Abstract: A method for downlink transmission in a cloud radio access network for a number of users is applied in a central unit. The central unit determines a specific number of remote radio heads (RRHs) as non-serving RRHs based on a predetermined data compression ratio. For each of many pieces of user equipment (UEs), the central unit determines a combination of RRHs which are non-serving in coordinated multi-point transmission (CoMP) from a plurality of RRHs based on the determined specific number, and then performs CoMP downlink transmission based on the combination of RRHs which are non-serving in the CoMP.

Abstract: A MIMO symbol detection and search method, a decoding circuit and a receiving antenna system are provided. The signal detection and search method includes the following steps. A symbol search tree is obtained, and a plurality of candidate symbols at each layer of the symbol search tree are sorted. The candidate symbols are traversed in sequence at each layer of the symbol search tree. At each layer of the symbol search tree, if a cumulative partial Euclidean distance is greater than or equal to a threshold, un-scanned candidate symbols are excluded. If the cumulative partial Euclidean distance is less than the threshold, the threshold is updated by the cumulative partial Euclidean distance. When all of the candidate symbols have been calculated, an estimated symbol combination is outputted, and the scan of the symbol search tree is terminated.

Abstract: A method and a system for downlink pre-coding in cloud radio access networks uses a baseband unit, a number of remote radio heads, and a number of user equipments. The baseband unit determines a received signal expression for each user equipment based on system parameters and channel state information, and determines a sum rate expression which may be achievable for downlink transmission based on the received signal expression. The baseband unit then sets up a constrained optimal problem expression subject to a maximum transmitting power of each remote radio head with an objective function of sum rate maximization based on the achievable sum rate expression, and finally determines optimal solutions for the constrained optimal problem where the optimal solutions comprise downlink pre-coding used for downlink transmission.

Abstract: A method and a system for processing uplink signals in cloud radio access networks are disclosed The system comprising a baseband unit and a number of remote radio heads. The baseband unit and the remote radio heads are connected through fronthaul links. When one remote radio head receives a signal transmitted from a user equipment, the remote radio head first encodes the received signal according to a post-coding matrix, then quantizes the encoded signal according to a number of quantization bits allocated to the user equipment, and finally transmits the quantized signal to the baseband unit.

Abstract: A method for downlink transmission in a cloud radio access network for a number of users is applied in a central unit. The central unit determines a specific number of remote radio heads (RRHs) as non-serving RRHs based on a predetermined data compression ratio. For each of many pieces of user equipment (UEs), the central unit determines a combination of RRHs which are non-serving in coordinated multi-point transmission (CoMP) from a plurality of RRHs based on the determined specific number, and then performs CoMP downlink transmission based on the combination of RRHs which are non-serving in the CoMP.

Abstract: A method and a system for processing uplink signals in cloud radio access networks are disclosed The system comprising a baseband unit and a number of remote radio heads. The baseband unit and the remote radio heads are connected through fronthaul links. When one remote radio head receives a signal transmitted from a user equipment, the remote radio head first encodes the received signal according to a post-coding matrix, then quantizes the encoded signal according to a number of quantization bits allocated to the user equipment, and finally transmits the quantized signal to the baseband unit.

Abstract: A method for downlink transmission in a cloud radio access network for a number of users is applied in a central unit. The central unit determines a specific number of remote radio heads (RRHs) as non-serving RRHs based on a predetermined data compression ratio. For each of many pieces of user equipment (UEs), the central unit determines a combination of RRHs which are non-serving in coordinated multi-point transmission (CoMP) from a plurality of RRHs based on the determined specific number, and then performs CoMP downlink transmission based on the combination of RRHs which are non-serving in the CoMP.

Abstract: A beamforming transmission device includes a baseband processing unit, at least one radio frequency unit, and an antenna array unit. The baseband processing unit provides at least one data stream and generates a control signal according to channel state information of at least two pieces of user equipment, wherein the data stream includes data of at least two pieces of user equipment. The radio frequency unit receives the data stream signal and generates at least one radio frequency signal. The antenna array unit receives the radio frequency signal and the control signal and adjusts gains and phases of the antenna array unit according to the control signal such that the radio frequency signal can be formed as a shared beamforming signal for transmitting to at least two pieces of user equipment, wherein the shared beamforming signal includes the data of at least two pieces of user equipment.

Abstract: A beamforming transmission device includes a baseband processing unit, at least one radio frequency unit, and an antenna array unit. The baseband processing unit provides at least one data stream and generates a control signal according to channel state information of at least two pieces of user equipment, wherein the data stream includes data of at least two pieces of user equipment. The radio frequency unit receives the data stream signal and generates at least one radio frequency signal. The antenna array unit receives the radio frequency signal and the control signal and adjusts gains and phases of the antenna array unit according to the control signal such that the radio frequency signal can be formed as a shared beamforming signal for transmitting to at least two pieces of user equipment, wherein the shared beamforming signal includes the data of at least two pieces of user equipment.

Abstract: A method for downlink transmission in a cloud radio access network for a number of users is applied in a central unit. The central unit determines a specific number of remote radio heads (RRHs) as non-serving RRHs based on a predetermined data compression ratio. For each of many pieces of user equipment (UEs), the central unit determines a combination of RRHs which are non-serving in coordinated multi-point transmission (CoMP) from a plurality of RRHs based on the determined specific number, and then performs CoMP downlink transmission based on the combination of RRHs which are non-serving in the CoMP.

