Application of MLSE to GMSK signal reception using frequencydemodulator

The applicability of the maximum likelihood sequential estimator (MLSE) to 16 kbit/s GMSK signal reception using a frequency demodulator is investigated. The experimental results for GMSK with a premodulation filter bandwidth-bit duration product of B_bT=0.25 show that the bit error rate performance with MLSE approaches that of MSK, with a loss of about 2.5 dB in the signal energy per bit/noise power spectral density ratio and about 3.5 dB in the desired signal/cochannel interference ratio. The experimental block error rates are also reported     

The Minimum Likelihood--A New Concept for Bit Synchronization

A new bit synchronization concept based on the "minimum likelihood" criterion instead of the conventional "maximum likelihood" concept is developed. The minimum likelihood situation is even easier to reach than the maximum likelihood because the derivative of the log likelihood function becomes identically zero there. Minimum likelihood implies "least likely" for synchronization (the worst case synchronization error) or an "orthogonal" timing condition which simply means that the locally generated clock is synchronized correctly, but with a delay of a half bit period. The structure and performance of the minimum likelihood bit synchronizer are discussed in detail in this paper. The results indicate that the minimum likelihood bit synchronizer has a much simpler structure, but with performance very close to the optimal maximum likelihood synchronizer.     

Performance of Narrow-Band Manchester Coded FSK with Discriminator Detection

Due to the large discrepancies m the published results, the bit error rate (BER) performance of narrow-band Manchestercoded frequency-shift-keyed systems (MCFSK) with discriminator detection is reviewed and new results are presented which agree closely with measurements. It is found that a minimum BER is obtained for a peak-to-peak frequency deviation of about 1.35 times the bit rate and a receiver bandwidth of about 1.8 times the bit rate. The published results are shown to be rather optimistic. A coherent MCFSK demodulator is then shown to perform 3 dB better than discriminator detection. It is further shown that in the range of receiver bandwidths larger than the bit rate, it is sufficient to consider the intersymbol interference effects to have come only from the two bits adjacent to the bit being detected. Finally, if the phase noise components are assumed to be Gaussian distributed, the error probability formulas obtained do not predict the correct error performance.     

Digital demodulation by a non-coherent differential PSK modem

A DPSK demodulator which uses a digital delay line is presented. By digitising the demodulation process, the hardware design for the receiver is simplified. This also gives a greater flexibility to demodulate different carrier frequencies and data bit rates with the same receiver. The performance of the digital demodulator is compared with the theoretical values, for a range of error rates.<>     

Performance Limit of Chaotic Digital Waveform Communication Systems: Approach of Maximizing a Posteriori Probability

In this paper, we investigate a bandpass chaotic waveform communication system in an additive white Gaussian noise channel environment. By making use of the signalspace diagram and maximizing the a posteriori probability, we derive the conditions under which the optimum bit error performance can be achieved. In particular, we make use of a binary communication system to illustrate how the modulator and demodulator should be constructed in order to achieve the best error performance. Finally, the noise performance bound is determined for chaotic digital waveform communications.     

Decision feedback postprocessor for zero-crossing digital FMdemodulator

A baseband digital narrow-band FM receiver, called zero-intermediate frequency zero-crossing demodulator (ZIFZCD), has been developed. This demodulator may offer low complexity and simple implementation. However, the bit error rate (BER) performance of the ZIFZCD is inferior to that of the limiter-discriminator-integrate-and-dump (LDI) demodulator. In this paper, a simple decision feedback postprocessor (DFP) is proposed to improve the performance of the ZIFZCD. Analysis and simulation BER results of the ZIFZCD with the DFP are presented for minimum-shift keying (MSK) and Gaussian MSK (GMSK) signals under additive white Gaussian noise (AWGN) and mobile fading environments     

GMSK信号的后解码相干解调

为提高现有通信系统中高斯最小频移键控(GMSK)信号的接收性能,提出了一种基于后解码的GMSK相干解调方法.对于接收到的GMSK基带信号,首先完成相位和载波的同步,将信号的初始相位补偿到零相位;然后通过交替抽取GMSK基带信号的虚部与实部幅度采样值完成信息提取;最后通过后续解码处理完成信号解调.仿真表明,在误码率为10-3时,基于后解码的GMSK解调性能仅比预编码GMSK相干解调差0.5 dB,与传统基于维特比迭代处理的GMSK相干解调性能基本相当,但算法实现更为简化,有利于在现有非相干解调GMSK通信系统中的性能提升实现.     

