Noncoherent SPRT-based acquisition scheme for DSSS

A noncoherent sequential PN code acquisition scheme is proposed. The out-of-phase and on-phase sequences are properly modelled to avoid significantly high error probabilities occurring with the conventional SPRT-based acquisition. In addition, data modulation and frequency offset can be effectively overcome using this technique     

GSM系统中高效数据传输业务的实现

本评议提出了一个基于GSM系统的高效数据传输方案,它采用RS码与TCM级联的编码调制结构替代GSM原有的GMSK调制方案,以提供384kbit/s的数据业务,并引用相位校正单元以克服恶劣的无线传输环境所造成的相位噪声,该方案被集成在GSM平台上,并在典型的无线传输模型下与GSM的96kbit/s全速率业务的信道进行了比较,结果表明该编码调制方案在将编码调制效率提高一倍的前提下,仍然能保证传输的可靠性。     

Noncoherent detection for trellis-coded MPSK

This letter shows several methods for improving the decoding of noncoherent trellis-coded M-ary phase-shift keying. We propose two new metrics for the basic decision-feedback algorithm. These metrics are derived based on the idea of reducing the effect of incorrect amplitude of the reference signal. We also propose a new decoding algorithm that uses a simple way to estimate the metric of the future sequence     

Noncoherent sequence detection

New noncoherent sequence detection algorithms for combined demodulation and decoding of coded linear modulations transmitted over additive white Gaussian noise channels, possibly affected by intersymbol interference, are presented. Optimal sequence detection in the presence of a random rotation of the signal phase, assumed to be constant during the entire transmission, requires a receiver complexity exponentially increasing with the duration of the transmission. Based on proper approximations, simple suboptimal detection schemes based on the Viterbi algorithm are presented, whose performance approaches that of coherent detection. In a companion paper by Colavolpe and Raheli (see ibid., vol.47, no.9, p.1303-7, 1999), noncoherent sequence detection is extended to continuous phase modulations. In the proposed schemes, the tradeoff between complexity and performance is simply controlled by a parameter, referred to as implicit phase memory, and the number of states of a trellis diagram. Besides being realizable, these schemes have the convenient feature of allowing us to remove the constant phase assumption and encompass time-varying phase models. The proposed schemes compare favorably with other solutions previously proposed in the technical literature     

Noncoherent decision-feedback multiuser detection

The problem of noncoherent multiuser detection for multipulse modulation over the Gaussian multiuser channel is studied. It is assumed that neither the energies nor the carrier phases of the signals of any of the users are available at the receiver. Previously, a post-decorrelative generalized likelihood ratio test (GLRT) based detector was proposed as a solution to this problem. In this paper, we introduce the concept of noncoherent decision feedback (DF) that forms the basis for an improved solution to the same problem. The users are detected sequentially in some fixed order, and the decision for a particular user takes advantage of the reduction of uncertainty associated with the signal space resulting from decisions already made for previous users. In contrast to coherent DF, therefore, the feedforward and feedback transformations in the noncoherent case are themselves functions of the matched filter outputs. An efficient implementation of the noncoherent DF detector for M-ary modulation and ρ-dimensional signal space requires O(M_ρ) computational complexity per user. Upper and lower bounds on its symbol error probability are obtained. It is shown that significant improvements over the post-decorrelative GLRT-based detector are often possible. Sufficient conditions are obtained which guarantee, without ignoring error-propagation effects, that the high signal-to-noise performance of the DF strategy can be as good as its genie-aided version in which perfect past users' decisions are used     

Noncoherent sequence detection receiver for Bluetooth systems

The design of power efficient receivers for Bluetooth systems is a challenging task due to stringent complexity constraints. In this paper, we tackle this problem and present a receiver design consisting of a single filter and a subsequent noncoherent sequence detector. This receiver outperforms the conventional discriminator detector by more than 4 dB for typical Bluetooth channels. Thereby, the proposed noncoherent sequence detection (NSD) algorithm is both favorably low complex as it operates on a two-state trellis and highly robust against channel phase variations caused by low-cost local oscillators. The particular filter design accomplishes effective out-of-band interference suppression. Different from previous work on sequence detector receivers published in the literature, we take possible variations of the Bluetooth modulation parameters into account, and we also devise efficient methods for combined NSD and forward error correction decoding. Hence, the presented receiver design is an attractive solution for practical Bluetooth devices.     

