A communication apparatus includes a circuitry and a transmitter. In operation, the circuitry generates a Demodulation Reference Signal (DMRS) and generates downlink control information indicating a mapping pattern of the DMRS from a plurality of mapping patterns, and the transmitter transmits the DMRS and the downlink control information. The plurality of mapping patterns include a first mapping pattern and a second mapping pattern. Resource elements used for the DMRS of the second mapping pattern are same as a part of resource elements used for the DMRS of the first mapping pattern. A number of the resource elements used for the DMRS of the first mapping pattern is larger than a number of the resource elements used for the DMRS of the second mapping pattern.

Methods and apparatus are provided for calibrating an antenna array in a receiver. A training signal for calibrating the antenna array is injected into a data signal received on each receive path to generate combined signals on each receive path. The combined signals are equalized by respective equalizers. The coefficients of the equalizers are determined by comparing a feedback signal for each receive path with the equalized signal to estimate the impairment on each received path. The estimated impairment on each receive path is used to adapt the equalize coefficients for a respective equalizer to compensate for the impairment. After equalization, an estimate of the observed training signal on each receive path is subtracted from the equalized signal for the same receive path to generate estimates of the received data signals for demodulation and decoding.

A small base station executes radio communication using multiple antennas. There are set multiple antenna groups that each include all or a portion of the antennas and multiple antenna group patterns that each include at least one of the antenna groups. The small base station transmits reference signals with sequences that differ from one another between antenna groups that are included in the same antenna group pattern. A user apparatus receives the reference signals. Based on a reception result of the reference signals, a use antenna group pattern and at least one use antenna group that are to be used for transmission of a radio signal from the small base station are determined.

Certain aspects of the present disclosure relate to methods and apparatus for pilot design for Narrow-Band Internet of Things (NB-IoT). In certain aspects, the method generally includes determining at least one binary code sequence to use as a demodulation reference signal (DMRS) for a channel transmitted across one or more subframes using one or more tones within a resource block (RB) allocated to the UE for narrowband communication, and transmitting the channel including the DMRS using the one or more tones and the determined binary code sequence. In certain aspects, the binary code sequence may be determined based on a binary random sequence, such as pseudo noise (PN) or Gold sequence.

Provided is a method for transmitting, by a user equipment (UE), a demodulation reference signal (DMRS) for a physical uplink shared channel (PUSCH) in a wireless communication system. A terminal receives a cyclic shift field, which indicates a first value and a second value, through a physical downlink control channel (PDCCH) from a base station, generates a first DMRS sequence and a second DMRS sequence, which are associated with a first layer and a second layer respectively, by using a first cyclic shift and a second cyclic shift, respectively, which are determined based on the first value and the second value respectively, and transmits the first DMRS sequence and the second DMRS sequence to the base station. Furthermore, the first value and the second value are separated by a maximum value corresponding to a total number of possible cyclic shifts.

Disclosed is a sounding reference signal transmission method which is efficient in an uplink wireless telecommunications system using a multiple antenna technique and sounding reference signal hopping. A terminal is equipped with a plurality of antennas, and a base station receives the sounding reference signal transmitted from these antennas and estimates the uplink channel state of each antenna. The sounding reference signal performs frequency hopping so that the base station determines the channel condition for the entire bandwidth to which data is transmitted in the uplink system. In this environment, the sounding reference signal is transmitted through an antenna pattern through the entire data transmission bandwidth of the uplink system for each antenna of the terminal without additional overhead.

The present invention relates to a wireless communication system. More particularly, the present invention relates to a method in which a terminal transmits control information in a wireless communication system, and to an apparatus for the method, wherein the method comprises the following steps: spreading a control information block corresponding to one single carrier frequency division multiplexing (SC-FDMA) symbol, such that the spread control information blocks correspond to a plurality of first SC-FDMA symbols; performing a discrete Fourier transform (DFT) precoding process on the spread control information blocks on an SC-FDMA symbol basis; transmitting, in the plurality of first SC-FDMA symbols in a subframe, the DFT precoded control information blocks; and transmitting, in a plurality of second SC-FDMA symbols in the subframe, a reference signal sequence, wherein an orthogonal code is applied to the plurality of second SC-FDMA symbols in a time domain.

A method for receiving downlink signal and an apparatus therefor are disclosed. A method for enabling a user equipment (UE) to receive a downlink signal from an eNB including a plurality of antenna ports in a wireless communication system includes: receiving a precoded reference signal according to a precoded reference signal configuration for the plurality of antenna ports; measuring receive (Rx) power of the reference signal for each of the plurality of antenna ports; and reporting, to the eNB, at least one of Rx power values of the reference signal, measured for the plurality of antenna ports. The reference signal is for serving cell search of the UE and precoding is applied to the plurality of antenna ports through which the reference signal is transmitted.

A radio base station, user equipment (UE), and method of control signaling in wireless communication systems. Control information is transferred from a base station to at least one UE, via a plurality of common pilot channels. A set of unique pilot sequences is predefined, and the base station assigns specific pilot sequences from the set of pilot sequences to specific common pilot channels, forming a pilot sequence assignment pattern representing specific control information. The UE, having knowledge of the relations between pilot sequence assignment patterns and control information, interprets the received pilot sequence assignment pattern as specific control information. The method is particularly well suited for broadcast type control information.

A method for transmitting a channel state information reference signal (CSI-RS) in a specific downlink subframe having an extended cyclic prefix (CP) in a wireless communication system according to an embodiment of the present invention includes: generating a CSI-RS sequence and mapping the CSI-RS sequence to CSI-RS complex-valued modulation symbols; and mapping the CSI-RS complex-valued modulation symbols to at least one pattern of a first CSI-RS pattern set composed of a plurality of CSI-RS patterns and a second CSI-RS pattern set composed of a plurality of CSI-RS patterns, the CSI-RS patterns being composed of REs to which CSI-RS complex-valued modulation symbols are mapped, wherein the second CSI-RS pattern set is available when 2 OFDM symbols are used for a physical downlink control channel in the downlink subframe or a specific downlink control information format is configured.