A user equipment (UE) may receive a configuration that indicates a set of channel state information reference signals (CSI-RSs) to be measured by the UE for deriving channel state information (CSI), one or more time domain resources for which the UE is to derive the CSI, and a time domain resource for transmission of a CSI report that includes the CSI, wherein the one or more time domain resources for which the UE is to derive the CSI occur after the time domain resource for transmission of the CSI report; determine that the UE cannot measure a first subset of CSI-RSs included in the set of CSI-RSs; derive one or more parameters for the CSI report based at least in part on measuring a second subset of CSI-RSs included in the set of CSI-RSs; and transmit the CSI report in the time domain resource for transmission of the CSI report.

The present disclosure relates to a mobile terminal, a base station and respective operation methods. The mobile terminal comprises circuitry, which in operation assumes that a base station is configured to use one of a plurality of transmission beams, receives a downlink control channel candidate and a corresponding demodulation reference signal using one of a plurality of reception beams corresponding to the assumed one of the plurality of transmission beams, performs channel estimation based on the received demodulation reference signal, and, depending on the quality, demodulates the downlink control channel candidate using the channel estimation. The channel estimation is performed using a demodulation reference signal sequence which is generated observing an association which is associating the generated sequence with the assumed one of the plurality of transmission beams such that at least two of the plurality of transmission beams are associated with different demodulation reference signal sequences.

This disclosure describes systems, methods, and devices related to a trigger-based null data packet (NDP) for channel sounding system. A device may send a trigger frame to a group of station devices, the group of station devices including a first station device, the trigger frame indicating a high efficiency (HE) long training field (HE-LTF) mode and a guard interval duration. The device may identify a HE trigger-based (TB) null data packet (NDP) received from the first station device, the HE TB NDP including a first packet extension field, wherein the HE TB NDP is associated with the HE-LTF mode and the guard interval duration indicated in the trigger frame. The device may send a downlink NDP including a second packet extension field, a second HE-LTF mode, and a second guard interval duration. The device may determine channel state information based on HE TB NDP received from the first station device.

Examples of wireless OFDM communication systems are described herein which replace pilot subcarriers having known modulation with lower dual subcarriers. At the transmitter, for each resource block, the bits that modulate a few payload subcarriers are selected and then encoded with a short dual code thereby forming dual systematic bits and dual check bits. Such selected payload subcarriers are designated as upper dual subcarriers and the dual check bits modulate the lower dual subcarriers, At the receiver, for each resource block, the dual subcarriers are phase adjusted, demodulated, decoded using the short dual code, and re-modulated thereby forming the original dual subcarrier modulation without phase noise nor channel impairments. The re-modulated dual subcarriers are compared against the received dual subcarriers for channel estimation or carrier phase-locked-loop purposes. For example, prior-art OFDM systems with 4 pilots per resource block could be replaced with 8 dual subcarriers for a rate 1/2 short dual code. An increase in the number of subcarriers used for channel estimation or carrier phase-locked-loop tracking has less error in the channel estimate or phase estimate. Lower error permits lower payload BER, lower transmit power, or wider PLL bandwidth to track higher Doppler frequency shifts.

A channel estimation method and circuit. The channel estimation method, adapted for a receiving device of a multi-input multi-output wireless LAN system, comprises the following steps. Firstly, performing a first channel estimation operation on a long training field to obtain a plurality of first composite channel estimation values related to the long training field. Then, performing a second channel estimation operation on a signal field to obtain a plurality of second composite channel estimation values related to the signal field, and performing a third channel estimation operation on a data segment to obtain a plurality of first channel estimation values related to the data segment. Next, obtaining a plurality of second channel estimation values according to the first composite channel estimation values and the second composite channel estimation values, and adjusting the first channel estimation values related to the data segment according to the second channel estimation values.

A user terminal according to the present invention calculates a channel estimation value for each subcarrier by using a demodulation RS, calculates the time fluctuation amount of each symbol by using a correction RS mapped on a symbol following a symbol on which the modulation RS is mapped, corrects the channel estimation value for the subcarrier of a resource element on which a data signal to be demodulated is mapped, by using the time fluctuation amount of the symbol of the resource element, and calculates the channel estimation value of the resource element.

A method for a user equipment (UE) to receive physical downlink control channels (PDCCHs) is provided. The UE receives configuration information for a first control resource set that includes a number of symbols in a time domain and a number of resource blocks (RBs) in a frequency domain, configuration information indicating a first number of N.sub.bundle,1 frequency-contiguous RB s, and a PDCCH in the first control resource set in a number of frequency distributed blocks of N.sub.bundle,1 RBs. The UE assumes that a demodulation reference signal associated with the reception of the PDCCH has a same precoding over the N.sub.bundle,1 RBs. A method for constructing a search space to reduce a number of channel estimations that the UE performs for decoding PDCCHs, relative to conventional search spaces, is also provided.

A base station may determine a Doppler metric associated with a wireless channel and a user equipment (UE). The Doppler metric may be determined from received information related to Doppler effects measured by the UE or from directly measured Doppler effects associated with uplink data received from the UE. Based on the determined Doppler metric, the base station may select one or both of a reference signal (RS) density and a channel estimation technique for the wireless channel and associated UE. The base station may transmit an indication of the RS density to the UE. Downlink data bursts and uplink data bursts may include RSs and data according to the indicated RS density. Further, the base station may transmit to the UE, an indication to communicate using the selected wireless channel estimation technique.

A communication system that minimizes the transmission of pilot symbols while ensuring real-time channel tracking and symbol detection. The system employs a multiple-input multiple-output (MIMO) transmitter-receiver pair where there are many more receive antennas than transmit antennas. Communication occurs over a wide band RF channel via orthogonal frequency division multiplexing (OFDM) that employs a large number of sub-carriers.

A reciprocity-based precoding algorithm is provided that accommodates for the specific type of uncertainty arising from the delay in channel estimation as a function of the velocity of moving wireless communication devices (103a-c). Account is taken of time delay from reference symbols previous sounding times as well as the velocity of the wireless communication devices (103a-c) thereby providing an effective precoding scheme for beamforming.