Error performance of multiple-symbol differential detection of PSKsignals transmitted over correlated Rayleigh fading channels

The error performance of multiple-symbol differential detection of uncoded QPSK signals transmitted over correlated Rayleigh fading channels is studied. The optimal detector is presented, along with an exact expression for the corresponding pairwise error event probability. It is shown that multiple-symbol differential detection is a very effective strategy for eliminating the irreducible error floor associated with a conventional differential detector. In all of the cases investigated, a detector with an observation interval as small as two symbols is sufficient for this purpose. It is also found that the error performance of a multiple-symbol differential detector is not sensitive to the mismatch between the decoding metric and the channel fading statistics     

空时分组码的差分检测和多符号差分检测

在介绍差分空时分组码编译码原理的基础上,给出了基于最大似然判决的差分检测和多符号差分检测方案,并对这两种译码方案的性能进行了比较。相对于普通的相干译码,这两种方案在发射和接收端都不需要对传输信道进行估计,因此具有较低的译码复杂度。最后,通过仿真结果可以看出相干检测、差分检测和多符号差分检测性能间的差异。     

Multiple symbol differential detection for trellis-coded MPSK overRayleigh fading channels

This paper presents a multiple-symbol differential detection scheme for coded and interleaved transmission of MPSK data. The performance of this scheme is then evaluated for transmission of digitized voice over a Rayleigh fading channel. It is found that in terms of bit error rate, the improvement given by using multiple-symbol differential detection is minimal, but when evaluated in terms of frame-error rate, the multiple-symbol scheme gives about 1.25-dB improvement. Another 0.75-dB improvement can be obtained by also using a serial list Viterbi algorithm     

HDR codec with concatenated multilevel codes and multiple-symboldifferential detection for satellite application

The performance of the multilevel code based high data rate (HDR) codec is evaluated with multiple-symbol differential detection over satellite channels. It is shown that multiple-symbol observation effectively fills the gap between conventional differentially coherent detection and ideal coherent detection with differential encoding. Being especially suitable for HDR application where carrier acquisition and tracking is extremely difficult, the codec reliably supports broadband ISDN transmission over a 72 MHz satellite transponder     

Multiple-symbol differential detection of MPSK

A differential detection technique for MPSK (multiple-phase shift keying), which uses a multiple-symbol observation interval, is presented, and its performance is analyzed and simulated. The technique makes use of maximum-likelihood sequence estimation of the transmitted phases rather than symbol-by-symbol detection as in the conventional differential detection. Thus, the performance of this multiple-symbol detection scheme fills the gap between conventional (two-symbol observation) differentially coherent detection of MPSK and ideal coherent of MPSK with differential encoding. The amount of improvement gained over conventional differential detection depends on the number of phases M and the number of additional symbol intervals added to the observation. What is particularly interesting is that substantial performance improvement can be obtained for only one or two additional symbol intervals of observation. The analysis and simulation results presented are for uncoded MPSK     

Multiple-symbol detection of MPSK in narrow-band interference andAWGN

We propose a new technique for rejection of narrow-band interference (NBI) based on multiple-symbol detection of coherent or differential phase-shift keying (DPSK). We first show that the direct use of multiple-symbol detection offers poor performance when NBI is dominant. Our proposed technique employs a special signaling or coding scheme which is shown to be robust against NBI. The evaluation of bit-error rate (BER) shows significant performance improvement in NBI vis-a-vis direct multiple-symbol detection. When viewed as a coding scheme, the proposed signaling scheme is significantly simpler for achieving the same coding gain than conventional error correction codes     

Differentially coherent communication with multiple-symbolobservation interval

A novel differential detection technique for multiple phase shift keying (MPSK), which uses multiple-symbol observation interval, is proposed and its performance is analyzed. The proposed technique detects the transmitted symbol with accumulation of the differential signal vector projected on the previously received symbol. As with the multiple-symbol differential detection (MSDD) technique, the performance of the proposed scheme fills the gap between the conventional differential and the ideal coherent detection. The amount of improvement depends on the number of phases M and the number of additional symbol intervals N of observation. Performance analysis and simulation show considerable improvement with only 1 or 2 additional symbol intervals of observation. In addition, the complexity increases linearly with observation interval and is smaller than that of Divsalar and Simon (1990) and of Edbauer (1992)     

