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    • 4. 发明授权
    • Method for reducing interference in OFDM wireless networks
    • 减少OFDM无线网络干扰的方法
    • US08811545B2
    • 2014-08-19
    • US13291546
    • 2011-11-08
    • Ramesh AnnavajjalaLiangbin LiPhilip Orlik
    • Ramesh AnnavajjalaLiangbin LiPhilip Orlik
    • H04L27/06H04L23/02
    • H04L5/0048H04J11/004H04L25/03171H04L27/2602H04L27/32H04L2025/03777
    • Interference in a received orthogonal frequency division multiplexing (OFDM) symbol, modulated according to selected constellation points sk, is reduced. The symbol includes a set of pilot signals and a set of data signals yk, where k is a number of consecutive subcarriers used for the pilot and the data signals. The pilot signals are thresholded to detect interfering pilot signals, which are then erased. Channels Ĥk are estimated using remaining pilot signals. The set of data signals are decoded based on the estimated channels Ĥk, and, for each bit bi in the set of data signals, a logarithmic likely ratio (LLR) log ⁢ ∑ s k : b i = 0 ⁢ 1  y k - H ^ k ⁢ s k  2 ∑ s k : b i = 1 ⁢ 1  y k - H ^ k ⁢ s k  2 is determined. The LLR is an indicator of the likely interference.
    • 根据所选择的星座点sk进行调制的接收正交频分复用(OFDM)符号中的干扰被减少。 符号包括一组导频信号和一组数据信号y k,其中k是用于导频和数据信号的连续副载波的数量。 导频信号被阈值以检测干扰导频信号,然后擦除导频信号。 使用剩余的导频信号估计信道Ĥk。 基于估计的信道Ĥk对该组数据信号进行解码,并且对于数据信号组中的每个比特bi,存在对数可能比(LLR)logΣΣsk:bi = 0 1yk-H ^ k skë2Σsk:bi = 1 1yk-H ^ k sk守2。 LLR是可能的干扰的指标。
    • 5. 发明申请
    • Method and System for Estimating Time of Arrival of Signals Using Maximum Eigenvalue Detection
    • 使用最大特征值检测估计信号到达时间的方法和系统
    • US20130176174A1
    • 2013-07-11
    • US13346889
    • 2012-01-10
    • Ramesh AnnavajjalaPhilip Orlik
    • Ramesh AnnavajjalaPhilip Orlik
    • G01S1/24
    • G01S5/0221
    • A method estimates the time-of-arrival (ToA) of signals received via multipath channels. The received signal of a number of trials is first passed through a band-pass filter and then sampled. The presence of a channel tap within a time window is estimated by comparing a threshold to a largest eigenvalue of the covariance matrix of a time window. The signal samples are used to calculated a band region of a complete covariance matrix. After the band region has been updated for all signal samples, the covariance matrices for a moving window can be extracted from the band region. The ToA is estimated as the ending time of the leading window, which is the earliest window, such that the largest eigenvalue is larger than a given threshold.
    • 一种方法估计通过多径信道接收的信号的到达时间(ToA)。 多次试验的接收信号首先通过带通滤波器,然后采样。 通过将阈值与时间窗的协方差矩阵的最大特征值进行比较来估计时间窗内的通道抽头的存在。 信号样本用于计算完整协方差矩阵的带区域。 在针对所有信号样本更新了带区域之后,可以从带区域提取用于移动窗口的协方差矩阵。 ToA被估计为作为最早窗口的前导窗口的结束时间,使得最大特征值大于给定阈值。
    • 6. 发明授权
    • Method for estimating time-varying and frequency-selective channels
    • 估计时变频率选择频道的方法
    • US08509330B2
    • 2013-08-13
    • US12894994
    • 2010-09-30
    • Ramesh AnnavajjalaHobin Kim
    • Ramesh AnnavajjalaHobin Kim
    • H04K1/10
    • H04L5/0048H04L5/0007H04L25/0204H04L25/0212H04L25/022H04L25/0228H04L25/0242
    • Time-varying and frequency-selective channels in an orthogonal frequency division multiplexing (OFDM) network are estimated by first storing, in a buffer at a receiver, a received signal corresponding to a set of pilot tones of a set of OFDM symbols. The pilot tones are predetermined and inserted in frequency subcarriers and time slots of the OFDM symbol. A covariance matrix of the received signal is estimated. A diagonal matrix is estimated based on the covariance matrix and a variance of noise in the received signal. The diagonal matrix indicates delays of non-zero paths in a time domain. A channel impulse response (CIR) for each OFDM symbol is estimated using the diagonal matrix, and the received signal. Then, the CIR is transformed to the frequency domain to obtain the channel frequency response (CFR).
    • 通过首先在接收机的缓冲器中存储对应于一组OFDM符号的一组导频音调的接收信号来估计正交频分复用(OFDM)网络中的时变和频率选择信道。 导频音被预先确定并插入在OFDM符号的频率子载波和时隙中。 估计接收信号的协方差矩阵。 基于协方差矩阵和接收信号中的噪声方差来估计对角矩阵。 对角矩阵表示时域中非零路径的延迟。 使用对角矩阵和接收信号来估计每个OFDM符号的信道脉冲响应(CIR)。 然后,将CIR转换到频域以获得信道频率响应(CFR)。
    • 8. 发明授权
    • Beamforming in wireless vehicular networks
    • 无线车载网络中的波束成形
    • US08023915B2
    • 2011-09-20
    • US12413868
    • 2009-03-30
    • Philip V. OrlikRaymond YimRamesh AnnavajjalaJinyun Zhang
    • Philip V. OrlikRaymond YimRamesh AnnavajjalaJinyun Zhang
    • H04B1/06H04B7/00
    • H04B7/0617H04B7/086
    • Beams are used to communicate in a wireless network including mobile and stationary receivers. The network operates according to the IEEE 802.11p in wireless access to vehicular environments (WAVE). A direction from the mobile transceiver to the stationary receiver is predicted using geographic information available to the mobile transceiver. A set of signals are received in the mobile transceiver from the stationary transceiver, wherein the signals are received by an array of antennas, and wherein the signals are received using a set of beams, and wherein each beam is approximately directed at the stationary receiver. A signal-to-noise ratio (SNR) is measured for each beam, and the beam with an optimal SNR is selected as an optimal beam for communicating data between the mobile transceiver and the stationary transceiver.
    • 光束用于在包括移动和固定接收机的无线网络中进行通信。 该网络根据IEEE 802.11p在无线接入车辆环境(WAVE)中运行。 使用可用于移动收发机的地理信息来预测从移动收发机到固定接收机的方向。 在固定收发器中的移动收发器中接收一组信号,其中信号由天线阵列接收,并且其中使用一组波束接收信号,并且其中每个波束近似地指向固定接收机。 测量每个波束的信噪比(SNR),并且选择具有最佳SNR的波束作为用于在移动收发器和固定收发器之间传送数据的最佳波束。