A VLSI Architecture for Novel Decision Feedback Differential Phase Detection with an Accumulator

This paper proposes a novel decision feedback differential phase detection (DF‐DPD) for M‐ary DPSK. A conventional differential phase detection method for M‐ary Differential Phase Shift Keying (DPSK) can simplify the receiver architecture. However, it possesses a poorer bit error rate (BER) performance than coherent detection because of the prior noisy phase sample. Multiple‐symbol differential detection methods, such as maximum likelihood differential phase detection, Viterbi‐DPD, and DF‐DPD using L‐1 previous detected symbols, have attempted to improve BER performance. As the detection length, L, increases, the BER performance of the DF‐DPD improves but the complexity of the architecture increases dramatically. This paper proposes a simplified DF‐DPD architecture replacing the conventional delay and additional architecture with an accumulator. The proposed architecture also improves BER performance by minimizing the current differential phase noise through the accumulation of previous differential phase noise samples. The simulation results show that the BER performance of the proposed architecture approaches that of a coherent detection with differential decoding.     

BER analysis of MPSK space-time code with differential detection over correlated block-fading Rayleigh channel

MIMO technology proposed in recent years can effectively combat the multipath fading of wireless channel and can considerably enlarge the channel capacity, which has been investigated widely by researchers. However, its performance analysis over correlated block-fading Rayleigh channel is still an open and challenging objective. In this article, an analytic expression of bit error rate （BER） is presented for multiple phase shift keying （MPSK） space-time code, with differential detection over correlated block-fading Rayleigh channel. Through theoretical analysis of BER, it can be found that the differential space-time scheme without the need for channel state information （CSI） at receiver achieves distinct performance gain compared with the traditional nonspace-time system. And then, the system simulation is complimented to verify the above result, showing that the diversity system based on the differential space-time block coding （DSTBC） outperforms the traditional nonspacetime system with diversity gain in terms of BER. Furthermore, the numerical results also demonstrate that the error floor of the differential space-time system is much lower than that of the differential nonspace-time system.     

Joint frequency-domain differential detection and equalization for DS-CDMA signal transmissions in a frequency-selective fading channel

It has been revealed that direct sequence code-division multiple access (DS-CDMA) can achieve a good bit-error rate (BER) performance, comparable to multicarrier CDMA (MC-CDMA), by using coherent frequency-domain equalization (FDE) instead of coherent Rake combining. However, coherent FDE requires accurate channel estimation. Pilot-assisted channel estimation is a practical solution, but its accuracy is sensitive to the Doppler spread. In this paper, a frequency-domain differential encoding and detection scheme is proposed for a DS-CDMA mobile radio. Joint frequency-domain differential detection and equalization (FDDDE) based on minimum mean-square error (MMSE) criterion is presented, where a simple decision feedback filter is used to provide a reliable reference signal for MMSE-FDDDE. Also presented is an approximate BER analysis. It is confirmed by both approximate BER analysis and computer simulation that MMSE-FDDDE provides good BER performance close to the coherent MMSE-FDE and shows high robustness against the Doppler spread; it outperforms coherent MMSE-FDE for large Doppler spreads. The proposed MMSE-FDDDE can also be applied to MC-CDMA. A performance comparison between uncoded DS- and MC-CDMA shows that DS-CDMA with MMSE-FDDDE achieves better BER performance than MC-CDMA with MMSE-FDDDE for small spreading factors.     

Differentially detected GMSK signals in CCI channels for mobilecellular telecommunication systems

The performance of conventional and decision feedback differential detection receivers for Gaussian minimum-shift keying (GMSK) signals transmitted in the presence of cochannel interference (CCI) and additive white Gaussian noise (AWGN) is evaluated. For the interference, the authors adopt a model which includes N statistically independent static as well as faded CCI. Various bit-error-rate (BER) performance evaluation results have indicated that the receiver under investigation performs better as compared to other more conventional receiver structures. Especially significant BER improvements are obtained for the static CCI channel. For example, it is shown that with a carrier-to-interference ratio of 14 dB, the performance of a 2-b decision feedback differential receiver outperforms a conventional 2-b differential detector by more than 14 dB (at a BER 10^-3). For the faded CCI, the improvement is less: mainly they result in error-floor reductions of about half an order of magnitude. By comparing the performance of static and faded CCI, it was also found that for a given C/I, the performance of the former would depend on the number of interferers, whereas this is not the case for the latter     

符号间干扰对频域差分OFDM误码率性能的影响

在多径衰落信道条件下,分析了符号间干扰对频域差分正交频分复用系统误码率性能的影响,得到了误码率的解析表达式,分析和仿真的结果表明,频域差分的误码率性能受到符号间干扰的影响,但在不同的信道条件下,符号间干扰对系统性能的影响程度也有不同。     

Error rate analysis of differentially encoded and detected 16APSKunder Rician fading

