# US 10,312,987 B2 · CSI request procedure in LTE/LTE-A with unlicensed spectrum > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,312,987 B2 - Document ID: US10312987B2 - Status: Granted - Kind: B2 - Application number: 15/870,796 - Filed: 2018-01-12 - Published: 2018-06-07 - Granted: 2019-06-04 - Earliest claimed: 2014-08-12 - Assignees: QUALCOMM Incorporated - Applicants: QUALCOMM Incorporated - Inventors: Siddhartha Mallik; Tao Luo - Web page: https://patentgrep.com/patent/US10312987B2 ## CPC - H04B 7/0626: {Channel coefficients, e.g. channel state information [CSI]} - H04B 7/0643: {Feedback on request} - H04L 1/0026: {Transmission of channel quality indication} - H04W 24/10: Scheduling measurement reports {; Arrangements for measurement reports} - H04W 72/23: in the downlink direction of a wireless link, i.e. towards a terminal - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract Channel state information (CSI) request procedures are disclosed for use in long term evolution (LTE)/LTE-Advanced (LTE-A) networks with unlicensed spectrum. Instead of relying on periodic reference signals which may not be transmitted because of failed clear channel assessment (CCA) operations, an aperiodic reference signal is defined that provides an on-demand reference signal and CSI request for user equipment (UE). The serving base station transmits an identifier, which signals that the aperiodic reference signal will be transmitted, either in the same subframe or a future subframe, and then transmits the aperiodic reference signal in the designated subframe. UEs served by the base station will receive the identifier, identify a CSI request, either implicitly through the identifier signal received from the base station or explicitly through a UE-specific CSI request, and then generate a CSI report based on the aperiodic reference signal for transmission back to the serving base station. ## Claims ### Claim 1 A method of wireless communication, comprising: transmitting, by a base station, an identifier signaling presence of an aperiodic reference signal, the identifier being transmitted over a physical downlink control channel (PDCCH); transmitting, by the base station, the aperiodic reference signal and a physical downlink shared channel (PDCCH) rate matched around the aperiodic reference signal; and receiving, by the base station, a channel state information (CSI) report from one or more user equipments (UEs), wherein the CSI report is based on the aperiodic reference signal. ### Claim 2 (depends on 1) The method of claim 1, further comprising: transmitting, by the base station, a UE-specific CSI request to each of the one or more UEs. ### Claim 3 (depends on 2) The method of claim 2, wherein the UE-specific CSI request includes identification of a type of CSI report requested. ### Claim 4 (depends on 1) The method of claim 1, wherein the identifier is transmitted in a common search space of a control channel. ### Claim 5 (depends on 1) The method of claim 1, wherein the aperiodic reference signal includes a pattern of reference signal resources transmitted on a single subframe. ### Claim 6 (depends on 5) The method of claim 5, further comprising: semi-statically configuring, by the base station, the pattern of reference signal resources from a plurality of patterns of reference signal resources, wherein the identifier further identifies the pattern of reference signal resources configured. ### Claim 7 (depends on 1) The method of claim 1, wherein the aperiodic reference signal is associated with at least one of: a CSI-reference signal (CSI-RS); an interference measurement resource (IMR); or a common reference signal (CRS). ### Claim 8 (depends on 1) The method of claim 1, wherein the identifier and the aperiodic reference signal are transmitted in a same subframe; or wherein the identifier is transmitted in a first subframe and the aperiodic reference signal is transmitted on a different subframe after the first subframe. ### Claim 9 A method of wireless communication, comprising: receiving, by a user equipment (UE), an identifier signaling presence of an aperiodic reference signal in a subframe, the identifier being received over a physical downlink control channel (PDCCH); receiving, by the UE, the aperiodic reference signal in the subframe, wherein a physical downlink shared channel (PDSCH) is rate matched around the aperiodic reference signal; generating, by the UE, a CSI report based on the aperiodic reference signal; and transmitting, by the UE, the CSI report to a base station. ### Claim 10 (depends on 9) The method of claim 9, further comprising identifying a CSI request from the base station by at least one of: receiving a UE-specific CSI request from the base station; or receiving the identifier in a common search space of the PDCCH from the base station. ### Claim 11 (depends on 10) The method of claim 10, wherein the UE-specific CSI request includes identification of a type of CSI report requested. ### Claim 12 (depends on 9) The method