# US 2016/0262188 A1 · Mitigation of inter-base station resynchronization loss in lte/lte-a networks with contention-based shared frequency spectrum > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2016/0262188 A1 - Document ID: US20160262188A1 - Status: Published application - Kind: A1 - Application number: 15/041,635 - Filed: 2016-02-11 - Published: 2016-09-08 - Earliest claimed: 2015-03-06 - Assignees: QUALCOMM Incorporated - Applicants: QUALCOMM Incorporated - Inventors: Xiaoxia Zhang; Vikas Jain; Srinivas Yerramalli; Tao Luo; Aleksandar Damnjanovic; Kiran Kumar Somasundaram - Web page: https://patentgrep.com/patent/US20160262188A1 ## CPC - H04J 11/0056: {Inter-base station aspects} - H04W 74/006: {in the downlink, i.e. towards the terminal} - H04W 74/0808: using carrier sensing, e.g. carrier sense multiple access [CSMA] - H04B 7/2687: {Inter base stations synchronisation} - H04W 16/14: Spectrum sharing arrangements {between different networks} - H04W 72/1268: of uplink data flows - H04W 74/0816: with collision avoidance - H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H04B: TRANSMISSION ## Abstract Mitigation of inter-base station resynchronization loss in wireless networks including contention-based shared frequency spectrum is discussed. Aspects of such mitigation provide for base stations entering into an idle mode when a transmission opportunity occurs in a radio frame of the next resynchronization occasion. Additional aspects provide for the base station to signal a flexible listen before talk (LBT) frame length to the user equipment (UE), either with or without explicit signaling of the downlink-uplink division. Further aspects provide for the base station to signal a reset indication to UEs that will prompt the UEs to monitor for downlink channel reserving signals prior to the current LBT frame ending by the resynchronization occasion. ## Claims ### Claim 1 A method of wireless communication, comprising: detecting a downlink channel reserving signal from a serving base station; obtaining a listen before talk (LBT) frame length from a downlink channel with the downlink channel reserving signal, wherein the LBT frame length identifies a length of a downlink portion of a next LBT frame; monitoring for an uplink grant for one or a plurality of subframes of the next LBT frame; and determining to transmit on at least one subframe within the next LBT frame based on the uplink grant. ### Claim 2 (depends on 1) The method of claim 1, further including: performing a clear channel assessment (CCA) check of a contention-based shared resource in response to the uplink grant and having uplink data for transmission; transmitting the uplink data in response to the CCA check being successful; and refraining from transmitting in one or more remaining subframes of the next LBT frame after the transmitting. ### Claim 3 (depends on 2) The method of claim 2, further including: determining whether the CCA check is successful prior to a guaranteed channel reserving signal boundary, wherein the guaranteed channel reserving signal boundary includes a minimum duration of one or more channel reserving signals transmitted before uplink transmission on a next uplink subframe; and transmitting the one or more channel reserving signals beginning at the guaranteed channel reserving signal boundary in response to determining the CCA check is successful prior to the guaranteed channel reserving signal boundary, wherein the transmitting the uplink data is further in response to completion of the one or more channel reserving signals. ### Claim 4 (depends on 1) The method of claim 1, further including: detecting a user equipment (UE) status triggering a random access procedure; and sending a random access message after a successful clear channel assessment (CCA) check in response to one of: a last subframe of the next LBT frame when the uplink grant is detected; or a next periodic random access occasion, wherein a periodicity of the next periodic random access occasion is obtained from a system broadcast message. ### Claim 5 (depends on 1) The method of claim 1, wherein the monitoring for the uplink grant includes: monitoring a downlink control channel on a primary component carrier of a non-contention-based frequency band, and wherein the determining to transmit includes: detecting the uplink grant in subframe n; and beginning to monitor for a next channel reserving signal after subframe n+k, where k is an associated time line for response of uplink transmission from uplink grant. ### Claim 6 (depends on 1) The method of claim 1, wherein the determining to transmit includes: detecting the uplink grant in subframe n; and assuming the next LBT frame continues until subframe n+k, where k is an associated time line for response of uplink transmission from uplink grant. ### Claim 7 (depends on 1) The method of claim 1, further including: receiving a signal from the serving base station; and blind decoding the signal to determine one or more of: a subframe during which the signal is received is a downlink subframe; and the signal includes a channel state information reference signal (CSI-RS). ### Claim 8 (depends on 1) The method of claim 1, further including: obtaining a downlink-uplink configuration from the next LBT frame in the frame format indicator transmitted with the downlink channel reserving signal, wherein the downlink-uplink configuration identifies a division of the plurality of subframes between downlink, uplink, and special subframes. ### Claim 9 A method of wireless communication, comprising: determining