Mobile radio systems require highly bandwidth efficient digital modulation schemes because of the limited resources of the available radio spectrum. A theoretical analysis of bit error rate (BER) is presented for the differential detection of differentially encoded 16-level amplitude/phase shift keying (16DAPSK) under Rician fading in the presence of Rayleigh faded co-channel interference (CCI) and additive white Gaussian noise (AWGN). Differential detection comprises eight-level differential phase detection (DPD) and two-level amplitude ratio detection (ARD). Exact expressions for probability distributions of differential phase noise and amplitude ratio are derived for the BER calculation. The calculated BER performance of 16DAPSK is presented for various values of Rician fading K factor, Doppler spread of diffused component, and Doppler shift of the specular component, and is compared with that of 4-16DPSK. It is shown that 16DAPSK is superior to 16DPSK and requires 1.7 (1.6) dB less E_b/N₀ (SIR) at BER=10^-3 in Rician channels with K=5 dB     

频率选择性衰落信道SFH/GMSK误码性能分析

针对存在频偏和频率选择性的慢衰落信道,分析给出了1比特差分相位检测SFH/GMSK系统的误码率闭式解;在此基础上,研究了载波噪声比、载波延迟比与误码率的关系,探讨了高载波噪声比下频偏和跳频速率对误码率的影响;利用Monte Carlo仿真验证了闭式解的准确性.研究表明:信道特性和跳频速率显著影响误码性能,频率偏移与误码率之间近似存在"门限效应".     

Comparison of pilot symbol-assisted and differentially detectedBPSK for DS-CDMA systems employing RAKE receivers in Rayleigh fadingchannels

The capacity of a code-division multiple-access (CDMA) system is a function of the bit error rate (BER) performance of individual users. Therefore, it is important to optimize the individual links before proceeding to system level analysis. This is particularly true for operating in a fading channel where the performance without diversity reception is rather poor. This paper compares the BER performance of differential detection and pilot symbol-assisted coherent detection of a direct-sequence (DS) spread-spectrum (SS) signal on a frequency-selective Rayleigh fading channel using RAKE reception. Both equal gain and maximal ratio combining are considered, and the effect of convolutional coding with interleaving is studied. It is shown that in the particular cases considered in this paper, rate 1/8 convolutionally encoded pilot symbol-assisted BPSK performs better than coded differential detection, thus providing a higher system capacity     

Quality Monitoring of DxPSK Signals by Using Differential Phasor Diagram

We describe a new method for quantitative evaluation of the quality of multilevel differential phase-shift-keyed (DxPSK) signals by using a differential phasor monitor. This method measures the phase deviation of the symbols in the differential phasor diagram and estimates the bit-error rate (BER) by using a simple relation based on the Q -factor defined for multilevel DxPSK signals. We demonstrate that the proposed method can accurately estimate the BER of differential quadrature PSK and 8-ary PSK signals.     

一种新的低复杂度准正交酉空时调制

基于非相干U-空时调制,介绍了一种MIMO（多输入多输出）的低复杂度差分检测,接受端用最大似然准则判决时搜索空间大小只与传送速率成线性关系,且避免了星座扩展。并与OFDM（正交频分复用）结合实现了MIMO-OFDM的差分检测。虽然只能取得部分发射分集,但仿真结果表明,与全分集的差分检测相比,此差分检测在低信噪比时具有较低的误比特率。     

DSTBC Impulse Radios with Autocorrelation Receiver in ISI-Free UMD Channels

For transmitted-reference impulse radio, it has been experimentally shown that multiple transmit antennas can provide an energy boost in the received signal. Here, we propose a 2-transmit and Q-receive differential space-time block coded impulse radio with autocorrelation receiver. A mathematical model for predicting the system bit-error-rate (BER) performance is derived for intersymbol interference-free transmission over an ultra-wideband channel, and validated with computer simulated results. From the results, it is observed that in migrating from 1-transmit to 2-transmit antennas, a signal-to-noise ratio gain of 3 dB, 2 dB and 1 dB at BER = 10^-5 can be achieved, respectively, for the case of 1-, 2- and 4-receive antennas.     

最小移频键控信号的检测和误码性能分析

首先介绍了MSK信号差分检测原理。其次,分析了存在相关高斯噪声和信道有瑞利衰落时MSK的抗噪声性能。结果表明,在高斯噪声时的差分MSK的误码率与DPSK相同;而当信道存在瑞利衰落时将严重影响系统的抗噪声性能。所得结论能为系统的设计提供重要依据。     

PN code synchronization effects on narrow-band interferencerejection in a direct-sequence spread-spectrum receiver

The impact of imperfect synchronization on the performance of prediction-error interference rejection filters in noncoherent direct-sequence (DS) spread-spectrum communications is considered. Bit-error-rate analysis (BER) analysis (BER) of binary DPSK (differential phase-shift keying) data modulation used in conjunction with direct-sequence spread-spectrum is used as a performance measure. A first-order noncoherent delay-lock loop is used for the pseudonoise (PN) code tracking. Conditional BER results for the DS/DPSK systems for fixed values of the code tracking error are obtained. The average BER of the system is then evaluated by averaging the conditional BER expressions over the probability density function of the code tracking error. Results include the effects of both a single fading tone and a narrowband Gaussian interferer on the overall system performance. Interferer offset frequency is considered in determining the code tracking loop noise as well as the receiver BER     

