approach to mitigate the peak-to-average power ratio (PAPR) problem is based on signal transformation using phase modulation (PM). A phase modulation based systems have the advantage of constant envelope (CE) signals and the ability to improve the diversity of multipath channels. In this paper, a different implementation of discrete Fourier transform DFT-OFDMA system which is based on discrete cosine transform (DCT) is proposed. The DCT-OFDMA system is then used to develop a new transceiver system called DCT-OFDMA-PM which refers to discrete cosine OFDMA with phase modulation. The PM input signal to be modulated must be real which can be produced using DCT-OFDMA with pulse amplitude modulation (M-PAM). The new system involves a signal transformation prior to amplification. This gives the advantage of CE (i.e. 0 dB PAPR). The proposed system is implemented with frequency domain equalization (FDE) to obtain high diversity gains over the frequency multipath channel. Simulation the PM-based systems with multipath fading can outperform that with single path fading.     

Variable Interleaver Allocation for Downlink OFDM-IDMA

In this letter, a variable interleaver allocation scheme is proposed to alleviate the high peak-to-average power ratio (PAPR) of downlink OFDM-IDMA (orthogonal frequency division multiplexing-interleave division multiple access). The basic idea is to allocate multiple interleaving patterns for each user, so as to decide the best pattern with the lowest peak value. Furthermore, a variable interleaver design scheme is combined to generate multiple patterns from an original one. It is shown that the proposed scheme can achieve the theoretical bound of PAPR reduction performance, while making a good tradeoff among PAPR reduction, system performance and computational complexity.     

Raised Cosine-Like Companding Scheme for Peak-to-Average Power Ratio Reduction of SCFDMA Signals

The 3rd generation partnership project long term evolution standard uses orthogonal frequency division multiplexing access in downlink and single carrier frequency division multiple access (SCFDMA) scheme for the uplink transmissions, which utilizes single carrier modulation and frequency domain equalization. In this paper, we proposed a Raised Cosine-like companding scheme to reduce the peak-to-average power ratio (PAPR) of SCFDMA signals. The proposed scheme can transform the original SCFDMA signals into Raised Cosine-like-distributed. Moreover, this scheme can compress the large signals, while maintaining the average power constant. Computer simulation results show that the proposed companding scheme can offer better PAPR reduction by properly choosing the parameters.     

Efficient PAPR Reduction in DCT-SCFDMA System Based on Absolute Exponential Companding Technique with Pulse Shaping

Discrete Cosine Transform based Single carrier frequency division multiple access (DCT-SCFDMA) is a prominent technique for providing high data rates in multimedia services. It also provides high Quality of Service to the users by mitigating the fading of signals. But High peak-to-average power ratio (PAPR) is a technical challenge which reduces the efficiency of RF power amplifiers. In this article, a novel joint scheme of PAPR reduction method is proposed and analyzed based on pulse shaping and absolute exponential companding (AEXP) technique. Our method proposes the use of standard raised cosine filter and square root raised cosine filter along with the AEXP companding process separately in DCT-SCFDMA system for different subcarrier mapping techniques e.g. interleaved frequency division multiple access and localized frequency division multiple access. Through extensive simulations, the numerical analysis presents that proposed architecture achieves significant improvements over the existing standard pulse shaping methods when used alone in DCT-SCFDMA system as far as the lowest PAPR is concerned.     

PAPR reduction in mobile WiMAX: a novel DST precoding based random interleaved OFDMA uplink system

Mobile WiMAX is a 3rd generation broadband wireless technology that enables the convergence of mobile and fixed broadband networks through a wide area radio-access. Since January 2007, the IEEE 802.16 working group has been developing a new amendment the IEEE 802.16 standard i.e. IEEE 802.16 m as an advanced air interface to meet the requirements of ITU-R/IMT-Advanced for 4G systems. The mobile WiMAX air interface adopts orthogonal frequency division multiple access (OFDMA) as multiple access technique for its uplink and downlink to improve signal performance affected by multipath distortion. All OFDMA based networks, including mobile WiMAX, experience the problem of high peak-to-average power ratio (PAPR). This paper presents a discrete-sine-transform precoding technique based random-interleaved OFDMA (RI-OFDMA) uplink system for PAPR reduction in mobile WiMAX. The PAPR of proposed system is analyzed with root-raised-cosine pulse shaping filter to keep out of band radiation low and to fulfill the spectrum mask requirements. Simulation results show that, the proposed system has low PAPR compared to the Hadamard transform precoded RI-OFDMA uplink systems and the conventional RI-OFDMA uplink systems.     

基于脉冲成形技术降低OFDM峰均比

正交频分复用（OFDM）利用相互正交的多个子载波来传输信息,具有较高的频谱利用率和良好的抗多径干扰能力,适用于高速数据传输,成为第四代移动通信的核心技术之一。但OFDM系统中一个最主要的缺点在于OFDM信号的峰值平均功率比（PAPR）很大,这容易导致系统线性功放的效率降低。研究了将脉冲成形应用到OFDM系统来降低PAPR的技术,以及脉冲波形的选取。仿真结果表明该方法能有效降低OFDM系统的PAPR,而且不影响系统的BER性能。     

Inter-antenna and subblock shifting and inversion for peak-to-average power ratio reduction in MIMO-OFDM systems

In this article, an inter-antenna inter-subblock shifting and inversion (IASSI) scheme is proposed to reduce the peak-to-average power ratio (PAPR) in multi-input multi- output orthogonal frequency division multiplexing (MIMO- OFDM) systems. It exploits multiple antennas and subblocks to provide additional degrees of freedom to benefit the system. To reduce the implementation complexity of the proposed scheme, two simple suboptimal schemes are further presented based on the minimum current maximum criterion; one adopts sequential search and the other employs random binary grouping. The simulation results exhibit the effectiveness of these proposed schemes.     

Interference-free code design for MC-CDMA uplink transmissions

In a recent study, solutions have been proposed for completely suppressing the multiple access interference (MAI) arising in the uplink of a quasi-synchronous multicarrier codedivision multiple-access network as a consequence of multipath distortions and carrier frequency offsets. This result is achieved by employing exponential orthogonal codes or selecting a particular subset of the Walsh-Hadamard code family without the need for any channel state information at the transmitter side. In the present letter, we revisit this problem and show that MAI suppression can be achieved by following a different line of reasoning which leads to a transmission scheme exhibiting a lower peak-to-average power ratio.     

基于三级调制的多带OFDM-UWB多址算法

根据多带OFDM-UWB通信系统的特点，提出一种基于三级调制的多带OFDM-UWB多址算法—TSM-MA算法。该算法通过MC-CDMA、OFDMA与FHMA技术的融合，实现多种技术的优势互补，减少了多用户间的干扰，充分利用了各子载波的可用资源。为了降低接收机的复杂度，TSM-MA算法采用了二级扩频与二级跳频的机制。结果表明，TSM-MA算法的多址性能要明显优于时频多址算法的性能，可以改善系统信噪比3dB左右，并且在接收机的复杂度方面也有一定的优势。     

MQAM-OFDM系统中降低峰均比与残余载波频偏同步联合算法

针对OFDM系统对频偏敏感及峰均比高的问题,提出一种用MQAM调制值的共轭码对残余载波频偏进行跟踪的方法,该共轭码同时可以降低系统峰均比.用频域MQAM数值的共轭来调制导频子载波以抵消相位,降低系统的峰值功率.同时利用这种共轭关系估计残余载波频偏引起的相位旋转,在时域或频域进行纠正.仿真结果表明利用这种共轭码可有效的跟...