a radio frame in which a next resynchronization occasion is located; detecting an opportunity to contend for a contention-based resource for the radio frame; remaining idle in response to the opportunity detected in the radio frame; and performing a clear channel assessment (CCA) check at the next resynchronization occasion. ### Claim 10 (depends on 9) The method of claim 9, wherein the detecting the opportunity includes one or more of: detecting an end to a current listen before talk (LBT) frame; and detecting data for transmission in a buffer. ### Claim 11 A method of wireless communication, comprising: obtaining a reset indicator from a base station, wherein the reset indicator identifies a subframe during which a user equipment (UE) is to monitor for a downlink channel reserving signal of the base station; and monitoring for the downlink channel reserving signal at the subframe indicated by the reset indicator regardless of a last subframe a previous downlink channel reserving signal was detected. ### Claim 12 (depends on 11) The method of claim 11, further including: detecting the previous downlink channel reserving signal of the base station; initiating a listen before talk (LBT) frame timer in response to the previous downlink channel reserving signal, wherein a duration of the LBT frame timer corresponds to an LBT frame length; and ending the LBT frame timer in response to the reset indicator regardless of expiration of the LBT frame timer. ### Claim 13 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 detect a downlink channel reserving signal from a serving base station; to obtain a listen before talk (LBT) frame length from a downlink channel with the downlink channel reserving signal, wherein the LBT frame length identifies a length of a downlink portion of a next LBT frame; to monitor for an uplink grant for one or a plurality of subframes of the next LBT frame; and to determine to transmit on at least one subframe within the next LBT frame based on the uplink grant. ### Claim 14 (depends on 13) The apparatus of claim 13, further including configuration of the at least one processor: to perform a clear channel assessment (CCA) check of a contention-based shared resource in response to the uplink grant and having uplink data for transmission; to transmit the uplink data in response to the CCA check being successful; and to refrain from transmitting in one or more remaining subframes of the next LBT frame after the transmission. ### Claim 15 (depends on 14) The apparatus of claim 14, further including configuration of the at least one processor: to determine whether the CCA check is successful prior to a guaranteed channel reserving signal boundary, wherein the guaranteed channel reserving signal boundary includes a minimum duration of one or more channel reserving signals transmitted before uplink transmission on a next uplink subframe; and to transmit the one or more channel reserving signals beginning at the guaranteed channel reserving signal boundary in response to determining the CCA check is successful prior to the guaranteed channel reserving signal boundary, wherein transmitting the uplink data is further in response to completion of the one or more channel reserving signals. ### Claim 16 (depends on 13) The apparatus of claim 13, further including configuration of the at least one processor: to detect a user equipment (UE) status triggering a random access procedure; and to send a random access message after a successful clear channel assessment (CCA) check in response to one of: a last subframe of the next LBT frame when the uplink grant is detected; or a next periodic random access occasion, wherein a periodicity of the next periodic random access occasion is obtained from a system broadcast message. ### Claim 17 (depends on 13) The apparatus of claim 13, wherein the configuration of the at least one processor to monitor for the uplink grant includes configuration to monitor a downlink control channel on a primary component carrier of a non-contention-based frequency band, and wherein the configuration of the at least one processor to determine to transmit includes configuration of the at least one processor: to detect the uplink grant in subframe n; and to begin monitoring for a next channel reserving signal after subframe n+k, where k is an associated time line for response of uplink transmission from uplink grant. ### Claim 18 (depends on 13) The apparatus of claim 13, wherein the configuration of the at least one processor to determine to transmit includes configuration of the at least one processor: to detect the uplink grant in subframe n; and to assume the next LBT frame continues until subframe n+k, where k is an associated time line for response of uplink transmission from uplink grant. ### Claim 19 (depends on 13) The apparatus of claim 13, further including configuration of the at least one processor: to receive a signal from the serving base station; to blind decode the signal to determine one or more of: a subframe during which the signal is received is a downlink subframe; and the signal includes a channel state information reference signal (CSI-RS). ### Claim 20 (depends on 13) The apparatus of claim 13, further including configuration of the at least one processor to obtain a downlink-uplink configuration from the next LBT frame in the frame format indicator transmitted with the downlink channel reserving signal, wherein the downlink-uplink configuration identifies a division of the plurality of subframes between downlink, uplink, and special subframes.