一种对GSM信号的灵巧式屏蔽方法

常用手机信号屏蔽器存在干扰效率低,距离近,电磁频谱污染严重等问题.文中的思路是先侦测实际手机基站控制信道频率,然后采用时分多目标干扰方式对其实施干扰,使手机无法正常接收基站信号,从而实现屏蔽目的.该方法具有干扰效率高,功耗低,电磁频谱污染小等优点.     

Noncoherent sequence detection of CPM

Schemes in which noncoherent sequence detection based on the Viterbi algorithm are proposed for linearly modulated signals transmitted over additive white Gaussian noise channels, have recently been proposed by the authors. These schemes are attractive because their performance closely approaches that of coherent receivers with acceptable complexity, and they avoid the drawbacks of phase-locked loops. The authors extend these results to M-ary continuous phase modulation (CPM) signals     

Noncoherent detection of periodic signals

In this paper the optimal Bayes detector for a general periodic waveform having uniform delay and additive white Gaussian noise is examined. It is shown that the detector is much more complex than that for the we!l-known cases of pure sine waves (i.e., classical noncoherent detection)and narrow-hand signals. An interpretation of the optimal processor is presented, and several implementations are discussed.     

Noncoherent detection in asynchronous multiuser channels

The noncoherent demodulation of multiple differentially phase-shift-keyed signals transmitted simultaneously over an asynchronous code-division multiple-access (CDMA) channel with white Gaussian background noise is considered. A class of bilinear detectors is defined with the objective of obtaining the optimal bilinear detector. The optimality criterion considered is near-far resistance that denotes worst-case asymptotic efficiency over the signal energies and phases which are unknown at the receiver. The optimal bilinear detector is therefore obtained by solving a minimax optimization problem. In the finite packet length case, this detector is shown to be a time-varying multiinput multioutput linear decorrelating filter followed by differential decision logic. In the limit as packet lengths go to infinity, the time-varying decorrelating detector is replaced by a time-invariant multiinput multioutput decorrelating filter. Several properties of the optimally near-far resistant detector are established     

GSM系统中的寻呼重发优化与实现

主要研究GSM系统中的寻呼性能,根据现行GSM寻呼系统提出寻呼四次重发方案,将MSC重发方案和BTS重发方案进行对比讨论,选择BTS重发方案,详细介绍寻呼方案实现过程并给出测试结果,能够提高GSM系统的寻呼成功率,特别适用于无线信号差的环境。     

GSM/GPRS分裂信道高效重分配策略

现有GSM/GPRS系统各种信道分裂策略都仅限于话音呼叫,即仅允许分裂信道分配给话音呼叫而不允许分配给包呼叫.因而,当系统没有空信道时,即使可以提供分裂信道,一个新到达的包呼叫也将被阻塞.本文提出的分裂信道重分配策略允许话音呼叫和包呼叫均可获得分裂信道,论文还研究了包呼叫得到分裂信道的条件.研究结果表明,允许将分裂信道分配给新到达包呼叫可以获得更优越的性能;在本文的参数设置下,在门限参数θ＝2/3时,新策略的话音阻塞率和平均包传输时间没有明显恶化,而包阻塞率和平均信道利用率却得以显著改善.     

Noncoherent MLSE detection of M-DPSK for DS-CDMA wireless systems

This paper focuses on maximum-likelihood sequence estimation of noncoherent M-ary differential phase-shift keying (M-DPSK) receivers for code division multiple-access (CDMA) systems, which make use of direct-sequence spread-spectrum modulations. A typical frequency-selective Rayleigh environment with multipath diversity at the receiver is considered. In this scenario, the optimum noncoherent decision metric, which requires an estimation of the channel tap weights envelope, is derived. Then, in order not to increase the receiver implementation complexity, a joint channel and data estimation strategy is proposed, which does not require the transmission of a known training sequence (blind estimation). In this case, the decision metric becomes a simple equal gain combining of multiple-symbol square-law detection decision metrics. For this suboptimum noncoherent detector, useful bounds on the bit error probability are provided through a theoretical analysis. Nonconstant and constant multipath intensity profiles are both considered for this purpose. Simulations are also carried out in order to verify the accuracy of the theoretical bounds     

Noncoherent sequence detection of continuous phase modulations

In this paper, noncoherent sequence detection, proposed in a companion paper by Colavolpe and Raheli (see ibid. vol.47, no.9, p.1376-85, 1999), is extended to the case of continuous phase modulations (CPMs). The results in the companion paper on linear modulations with intersymbol interference (ISI) are used here because a CPM signal is mathematically equivalent to a sum of ISI-affected linearly modulated components, according to the Laurent decomposition. The proposed suboptimal detection schemes have a performance which approaches that of coherent detection with acceptable complexity, allow for time-varying phase models, and compare favorably with previously proposed solutions     

