Methods and apparatus for sub-block based architecture of Cholesky decomposition and channel whitening. In an exemplary embodiment, an apparatus is provided that parallel processes sub-block matrices (R.sub.00, R.sub.10, and R.sub.11) of a covariance matrix (R) to determine a whitening coefficient matrix (W). The apparatus includes a first LDL coefficient calculator that calculates a first whitening matrix W.sub.00, lower triangle matrix L.sub.00, and diagonal matrix D.sub.00 from the sub-block matrix R.sub.00, a first matrix calculator that calculates a lower triangle matrix L.sub.10 from the sub-block matrix R.sub.10 and the matrices L.sub.00 and D.sub.00, and a second matrix calculator that calculates a matrix X from the matrices D.sub.00 and L.sub.10. The apparatus also includes a matrix subtractor that calculates a matrix Z from the matrix X and the sub-block matrix R.sub.11, a second LDL coefficient calculator that calculates a third whitening matrix W.sub.11, lower triangle matrix L.sub.11, and a diagonal matrix D.sub.11 from the matrix Z, and a third matrix calculator that calculates a second whitening matrix W.sub.10 from the matrices L.sub.00, L.sub.10, L.sub.11, and D.sub.11.

Disclosed is a method of estimating, by a user equipment, a reception delay time of a reference signal, the method including receiving a reference signal from a base station; setting a plurality of summation time intervals within a time interval in which the reference signal is received, and acquiring a plurality of snapshot vectors corresponding to the plurality of summation time intervals; calculating a covariance matrix based on the plurality of snapshot vectors; and estimating a reception delay time of the reference signal based on the covariance matrix.

A wireless communication method includes receiving, by a first wireless device during a training phase, reference tones using a first number of resource elements from a transmitter of a second wireless device, wherein the first wireless device comprises multiple receiving antennas, estimating, by the first wireless device, from the receiving the reference tones, a second order statistics of wireless channels between the multiple receiving antennas and the transmitter of the second wireless device, and performing channel estimation, during an operational phase subsequent to the training phase, using the second order statistics and reference tones received on a second number of resource elements, wherein the second number is less than the first number.

Disclosed are a user detection technique, and a method and apparatus for channel estimation in a wireless communication system supporting massive multiple-input multiple-output. The method comprises the steps of: receiving a superimposed signal including a transmission signal of at least one user equipment (UE) from among a plurality of user equipments, wherein each transmission signal includes a pilot signal of a corresponding user equipment; calculating a sample covariance matrix from the received superimposed signal by using the number of antennas of a base station and a pilot signal matrix of the at least one user equipment; calculating a likelihood function indicating the likelihood probability of the received superimposed signal, on the basis of the number of antennas of the base station and the received superimposed signal; detecting a user index set indicating whether or not the plurality of user equipments have transmitted signals, by using the calculated likelihood function and sample covariance matrix; and performing channel estimation of the at least one user equipment that is transmitting the signal, on the basis of the detected user index set.

Aspects of the subject disclosure may include, for example, determining a coherence block for each user equipment (UE) of a plurality of UEs being served by the first cell, resulting in a plurality of coherence blocks, responsive to the determining, identifying a smallest coherence block from the plurality of coherence blocks, identifying a pilot sequence length based on the smallest coherence block, determining a plurality of orthogonal pilot sequences based on the identifying the pilot sequence length, designating, from the plurality of orthogonal pilot sequences, a first group of orthogonal pilot sequences for use in the first cell, and distributing, to each neighboring cell of a plurality of neighboring cells adjacent to the first cell, a respective group of orthogonal pilot sequences from a remainder of the plurality of orthogonal pilot sequences, to prevent pilot contamination between the first cell and the plurality of neighboring cells. Other embodiments are disclosed.

The present disclosure discloses a method for performing analog CSI feedback in a user equipment, comprising: a. obtaining an analog CSI matrix corresponding to the user equipment, the analog CSI matrix satisfies a condition below: X X.sup.H=D, where X denotes the analog CSI matrix, H denotes conjugate transpose of matrix, and D denotes a diagonal matrix; b. obtaining dominated element information corresponding to the analog CSI matrix according to predetermined index information, and transmitting the dominated element information to a base station. The solution according to the present disclosure can reduce feedback overheads to a greater extent, has a high CSI feedback quality, and can reliably implement CSI recovery at the base station side.

A node is configured to be connected to a massive multiple-input, multiple-output (MIMO) array to provide spatially multiplexed channels to a plurality of user equipment in an unlicensed frequency band. The node includes a processor configured to allocate a number of degrees of freedom of the massive MIMO array to interference suppression based on an outcome of a first listen-before-talk (LBT) operation performed by the node to acquire the unlicensed frequency band. The processor is also configured to generate a spatial filter based on the number of degrees of freedom allocated to interference suppression. The node also includes a transceiver configured to perform a second LBT operation using the spatial filter.

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may receive, from a network node, one or more downlink reference signals during a beam training procedure. The UE may estimate, based at least in part on one or more metrics associated with the one or more downlink reference signals received during the beam training procedure, a covariance matrix associated with multiple candidate beam quads used to transmit or receive the one or more downlink reference signals. The UE may select, from among the multiple candidate beam quads, a beam quad that corresponds to a group of four beams to optimize one or more parameters associated with the covariance matrix. The UE may communicate with the network node using the selected beam quad. Numerous other aspects are described.

This disclosure relates generally to resuming packet services in a mobile network. A device, method, and/or system may include switching, with user equipment, from communicating with a first radio access network to communicating with a second radio access network, setting, with a processor of the user equipment, a register of the user equipment to initiate packet services with the first radio access network, and transmitting, with the user equipment, a request to a core network node of the first radio access network to resume communications with the first radio access network based, at least in part, on the register.

A CSI measurement method, a CSI acquisition method, a terminal and a network device are provided, to measure CSI. The terminal performs interference measurement to acquire initial interference measurement result, determine the CSI based on the initial interference measurement result and an interference measurement parameter configured by the network device, and then report the determined CSI to the network device. The interference measurement parameter is configured by the network device, so the interference measurement parameter configured by the network device is capable of reflecting an actual situation of interference information, and interference information acquired by the terminal based on the interference measurement parameter matches interference information for actual transmission in a better manner. As a result, it is able to improve a matching degree between the interference information acquired by the terminal and the interference information for the actual transmission, thereby to enable a network to select a more appropriate parameter for link adaptation.