On the achievable average power reduction of MSM optical signals

In this letter, we consider the achievable average power reduction of multiple subcarrier modulated optical signals by using optimized reserved carriers. Based on Nehari's result we present a lower bound for the maximum average power of the signal after adding the reserved carriers. Simulations show that the mean value of the average required power behaves very close to /spl radic/(2nloglogn) for binary phase-shift keying (BPSK) constellations where n is the number of subcarriers. We further remark on evaluating optimum values for reserved carriers using convex optimization and Nehari's result.     

创新节能技术助制造商设计出媒体丰富的手机产品

移动设备曾有一段时间使用黑白显示器,其背光使用两个绿色发光二极管,背光功耗仅占移动设备总功耗的10％。而今,多媒体设备使用面积更大、清晰度更高的彩色显示器,显示器使用的时间也增长了,背光功耗已提高到总功耗的50％以上。     

降低OFDM信号峰均功率比的分段线性压扩变换

为了降低OFDM信号的峰均功率比(PAPR),设计了一种分段线性压扩变换.对小幅度通过数乘变换进行线性放大,而对大幅度先利用数乘变换进行线性缩小,再对缩小后的幅度进行等量放大.得到的压扩变换是分段线性且连续的,用低复杂度的线性运算抑制峰均比,同时用分段的方法减小压扩对系统性能的影响.理论分析和仿真表明,通过数乘因子和增...     

Power reduction techniques for multiple-subcarrier modulated diffuse wireless optical channels

In this paper, two novel techniques are proposed to reduce the average optical power in wireless optical multiple- subcarrier modulated (MSM) systems, namely in-band trellis coding and out-of-band carrier design. Data transmission is confined to a bandwidth located near DC. By expanding the signal set and coding over the increased degrees of freedom, an in-band trellis coding technique achieved an average optical power reduction up to 0.95 dBo over conventional MSM systems while leaving the peak optical power nearly unaffected. With a symbol-by-symbol bias, the received DC level can be detected to provide a degree of diversity at the receiver. In this manner, an additional average optical power reduction up to 0.50 dBo together with a peak power reduction of 0.46 dBo is achieved. Moreover, the unregulated bandwidth available in wireless optical channels is exploited and out-of-band carrier signals are designed outside the data bandwidth to reduce the average optical power. Average optical power reduction as high as 2.56 dBo is realized at the expense of 4 out-of-band carriers and an increase in the peak optical power. Finally, combining the three techniques achieves the best average optical power reduction of 2.63 dB optical.     

Characterization and modeling of run-time techniques for leakage power reduction

While some leakage power reduction techniques require modification of the process technology, others are based on circuit-level optimizations and are applied at run-time. We focus our study on the latter and compare three techniques: input vector control, body bias control, and power supply gating. We determine their limits and benefits in terms of the potential leakage reduction, performance penalty, and area and power overhead. The leakage power savings trends considering technology scaling are also presented. Due to the differences in the properties of datapath logic and memory structures, different implementations are recommended. Finally, the use of the "minimum idle time" parameter, as a metric for evaluating different leakage control mechanisms, is shown.     

OFDM峰均功率比降低方法概述

OFDM技术具有抗干扰能力强、频谱效率高、数据传输速率高等优点，但其主要缺点是有很高的峰均功率比（PAPR），影响其的实际应用。现对不同降低OFDM峰均功率比方法分别进行了概述，并给出比较。     

Complement block coding for reduction in peak-to-average power ratio of OFDM signals

