In-room transmission BER performance of anti-multipath modulationPSK-VP

The BER (bit error rate) performance of an anti-multipath modulation π/4-QPSK-VP is evaluated in comparison to a conventional differential π/4-QPSK, when applied to high-speed digital radio transmission within a room where both transmitting and receiving antennas are set up, using a transmission experiment and a BER calculation. Through this transmission experiment at about 3 and 6 Mb/s, π/4-QPSK-VP was confirmed to improve the BER significantly for both data rates in two test rooms. A delay profile measurement was additionally carried out to characterize the propagation channels of the test rooms and to find out an appropriate channel model. The BER calculation based on the above channel model, which was confirmed to estimate the upper bound of a floor error rate sufficiently in comparison to the transmission experiment, reveals the relationship between the data rate and the BER and indicates an optimum and a maximum data rate for π/4-QPSK-VP with respect to the maximum delay spread of the room. The results show that π/4-QPSK-VP is estimated to raise the available data rate up to about 20 times over that of π/4-QPSK for a BER of 10^-4, although π/4-APSK-VP requires twice the transmission bandwidth     

A scheme for high performance real-time BER measurement

A statistically based method of bit error rate (BER) which does not necessitate the transmission of test patterns or the interruption of data for measurement purposes is presented. It is demonstrated that the method allows accurate estimation of BER several orders of magnitude faster than the Monte Carlo method. Design of an optimal BER estimator based on the maximum-likelihood principle is proposed. The performance of the technique is demonstrated by simulations for the case of QPSK modulation in AWGN and for a live Rayleigh-fading HF link. The ability of the method to accurately predict BER using relatively few samples means that it is particularly suitable for high-speed BER estimation     

双伽马湍流信道下多阶脉冲位置调制误码率性能分析

基于双伽马(Gamma-Gamma)大气湍流信道,研究了采用脉冲位置调制(PPM)技术的无线光通信系统的误码率(BER)性能。推导出平均EBR的闭合表达式,该表达式适用于任意湍流强度和任意调制阶数,与数值积分相比,可显著提高计算速度。对于给定的平均EBR,对比分析了在不同湍流条件下PPM调制阶数与平均发射功率需求间的关系。结果表明,在无湍流高斯信道和弱湍流信道下,增加调制阶数可以减小平均发射功率需求;然而随着湍流的增强这种作用逐渐减小,在强湍流区,甚至出现了调制阶数越高,平均发射功率需求越大的现象。因此,在实际系统设计时,应考虑可能的湍流环境,再选择合适的调制阶数。     

Postdetection switched combining - a simple diversity scheme with improved BER performance

This paper develops, analyzes, and optimizes a simpler form of dual-branch switch-and-stay combining (SSC), namely, one that relies on the output signal plus noise rather than the instantaneous signal-to-noise ratio (SNR) to trigger the switching between the diversity branches. Analysis supported by numerical results show that the newly proposed postdetection SSC scheme outperforms predetection SSC and this performance gain increases as the channel conditions improve in terms of average SNR and/or severity of fading. In brief, when simplicity of implementation is of primary concern, as is the case, for example, in mobile units, the proposed scheme offers an attractive low-complexity solution to mitigate the deleterious effects of multipath fading.     

一种抗多径效应的非相干无人机测距方案

多径效应是造成无人机测控系统可用性降低的重要原因之一。为了降低多径效应对无人机（UAV）测控系统的影响,提出了一种非相干测距技术方案。该方案利用了单载波频域均衡（SC-FDE）技术以及优化遥控帧与伪码速率关系及发送位置的方法,降低了机上测距数据下传误码率,同时提高了机上采样精度。经仿真验证,在反射路径信号比直达路径小6 dB且信噪比大于7 dB时,系统的测距精度满足无人机测控系统的指标要求。     

基于Exponentiated Weibull模型的M-PPM调制空间光链路误码性能

本文研究了Exponentiated Weibull 大气湍流下光链路误码性能,考虑大气湍流和指向误差对误码率的联合影响,利用Meijier′G函数推导出误码率的闭合表达式。根据误码率闭合表达式进行了仿真,分析了在不同大气湍流强度、PPM调制阶数、抖动标准差和波束宽度条件下,链路误码率随发射功率变化的关系。通过仿真分析证明:不同调制阶数,增大发射功率对链路误码性能的改善近乎相同;随着湍流强度、抖动标准差和波束宽度的增加,误码率增加。     

An opportunistic cooperation scheme and its BER analysis

The cooperative communication technology proposed in recent years enables network nodes to share their antennas to achieve diversity gain. In this paper, an efficient variation scheme on opportunistic cooperation is proposed by using an outage criterion, in which the cooperation mode will be adopted only when the channel from source to relay does not occur outage event. We derive a closed-form BER (bit error rate) expression for the proposed scheme over Rayleigh fading channels, showing that the full diversity is achieved by the new scheme. Also, the BER performance of the known coded cooperation is presented for the purpose of comparison with our scheme. Numerical results illustrate the superiority of the proposed scheme over the coded cooperation in terms of BER performance. It is pointed out that the corresponding BER advantage of the proposed scheme comes at the expense of increasing system overhead since the new scheme needs some feedback from relay to both source and destination.     