Abstract: A beamforming transmission device includes a control unit, at least one radio frequency unit, and at least one signal transmission unit. The control unit is configured to receive a radio frequency signal and channel state information of at least two pieces of user equipment, and to generate a control signal according to the radio frequency signal and the channel state information of the at least two pieces of user equipment. The radio frequency unit is coupled to the control unit. The radio frequency unit is configured to receive the control signal and generate a beamforming signal according to the control signal. The signal transmission unit is coupled to the radio frequency unit. The signal transmission unit is configured to transmit the beamforming signal to the at least two pieces of user equipment.

Abstract: A millimeter wave channel estimation method comprises sending signals through a millimeter wave channel according to a first beamforming matrix, performing a channel estimation on the millimeter wave to generate a first measured matrix, and estimating and obtaining at least one angle of departure of the millimeter wave channel according to the first measured matrix and an angle compressive sensing matrix. The first beamforming matrix comprises a plurality of first beamforming vectors, and the first beamforming vectors respectively corresponds to a plurality of first beamforming patterns. The first measured matrix comprises a plurality of first measured parameters respectively corresponding to the first beamforming vectors.

Abstract: A millimeter wave channel estimation method comprises sending signals through a millimeter wave channel according to a first beamforming matrix, performing a channel estimation on the millimeter wave to generate a first measured matrix, and estimating and obtaining at least one angle of departure of the millimeter wave channel according to the first measured matrix and an angle compressive sensing matrix. The first beamforming matrix comprises a plurality of first beamforming vectors, and the first beamforming vectors respectively corresponds to a plurality of first beamforming patterns. The first measured matrix comprises a plurality of first measured parameters respectively corresponding to the first beamforming vectors.

Abstract: A calibration method for achieving channel reciprocity is provided. The method is used in a wireless communication device and includes: receiving environment information between a root node and each of a plurality of child nodes and between each of the child nodes and one of the other child nodes transmitted by the root node and the child nodes; obtaining evaluation parameters between each of the child nodes and the root node and between each of the child nodes and one of the other child nodes according to the environment information; determining links between the root node and the child nodes according to the evaluation parameters to form a first tree network topology; and obtaining calibration parameters according to the first tree network topology to calibrate reciprocity of the root node and the child nodes.

Abstract: A channel estimation system and method thereof is provided. By utilizing the nature of the millimeter-wave channel with sparse path, the channel estimation problem is transformed from estimating the entire channel matrix to estimating independent parameters of the millimeter-wave channel. These parameters are angle of arrival (AoA) and angle of departure (AoD), and complex gain of the channel paths.

Abstract: A calibration method for achieving channel reciprocity is provided. The method is used in a wireless communication device and includes: receiving environment information between a root node and each of a plurality of child nodes and between each of the child nodes and one of the other child nodes transmitted by the root node and the child nodes; obtaining evaluation parameters between each of the child nodes and the root node and between each of the child nodes and one of the other child nodes according to the environment information; determining links between the root node and the child nodes according to the evaluation parameters to form a first tree network topology; and obtaining calibration parameters according to the first tree network topology to calibrate reciprocity of the root node and the child nodes.

Abstract: An apparatus for low complexity sub-Nyquist sampling of sparse wideband signals is provided, including a mixer, a periodic random sequence generator and a filter bank. The periodic random sequence generator generates a periodic pseudo-random sequence. The mixer is connected to the periodic random sequence generator for receiving the periodic pseudo-random sequence and mixing with an input signal to obtain a modulated signal. The filter bank further includes a plurality of filters and is connected to the mixer for filtering the modulated signal. The sub-Nyquist sampling apparatus may further includes a plurality of analog-to-digital convertors (ADCs), with each ADC connected to each filter of the filter bank to sample the signal from the filter bank and output a sampling signal.

Abstract: A transmitting terminal includes a signal processing unit, MS RF units, MT transmit antennas and a switch unit. The signal processing unit has K precoders for precoding K data streams corresponding to K receiving terminals. The MS RF units output MS up-converted transmit signals based on the precoded K data streams. The switch unit is coupled between the RF units and the transmit antennas and controlled by the signal processing unit for selection of the transmit antennas. The signal processing unit sets the MT transmit antennas as a universal set, calculates a plurality of sum rates corresponding to a plurality of subsets, each subset excluding an ith transmit antenna, according to channel state information, selects the subset with a maximum sum rate as the universal set of a next iteration, and then repeats the calculating and selecting steps until the subset with the maximum sum rate remaining MS transmit antennas.

Abstract: A spatial mapping matrix searching apparatus may include a plurality of antennae configured to receive a plurality of transmission signals, a post-coding module configured to generate a post-coding information according to the received plurality of transmission signals and generate a received signal from the received plurality of transmission signals, and a pre-coding module configured to generate a pre-coding information according to the post-coding information.

Abstract: A transmitting terminal includes a signal processing unit, MS RF units, MT transmit antennas and a switch unit. The signal processing unit has K precoders for precoding K data streams corresponding to K receiving terminals. The MS RF units output MS up-converted transmit signals based on the precoded K data streams. The switch unit is coupled between the RF units and the transmit antennas and controlled by the signal processing unit for selection of the transmit antennas. The signal processing unit sets the MT transmit antennas as a universal set, calculates a plurality of sum rates corresponding to a plurality of subsets, each subset excluding an ith transmit antenna, according to channel state information, selects the subset with a maximum sum rate as the universal set of a next iteration, and then repeats the calculating and selecting steps until the subset with the maximum sum rate remaining MS transmit antennas.