Quelques résultats théoriques et expérimentaux sur la modulation par déplacement de fréquence à deux états et à phase continue d’indice 0,5 (MSK)

Minimumshift keying modulation seems to be very attractive for digital transmission systems in particular because an only small degradation can be expected on non linear channels. In the first part of this paper, some general features of the signal are recalled. After a theoretical method for the calculation of the bit error rate in presence of inter symbol interference is described; the results are compared with experimental values, obtained with a modulator demodulator build incnet laboratories in Lannion.     

Adaptive joint maximum‐likelihood detection and minimum‐mean‐square error with successive interference canceler over spatially correlated multiple‐input multiple‐output channels

We develop an efficient hard detector for multiple‐input multiple‐output (MIMO) channels, which adaptively combines maximum‐likelihood detection (MLD) and minimum‐mean‐square error with a successive interference canceler together. Unlike the conventional joint combination scheme, which may suffer from considerable degradation in bit‐error‐rate (BER) performance over correlated channels and where only one data stream is detected by MLD, our proposed scheme adaptively controls the number of data streams to be detected by MLD based on an analytical characterization of reliability for the detection. Simulation results illustrate that near‐optimal BER performance can be obtained at much lower computational complexity by the proposed method as compared with existing techniques, regardless of the spatial correlation of the MIMO channels. Copyright © 2012 John Wiley & Sons, Ltd.     

ASK digital demodulation scheme for noise immune infrared data communication

A high performance architecture is proposed for the ASK (Amplitude Shift Keying) digital demodulation, which is dedicated to the noise immune wireless infrared data communication. In this architecture, an infrared subcarrier detected by a photodetector is digitized into TTL interface level pulses, and the digitized subcarrier is demodulated by a 1‐bit digital demodulator. To improve the noise immunity against fluorescent lamps, the optical noises from the lamps are analyzed and the behavior of an ASK infrared communication link is modeled under these noises. On the basis of this model, a digital demodulator is synthesized by means of a high level synthesis tool, aiming at implementing an algorithm of discriminating the subcarrier from optical noises. A part of experimental results shows that the ASK receiver realized with the use of this digital demodulator can achieve an error free infrared link even under the intense noises from fluorescent lamps. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development and Performance Investigation of a Single-Channel 160 Gbps Free Space Optics Transmission Link Using Higher Order Modulation Scheme

This article reports the development of a high bit rate terrestrial free space optics (FSO) transmission link. Spectral-efficient polarisation division multiplexed-quadrature phase-shift keyed signals are used to transmit high bit rate data. Coherent receiver is proposed to ameliorate the demodulator performance under environmental conditions. Also, digital signal processing techniques at the receiver are used to mitigate the adverse channel effects on the information signal. The bit error rate analysis for different environmental conditions is carried out using numerical simulations and the results demonstrate reliable 160 Gbps transmission. The impact of atmospheric scintillation due to turbulent channel conditions on the link performance is also investigated. Further, the transmission performance is compared with previous reported studies which shows that the system demonstrates better achievable range and information bit rate performance. The reported work provides a suitable reference to realize bandwidth-efficient high-capacity FSO links under dynamic weather conditions.

     

4-phase p.s.k. differential demodulator using a.s.w. delay lines

The letter describes a cheap and reliable solution, using acousticsurface-wave delay lines, for the differential demodulation of phase-shift-keyed digital signals at low digital rates (up to 20 Mbit/s). Results on 4-phase p.s.k. differential demodulators operating at 2.048 Mbit/s are reported in terms of bit error rate against energy per bit/noise spectral density ratio. In addition, using the same technology, a new multidifferential demodulator has been implemented. Owing to multiple differential demodulations carried out on the same signal, a significant improvement in both theoretical and experimental bit error rate is obtained.     

基于商业零中频芯片的BPSK/QPSK解调器设计

提出基于商业零中频芯片MAX2837的BPSK/QPSK解调器设计,详细分析了零中频芯片MAX2837的特性、AGC环路、载波同步及位同步环路的设计.工程实测结果表明:该系统在误比特率为10-5时,解调损耗约2.5 dB,完成系统设计要求;该系统集成度高、体积小、重量轻、成本低.     

