Methods, systems, and devices for wireless communications are described. A first transmission/reception point (TRP) may coordinate with a second transmission/reception point to configure code division multiplexing group hopping for a user equipment (UE). The first TRP may transmit a signal to the UE indicating that code division multiplexing group hopping is enabled for the first transmission/reception point and the second transmission/reception point. The first TRP may transmit, during a first instance of the code division multiplexing group hopping, a first reference signal to the UE according to a first code division multiplexing group. The first TRP may transmit, during a second instance of the code division multiplexing group hopping, the first reference signal to the UE according to a second code division multiplexing group.

Communication in a wireless network using a phase-tracking reference signal (PT-RS) for orthogonal frequency division multiplexing (OFDM) includes determining one or more PT-RS groups of adjacent subcarriers in a resource allocation for a physical uplink shared channel (PUSCH) or a physical downlink shared channel (PDSCH), encoding data to be transmitted by the PUSCH or the PDSCH in data subcarriers within the resource allocation for the PUSCH or the PDSCH, and encoding phase-tracking reference signals within the one or more PT-RS groups of adjacent subcarriers.

The present invention provides methods for transmitting an RS in a wireless access system supporting a multiple connection mode, in which user equipment is connected to two or more small cells, and devices supporting same. According to one embodiment of the present invention, a method for user equipment transmitting a scheduling request (SR) in the wireless access system supporting the multiple connection mode, comprises the steps of: receiving, from a first small cell in the multiple connection mode, an upper layer signal comprising SR parameters for transmitting the SR; generating the SR based on the SR parameters; and transmitting the SR by using a physical uplink control channel (PUCCH) signal, wherein the SR parameters are pre-established through negotiation with the first small cell and a second small cell in the multiple connection mode, the user equipment in the multiple connection mode maintains connection with the two or more small cells including the first small cell and the second small cell, and wherein the first small cell and the second small cell can be mutually connected through a non-ideal backhaul link.

Provided herein is a method for interference cancellation for a UE having interference cancellation capability in a wireless communication system, the method comprising: receiving information on a reference signal transmitted from an interfering cell having the possibility of causing inter-cell interference; and attempting to detect the reference signal using the received information on the reference signal, wherein the information on the reference signal is received when the interfering cell and a serving cell of the UE have the same cyclic prefix (CP) length and are synchronized with each other.

An apparatus in a user equipment node (UE) is configured to perform a method for channel feedback. The method includes determining, based on a common reference signal received from a base station and one or more channel conditions, a plurality of values for a receiver table. The method also includes determining a plurality of values for a decision table based on corresponding values in the receiver table and a predetermined interference table. The method further includes selecting a value from the decision table. In addition, the method includes transmitting, to the base station, at least one of a rank indicator (RI) value and a precoding matrix indicator (PMI) value associated with the selected value in the decision table.

The present invention provides methods for transmitting channel status information (CSI) in a wireless access system that supports a multi-connection mode in which a terminal is connected to two or more small cells, and devices for supporting the same. A method by which a terminal reports CSI in a wireless access system that supports a multi-connection mode, according to one embodiment of the present invention, comprises the steps of: receiving a first physical downlink control channel (PDCCH) signal including first resource allocation information from a first small cell which is in a multi-connection mode state; receiving a second PDCCH signal including second resource allocation information from a second small cell which is in a multi-connection mode state; and reporting the CSI on the basis of the first resource allocation information and the second resource allocation information. At this point, the terminal maintains a plurality of connections with two or more small cells including the first small cell and the second small cell in a multi-connection mode, and the first small cell and the second small cell are arranged at different physical positions and can be connected to each other through an abnormal backhaul link.

A method of performing downlink measurement at a user equipment in a wireless communication system is described. Information indicating one or more subframes on which downlink measurement is to be performed is received from a base station. The downlink measurement is performed in the one or more subframes configured by the information. The one or more subframes are configured based on a subset of subframes with reduced activity of a neighbor base station which performs inter-cell interference coordination with the base station.

Wireless devices may receive channel state information (CSI) measurement resources for a plurality of cells, including cells of a first transmission point and cells of a second transmission point. The wireless device may measure CSI for each cell, and may quantize the measured CSI jointly across the cells. The wireless device may send the jointly quantized CSI to a base station, and the jointly quantized CSI may be used in communications via the first transmission point and the second transmission point.

The application relates to the selection of cells to form a cell coordination group for which interference management techniques such as COMP are to be applied. The cells to be selected to improve the performance of a UE in terms of throughput or delay are not necessarily the ones which are geographically the closest because in city environments shadowing effects of buildings exist. Thus, choosing the closest cells for coordinated interference management will not be a good solution in many cases. Hence, there is a need to develop another method and mechanism for more accurately generating a cell coordination group for interference management activities. This problem is solved by the application in that either the downlink interference toward the UE from the neighboring cells is estimated or the neighbor cells listen for the UE and then predict the downlink interference. Furthermore, the algorithm starts with an initial list of cells comprising the most likely handover candidates. Furthermore, cells are eliminated if the interconnection link to the serving base station is not fast enough for the interference reducing algorithms.

To mitigate interference by using effective knowledge or information as to an interference signal, there is provided a base station apparatus including a higher layer which configures, in a terminal apparatus, first interference information used in the terminal apparatus in order to mitigate interference from a cell-specific reference signal and at least one of second interference information used in the terminal apparatus in order to mitigate interference from a downlink shared channel, third interference information used in the terminal apparatus in order to mitigate interference from a downlink control channel, and fourth interference information used in the terminal apparatus in order to mitigate interference from an enhanced downlink shared channel, in which each of the second interference information, the third interference information, and the fourth interference information is configured in a case where the first interference information is being configured.