The cascading of a discrete Fourier transform processor and a digital polyphase network is shown to reduce the computation rate in frequency multiplexing-demultiplexing systems to a value close to minimum. Implementation advantages of that technique are pointed out. The highest efficiency is achieved when the number of channels is close to a power of 2, which is demonstrated by the '60-channel frequency-division-multiplexing (FDM)-2 X 30-channel time- division-multiplexing (TDM) transmultiplexer; a rough estimate of the computation rate is carried out in a practical case and appears to be quite within reach of the present technological capabilities. Significant cost advantage over equivalent analog equipment is expected. A digital version of the 12-channel FDM system using the same technique is also considered.

TDM-FDM Transmultiplexer: Digital Polyphase and FFT

A noise reduction. A hollow body 1 is traversed by several passages 2, juxtaposed and separated, oriented in the direction of noise propagation, and length decreasing as one moves away from a vertical area. Noise can pass freely beyond the body 1 and intersects the noise that has passed through the passages 2 and is out of phase, resulting in an attenuation zone in rear of the device. Application protection against trains and road noise.

A noise reduction

The present invention discloses a data transmission method and apparatus. A first access point determines a current working uplink receiving beam, and broadcasts an identifier of the current working uplink receiving beam of the first access point, so that when a first station associated with the first access point determines, according to the identifier of the current working uplink receiving beam of the first access point, that a first transmitting beam at which the first station is currently working is the current working uplink receiving beam of the first access point, the first station performs data transmission with the first access point by using the first transmitting beam. The current working uplink receiving beam of the first access point and a current working uplink receiving beam of a second access point do not overlap in space.

Data transmission method and apparatus

As a novel staring imaging technique, radar coincidence imaging (RCI) shows great potentials in various applications. However, the array position error, exists in array radar generally, has a bad influence on RCI and impairs the imaging performance extremely. In this paper, the mathematical model of RCI in the presence of array position error is established and to obtain the analytic result, the nonlinear relationship between the received signal and array position error is approximated linearly by the first-order Taylor expansion. Thus, the alternating iterative imaging algorithm is designed to compensate the array position error based on basis pursuit. Simulation results are presented to show the effectiveness of the proposed algorithm.

http://ieeexplore.ieee.org/iel7/7324296/7338753/07338780.pdf

Radar coincidence imaging with array position error

A coding method and apparatus are provided to provide a uniform coding method for ultra short codes. The method is as follows: obtaining, by a transmit end, to-be-coded information bits; performing, by the transmit end, PC-polar coding on the to-be-coded information bits based on first constructor parameters, to obtain a coded bit sequence; and sending the coded bit sequence, where a check equation of the first constructor parameters include a first element representing a check-required information bit position and a second element representing a check bit position, the first element corresponds to a first vector in a generator matrix for PC-polar codes, the second element corresponds to a second vector in the generator matrix, and if a first Hamming weight of the first vector is the same as a second Hamming weight of the second vector, a third Hamming weight of an addition modulo 2 vector is greater than the first Hamming weight and greater than the second Hamming weight, or if the first Hamming weight is different from the second Hamming weight, the third Hamming weight is greater than a smaller one of the first Hamming weight and the second Hamming weight.

Coding method and device

The invention discloses a pilot frequency pollution reduction method based on partial pilot frequency multiplexing in a large-scale MIMO system, and belongs to the field of communications. The pilot frequency pollution reduction method comprises the following steps: first, dividing pilot frequency sequences allocated to cell users into a multiplexing pilot frequency sequence group and an orthogonal pilot frequency sequence; second, dividing the users in the cell into pilot frequency multiplexing users and orthogonal pilot frequency users according to numerical value features from the users to a large-scale fading coefficient of a target base station channel, randomly allocating the pilot frequency of the multiplexing pilot frequency sequence group to the pilot frequency multiplexing users, wherein the group of pilot frequency sequences is multiplexed in other cells, and allocating the pilot frequency of the orthogonal pilot frequency sequence to the orthogonal pilot frequency users, wherein the group of pilot frequency sequences is not multiplexed in other cells; and third, processing and receiving the uplink data of the users at a base station end, maximizing the total spectral efficiency of an uplink target cell to figure out an optimal partial pilot frequency multiplexing factor, and realizing optimized configuration of the pilot frequency based on this, so as to obviously reduce the pilot frequency pollution.

