CPM调制的迭代检测技术

CPM信号具有包络恒定、峰均比小、功率利用率高的优点。针对CPM信号的特征,比较了最大似然序列检测Viterbi算法和逐符号的最大后验概率(MAP)解调算法的特点,重点研究了使用迭代检测技术进行软输入输出解调及译码的MAP解调方法。在AWGN信道条件下对CPM全响应和部分响应信号进行了误码性能仿真,结果表明采用相干解调和译码,迭代检测方案可得到较高的编码增益。     

Fast computation algorithm for multiple symbol detection of uncodedMPSK sequences over an AWGN channel

A fast computation algorithm is presented for multiple symbol detection of MPSK sequences over an AWGN channel with unknown carrier phase. The central idea is to define a decision statistic for each symbol based on the information of the past decided symbol sequence and to establish a simple relation between successive symbol decision statistics. Simulation results for uncoded 4PSK and 8PSK show a good performance     

基于5G系统的随机接入前导检测算法

针对已有的随机接入前导算法存在难以在实际基站中实现以及算法运算量大的缺点,文章提出了5G随机接入前导检测算法。首先将接收到的信号经过发送端的逆过程处理得到频域前导,然后生成频域ZC序列并进行分组,将各个组内频域ZC序列相加并与频域前导相关,最后通过设置阈值来检测前导序列,利用多天线分集梳理修改相对阈值的累积分布函数,根据相对检测阈值确定绝对检测阀值,即相对检测阈值与时变噪声电平的乘积。仿真结果表明,与频域固定阈值前导检测算法相比,在加性高斯白噪声信道中,所提算法的正确检测概率性能提升了1 dB;在节拍延迟线(TDLC300-100)信道中,所提算法的正确检测概率性能提升了2 dB。     

An analysis of decision feedback detection of differentiallyencoded MPSK signals

A decision feedback detection scheme for differentially encoded MPSK signals based on the maximum likelihood algorithm is proposed. The performance on the symbol error rate of the system for an AWGN channel is derived by taking the error propagation into account. The error propagation can be stopped by introducing an error propagation detection technique     

Dynamic quantization for maximum likelihood sequence detection ofPAM signaling

Maximum likelihood sequence detection (MLSD) provides optimum detection for intersymbol interference (ISI) channels subject to additive white Gaussian noise (AWGN). This decoding process dynamically searches the most likely path through the intersymbol interference (ISI) channel trellis, using the Viterbi algorithm (VA). In this paper, we exploit the structure of this trellis and, for an M-point pulse amplitude modulation (PAM) constellation, present a new scheme based on dynamic quantization. This scheme becomes extremely efficient for the single memory unit channel 1+f₁D, as it achieves optimum MLSD with O(M) computations per decoding step, instead of O(M²) for the VA. Generalization to any finite length channel is also possible and conserves good computational efficiency     

Breadth-first maximum-likelihood sequence detection: geometry

SA(B, C) is an algorithm penetrating a tree (or trellis) breadth first. It performs maximum-likelihood sequence detection (MLSD) under that structural constraint, and also under the complexity constraints determined by the parameters B and C. First, C is the number of partitions into which the states are distributed, and B denotes the number of paths in each partition. Recursively selecting paths which are closest to the received signal in the Euclidean distance (Hamming distance) sense guarantees constrained MLSD for the additive white Gaussian (binary symmetric) channel. The previously presented vector Euclidean distance (VED) is an important tool for analyzing SA(B, C) over the additive white Gaussian noise (AWGN) channel. A geometric interpretation of the signals involved clarifies the basic properties of this VED and other relevant general results (invariance, monotonicity). These results also form a basis for the construction of an algorithm for the efficient and fast calculation of minimum VEDs (of interest for large signal-to-noise ratio, SNR, detection performance). This, in turn, reveals the necessary complexity requirements to meet specified performance requirements for concrete trellis-coded systems. Here, the simple example of convolutionally coded (rate 1/2) with Gray-coded quaternary phase-shift keying over the AWGN channel is considered. When C=1 and choosing B/spl sim//spl radic/S (S being the number of states in the code trellis) gives the same asymptotic detection performance (large SNR) as unconstrained MLSD (e.g., implemented using the Viterbi algorithm).     