Performance Analysis and Optimization of Multi-User Differential Chaos-Shift Keying Communication Systems

Bit-error rate (BER) performance of a generalized multi-user differential chaos-shift-keying (DCSK) digital communication system is analyzed and optimized in this paper using baseband models. The generalized version of DSCK involves use of multiple nonrepeating chaotic spreading segments and energy adjustments and allows considerable system optimization. Theoretical BER analysis of correlation decoders based on a mathematical two-stage exact conditional approach is given as the foundation of subsequent performance studies. The consequent fully theoretical BER result gives an odd-symmetric spreading map condition for the BER to be unaffected by the mix of transmitted bits. The basis of the theoretical result is used to improve on the traditional simple Gaussian approximation (SGA) approach to the calculation of BER; this is inaccurate because it does not recognise the chaotic dynamics of DCSK. To overcome this drawback, a dynamically improved Gaussian approximation (DIGA) is developed. The DIGA approach is compared with the SGA approach, with simulation results demonstrating its accuracy and efficiency, certainly for more than five to ten users. Not only does the DIGA approach provide a more accurate BER than the SGA approach, its simple form also makes optimization of the DCSK system practically possible. The BER lower bound for the multi-user DCSK system is deduced from the DIGA approach. It is shown how the parameters and structure of the multi-user DCSK communication system can be optimized to achieve this lower bound. The work gives an exact theoretical basis of DCSK and covers several aspects which have not been treated in earlier research or have been inexactly treated.     

QDPSK signal transmission performance with postdetection selectiondiversity reception in land mobile radio

The bit error rate (BER) performance of 16-128 kb/s Nyquist raised-cosine filtered quaternary differential phase-shift keying (RC-QDPSK) signal transmission was experimentally investigated. Two-branch postdetection selection diversity reception was employed. Measured results are presented for the BER performance due to additive white Gaussian noise (AWGN), cochannel interference, and multipath channel delay spread. Field BER measurements were also conducted at a carrier frequency of 1.45 GHz in an area characterized by high-rise buildings and in an area surrounded by mountains. The results show that postdetection selection diversity is a simple yet powerful technique to improve the BER performance in fading mobile radio channels     

基于差分空时调制的混沌慢跳频系统

提出一种慢跳频系统中基于差分空时调制的混沌保密通信方法。此方案集成了差分空时编码和混沌跳频扩频技术的优点。一方面,在跳频系统中,使用混沌序列代替伪随机(PN)码,增强了抗截获和抗预测的性能;另一方面,通过差分空时调制产生分集增益,降低了多径衰落效应的影响。仿真结果证实了此方案的有效性。     

Bit error rate analysis of reduced-state Viterbi differentialdetection of M-ary DPSK signals

A tight upper bound or bit error rate (BER) is derived for approximate maximum likelihood differential detection (DD) implemented by the reduced state Viterbi algorithm (VA) known as RSVDD. The BER performance of RSVDD is compared with Viterbi DD (VDD) for M-ary DPSK in additive white Gaussian noise (AWGN) channels     

多径衰落信道下频域差分检测OFDM系统的误码率分析

在多径衰落信道条件下，分析了正交频分复用系统中频域差分检测的误码率性能，并进行了仿真验证。分析与仿真结果表明，信道相干时间和相干带宽均影响频域差分检测的误码率性能，信道相干带宽对频域差分检测的影响比信道相干时间的影响更大，频域差分检测适合于多径延迟扩展比较小的信道。     

Stratified Sampling Monte Carlo Algorithm for Efficient BER Estimation in Long-Haul Optical Transmission Systems

We propose an efficient stratified sampling (SS) algorithm for estimating the bit error rate (BER) of a digital communication system. Our algorithm efficiently exploits the observations of an approximate, but usually fast, model of the system under investigation to drive a clever Monte Carlo (MC) estimation based on SS. The proposed method is faster than standard MC even at BER in the range $10^{-3}$ to $10^{-5}$ . Moreover, it is possible to evaluate the estimated standard deviation of the measured BER, such as in an MC simulation, so that it is possible to associate a confidence to the results. We test the algorithm both in a simple optical system distorted by group velocity dispersion (GVD) and in more complex differential quadrature phase shift keying (DQPSK) systems. In the last case, we measured computational savings up to 70% compared with standard MC.      

Bit error rate analysis of M-ary DPSK in frequency selective Ricianfading

A simple, exact expression for the probability distribution of differential phase noise is derived for calculating the average bit error rate (BER) of M-ary DPSK in frequency selective Rician fading. The irreducible BER due to multipath delay spread is evaluated for M=2-16 assuming a double-spike delay profile of the Rayleigh faded diffused component and a spectrally raised cosine Nyquist filter response