Pilot frequency pollution reduction method based on partial pilot frequency multiplexing in large-scale MIMO system

The invention discloses a codebook construction method suitable for an MU (multi-user) massive multiple input multiple output (MIMO) system and belongs to the technical field of wireless communication. The codebook construction method includes that massive MIMO precoding codebooks are generated according to BD-DFT expansion and coexist in a base station terminal and a user terminal, users select precoding codewords capable of enabling the users to obtain maximized channel gains according to corresponding channel state information (CSI), an precoding matrix index (PMI) corresponding to the optimal codeword is fed back to the base station terminal, the base station terminal restores the corresponding precoding codeword according to received feedback information, and data sent by the users can be subjected to precoding processing. By the codebook construction method and a homogeneous array system of a cross polarized antenna, channel spaces are more matched, co-channel interference (CCI) of multiple users can be effectively restricted, and a simple and efficient implementation scheme is provided for the massive MU-MIMO system.

Codebook construction method based of 3D (three dimensional) cross polarization channel based massive multiple input multiple output (MIMO) system

We provide a comprehensive analysis of the time-varying modified DFT (MDFT) filter bank based on the general time-varying filter bank theories (Wang, 2005, 2006, 2008, 2009) in both the time domain and frequency domain. We give firstly the description of the time-invariant MDFT filter bank including its perfect reconstruction (PR) condition, its mechanism of aliasing error cancellation and the relationship with the cosine-modulated filter bank in detail. Then, the time-varying MDFT filter bank is analyzed according to the time-domain description. Finally, the window switching method is introduced to design the prototype filter in the time-varying MDFT filter bank with examples. The error analysis shows that the introduced design approach is useful in practice.

/pdf/analysis-and-properties-of-time-varying-modified-dft-filter-2gb2nid7hh.pdf

Analysis and Properties of Time-Varying Modified DFT Filter Banks

The invention discloses a large-scale MIMO system limiting feedback method based on compressive sensing. In a large-scale MIMO limiting feedback system, an Nh*Nv-dimensional uniform planar array (UPA) is adopted at a base station, and a linear array is adopted at a user terminal. The large-scale MIMO system limiting feedback method comprises the following steps: firstly, seeking a sparse base matched with a large-scale MIMO horizontal-dimensional channel and a vertical-dimensional channel by using a compressive sensing (CS) theory, thereby furthermore obtaining a two-dimensional united sparse base matched with a large-scale MIMO channel according to a Kronecker product; secondly, projecting an observation matrix irrelevant to the sparse base to a low-dimensional space, thereby obtaining an observation signal, quantifying the signal, and feeding the quantified signal back to the base station; finally, reconstructing channel state information at the base station by using an orthogonal matching pursuit (OMP) algorithm. The utility model provides a simple and efficient implementation method for the large-scale MIMO limiting feedback system.

Large-scale MIMO system limiting feedback method based on compressive sensing

The invention discloses a two-dimensional interpolation limited feedback method suitable for an LTE (Long Term Evolution) system, and the method belongs to the communication field. The method comprises the following steps of: estimating a channel matrix corresponding to current data frames by a receiving terminal according to pilot frequency information, and obtaining a channel prediction matrix through predicting a channel matrix corresponding to subsequent data frames; forming feedback data blocks by carrying out block processing according to subcarriers on the basis of the channel matrix; selecting optimal code words corresponding to four vertex positions of each feedback data block, carrying out time domain and frequency domain interpolation processing according to the optimal code words, and calculating optical rotational vectors corresponding to the feedback data blocks; and feeding back an optimal code word index and an optical rotational vector index back to a transmitting terminal by the receiving terminal so as to determine precoding matrixes corresponding to all subframes and subcarriers in each feedback data block, and realizing the precoding of the transmitting terminal. By adopting the method, the feedback quantity of limited feedback can be effectively reduced, the performance loss caused by feedback time delay on the system can be effectively restrained, and the system transmission performance can be improved.

Zhang Zufan

Papers

Pilot frequency pollution reduction method based on partial pilot frequency multiplexing in large-scale MIMO system

Codebook construction method based of 3D (three dimensional) cross polarization channel based massive multiple input multiple output (MIMO) system

Analysis and Properties of Time-Varying Modified DFT Filter Banks

Large-scale MIMO system limiting feedback method based on compressive sensing

Two-dimensional interpolation limited feedback method based on channel prediction in LTE system