差分跳频通信系统的特点及性能

文章介绍了一种新型的短波跳频通信技术——差分跳频,分析了差分跳频技术区别于常规跳频技术的主要特点。针对按序列检测的信号接收方法,对差分跳频通信系统在AWGN信道下的性能进行了理论分析,同时做出相应的计算机仿真,证实了差分跳频通信技术和按序列检测方法的结合,使通信系统在AWGN信道下的性能得到了比较显著的提升。     

Performance of Frame Sync Acquisition Algorithms on the AWGN Channel

Performance of the threshold coherent frame sync acquisition (TCFSA) algorithm on the AWGN channel is analyzed and compared with the performance of the algorithm for the BSC. Cases both with and without binary phase ambiguity are considered. Analytical and simulation results are presented and the agreement between the two is shown to he very close. It is shown that the threshold frame sync acquisition algorithm on the BSC outperforms the TCFSA algorithm on the AWGN channel whenP_{e} leq 0.1, while it is inferior whenP_{e} geq 0.13in cases of practical interest. A modified acquisition algorithm on the AWGN channel is then proposed. Analytical and simulation results for the modified algorithm show that it is superior to conventional algorithms on the BSC and the AWGN channel.     

On the design and selection of convolutional codes for anuninterleaved, bursty Rician channel

This article focuses on code design and code selection rules under power and decoding delay constraints for an antipodal (BPSK) modulated and convolutionally encoded communication system. The system operates over a slowly fading AWGN channel, described by the block-fading model. We emphasize perfect coherent detection with maximum likelihood decoding assuming ideal channel information (the instantaneous fading values). The dominant design criterion in this scenario is the code diversity level in terms of blocks while the standard Hamming distance plays a secondary role. A code design procedure, based on maximum distance separable (MDS) cyclic block codes is presented along with a code-search algorithm. The performance results of selected codes are assessed via simulation and compared to those achieved by Reed-Solomon codes with erasure and error decoding     

利用功率谱最大最小值的频谱感知算法

为了提高频谱感知性能,首先利用功率谱函数特性和瑞利熵概念,从理论上分析了基于功率谱的频谱感知算法原理,提出一种以功率谱的最大最小值之差作为检测统计量的频谱感知新算法;然后推导给出了检测门限和检测概率表达式;最后给出了仿真结果。理论分析和仿真结果表明,在AWGN信道和Rayleigh衰落信道中本文算法都具有良好的检测性能,性能优于已有的利用功率谱的频谱感知算法,该算法不需要主用户信息,不用进行复杂的特征值分解,当虚警概率确定时,检测门限能准确给出。      

Performance of sequence estimation scheme of narrowband digital FMsignals with limiter-discriminator detection

A communication scheme using binary FM with noncoherent limiter-discriminator detection has been well known. Up to now, the improvement of bit error rate at the receiver side has been carried out through the bandwidth optimization of the IF filter, the decision feedback equalization (DFE), or simple two-state maximum likelihood sequence estimator (MLSE). This channel is inherently the intersymbol interference (ISI) channel due to the premodulation baseband filtering as well as the narrowband IF filtering. So the sequence estimation scheme using the Viterbi algorithm can be applied successfully, although the channel is not additive white Gaussian and maximum likelihood in the strict sense. In this paper, through computer simulations, we examine the actual BER improvement of the sequence estimation scheme with multiple-state trellis especially for MSK and GMSK signals. We mainly consider static AWGN and frequency nonselective Rician fading channels. Consequently, by adjusting the IF filter bandwidth, very large estimation gains are obtained compared to the conventional DFE or MLSE detector for AWGN and Rician fading channels. This scheme does not produce large demodulation delay and is implemented only by adding the signal processing part to the final stage of the receiver. This scheme seems to be very useful for any applications including satellite mobile channels     

利用训练序列的OFDM系统定时同步算法

在OFDM系统中,定时同步的好坏严重影响到接收端的接收。通过对各种已有定时同步方法的分析,利用CAZAC序列的良好特性,提出一种基于CAZAC训练序列的定时同步方法。改进后的算法能够很好地改善原有经典算法的峰值平台及测量不精确的问题。通过高斯白噪声信道仿真,证明了改进算法在定时同步方面较经典算法有明显提高。     

TCM信号序列的自由空间距离的矩阵算法

本文研究了TCM信号序列的自由空间距离的计算问题,提出一种新的算法矩阵算法,同时在理论上解决了计算TCM信号序列的自由空间距离所需状态转移次数问题。此矩阵算法的推导基于Viterbi算法,它是Viterbi算法的矩阵实现。与已有的算法相比,此算法的优点在于:(1)给出了显式解,使得计算的复杂度相对减小。(2)对空间距离的变化具有更强的适应性。作为实例,给出了高斯信道和衰落信道上的一些TCM信号序列的自由空间距离的计算结果。     

Optimal blind transport format detection for the UMTS uplink

In this paper, we describe a CRC-based optimal blind transport format determination algorithm with application to the UMTS uplink. The derivation, based on MAP detection, is presented and simulation results under both AWGN and fading channel conditions are given.     

