On the architecture and performance of an FFT-based spread-spectrumdownlink RAKE receiver

This paper describes a spread-spectrum downlink RAKE receiver that computes data detection in the frequency domain. We assume a pilot signal is transmitted with data signals for channel sounding. The pilot signal does not degrade the receiver bit error rate (BER) performance because the receiver estimates the pilot signal and subtracts the estimated pilot signal from the received signal before data detection. A spreading code matched filter, a channel matched filter, and a sounding receiver are implemented by fast Fourier transform (FFT)-based matched filtering and integrated in a unified architecture. Monte Carlo simulation is used to evaluate the receiver BER performance in both a static channel and a mobile radio channel. Simulation results show that the RAKE receiver performs well in both kinds of channels     

Simulation issues for future wireless modems

Mobile communication systems present several design challenges that stem from the mobility of users throughout the system and the time-varying multipath channel and interference. To address these challenges, future wireless modems will rely on performance enhancing techniques such as adaptive antennas, DSP-based interference rejection techniques, and real-time signal processing for capacity improvement. The authors present an overview of key simulation issues for wireless communications systems. First, the burst error characteristics of the mobile channel require the selection of appropriate performance measures. Second, accurate simulations require realistic channel models that include the effects of attenuation, multipath propagation, noise, and interference. Third, link-level simulation of wireless systems requires attention to details of system implementation including the effects of nonlinearities. Finally, efficient simulation of CDMA systems may require a combination of analytic and simulation techniques     

短波信道特征参数对通信误码率影响的试验分析

介绍了一种融短波通信与电离层斜向探测于一体的联合试验平台,该平台信道探测与通信同时进行,共用一套硬件设备,克服了设备不匹配及探测信道参量失效等问题,并基于该平台实录数据提取了通信误码率及信道特征参量包括信噪比、衰落深度、衰落率、多径扩展、各模式信号幅度、群距离、主模式相位、多普勒频移及多普勒扩展等,统计分析了各信道参量对通信误码率的影响,得出了一些有意义的结论。     

Simulation of bit error performance of FSK, BPSK, and π/4 DQPSKin flat fading indoor radio channels using a measurement-based channelmodel

The results of a simulation study that provides insight into the simulation methodology and bit error rate (BER) performance of frequency-shift keying (FSK), binary phase-shift keying (BPSK), and π/4 differential phase-shift keying (π/4 DQPSK) in flat fading channels inside open plan buildings are presented. A detailed measurement-based propagation channel model, SIRCIM (simulation of indoor radio channel impulse response models), which generates over 1000 closely spaced baseband equivalent complex impulse responses for a mobile radio operating at 1.3 GHz and traveling over a 1-m path, is used. The small-scale channel model, the communication system models used in the analysis and the methods used to predict BER are described. The channel simulator and the systems models have been thoroughly tested, and results from average instantaneous BER simulations are shown. The BER performances of the modulation techniques are presented. It is found that BPSK offers between a 2.8-dB and 3.0-dB improvement over π/4 DQPSK, although the latter offers a 3-dB increase in capacity for a given spectrum allocation     

Modelling,Performance Analysis and Design of WPAN Systems

This paper covers the main issues that must be solved in order to design and analyse the performance of Wireless Personal Area Networks (WPANs) with the aid of simulation tools. We review state-of-the-art channel models to account for small- and large-scale propagation conditions in waveform- and system-level simulations. When dealing with waveform simulations, we also look at Montecarlo and importance sampling techniques that allow efficient estimation of error probabilities. Additionally, discrete channel models are introduced to efficiently link both waveform- and system-level approaches and we point out some methods to obtain the model parameters that are suitable for the wireless environment. The discussion of these techniques is complemented with two application examples that show the use of the different simulation levels for system design and performance study. With the paradigm of Bluetooth piconets we illustrate the usefulness of discrete channel models and we consider the design of an OFDM-based WPAN system to exemplify simulation from a waveform-level point of view.     