Quasi-maximum-likelihood multiple-symbol differential detection for time-varying Rayleigh fading channel

The maximum-likelihood multiple-symbol differential detector (ML-MSDD) has better bit-error-rate performance than many other detectors for differential modulation. Unfortunately, the computational complexity of ML-MSDD quickly becomes prohibitive as the observation window size grows. While low-complexity MSDD algorithms for the time-invariant Rayleigh fading channel have been considered before, there is a need for low-complexity MSDD algorithms for general time-varying Rayleigh fading channels. A polynomial-time complexity approach called semi-definite relaxation (SDR) is employed to achieve differential detection with near maximum-likelihood (ML) performance. The proposed SDR quasi-maximum-likelihood (QML) multiple-symbol differential detection (SDR-QML-MSDD) is efficient in that its complexity is polynomial in the observation window size, even in the worst case, while it exhibits almost the same performance as ML-MSDD does.     

Multiple-bit differential detection of offset QPSK

Analogous to multiple-symbol differential detection of quadrature phase-shift keying (QPSK), a multiple-bit differential detection scheme is described for offset QPSK that also exhibits continuous improvement in performance with increasing observation interval. Being derived from maximum-likelihood considerations together with the representation of differentially encoded offset QPSK as a continuous phase modulation, the proposed scheme is purported to be the most power-efficient scheme for such a modulation and detection method.     

Multiple-symbol differential detection for MPSK space-time block codes: decision metric and performance analysis

Approximately 3 dB signal-to-noise ratio (SNR) loss is always paid with conventional differential space-time block codes (STBCs), compared with coherent STBCs. In this paper, a multiple-symbol differential detection (MSDD) technique is proposed for M-ary phase-shift keying (PSK) STBCs. The new scheme can greatly narrow the 3-dB performance gap by extending the observation interval for differential decoding. The technique uses maximum-likelihood sequence detection instead of traditional symbol-by-symbol detection, and is carried out on the slow, flat Rayleigh fading channel. A generalized decision metric is derived for an observation interval of arbitrary length. It is shown that for a moderate number of symbols, MSDD provides approximately 1.5 dB performance improvement over conventional differential detection. In addition, a closed-form pairwise error probability and approximate bit-error probability (BEP) are derived for multiple-symbol differential binary PSK STBC. Results show that the theoretical BEP matches simulation results well. The BEP is shown to converge asymptotically with the number of symbols in the observation interval to that of the differential scheme with coherent detection.     

Multiple-symbol differential sphere decoding

In multiple-symbol differential detection (MSDD) for power-efficient transmission over Rayleigh fading channels without channel state information, blocks of N received symbols are jointly processed to decide on N-1 data symbols. The search space for the maximum-likelihood (ML) estimate is therefore (complex) (N-1)-dimensional, and maximum-likelihood MSDD (ML-MSDD) quickly becomes computationally intractable as N grows. Mackenthun's low-complexity MSDD algorithm finds the ML estimate only for Rayleigh fading channels that are time-invariant over an N symbol period. For the general time-varying fading case, however, low-complexity ML-MSDD is an unsolved problem. In this letter, we solve this problem by applying sphere decoding (SD) to ML-MSDD for time-varying Rayleigh fading channels. The resulting technique is referred to as multiple-symbol differential sphere decoding (MSDSD).     

Decision-feedback differential detection scheme for 16-DAPSK

A novel decision-feedback differential detection (DF-DD) scheme for 16-level differentially encoded amplitude phase shift keying signals is proposed. It is shown that, by using the new technique based on multiple-symbol detection, a significant performance gain may be obtained compared to a previously proposed DF-DD scheme. This gain increases with decreasing number of feedback symbols, which makes the novel scheme attractive for implementation     

A new reduced-complexity algorithm for multiple-symbol differential detection

Although multiple-symbol differential detection (MSDD) provides much better error performance than conventional differential detection, its complexity is much higher. We propose a reduced-complexity algorithm for MSDD. Our simulations show that the performance of the reduced complexity receiver is nearly identical to that of the original receiver, but with typical parameters, the number of phase sequences searched can be reduced by a factor of sixteen for QPSK to over four thousand for 16-PSK thereby leading to significant receiver complexity reduction.     

