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    • 71. 发明授权
    • Transmitter optimization for spectrally congested radio communication
systems
    • 频谱拥塞无线电通信系统的发射机优化
    • US5363407A
    • 1994-11-08
    • US939747
    • 1992-09-02
    • Rajaram RameshSandeep Chennakeshu
    • Rajaram RameshSandeep Chennakeshu
    • H04B1/04H04B15/00H04B14/04
    • H04B15/00H04B1/0475
    • A method of configuring an optimum communication system for communicating on adjacent frequency bands with minimal interference between adjacent channels comprises serially coupling a selected encoder to a mapper, a transmit filter, a low pass filter and a modulator, and constructing a receiver with a seriallycoupled receive filter and decoder. The transmit filter is optimized by choosing transmit filter coefficients d.sub.opt which maximize the inband to adjacent-band power. Transmitter coefficients d.sub.opt are obtained by solving an eigenvalue problem which takes into account the power spectrum of the encoder, mapper and receive filter. The optimum transmitter coefficients are then employed in the transmitter to shape the transmitted signal, increasing the adjacent channel interference protection ratio (ACIPR). In an alternative embodiment, further constraints are placed upon the system, such as reducing the combined impulse response of the transmit filter, low pass filter and the receive filter to zero at the beginning of subsequent symbol periods. The resulting system then exhibits an increased ACIPR along with a reduced intersymbol interference.
    • 配置用于以相邻信道之间的最小干扰在相邻频带上通信的最佳通信系统的方法包括将所选择的编码器串行耦合到映射器,发射滤波器,低通滤波器和调制器,以及构造具有串联接收的接收机 滤波器和解码器。 通过选择将带内最大化为相邻带功率的发射滤波器系数dopt来优化发射滤波器。 通过求解考虑到编码器,映射器和接收滤波器的功率谱的特征值问题来获得发射机系数dopt。 然后在发射机中采用最佳发射机系数来对发射信号进行整形,增加相邻信道干扰保护比(ACIPR)。 在替代实施例中,进一步的约束被放置在系统上,诸如在随后的符号周期开始时将发射滤波器,低通滤波器和接收滤波器的组合脉冲响应减小到零。 所得到的系统随后表现出增加的ACIPR以及减少的符号间干扰。
    • 72. 发明授权
    • Adaptive MLSE-VA receiver for digital cellular radio
    • 用于数字蜂窝无线电的自适应MLSE-VA接收机
    • US5285480A
    • 1994-02-08
    • US753578
    • 1991-09-03
    • Sandeep ChennakeshuAnand NarasimhanJohn B. Anderson
    • Sandeep ChennakeshuAnand NarasimhanJohn B. Anderson
    • H04B7/26H04L25/03H03K5/159H03D1/06
    • H04B7/2643H04L25/03038H04L25/03254H04L2025/03477H04L2025/03726H04L25/03229H04L25/03299
    • 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.
    • 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。
    • 73. 发明授权
    • Decision feedback equalization for digital cellular radio
    • 数字蜂窝无线电的决策反馈均衡
    • US5283811A
    • 1994-02-01
    • US754105
    • 1991-09-03
    • Sandeep ChennakeshuAnand NarasimhanJohn B. Anderson
    • Sandeep ChennakeshuAnand NarasimhanJohn B. Anderson
    • H03H21/00H04L7/02H04L7/10H04L25/03H03H7/30
    • H04L7/0062H03H21/003H04L25/03057H04L7/10
    • 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.
    • 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。