of claim 9, wherein the aperiodic reference signal includes a pattern of reference signal resources transmitted on a single subframe. ### Claim 13 (depends on 12) The method of claim 12, wherein the identifier further identifies the pattern of reference signal resources from a plurality of patterns of reference signal resources. ### Claim 14 (depends on 9) The method of claim 9, wherein the aperiodic reference signal is associated with at least one of: a CSI-reference signal (CSI-RS); an interference measurement resource (IMR); or a common reference signal (CRS). ### Claim 15 (depends on 9) The method of claim 9, wherein the identifier and the aperiodic reference signal are received in a same subframe; or wherein the identifier is received in a first subframe and the aperiodic reference signal is received on a different subframe after the first subframe. ### Claim 16 An apparatus configured for wireless communication, the apparatus comprising: at least one processor; and a memory coupled to the at least one processor, wherein the at least one processor is configured: to receive, by a user equipment (UE), an identifier signaling presence of an aperiodic reference signal in a subframe, the identifier being received over a physical downlink control channel (PDCCH); to receive, by the UE, the aperiodic reference signal in the subframe, wherein a physical downlink shared channel (PDSCH) is rate matched around the aperiodic reference signal; to generate, by the UE, a CSI report based on the aperiodic reference signal; and to transmit, by the UE, the CSI report to a base station. ### Claim 17 (depends on 16) The apparatus of claim 16, further comprising configuration of the at least one processor to identify a CSI request from the base station by at least one of: receiving a UE-specific CSI request from the base station; or receiving the identifier in a common search space of the PDCCH from the base station. ### Claim 18 (depends on 17) The apparatus of claim 17, wherein the UE-specific CSI request includes identification of a type of CSI report requested. ### Claim 19 (depends on 16) The apparatus of claim 16, wherein the aperiodic reference signal includes a pattern of reference signal resources transmitted on a single subframe, and wherein the identifier further identifies the pattern of reference signal resources from a plurality of patterns of reference signal resources. ### Claim 20 (depends on 16) The apparatus of claim 16, wherein the aperiodic reference signal is associated with at least one of: a CSI-reference signal (CSI-RS); an interference measurement resource (IMR); or a common reference signal (CRS). ### Claim 21 (depends on 16) The apparatus of claim 16, wherein the identifier and the aperiodic reference signal are received in a same subframe; or wherein the identifier is received in a first subframe and the aperiodic reference signal is received on a different subframe after the first subframe. ### Claim 22 A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable to: receive, by a user equipment (UE), an identifier signaling presence of an aperiodic reference signal in a subframe, the identifier being detected over a physical downlink control channel (PDCCH); receive, by the UE, the aperiodic reference signal in the subframe, wherein a physical downlink shared channel (PDSCH) is rate matched around the aperiodic reference signal; generate, by the UE, a CSI report based on the aperiodic reference signal; and transmit, by the UE, the CSI report to a base station. ### Claim 23 (depends on 22) The non-transitory computer-readable medium of claim 22, wherein the code further comprise instructions executable to identify a CSI request from the base station by at least one of: receiving a UE-specific CSI request from the base station; or receiving the identifier in a common search space of the PDCCH from the base station. ### Claim 24 (depends on 23) The non-transitory computer-readable medium of claim 23, wherein the UE-specific CSI request includes identification of a type of CSI report requested. ### Claim 25 (depends on 22) The non-transitory computer-readable medium of claim 22, wherein the aperiodic reference signal includes a pattern of reference signal resources transmitted on a single subframe, and wherein the identifier further identifies the pattern of reference signal resources from a plurality of patterns of reference signal resources. ### Claim 26 (depends on 22) The non-transitory computer-readable medium of claim 22, wherein the aperiodic reference signal is associated with at least one of: a CSI-reference signal (CSI-RS); an interference measurement resource (IMR); or a common reference signal (CRS). ### Claim 27 (depends on 22) The non-transitory computer-readable medium of claim 22, wherein the identifier and the aperiodic reference signal are received in a same subframe; or wherein the identifier is received in a first subframe and the aperiodic reference signal is received on a different subframe after the first subframe.