The theoretical BER performance analysis of a cooperative diversity scheme in frequency selective fading channel

A novel cooperative diversity scheme based on Distributed Space-Time Block Coding and Multi-Carrier Code Division Multiple Access (DSTBC-MC-CDMA) is proposed which works well in frequency selective fading channels with multiple single-antenna users. And an analytical error model is established to describe the symbol decoding errors between interusers, based on which a close form expression for theoretical Bit Error Rate (BER) performance of the scheme is derived to analyze the influence of the interuser decoding errors on the BER performance of the scheme. Then simulation is complimented to verify the analytic result above, which also shows that the BER performance of DSTBC-MC-CDMA outgoes that of non-cooperative MC-CDMA with considerable gains. Further- more, the simulations coincide with the theoretical results well.     

Improving BER performance of virtual QOSTBC

In this paper, we propose a new solution for improving BER performance of virtual quasi orthogonal space-time block coding (QOSTBC). The proposed solution is compared with virtual QOSTBC and virtual orthogonal space-time block coding (OSTBC). One of the main disadvantages of virtual OSTBC is its code rate, while on the other side code rate of QOSTBC equals 1, but with BER performance degradation as a consequence. The scheme proposed here provides improved BER performance in comparison with QOSTBC, and has preserved code rate of 1. The considered schemes are used for creating virtual 4 × 1 multiple input-single output channel. These schemes include one base station, one relay station, both equipped with two antennas, and one mobile station with a single antenna.     

A simple modulation scheme for error performance improvement oflow-deviation digital FM

The paper proposes a simple digital modulation scheme named LF (lowpass filtered)-π/2 TFSK. Since it is essentially a constant envelope modulation scheme, it can be applied to severely band-limited channels such as land mobile and satellite mobile radio channels. Its error performance is superior to that of MSK modulation in band-limited channels at the cost of a slightly wider bandwidth (approximately 1.06 times) than GMSK. The required E_b/N₀ with 2-bit differential detection at the error rate of 10^-5 is 2.3 dB smaller than that of GMSK in an additive Gaussian channel and 3 dB smaller at the average error rate of 10^-4 in a fast Rayleigh fading channel. The above result, obtained by an exact error rate analysis, was confirmed by laboratory experiments at a frequency of 880 MHz. The spectral characteristics were analyzed through computer simulations and the results were found to agree with those obtained from a hardware implementation     

BER performance of multiple-antenna OFCDM with imperfections

This letter investigates the performance degradation due to the imperfect parameters in orthogonal frequency- and code-division multiplexing (OFCDM) systems with multiple antennas. For the performance evaluation, the average bit error rate (BER) expression is generalized to the multiple-antenna case in the presence of the channel estimation error and frequency offset. Derived results show that the multiple-antenna OFCDM systems experience a severe BER degradation regardless of the number of users.     

Multirate modulation: a bandwidth- and power-efficient modulation scheme

Multirate (MR) modulation resembles block-coded modulation (BCM), since matrices are being used to transform binary input vectors to multilevel output vectors (blocks) of length K. Unlike BCM, attention is given to the spectral shaping of the signal to be transmitted. Hence, the encoding matrices are designed to provide simultaneous spectral shaping and Euclidean distance. The encoding matrices can be implemented by using MR digital filters of low complexity. MR modulation also resembles partial response (PR) modulation since, in both cases, a transmitter and receiver filter is used with an overall duobinary impulse response. It will be shown that MR modulation has a number of significant advantages compared with PR modulation. Thus, for example, with MR modulation, loss of synchronization or gain control, as can occur with PR modulation, cannot happen in the receiver. Furthermore, computer simulations for an additive white Gaussian noise channel demonstrate that, for a bit-error rate of 10/sup -6/, MR modulation (with K=10) gives a gain of 1.5 dB, compared with PR modulation and symbol-by-symbol detection. However, MR modulation requires a slightly higher bandwidth. It is also explained how, for block lengths K/spl ges/10, MR modulation gives a larger bandwidth efficiency than M-ary pulse-amplitude modulation with raised-cosine pulses and a rolloff factor /spl alpha//spl ges/0.1.     