Noncoherent detection of convolutionally encoded continuous phasemodulation

The authors consider the error probability at large signal-to-noise ratios of rate-1/2 convolutionally encoded CPFSK (continuous-phase frequency-shift keying) with an optimum noncoherent detector on an additive white Gaussian noise channel. The performance is given in terms of a parameter called the minimum squared normalized equivalent Euclidean distance which plays the same role mathematically as the minimum squared normalized Euclidean distance used for coherent detectors. It is shown that by introducing convolutional coding the error performance is significantly improved. The authors propose a decoding algorithm for these convolutionally encoded CPM schemes which is based on a limited tree search algorithm and uses the maximum-likelihood decision rule for noncoherent detection. Computer simulations show that the degradation in error performance compared to the performance of the optimum coherent Viterbi detector is less than 1 dB with a relatively simple noncoherent detector on an additive white Gaussian noise channel for most of the schemes considered     

基于GSM模块的光线检测系统设计

开关量信号采样是工业过程领域中一种常见的数据采集技术。本系统由单片机控制系统、显示模块、发送模块和光线检测模块等组成,采用AT89S51单片机作为系统的控制器,实现对开关量信号的采集和处理,并通过TC35 GSM模块发送处理后的信息。系统工作正常,运行稳定。     

Noncoherent detection of preamble-signal-assisted differentiallyphase-encoded APSK signals

A noncoherent detection scheme for differentially encoded amplitude- and phase-shift-keyed data transmission, assisted with differentially phase-shift-keyed preamble signals, is presented and analyzed for an additive white Gaussian noise channel. It is analytically shown that, despite a controllable reduction in bandwidth efficiency, the proposed scheme yields an error performance approaching that of the quadrature amplitude modulation scheme with ideal coherent detection within a loss of approximately 1 dB     

Noncoherent maximum-likelihood block detection of orthogonalNFSK-LDPSK signals

This paper investigates the noncoherent block detection of orthogonal N frequency-shift keying (FSK)-L differential phase shift keying (DPSK) signals transmitted over the additive white Gaussian noise channel, based on the principle of maximum-likelihood (ML) sequence estimation. By virtue of a union bound argument, asymptotic upper bounds for the bit error probability of the developed ML block receiver are derived and verified by simulation. It is analytically shown that the noncoherent NFSK-LDPSK ML block receiver performs comparably with the ideal coherent NFSK-L phase shift keying (PSK) receiver for L = 2 and 4, as the observation block length is large enough. Furthermore, substantial performance improvement can be achieved by the ML block detection of the NFSK-LDPSK signal with L > 2 by increasing the observation block length     

Noncoherent multiuser detection for nonlinear modulation over the Rayleigh-fading channel

The jointly optimum noncoherent multiuser detector is obtained for nonlinear nonorthogonal modulation over the frequency nonselective Rayleigh-fading multiple-access channel. Upper and lower bounds on the average bit-error probability are derived. While these bounds are numerically computable, they are too complicated to give insight into the relative influence of the system parameters on the essential behavior of the bit-error rate. Hence this paper develops an asymptotic analysis of the average bit-error probability. In particular, it is shown that the upper and lower bounds are asymptotically convergent. An exact formula for the asymptotic efficiency of the optimum noncoherent detector is derived. Interestingly, the asymptotic efficiency is found to be positive and independent of the signal strengths of the interfering users. In contrast, the noncoherent detector which would be optimal in a single-user channel (the "conventional detector"), when used over the multiuser channel, has an asymptotic efficiency that is identically equal to zero no matter what the powers of the interferers may be. While the performance analysis of the optimum detector provides the fundamental limit on achievable error rate, the implementational complexity of the optimum detector is exponential in the number of users. As a low-complexity alternative, a decorrelative energy detector is also proposed and analyzed in terms of error probability and asymptotic efficiency.     

Noncoherent sequence detection in frequency nonselective slowlyfading channels

A new class of noncoherent sequence detection (NSD) algorithms for combined demodulation and decoding of any coded linear and continuous phase modulations, transmitted over additive white Gaussian noise (AWGN) channels, has been previously presented. In this paper, this class is generalized to the case of frequency nonselective Rayleigh or Rice slowly fading channels, in the presence or absence of channel state information. Coded linear modulations, namely M-ary phase shift keying (M-PSK) and quadrature amplitude modulation (M-QAM), are considered. The proposed detection schemes have a performance which approaches that of coherent detectors, are very robust to phase and frequency instabilities, and compare favorably to other solutions previously proposed in the technical literature