Method and apparatus for using channel state information reference signal in wireless communication system

A method for wireless communication, comprising:

• receiving, by a user equipment (UE), a channel state information reference signal (CSI-RS) in a CSI-RS subframe at a first time according to a cell-specific CSI-RS resource pattern comprising a pattern of resource elements assigned to the transmission of the CSI-RS signal within the CSI-RS subframe, the cell-specific CSI-RS resource pattern being non-colocated with another resource pattern assigned to a reference signal other than the CSI-RS, the CSI-RS subframe not including a synchronization signal, a paging signal, and/or a broadcast signal;
• performing, by the UE, a channel quality estimate based on the CSI-RS;
• reporting, by the UE, the channel quality estimate to a base station;
• and
• receiving the CSI-RS at a second time, wherein an index of the CSI-RS subframe is hopped between the first time and the second time based on a cell ID and any combination of a number of CSI-RS antenna ports, a number of CSI-RS subframes within a frame, and a system time.

An apparatus comprising:

• a processor;
• a memory in communication with the processor, wherein the processor and the memory are configured to:
• select a cell-specific channel state information reference signal (CSI-RS) resource pattern comprising a pattern of resource elements assigned to the transmission of the CSI-RS signal within a CSI-RS subframe of a plurality of CSI-RS subframes, the cell-specific CSI-RS resource pattern being non-colocated with another resource pattern assigned to a reference signal other than the CSI-RS, the CSI-RS subframe not including a synchronization signal, a paging signal and/or a broadcast signal, and an index of the CSI-RS resource pattern being hopped for each CSI-RS subframe of the plurality of CSI-RS subframes based on a cell ID and any combination of a number of CSI-RS antenna ports, a number of CSI-RS subframes within a frame, and a system time;
• allocate the cell-specific CSI-RS resource pattern to a plurality of antennas for transmitting the CSI-RS by grouping the CSI-RS resource pattern in a plurality of groups of resource elements and assigning each group of resource elements to a different antenna of the plurality of antennas;
• and
• transmit, using the plurality of antennas, the CSI-RS according to the cell-specific CSI-RS resource pattern.

A user equipment (UE) comprising:

• a processor;
• an antenna controlled by the processor;
• and
• a memory in communication with the processor, wherein the processor and the memory are configured to:
• receive, via the antenna, a channel state information reference signal (CSI-RS) in a CSI-RS subframe at a first time according to a cell-specific CSI-RS resource pattern comprising a pattern of resource elements assigned to the transmission of the CSI-RS signal within the CSI-RS subframe, the cell-specific CSI-RS resource pattern being non-colocated with another resource pattern assigned to a reference signal other than the CSI-RS, the CSI-RS subframe not including a synchronization signal, a paging signal, and/or a broadcast signal;
• perform a channel quality estimate based on the CSI-RS;
• report, via the antenna, the channel quality estimate to a base station;
• and
• receive, via the antenna, the CSI-RS at a second time, wherein an index of the CSI-RS subframe is hopped between the first time and the second time based on a cell ID and any combination of a number of CSI-RS antenna ports, a number of CSI-RS subframes within a frame, and a system time.