Breadth-first trellis decoding with adaptive effort

A breadth-first trellis decoding algorithm is introduced for application to sequence estimation in digital data transmission. The high degree of inherent parallelism makes a parallel-processing implementation attractive. The algorithm is shown to exhibit an error-rate versus average-computational-complexity behavior that is much superior to the Viterbi algorithm and also improves on the M-algorithm. The decoding algorithm maintains a variable number of paths as its computation adapts to the channel noise actually encountered. Buffering of received samples is required to support this. Bounds that are evaluated by trellis search are produced for the error event rate and average number of survivors. Performance is evaluated with conventional binary convolutional codes over both binary-synchronous-communication (BSC) and additive-white-Gaussian-noise (AWGN) channels. Performance is also found for multilevel AM and phase-shift-keying (PSK) codes and simple intersymbol interference responses over an AWGN channel. At lower signal-to-noise ratio Monte Carlo simulations are used to improve on the bounds and to investigate decoder dynamics     

ESPRIT算法在CHESS电台频率检测中的应用研究

差分跳频(DPH)是一种新的高速短波通信体制,它利用相邻跳变频率的变化而不是载频本身来携带信息.跳变频率检测是实现DFH的关键技术之一.文章中研究了高斯噪声下基于ESPRIT算法的DFH信号频率检测.同时通过仿真与MUSIC算法和FFT算法进行了比较,仿真结果表明该方法的检测性能明显优于FFT算法,与MUSIC算法的检测性能基本相同,计算量却小于MUSIC算法.     

A MATRIX ALGORITHM FOR COMPUTING THE FREE SPACE DISTANCE OF TCM SIGNAL SEQUENCES

In this paper, the problem of computing the free distance of Trellis Coded Modulation (TCM) signal sequence has been discussed; a new algorithm-the matrix algorithm is proposed; and the step-number estimation problem for state transmission to compute the free distance of TCM signal sequence has been theoretically solved. The matrix algorithm is derived from the Viterbi algorithm, and is an implementation of Viterbi algorithm in the form of matrix. Compared with other algorithms, the matrix algorithm gains two advantages: (1) The explicit solution, and its relatively less complexity. (2) More reflexible ability to the signal space distance variation. As examples, the results of some TCM signal sequence on AWGN channel and fading channels have been presented.     

用于CMMB的低运算复杂度LDPC解码算法

 本文提出了两种基于变量节点可靠度的LDPC解码算法. 第一,针对传统的可靠度判决算法会产生比较严重的误判现象, 导致译码性能降低. 本文提出了一种改进的可靠度判决算法,它降低了变量节点的误判概率. 在AWGN和瑞利信道仿真中,性能都有显著的提高,性能超过了标准BP算法. 第二,提出了分层可靠度算法. 和标准BP算法相比较,性能提高了0.1dB,收敛速度提高了一倍,计算复杂度降低大约65%.     

Asynchronous QR-RLS-CMOE Blind Multiuser Detection

DS/CDMA communication systems are widelyused because of their obvious advantages, such as softcapacity, soft handover, higher spectral efficiency andthe ability to mitigate the effects of multi-path fading.However, the multiple access interference (MAI) andnear-far problem in DS/CDMA limit the furtherapplications of this technique. The structure of the conventional single-userdetector (CD), which neglects the presence of MAI, issimple, but its performance is limited, and the receiversuf…     

Improving differential detection of MDPSK by nonlinear noiseprediction and sequence estimation

A new technique is proposed to improve the performance of differential detection (DD) of M-ary differential phase-shift keying (MDPSK) significantly, applying sequence estimation. In order to obtain an appropriate representation of the received signal, a nonlinear time-variant finite impulse response or infinite impulse response prediction-error filter is used. For both filter structures the optimum coefficients are derived, assuming transmission over an additive white Gaussian noise (AWGN) channel. Delayed decision-feedback sequence estimation (DDFSE) is employed to estimate the transmitted symbol sequence. It is shown by simulations that even for decision-feedback equalization, which is a simple special case of DDFSE, a significant performance improvement of conventional DD under AWGN conditions results. In contrast to other noncoherent low-complexity receivers proposed in literature, this receiver is very robust under flat fading (Rayleigh and Ricean) conditions