Wide-band measurement and analysis techniques for the mobile radiochannel

The appearance of high bit rate digital radio systems would appear to demand the existence of wide-band channel models, planning tools, and simulation capabilities. The authors present an overview of various approaches to wide-band channel data acquisition (channel sounding) and data analysis for the locally QWSSUS channel. They outline how high-speed digital signal processing techniques can be employed to construct a nearly ideal real-time wide-band channel sounder. The digital sounder described employs a TMS32050A to implement a matched filter type receiver. The probe signal is a carrier BPSK modulated with a binary maximal length sequence; the received signal is processed in real time, yielding a complex time variant channel impulse response. A dynamic range in excess of 40 dB is achieved. They also briefly discuss techniques to use this data for stored channel simulation. Finally, by way of pointing out that much more information can be extracted from channel sounding data than is generally appreciated, they briefly discuss the use of probability theory (Bayesian techniques) in model selection     

Iterative frequency domain channel estimation for dft-precoded ofdm systems using in-band pilots

We consider two techniques of in-band frequency domain multiplexed (FDM) pilots using interleaved frequency domain multiple access (IFDMA) signal with a Chu sequence for DFT-precoded OFDM (or single-carrier (SC)) systems. One, called frequency domain superimposed pilot technique (FDSPT), superimposes pilot tones onto scaled or deleted data tones, which preserves spectral efficiency at the expense of a slight performance loss. The other, called frequency expanding technique (FET), multiplexes pilot tones by displacing data tones, which slightly reduces spectral efficiency. Using FDM pilots in SC systems facilitates flexible and efficient assignment of signals to available spectrum. We propose an iterative frequency domain decision-directed interference cancellation technique to reduce the intersymbol interference level of SC signals with FDSPT pilots (resulting from the suppression of data tones). Moreover, we propose a low complexity frequency domain iterative decision-directed channel estimation (IDDCE) technique for SC systems using FDM pilots. Using IDDCE, the frame error rate (FER) performance for coded SC systems using FET and FDSPT pilots with interference cancellation is found to be about 0.2 dB and about 0.5 dB, respectively, away from the FER performance with known channel frequency response at FER=10^-2. FDSPT pilots can also be used for OFDM systems with channel coding. It is found that an extra 1 dB of SNR is required at FER=10^-2,compared with that using the conventional FET pilots for OFDM systems.     

“AQUA”: A New Audio Quality Monitoring Algorithm for the Performance of DRM Receivers in Fading Channels

This paper presents a new Audio QUAlity monitoring algorithm: “AQUA” for assessing the performance of Digital Radio Mondiale (DRM) receivers. AQUA targets performance evaluation of consumer grade receivers in fading channels objectively. Consumer grade DRM receivers do not generally possess a Receiver Status and Control Interface (RSCI), which prohibits the possibility of analysing digitally decoded audio bit stream after reception. AQUA relies on the analysis of the received analog audio output signal instead. The paper describes the development of the AQUA algorithm and the measurement system used for receiver audio quality testing. The performance of AQUA is compared to conventional RSCI derived metrics like Bit Error Rate (BER) and Frame Error Rate (FER) of the decoded audio data. A series of tests are conducted in a variety of propagation conditions using a DRM dedicated testing system with a fading channel emulator. It is shown that FER estimates using AQUA are in good agreement with conventional FER figures derived from RSCI in different fading channel scenarios. This allows AQUA to be used as a reliable alternative to conventional FER performance analysis for automated objective testing of DRM receivers.      

二进制差分随机过程键控的结构与性能分析

提出了一种二进制差分随机过程键控的调制解调结构,推导出了在高斯信道和准静态衰落信道下的误比特率理论计算公式,并对系统进行了误比特率和二阶循环谱检测的仿真。仿真结果表明,提出的差分随机过程键控,在高斯信道下大约在?2 dB、在准静态瑞利衰落信道下大约在25 dB的信噪比下具有10?4数量级的误比特率。同时,所提出的差分随机过程键控调制方法,其广义二阶循环谱的不可检测性,使其具有很好的物理层隐蔽性。     

Cooperative communications with multilevel/AES-SD4-CPFSK in wireless sensor networks

In this paper, a new joint multilevel data encryption and channel coding mechanism is proposed, which is called ??multilevel/advanced encryption standard?Csystematic distance 4?Ccontinuous phase frequency shift keying?? (ML/AES-SD4-CPFSK). In the proposed scheme, we have not only taken advantage of spatial diversity gains but also optimally allocated energy and bandwidth resources among sensor nodes as well as providing high level of security and error protection for cooperative communications in wireless sensor networks. Relay protocols of cooperative communications, such as amplify-and-forward and decode-and-forward with/without adversary nodes, have been studied for 4CPFSK, 8CPFSK, and 16CPFSK of ML/AES-SD4-CPFSK. We have evaluated the error performances of multilevel AES for data encryption, multilevel SD-4 for channel coding, and various CPFSK types for modulation utilizing cooperative communications in wireless sensor networks. According to computer simulation results, significant diversity gain and coding gain have been achieved. As an example, bit error rate (BER) performance of 10^?5 value has been obtained at a signal-to-noise ratio (SNR) of ?6?dB for SD-4-CPFSK scheme in a compared related journal paper, whereas in our proposed system, we have reached the same BER value at a SNR of ?23?dB with amplify-and-forward with direct path signal protocol in 16-level AES, two-level SD-4 coded 16CPFSK, and at the same time, we have reached the same BER value at a SNR of ?22?dB with amplify-and-forward without direct path signal protocol in 16-level AES, two-level SD-4 coded 16CPFSK.     