In this article a new coding scheme, complement block coding (CBC), is proposed to reduce the PAPR of OFDM signals. This method utilizes the complement bits that are added to the original information bits, which can effectively reduce the PAPR of OFDM signals with random frame size N and the coding rate R /spl les/ (N - k)/N, where k is a positive integer and k /spl les/ N/2. The performance results obtained with CBC are given and compared with that of some well known schemes, such as simple block coding, modified simple block coding, simple odd parity code, and cyclic coding, for the same purpose. The results show that at the same coding rate 3/4, CBC can achieve almost the same performance as SBC and MSBC, but with lower complexity, and the same performance can be obtained with a higher coding rate using CBC. The PAPR reductions of CBC with coding rate (N - 1)/N are almost the same as with a coding rate less than (N - 1)/N, but almost the twice as these of SOPC when N /spl ges/ 16. Moreover, we can find that PAPR is the lowest for all block codes using CBC with coding rate 3/4. So modified CBC (MCBC) is also proposed and analyzed, combined with the subblock processing technique to make CBC effective for OFDM systems with large frame sizes. The flexibility in coding rate choice and low complexity make the proposed CBC more suitable for random frame size with high coding rate and can also provide error detection.     

Novel techniques for bus power consumption reduction inrealizations of sum-of-product computation

Novel techniques for power-efficient implementation of sum of product computation are presented. The proposed techniques aim at reducing the switching activity required for the successive evaluation of the partial products, in the busses connecting the storage elements where data and coefficients are stored to the functional units. This is achieved through reordering the sequence of evaluation of the partial products. Heuristics based on the traveling salesman problem are proposed to perform the reordering for different categories of algorithms. Information related to both data (dynamic) and coefficients (static) is used to drive the reordering. Experimental results from the application of the proposed techniques on several signal-processing algorithms have proven that significant switching activity savings can be achieved     

An overview of peak-to-average power ratio reduction techniques for multicarrier transmission

High peak-to-average power ratio of the transmit signal is a major drawback of multicarrier transmission such as OFDM or DMT. This article describes some of the important PAPR reduction techniques for multicarrier transmission including amplitude clipping and filtering, coding, partial transmit sequence, selected mapping, interleaving, tone reservation, tone injection, and active constellation extension. Also, we make some remarks on the criteria for PAPR reduction technique selection and briefly address the problem of PAPR reduction in OFDMA and MIMO-OFDM.     

Gaussian orthogonal matrix transform approach for PAPR reduction of optical OFDM signals

Optical orthogonal frequency division multiplexing (O-OFDM) has been widely adopted as a high-speed data transmission technique in visible light communication systems. This technique usually suffers from high peak-to-average-power ratio (PAPR). In this paper, a new PAPR reduction technique is proposed for O-OFDM signals. At the transmitter, a matrix transformation with the Gaussian elements is applied to the time-domain O-OFDM signal and at the receiver, the inverse matrix is used to recover the original signal. We show that the Gaussian orthogonal matrices can reconstruct the original signals without degrading the bit error rate (BER) performance. Gram-Schmidt technique is used to orthogonalize the Gaussian matrices. Computer simulations are conducted for 16-QAM baseband modulated symbols and about 3 dB PAPR reduction gain is achieved by the proposed approach compared with conventional O-OFDM.     

Distribution of light power and optical signals using embedded mirrors inside polymer optical fibers

Light and signal distributions through side-emitting ports along a polymer optical fiber are demonstrated using etched micro-mirrors. Low-cost serial and parallel mirror fabrication processes are described. Near uniform light distributions through as many as 200 such output ports along a single fiber was obtained. Back reflections of -19.4 dB and insertion loss of 0.7 dB were observed.     

Evaluating power saving techniques in passive optical access networks

This work proposes a resilient wheel-based wavelength-division-multiplexed passive optical network optical access network architecture for backhauling network traffic. This proposed resilient architecture can efficiently support not only the fixed users but also the mobile users in the downstream direction under normal and failure operating scenarios, while minimizing the average traffic delivery time and without using extra redundant fibers for protection purposes.