BER performance of vestigial sideband wideband CDMA systems

Using simulations, the authors evaluate the performance of the vestigial sideband QPSK modulated wideband CDMA (VSB/QPSK/W-CDMA) system. A VSB system is used to increase the spectrum efficiency by 30% compared to the conventional double sideband (DSB) system. The VSB/QPSK/W-CDMA scheme showed a comparable performance to the DSB/QPSK/W-CDMA scheme in the frequency flat fading channel. However, the VSB system showed an inferior performance in the presence of multipath fading and multiple access interference. It was shown that the use of additional Rake branches is effective in compensating for the VSB system's performance degradation     

BER performance of BPSK transmissions over multipath channels

A new closed form expression for the bit error rate (BER) performance of binary phase shift keying (BPSK) transmissions over frequency selective channels is presented. The expression is obtained through a novel approximation of the Gaussian Q(middot) function by a fixed series of sinusoids with exponentially decreasing amplitudes. Numerical results demonstrate the accuracy of the derived expression     

采用小波变换的OFDMA系统误码性能分析

针对LTE下行链路,建立一种基于小波变换的OFDMA(Wavelet Transform based Orthogonal Frequency Division Multiple Access,W-OFDMA)系统,克服频偏和相位噪声带来的不良影响,提升系统的误码性能.将小波作为系统的正交子载波,利用滤波器组的级联形式实现小波变换,取代原系统的快速傅里叶变换.利用Simulink建立W-OFDMA系统基带模型,分析比较高斯信道下基于不同小波的W-OFDMA系统的误码性能,并与传统的OFDMA系统进行比较.仿真结果表明,sym4小波为W-OFDMA系统的最佳子载波,且基于sym4的W-OFDMA系统的误码性能优于传统的OFDMA系统.     

MQAM-WPM-FH多载波跳频通信系统误码率性能分析

为了分析多进制正交幅度调制(MQAM)映射方式、小波滤波器长度和小波包树结构对小波包跳频通信系统（WPM-FH）的影响,首先利用多进制幅移键控(MASK)和MQAM之间的关系,推导了MQAM-WPM-FH系统在加性高斯白噪声(AWGN)信道中的误码率理论公式,分析了不同小波滤波器长度和小波包树结构对WPM-FH系统的影响。理论分析和仿真结果表明,与正交频分复用跳频（OFDM-FH）系统相比,MQAM-WPM-FH系统具有较高频带利用率和较好的性能;在给定带宽下,通过增大MQAM数据映射中的星座点数M和小波滤波器长度L,可以有效降低多址干扰(MAI)对系统的干扰;AWGN信道下,不同的小波包树结构对跳频系统的性能影响较小,但小波包调制结构的多样性可以提高系统的安全性。     

FSO中分层空时编码的误码性能

分层空时编码(BLAST)虽然具有极高的频谱效率,能成倍提高光通信系统的信息传输速率,但BLAST系统的误码率较大,严重影响了光通信系统的可靠性。在描述了湍流信道中多输入多输出(MIMO)系统的信道模型后,针对多进制脉冲位置调制(Q-PPM)技术,推导出了采用线性译码算法时分层空时码的极大似然判决准则及其误码率公式,并比较了最大似然译码算法、线性译码算法、串行干扰消除译码算法的误码性能。最后,利用仿真实验进行了验证。结果表明:在自由空间光通信(FSO)中,串行干扰消除译码算法的误码性能更接近最大似然译码算法的性能,明显优于线性译码算法。在4×4系统中,当误比特率为2×10-2时,相对于最小均方误差(MMSE)译码算法,最大似然译码算法和MMSE-SIC译码算法的信噪比分别改善了约14.5 dB和7 dB。理论分析与实验结果相一致。     

正交调制中多阶相位调制信号的误码率分析

光通信中如何提高传输速率和光谱效率已成为目前研究的热点,采用先进的调制格式是实现上述要求的关键途径,其中正交调制格式就是方法之一.文章介绍了一种研究计算多维多阶正交调制信号误码率的方法,首次推导出了多阶相位调制信号的解析表达式以及基于这种计算方法的仿真结果,并讨论了消光比等参数对误码率的影响.     

16PSK系统仿真及误码率性能分析

为实现16PSK应用到无线激光通信中,本文对16PSK系统性能进行了理论研究。介绍了16PSK调制解调原理,对两种不同信道的系统性能进行了研究,分析对比了在两种信道下的系统误码性能。为基于副载波16PSK无线激光通信系统的研究奠定了理论基础。     

BER performance analysis of a direct conversion receiver

Direct conversion receivers are increasingly popular for use in mobile terminals. This is due to advantages over other architectures such as heterodyne receivers in terms of cost, electrical current, and physical size. However, a direct conversion receiver often generates a DC-offset that has to be taken care of either by suppressing the DC-offset in the radio-frequency part of the receiver, or by taking care of it during baseband processing. A theoretical analysis of the bit error rate (BER) performance in a direct conversion receiver with different levels of DC-offset suppression is presented. Explicit results are presented on how the BER depends on the signal-to-noise ratio (SNR), the signal-to-DC-level, and the choice of pilot symbols both with M-QAM and M-PSK in a slow, flat Rayleigh fading channel. A design rule, which applies to the design of DC-compensation in direct conversion receivers, is also presented