This disclosure relates to performing cell measurements in unlicensed frequency bands and/or in channels with interference. According to some embodiments, a wireless user equipment (UE) device may define a reference symbol vector for a cell. Each respective element of the reference symbol vector may correspond to a respective subcarrier of the cell that carries a respective reference symbol. The UE may perform channel estimation at each respective element of the reference symbol vector. The UE may estimate the cell strength of the cell by cross-correlating channel estimates of different elements of the reference symbol vector.

A wireless communication method is provided in which beam training phases alternate with data transmission phases. The method includes estimating a first channel based on a signal received using one or more first training beams in a first beam training phase, and calculating, based on the estimated first channel and a first objective function corresponding to the estimated first channel, a first data beam for a first data transmission phase from the one or more first training beams in the first beam training phase, the first data transmission phase following the first beam training phase.

An example system comprises a first antenna and a modem. The first antenna is configured to receive a signal from a transmitting radio frequency unit. The signal includes data and a known sequence. The modem is configured to retrieve the known sequence from the signal, transform the known sequence and the data into a frequency domain, calculate averages of groups of neighboring frequency points in the frequency domain to reduce the effect of nonlinear noise in the signal, the neighboring frequency points corresponding to the preamble in the frequency domain, compare the calculated averages to an expected frequency response in the frequency domain, determine a correction filter to apply to the data based on the comparison, apply the correction filter on the data in the frequency domain to create corrected data, transform the corrected data from the frequency domain to the time domain, and provide the data.

Receiver and method in a receiver, for receiving a signal from a transmitter in a wireless communication system, based on OFDM. The method comprises: receiving a plurality of signals y from the transmitter; determining a group T of REs for which the CEE is assumed to be constant; extracting the determined group T of REs, from the received signals y; computing noise and CEE covariance matrix R.sub.ww for the extracted T REs, initialised as: R.sub.ww=(N.sub.0+Mσ.sup.2)I; computing a MMSE filter W.sup.MMSE, based on the computed noise and CEE covariance matrix R.sub.ww; and obtaining an MMSE estimate {circumflex over (x)} of payload data x comprised in the received signals y, associated with the extracted T REs by applying the computed filter W.sup.MMSE to the extracted T REs of the received signals: {circumflex over (x)}=W.sup.MMSEy.

Devices and methods for transmitting information in resource blocks between a base station and one or more communication devices are disclosed. In each resource block (RB) used for a data or control channel transmission, a plurality of non-overlapping regions of resource elements (REs) are defined. Each region is associated with one or multiple unique reference symbols (RSs). When user equipment (UE) demodulates the information it receives in a particular region of a resource block (RB), it uses the reference symbol (RS) associated with that region. The reference symbol (RS) information may be used, for example, to estimate a channel of the communication network or to demodulate and decode the data contained within the associated regions.

A receiver circuit for estimating a state of an uplink channel between a wireless communication unit and a base station in a wireless communication system computes a conditioned Channel Impulse Response (CIR), the amount of conditioning being based on the noise present in the channel. A CIR and a Noise Variance are estimated from a Sounding Reference Signal received from the wireless communication unit. The estimated CIR is conditioned by comparing it with an adaptive threshold value selected from a look up table that lists threshold values against Noise Variance values. The threshold value further conditions the CIR to eliminate noise and interference. The conditioned CIR is converted into the frequency domain and used to provide a channel gain estimate which, together with noise estimates, is used to determine a Signal to Interference Noise Ratio (SINR) for the channel.

A downlink channel estimation method and apparatus based on a sounding reference signal (SRS), and a communications system. The method includes: a base station receives a SRS sent by UE, the SRS being used for downlink channel estimation and supporting high-dimensional MU-MIMO; performing uplink channel estimation according to the SRS; and acquiring downlink channel information according to uplink channel information obtained in the uplink channel estimation. By means of embodiments of the present disclosure, downlink reference signal overheads and feedback overheads can be remarkably reduced, gain brought by large-scale antennas is obtained, and the system capacity can be further improved.

A method of demodulating a channel by a user equipment in a wireless communication system, include the steps of receiving information including a total power value of reference signals (RSs), a power difference value between power of a first RS for control information and a power of a second RS for data among the RSs, a port number of an additional RS, a cyclic shift (CS) value of the additional RS, and a power value of the additional RS and a power difference value between second RSs for the control information, performing channel estimation on a first channel on which the additional RS is received and a second channel received from a port identical to the port number of the additional RS and the second channel on which the first RS to which a CS value different from the CS value of the additional RS is applied is received, obtaining a power difference value between the power of the additional RS and the power of the first RS based on the channel estimation of the first and the second channels, and determining a number of rank of the second RS based on the total power value of the RSs, the power value of the additional RS, a power difference value between the power of the first RS and the power of the second RS, the obtained power difference value between the power of the additional RS and the power of the first RS, and the power difference value between the power of the second RSs.

A multi-carrier cellular wireless network (400) employs base stations (404) that transmit two different groups of pilot subcarriers: (1) cell-specific pilot subcarriers, which are used by a receiver to extract information unique to each individual cell (402), and (2) common pilots subcarriers, which are designed to possess a set of characteristics common to all the base stations (404) of the system. The design criteria and transmission formats of the cell-specific and common pilot subcarriers are specified to enable a receiver to perform different system functions. The methods and processes can be extended to other systems, such as those with multiple antennas in an individual sector and those where some subcarriers bear common network/system information.

In a system having a first communication device with a first plurality of radio-frequency (RF) chains coupled to a first plurality of antennas and a second communication device with a second plurality of RF chains coupled to a second plurality of antennas, the second communication device receives consecutive training packets that were transmitted by the first communication device, the consecutive training packets having been produced at the first communication device by a power level rule to the first plurality of RF chains. The second communication device determines respective channel measurements corresponding to the consecutive training packets based on the power level rule, and selects a transmit parameter based on the respective channel measurements, the transmit parameter to be used by the first communication device when transmitting to the second communication device. The second communication device transmits and indication of the selected transmit parameter to the first communication device.