     

EMI reduction in switched power converters using frequency Modulation techniques

Frequency-modulation techniques have been used to reduce electromagnetic interference (EMI) produced by the clock of digital systems working in the range of hundreds of megahertz. The working principle consists of modulating the original constant clock frequency in order to spread the energy of each single harmonic into a certain frequency band, thus reducing the peak amplitude of EMI at harmonic frequencies. Nowadays, the switching frequency of power converters has increased up to values that make interesting the application of such techniques to reduce EMI emissions due to switching of power circuits. This paper presents the theoretical principles of frequency modulation using deterministic profiles for the modulating function. It shows the effectiveness of such methods in terms of EMI reduction for different modulation profiles and other parameters. The method is compared with other methods using random modulation. Tests carried out on a buck converter are presented for experimental validation of the method. A short discussion on optimal modulation profiles and parameters is also included.     

多进制相移键控信号信噪比估计方法

信噪比(SNR)估计是信道估计的重要组成部分,很多先进通信系统和信号处理方法都将信噪比作为先验信息,因此对信噪比估计方法的研究尤为重要。基于多进制相移键控(MPSK)信号模型,对最大似然类、矩估计类和空间分解类算法进行了性能分析和仿真。在一定条件下,上述算法的估计偏差在[0,20] dB区间内均小于1 dB,其中最大似然类算法估计精确度最高,但易受解调误码率影响;矩估计类算法在低信噪比时性能较好,高信噪比时易受算法自噪声影响;空间分解类算法适应性最强,但实时性较差。通过对上述算法一致性和差异性分析,总结了信噪比估计的研究进展和主要问题,明确了复杂调制信号宽范围信噪比估计和空间分解方法的研究方向,为后续研究提供了解决思路和改进措施。     

Measurement techniques for conducted HPEM signals

High-power electromagnetic (HPEM) signals are a serious threat for modern electronic systems. Intentionally generated electromagnetic interferences might cause upsets or permanent defects in electronics, particularly in the electronics' interface. There are numerous military and especially civil targets, which might be interesting for criminals or terrorists to interfere. Therefore, there is a need to characterize the overall problem by means of simulations and measurements. This paper discusses measurement procedures for conducted HPEM signals. The measurement of transmission line coupled HPEM signals with a steepness in the order of 10-10E14 V/s is a very challenging task. This paper discusses the state of the art in electromagnetic pulse measurements with a focus on conducted ultra wide band and RPEM signals respectively.     

Average error rate for coherent MPSK signals in Nakagami fadingchannels

The error rate performance of coherent M-ary phase shift keyed signals in slow nonselective Nakagami fading and additive white Gaussian noise channel is analysed. For real values of the Nakagami fading parameter m, a simple formula is presented for the symbol error rate that can be easily evaluated via numerical integration. A closed-form expression is derived for integer values of m. The effect of N-order MRC diversity reception is also considered     

Digital demodulator for optical FSK signals

The authors present a novel FSK-demodulator for optical phase diversity receivers. It is based on a digital flip-flop and is shown to have a sensitivity of about 3 dB below that of a delay and multiply demodulator. The concept is a step towards a fully integrated low-cost FSK receiver.<>     

Approximations for lognormally fading optical signals

A lognormally distributed random variable can be used to approximate accurately a noncentral chi-square random variable, This letter uses this result to approximate the photoelectron count distribution of a lognormally fading optical signal.     

Novel electro-optical feedback technique for noise and distortion reduction in high-quality analogue optical transmission video signals

The use of electro-optical feedback in an analogue optical transmitter makes it possible to reduce both noise and distortion. Automatic gain control by means of an electronically controlled optical attenuator maintains linearity of the baseband amplifier. The performance of this high-quality optical video link and of the optical attenuator is presented.     

Average power analysis technique for erbium-doped fiber amplifiers

It is shown that an average power analysis technique similar to that used for semiconductor optical amplifiers can be used to analyze both the discrete and the distributed fiber amplifier for multiwavelength operation without the need for numerical integration. It is also shown to give results that are in excellent agreement with those from other studies. This approach gives performance insights that are not otherwise readily available