On noncoherent receivers for DSTM in spatially correlated fading

In this letter, we derive a multiple-symbol differential detection (MSDD) and a novel MSDD-based decision-feedback differential detection (MS-DFDD) receiver for differential space-time modulation transmitted over spatially correlated multiple-input multiple-output fading channels. We show that MS-DFDD outperforms previously proposed DFDD schemes that are based on scalar and vector prediction (SP-DFDD and VP-DFDD). In addition, we prove that at high signal-to-noise ratio (SNR) VP-DFDD is equivalent to SP-DFDD and thus fails to properly exploit the spatial fading correlations.     

On decision-feedback detection of differential space-time modulation in continuous fading

We show that linear prediction (LP)-based decision-feedback detection (DFD) for nondiagonal differential space-time modulation (DSTM) may suffer from a severe performance degradation in continuously fading channels. DSTM constellations that incur no degradation in LP-DFD are identified as those with a diagonal generator. To cater to other constellations, we propose a low-complexity DFD scheme by inserting decision-feedback symbols into the metric of multiple-symbol differential detection.     

π/4-DQPSK信号的判决反馈差分检测

π/4-DQPSK是一种比较适合在移动通信中使用的调制方式,传统的差分检测方法误码率比QPSK相干解调恶化大约2.3dB,利用判决反馈的信号估计出参考信号,对π/4DQPSK信号进行多码元差分检测。该方法与传统的检测方法相比,不需要增加乘法运算,易于工程实现。计算机仿真结果表明在高斯信道中,相对于传统的差分检测方法,无频率偏移时,判决反馈多码元差分检测方法在误码率为10-4时,性能改善大约1.6dB;剩余频率偏移值为符号速率的0.5%时,性能改善约1dB。     

连续衰落信道下差分空时DFD

一种适用于连续衰落信道的非对角差分空时调制方法被提出,该方法在线性预测的基础上,通过采用判定反馈检测技术,不仅解决了对角阵DSTM的性能衰减问题,而且通过在多符号差分矩阵中插入判定反馈符号,解决了非对角DSTM的性能衰减问题,同时降低了计算复杂度。仿真结果表明,这种新机制有效改善了DSTM的性能,适用于对角阵星座图,同时也适用于非对角阵星座图。     

声表面波扩频多符号检测器算法研究

基于多符号检测的DMPSK信号处理算法在改善系统检测性能方面是一条行之有效的方法．对于直接序列扩频系统，当采用DMPSK调制方式时，同样会存在检测性能恶化问题．为此，该文提出了基于SAW匹配滤波器的DMPSK直接序列扩频多符号检测器算法，并采用13位巴克码SAW抽头延迟线和固定延迟线组合设计对符号数N=3的DBPSK扩频多符号检测算法进行了实验系统验证，给出了相应结果。     

一种低复杂度的差分酉空时调制多符号球形译码算法

该文提出了一种瑞利衰落信道下差分酉空时调制系统中多符号差分球形译码的改进算法。该算法在执行球形译码的最大似然度量搜索时,仅对具有较小最大似然度量的部分测试符号进行搜索,从而大大减少了搜索的次数,同时提出了一种逐项进行的最大似然度量计算方法,可以尽早发现超过搜索范围的测试符号并终止计算,在避免无谓的运算负担的同时得到所需的具有较小最大似然度量的部分测试符号。仿真表明,在适中的信噪比范围内,该算法在牺牲少量系统性能的基础上降低了超过50%的运算量。     

Noncoherent receivers for differential space-time modulation

In this paper, noncoherent receivers for differential space-time modulation (DSTM) are investigated. It is shown that the performance of the previously proposed conventional differential detection (DD) receiver is satisfactory only for very slow flat fading channels. However, conventional DD suffers from a considerable loss in performance even for moderately fast fading, especially if more than one transmit antenna is used. In order to overcome this problem, two improved noncoherent receivers are considered. The first one is the multiple-symbol detection (MSD) receiver. Because of the high computational complexity of MSD, also a low-complexity decision-feedback differential detection (DF-DD) receiver is derived. Analytical and simulation results confirm that both receivers perform equally well and can take full advantage of the enhanced diversity provided by multiple transmit antennas even for fast fading