Semi-blind identification of ARMA systems using a dynamic-based approach

A novel dynamic-based semi-blind approach is proposed to identify an autoregressive and moving average (ARMA) system in this paper. By using a chaotic driving signal, an ARMA system can be identified accurately by a dynamic-based estimation method called the ergodic-based minimum phase space volume (EMPSV). A maximum-likelihood formulation of EMPSV is provided to certify its unbiasedness and asymptotical efficiency. Monte Carlo simulations show that the EMPSV approach has a smaller mean-square error performance than the minimum phase space volume method and the conventional identification approach based on least-squares estimation with white Gaussian probing signals. The proposed approach is then applied to blind deconvolution of real audio signals and semi-blind channel equalization for chaos communications. It is shown that the EMPSV approach has improved deconvolution and equalization performances compared to conventional techniques in both applications.     

Half-symbol-rate-carrier PSK modulation for bandwidth-efficient high-speed data communications

This paper proposes new quadrature phase-shift-keying (QPSK) modulation techniques for high-speed data communication systems that use two orthogonal half-symbol-rate-carrier (HSRC) signals by which channel bandwidth requirements are reduced compared to that of the conventional non-return-to-zero (NRZ) modulation. The simulation results show the HSRC-QPSK has almost the same bit-error-rate (BER) performance with reduced signal bandwidth compared to that of the NRZ modulation. This paper also analyzes the performance of the recently proposed HSRC offset-QPSK (HSRC-OQPSK), which improves spectral efficiency by reducing the side lobes of the signal spectrum. In addition, HSRC minimum-shift-keying (HSRC-MSK) modulation is also introduced. The performances and the simulation results of the proposed modulation techniques are studied and compared with those of the conventional ones.     

系统极化码的置信传播译码性能分析

置信传播( BP)算法可以为系统极化码提供软信息作为判决依据,也可以为系统极化码在级联迭代译码中提供交换软信息。在详细描述基于信道极化结构的置信传播算法基础上,比较了系统极化码在软信息判决方法和极化编码判决方法下错误率性能的差异。仿真结果表明,软信息判决方法可以提高系统极化码的误比特率,在高信噪比下误帧率方面也略有提高。     

Outer-loop control of target SIR for fast transmit power control inturbo-coded W-CDMA mobile radio

A technique for obtaining outer-loop control of the target SIR for closed-loop fast transmit power control (TPC) is presented for turbo-coded wideband DS-CDMA (W-CDMA) mobile radio systems. The frame error rate (FER) of an intermediate decoding output in the turbo-decoder. i.e. before the final iteration stage is reached, is measured to control the target SIR. The bit error rate (BER) after the final decoding iteration can be maintained accurately at the prescribed BER value, e.g. BER=10^-6, without losing the tracking ability in the presence of slowly changing propagation channel conditions. Computer simulation results supporting this ability are reported     

Channel estimation and error correction for UWOC system with vertical non-line-of-sight channel

Recently, underwater wireless optical communication (UWOC) system has placed more attention towards increasing data rate, high accuracy, higher bandwidth and providing highly secured transmission. Generally, light propagation in underwater medium is disturbed due to some degrading effects such as turbulence, scattering and absorption which will degrade the performance. Therefore, channel estimation is essential and need to adapt suitable correction techniques that compensate the errors due to those effects. In this work, channel estimation and error correction technique are proposed for the UWOC system with vertical non-line-of-sight channel based on MIMO-OFDM approach. Initially, input sequence error is eliminated by HVD Turbo coding method and error rectified signal is modulated with M-ary OAM-PPM modulation technique. Modulated signal is transmitted through Vertical NLOS channel. During transmission, the signal undergoes scattering, absorption and channel fading. In receiver side, channel characteristics are estimated by invariant embedding method. Finally, estimated signal is demodulated and decoded by same techniques. MATLAB environment is used to implement the proposed work. Resultant performances like channel capacity, BER, SNR, data rate, receiving power and MSE for different water types like pure sea water, ocean water, costal water and turbid water are compared and results are examined.