Signal Processing by Generalized Receiver in?DS-CDMA Wireless Communication Systems with?Frequency-Selective Channels

The generalized receiver (GR) based on a generalized approach to signal processing (GASP) in noise is investigated in a direct-sequence code-division multiple access (DS-CDMA) wireless communication system with frequency-selective channels. We consider four avenues: linear equalization with finite impulse response (FIR) beamforming filters; channel estimation and spatially correlation; optimal combining; and partial cancellation. We investigate the GR with simple linear equalization and FIR beamforming filters. Numerical results and simulation show that the GR with FIR beamforming filters surpasses in performance the optimum infinite impulse response beamforming filters with conventional receivers, and can closely approach the performance of GR with infinite impulse response beamforming filters. Channel estimation errors are taken into consideration so that DS-CDMA wireless communication system performance will not be degraded under practical channel estimation. GR takes an estimation error of a maximum likelihood (ML) multiple-input multiple-output (MIMO) channel estimation and GR spatially correlation into account in computation of minimum mean square error (MMSE) and log-likelihood ratio (LLR) of each coded bit. The symbol error rate (SER) performance of DS-CDMA employing GR with a quadrature sub-branch hybrid selection/maximal-ratio combining (HS/MRC) scheme for 1-D modulations in Rayleigh fading is obtained and compared with that of conventional HS/MRC receivers. Procedure of selecting a partial cancelation factor (PCF) for the first stage of a hard-decision partial parallel interference cancellation (PPIC) of the GR employed in DS-CDMA wireless communication system is proposed. A range of optimal PCFs is derived based on the Price’s theorem. Computer simulation results show superiority in bit error rate (BER) performance that is very close to that potentially achieved and surpasses the BER performance of the real PCF for DS-CDMA systems discussed in literature.     

Direct optical characterisation of DFB lasers for CPFSK system applications

The authors present a new optical characterisation method for single-frequency lasers that are to be applied in Gbit/s CPFSK systems. They use optical delay-demodulation to allow easy matching of the demodulator delay over a wide range of values. It is shown that for a particular device, when used in a 2.4 Gbit/s CPFSK system, the modulation index must be larger than 1.0 to obtain a bit error rate below 10/sup -11/. With a modulation index of 1.5, bit error rates below 5*10/sup -13/ have been measured.<>     

基于Henon混沌模型的随机交织器设计

本文对Turbo码中的关键组成部分-交织器作了分析，阐明了交织器在Turbo码中的重要作用；提出了一种基于Henon混沌模型的随机交织器设计方法，通过仿真实验，本文设计的交织器整体性能优于CDMA2000标准中Turbo码交织器性能，在高斯信道下，纠错性能平均改善0.15dB。     

A bit error probability analysis of a digital PLL based demodulatorof differentially encoded BPSK and QPSK modulation

Presents a bit error probability analysis of a digital phase-locked loop based demodulator, of differentially encoded BPSK and QPSK modulations. Differential decoding is a method of resolving a phase ambiguity, typical of fully modulated signals, that uses two consecutive demodulated symbols to estimate the information symbols. The effects of a noisy phase reference on demodulator performance are well documented for uncoded modulations (single symbol demodulation). The paper investigates performance for phase reference time variations between the two symbols. The time varying reference investigated is produced by a digital phase-locked loop. The noisy phase reference has negligible additional effect on the bit error probability for differentially encoded BPSK and QPSK     

Evaluation of Chaotic Demodulator for EBPSK Signals

Based on the theory of Duffing oscillator weak signal detection and the technology of extended binary phase shift keying (EBPSK) modulation, the chaotic demodulator using the Duffing oscillator for EBPSK signals was proposed. The proposed demodulator could avoid the problem of demodulation filters design, and shows the excellent anti-noise capability of chaotic oscillator detection. Numerical and experimental tests were taken to investigate the impact of modulation parameters τ and θ on bit error performance of the proposed method, and the performance limits were gotten. The results show that the proposed chaotic demodulator works well under a very low signal-to-noise ratio (SNR) conditions, and gets SNR gains about 20 dB to 30 dB from the impulse filter.     

On the Use of Polarity Coincidence Correlation Techniques for Differential Phase-Shift-Keyed Demodulation

The use of polarity coincidence correlation techniques can allow efficient use of digital logic elements for binary differential phase-shift-key demodulation. For the case of sinusoidal signals in the presence of additive Gaussian noise it is shown that an ideal hard limiter at the input to the demodulator adds no degradation to the bit error rate performance.     

Performance of Multiple-Access DCSK Communication over a Multipath Fading Channel with Delay Spread

The bit error rate (BER) performances of variant delay multiple-access differential chaos-shift keying (VDMA-DCSK) communication systems over a multipath fading channel with delay spread are investigated. The BER formula of the VDMA-DCSK over the fading channel is evaluated. A two-ray Rayleigh fading channel model is used to simulate the VDMA-DCSK system. The theoretical and simulation results are presented and they match each other, which supports the theoretical analysis. The multipath performance of the VDMA-DCSK is compared with that of a benchmark coherent MA-CSK system and with that of an invariant delay MA-DCSK system. The results show that in the multipath fading channel with delay spread environment the VDMA-DCSK system performance decreases least.