共查询到20条相似文献,搜索用时 15 毫秒
1.
A receiver structure, called a "pseudo maximum likelihood sequence estimation" (pseudo MLSE), which approximates MLSE with a simple hardware configuration, was derived. By introducting a tentatively estimated sequence, the pseudo MLSE detects the received sequence symbol by symbol, retaining the MLSE optimum decision property. The number of arithmetic operations required in one symbol duration is reduced fromM^{L + 1} to(L + 1)M in anM -ary signaling case with channel memory lengthL . An adaptation algorithm for the variation in the channel characteristics was also developed. Pseudo MLSE application to quadrature phase shift keying (QPSK) for a band-limited nonlinear channel is described. The most practical application of pseudo MSLE, named the "adaptive threshold detector with estimated sequence" (ATDES), detects symbols with threshold detection and is suitable for high bit rate operation. For both the pseudo MLSE processor and ATDES, most of the hardware is occupied by a replica memory stored in the receiver. Performance in a typical nonlinear satellite channel model is evaluated by computer simulation. Simulation results show a 0.8 dB improvement by ATDES with 64 replica memories and 1.3 dB improvement by the pseudo MLSE processor with 3072 replica memories. The tentative estimation error effect is estimated to be less than 0.1 dB in the simulated satellite channel. 相似文献
2.
Receiver designs for maximum likelihood sequence estimation of digital data transmission through randomly dispersive channels are developed. The random channels are constrained to have finite memory of durationL in the sense that the casual minimum mean square error estimate of the channel output at any given time is a function of only the most recentLT seconds of observations. Examples of the channels included are the time varying Rayleigh, Rician and lognormal fading channels whose covariance functions have finite support, phase unsynchronized channels which satisfy the finite-memory constraint and point process channels. The information sequence may be either a stream of independent, equally-likely symbols of binary orM -ary alphabets or the output sequence of a trellis or convolutional encoder. 相似文献
3.
A receiver structure based on maximum likelihood sequence estimation (MLSE) for receiving quaternary phase shift keyed signals over band-limited, nonlinear satellite channels, in the presence of additive downlink Gaussian noise, is derived. This work is an extension of work done by Mesiya et al. [2] for binary PSK transmission. Error performance of the receiver at low to moderate signal-to-noise ratios is estimated using computer simulation. For moderate to high signal-to-noise ratios, an upper bound on the probability of symbol error is obtained. A suboptimum receiver structure is then developed and its performance evaluated using computer simulation. It is shown that the performance of the suboptimum receiver is very close to that of the MLSE receiver. 相似文献
4.
5.
In Maximum Likelihood Sequence Estimation, the number of operations per symbol depends critically on the length of the Desired Impulse Response (DIR). In this paper it is shown that a short but complex DIR of length 2 may be sufficient to cope with most severe distortion impairments found in quadrature modulation systems, thus permitting MLSE data decoding at still manageable complexity. 相似文献
6.
A decision feedback receiver structure for receiving binary phase-shift keyed signals over bandlimited, nonlinear satellite channels, in the presence of both uplink and downlink additive Gaussian noise, is derived. As an illustrative example of the receiver, a hard-limiting channel model is considered in detail, and two special cases are examined. Based on the analysis, an alternative receiver structure which is more suitable for implementation is derived. The performance of the receiver is evaluated by computer simulation techniques, and it is shown that significant performance improvement over the single sample sign detector can be obtained. 相似文献
7.
8.
9.
We determine the fundamental impairment mechanism in the chromatic-dispersion (CD)-limited hybrid amplitude shift keying (ASK)-differential phase-shift keying (DPSK) modulation format and propose the employment of joint maximum likelihood sequence estimation (J-MLSE) for CD compensation to extend the transmission reach of such format. We find that it is not the intrasubchannel interference of the ASK or DPSK subchannel but the interaction between these two subchannels that limits the transmission distance. Therefore, electronic equalization of the two subchannels separately cannot improve the overall CD tolerance of the ASK-DPSK signal. J-MLSE, however, exploits the correlation information between the detected ASK and DPSK signals and is numerically shown to improve the CD tolerance of the ASK-DPSK signal significantly 相似文献
10.
The likelihood equation for the maximum likelihood estimate (MLE) of a temporal phase modulation (a sample function of a wide-sense stationary zero-mean Gaussian random process) received in a spatial aperture after transmission through a spatially turbulent channel and addition to a white Gaussian noise field is derived for unknown, Gaussian, and limiting cases of log-normal received signal fields. The received signal field estimation performed by the demodulator structure is explicitly exhibited and other clarifications made. The likelihood equation is linearized and solved and the resulting mean-square estimation error calculated. The Cramer-Rao lower bound is given. In an example it is shown that the linear estimate is efficient and has variance inversely proportional toM , the number of coherence areas required to disjunctly cover the receiver spatial aperture. A heterodyne receiver with an optimized aperture weighting is shown to use essentially only one coherence area; its asymptotic mean-square error is also calculated. 相似文献
11.
A new maximum likelihood decoding (MLD) algorithm for linear block codes is proposed. The new algorithm uses the algebraic decoder in order to generate the set of candidate codewords. It uses the exact probability for each codeword as a new likelihood metric and a method to generate the appropriate set of codewords similar to Kaneko, et al., and Tanaka-Kakigahara algorithms. The performance of the proposed algorithm is the same as that of MLD as it is proved theoretically and verified by simulation results. The comparison with these similar algorithms shows that the new one always requires less average decoding complexity than those of the other algorithms. Finally, we compare the algorithms for terrestrial and satellite channels. 相似文献
12.
13.
14.
15.
16.
17.
18.
Lender's partial response baseband system model is analyzed, extended and compared with two other partial response models. The feasibility of each system model in practical implementation is assessed. The effects of filter imperfections and of channel nonlinearities on the performance of QPRS digital radio systems is analyzed by means of computer simulation. 相似文献
19.
针对频率偏移对低速散射通信中相干检测性能的影响,提出了基于CORDIC算法的最大似然频差估计;详细推导了最大似然频差估计的原理和CORDIC算法的基本原理;提出了具体的设计过程以及试验结果。 相似文献
20.
利用多普勒信息的波达方向最大似然估计方法 总被引:8,自引:3,他引:8
为了充分利用信号的时域特性来改善信号波达方向(DOA)的估计性能,本文从最大似然估计出发,推导出了有限快拍,低信噪比情况下多普勒信号波达方向的迭代估计计算法,为进一步减小运算量,本文还推导了一种简化算法,本文提出的两种算法对低信噪比,少快拍数下多普勒信号的DOA估计性能比不利用时域特性的ML方法有明显改善,Monte-Carlo实验验证了本文方法的有效性。 相似文献