     

Performance analysis of hybrid transmit antenna selection/maximal‐ratio transmission in Nakagami‐m fading channels

Hybrid diversity systems have been of great importance because they provide better diversity orders and robustness to the fading effects of wireless communication systems. This paper focuses on the performance analysis of multiple‐input gle‐output systems that employ combined transmit antenna selection (TAS)/maximal‐ratio transmission (MRT) techniques (i.e., hybrid TAS/MRT). The probability density function, the moment generating function and the n ^th order moments of the output signal‐to‐noise ratio of the investigated diversity scheme are derived for independent identically distributed flat Nakagami‐m fading channels. The system capacity of the hybrid TAS/MRT scheme is examined from the outage probability perspective. Exact bit/symbol error rate (BER/SER) expressions for binary frequency shift keying, M‐ary phase shift keying and square M‐ary quadrature amplitude modulation signals are derived by using the moment generating function‐based analysis method. By deriving the upper bounds for BER/SER expressions, it is also shown that the investigated systems achieve full diversity orders at high signal‐to‐noise ratios. Also, by Monte Carlo simulations, analytical performance results are validated and the effect of feedback delay, channel estimation error and feedback quantization error on BER/SER performances are examined. Copyright © 2011 John Wiley & Sons, Ltd.     

Frame error rates for convolutional codes on fading channels andthe concept of effective Eb/N0

Estimation of Viterbi decoder performance over channels with time-varying received signal levels is the subject of this paper. This work is motivated by a desire to obtain good estimates of the frame error rate (FER) for convolutional codes with bit-level interleaving over fading channels subject to practical power control algorithms. The convolutional code performance is quantified through the FER and effective E_b/N₀. where the latter is defined as the E_b/N₀ on an additive white Gaussian noise (AWGN) channel that results in the same FER. Given a received vector of (time-varying) E_b/N₀ values, we compute analytic estimates for the probability of frame error and the effective E_b /N₀ for a Viterbi decoder and interleaver combination. In particular, we validate our analysis using the R=1/3 convolutional code and interleaver used on the IS-95 CDMA reverse channel. Comparisons with simulations show that even for E_b/N₀ vectors with very large variations, our proposed estimates are good to within 0.2 dB for the effective E_b/N₀, giving FER estimates within a factor of two-five of the simulations     

Enhancement of the ETP model: how to calculate BER due to ISI forwide-band digital transmission in Nakagami-Rice fading environments

The equivalent transmission-path model, which was proposed by the authors, has a function to assess the bit error rate (BER) due to intersymbol interference (ISI) in a Nakagami-Rice fading environment with a simple formula. In this paper, improvement of usability is pursued taking the similarity of BER map shape in the delay difference between two waves into account. Moreover, an extended method predicting overall BER and frame error rate (FER) affected by both thermal noise and ISI is proposed, and accuracy is evaluated by computer simulation. Finally, a self-consistent flowchart showing how to calculate overall BER and FER in Nakagami-Rice fading environments is presented     

一种支持QoS的WCDMA混合神经网络反向链路功率控制算法

本文提出了一种混合神经网络反向链路功率控制算法,其外环控制采用Adaline神经网络模型,以不同业务的目标误帧率为指标,实时检测链路的误码状况,调整SIR目标值.内环控制采用Hopfield神经网络模型,通过控制移动台的发射功率确保SIR达到该目标值.与固定步长功率控制算法相比,该算法提高了控制精度和系统的稳定性,能够获得更高的通信质量.仿真实验也验证了算法的有效性.     

Bit error simulation for π/4 DQPSK mobile radio communicationsusing two-ray and measurement-based impulse response models

An accurate software/hardware bit-by-bit error simulator for mobile radio communications is described. Simulation results in indoor and outdoor channels are compared with theoretical results. Bit error rate (BER) results in simulated frequency-selective fading channels generated by several channel models such as two-ray, constant amplitude, and simulated indoor radio channel impulse models (SIRCIMs) are presented. It is shown that BER is not only dependent on the RMS delay spread, but also on the distribution of temporal and spatial multipath components in local areas. An important result is that a two-ray Rayleigh fading model is a poor fit for indoor wireless channels and, if used, can underestimate the BER by orders of magnitude. A real-time bit error simulation of video transmission using the bit-by-bit error simulator is described. The simulator, called BERSIM, is shown to be a useful tool for evaluating emerging data transmission products for digital mobile communications