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71.发明授权Method and apparatus for bidirectional demodulation of digitally modulated signals 失效用于数字调制信号的双向解调的方法和装置
公开(公告)号：US5335250A
公开(公告)日：1994-08-02
申请号：US965848
申请日：1992-10-22
申请人： Paul W. Dent , Sandeep Chennakeshu
发明人： Paul W. Dent , Sandeep Chennakeshu
CPC分类号： H04L27/2337 , H04B7/0857 , H04L25/03178 , H04L2025/0356
摘要： A method and apparatus for demodulating data symbols transmitted through a fading communication channel. A plurality of first predetermined data symbols, a plurality of unknown data symbols, and a plurality of second predetermined data symbols are sequentially received. The received pluralities of data symbols are stored, and first and second sets of reference signals from the stored pluralities of first and second predetermined data symbols, respectively, are determined. The stored unknown data symbols based on the first set of reference signals are forward-demodulated, beginning with unknown symbols received nearer the first predetermined data symbols. The stored unknown data symbols based on the second set of reference signals are backward-demodulated, beginning with the unknown data symbols received nearer the second predetermined data symbols. Quality values indicative of demodulation qualities of the forward- and backward-demodulated data symbols are determined. The quality values are compared, and either the forward- or backward-demodulated data symbols are selected based on the comparison of quality values.
摘要翻译： 一种解调通过衰落通信信道发送的数据符号的方法和装置。 依次接收多个第一预定数据符号，多个未知数据符号和多个第二预定数据符号。 存储所接收的多个数据符号，并且分别确定来自存储的多个第一和第二预定数据符号的第一和第二组参考信号。 基于第一组参考信号的存储的未知数据符号被正向解调，从接近第一预定数据符号的未知符号开始。 基于第二组参考信号存储的未知数据符号被从第二预定数据符号更接近的未知数据符号开始被反向解调。 确定表示前向和后向解调数据符号的解调质量的质量值。 比较质量值，并且基于质量值的比较来选择前向或后向解调的数据符号。
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公开(公告)号：US5285480A
公开(公告)日：1994-02-08
申请号：US753578
申请日：1991-09-03
CPC分类号： H04B7/2643 , H04L25/03038 , H04L25/03254 , H04L2025/03477 , H04L2025/03726 , H04L25/03229 , H04L25/03299
摘要： A TDMA RF received signal is demodulated by first being filtered with a fixed transversal filter having a characteristic selected for matching a fixed square root raised cosine pulse characteristic of the received signal. The filtered signal is then adaptively filtered for compensating for a time varying impulse response of the channel. The adaptive filtering is performed initially during a synchronizing portion (preamble) of the filtered signal in accordance with a fast recursive least squares algorithm. Subsequent filter adaptation to a data portion of the filtered signal is accomplished in accordance with a computationally less expensive normalized least mean square procedure. The adaptive filter repetitively applies a modified Viterbi algorithm to blocks of 2D symbols, such that D symbols are released for adapting the adaptive filter means during the data portion of the filtered signal and the signal. The released symbols are also employed for adapting elements required in computing a metric for the modified Viterbi algorithm and the reconstructed signal used to form an error signal that drives the adaptation algorithms.
摘要翻译： 首先用固定的横向滤波器对TDMA RF接收信号进行解调，该固定横向滤波器具有选择用于匹配接收信号的固定平方根升余弦脉冲特性的特性。 滤波后的信号然后自适应滤波，以补偿信道的时变脉冲响应。 根据快速递归最小二乘法算法，最初在滤波信号的同步部分（前导码）期间执行自适应滤波。 根据计算上较便宜的归一化最小均方程序，完成对滤波信号的数据部分的后续滤波器适配。 自适应滤波器重复地将修改的维特比算法应用于2D符号的块，使得在滤波信号和信号的数据部分期间释放D符号以适应自适应滤波器装置。 释放的符号也用于调整计算修改的维特比算法的度量所需要的元素，以及用于形成驱动适应算法的误差信号的重建信号。
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公开(公告)号：US5283811A
公开(公告)日：1994-02-01
申请号：US754105
申请日：1991-09-03
CPC分类号： H04L7/0062 , H03H21/003 , H04L25/03057 , H04L7/10
摘要： An adaptive Decision Feedback Equalizer (DFE) (40) for a digital cellular mobile radio channel demodulator (30) employs a Complex Fast-Kalman Adaptation algorithm (56) to track channel variations. Sensitivity to sample timing jitter is reduced by providing the DFE with fractionally spaced feed-forward taps (50'). Deficiencies inherent in using a reduced precision implementation are overcome by adding a dither signal to sets of operations in the algorithm, the dither signal comprising an appropriately selected Gaussian random variable. For small delay spreads of approximately one third of a symbol duration or less, a resulting degradation in Bit Error Rate is avoided by switching the DFE out of the circuit or by reducing the number of taps of the DFE. For delay spreads of less than 40 microseconds and greater than approximately 10 microseconds, a (2,3) fractionally spaced DFE provides an adequate compromise between complexity and performance.
摘要翻译： 用于数字蜂窝移动无线电信道解调器（30）的自适应判决反馈均衡器（DFE）（40）采用复合快速卡尔曼适配算法（56）来跟踪信道变化。 通过为DFE提供分数间隔的前馈抽头（50'）来减少对采样定时抖动的灵敏度。 通过将抖动信号添加到算法中的操作集合来克服使用简化精度实现中固有的缺陷，抖动信号包括适当选择的高斯随机变量。 对于大约三分之一符号持续时间或更短的小延迟扩展，通过将DFE切换到电路外或通过减少DFE的抽头数来避免产生的误码率的降低。 对于小于40微秒和大于10微秒的延迟扩展，（2,3）分数间隔的DFE在复杂性和性能之间提供了充分的折中。
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74.发明授权Reduction of synchronous fading effects by time hopping of user slots in TDMA frames 失效通过TDMA帧中的用户时隙的跳时减少同步衰落效应
公开(公告)号：US5020056A
公开(公告)日：1991-05-28
申请号：US346760
申请日：1989-05-02
申请人： Sandeep Chennakeshu
发明人： Sandeep Chennakeshu
CPC分类号： H04J3/1629 , H04B7/2643 , H04L1/02 , H04B2001/6908
摘要： A method for the reduction of synchronous fading effects in a time-diversity multiple-access communications system, in which the data to/from a particular user is to appear in a particular assigned slot, varies the position of the time slot assigned to that particular user, so that the slot has a different position in each successive frame in which that assigned slot appears. The position may be set relative to a frame feature, such as its start time and the like. Selected-schedule patterns may be used, with the pattern either being preset at the various stations or being sent to the stations prior to use, as part of a preamble, in-band supervisory signaling and the like.
摘要翻译： 一种在时分多址通信系统中减少同步衰落效应的方法，其中来往/来自特定用户的数据将出现在特定分配的时隙中，改变分配给该特定用户的时隙的时隙的位置 用户，使得插槽在其中出现分配的插槽的每个连续帧中具有不同的位置。 该位置可以相对于帧特征设置，例如其开始时间等。 可以使用所选择的时间表模式，其模式可以在各个站点预设或者在使用之前发送到站点，作为前导码，带内监视信令等的一部分。
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