# US 11,451,963 B2 · False base station detection based on downlink silent periods > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,451,963 B2 - Document ID: US11451963B2 - Status: Granted - Kind: B2 - Application number: 17/016,610 - Filed: 2020-09-10 - Published: 2021-03-25 - Granted: 2022-09-20 - Earliest claimed: 2019-09-20 - Assignees: QUALCOMM Incorporated - Applicants: QUALCOMM Incorporated - Inventors: Huilin Xu; Gavin Bernard Horn; Ravi Agarwal; Ozcan Ozturk; Soo Bum Lee; Naga Bhushan - Web page: https://patentgrep.com/patent/US11451963B2 ## CPC - H04W 12/122: Counter-measures against attacks; Protection against rogue devices - H04W 12/037: of the control plane, e.g. signalling traffic - H04W 12/12: Detection or prevention of fraud - H04W 12/61: Time-dependent - H04W 12/73: Access point logical identity - H04W 12/79: Radio fingerprint - H04W 24/08: Testing, {supervising or monitoring} using real traffic - H04W 24/10: Scheduling measurement reports {; Arrangements for measurement reports} - H04W 56/0015: {one node acting as a reference for the others} - H04W 56/0025: {synchronizing potentially movable access points} - H04W 84/02: Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop] - H04W 88/02: Terminal devices - H04W 88/08: Access point devices - H04W 88/18: Service support devices; Network management devices - H04W 92/02: Inter-networking arrangements - H04W 92/10: between terminal device and access point, i.e. wireless air interface - H04W 92/20: between access points - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract Certain aspects of the present disclosure provide techniques for detecting false base stations and transmissions therefrom based on silent periods during which legitimate base stations are to refrain from transmitting at least certain downlink transmissions on at least some downlink resources. ## Claims ### Claim 1 An apparatus for wireless communications, comprising: at least one processor configured to: identify one or more silent periods during which at least a first base station is to refrain from at least certain downlink transmissions on at least some downlink resources; randomly choose at least one of the one or more silent periods; detect one or more downlink transmissions from a second base station during the one or more silent periods; determine the second base station is posing as the first base station based on the detection; and notify a network entity of the detection; and a memory coupled with the at least one processor. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the certain downlink transmissions comprise at least one of channel state information reference signal (CSI-RS), tracking reference signal (TRS), synchronization signal block (SSB), physical downlink control channel (PDCCH), or physical downlink shared channel (PDSCH) transmissions. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the one or more silent periods are identified based on a pattern, wherein the first base station generates the pattern, and wherein the at least one processor is further configured to receive a configuration indicating a pattern identifying the one or more silent periods. ### Claim 4 (depends on 3) The apparatus of claim 3, wherein receiving the configuration comprises receiving an encrypted message comprising the pattern identifying the one or more silent periods. ### Claim 5 (depends on 3) The apparatus of claim 3, wherein the pattern indicates at least one of: a first set of slots corresponding to the one or more silent periods; or sets of downlink symbols each within a slot of a second set of slots corresponding to the one or more silent periods, wherein the downlink symbols comprise symbols that can be determined as downlink semi-statically, semi-persistently or dynamically determined as downlink. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein one or more downlink transmissions detected from the second base station comprise at least one of a cell-specific signal or a user equipment (UE)-specific signal; wherein the cell-specific signal comprises at least one of: a synchronization signal block (SSB) that carries a same cell identifier (ID) as the first base station; or a first physical downlink control channel (PDCCH); or a first physical downlink shared channel (PDSCH); and wherein the UE-specific signal comprises at least one of: a second PDCCH scrambled by a UE-specific identifier (ID); or a second PDSCH scheduled by a third PDCCH scrambled by a UE-specific ID. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the apparatus comprises the first base station. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein: all of the one or more silent periods are randomly chosen by the first base station. ### Claim 9 (depends on 1) The apparatus of claim 1, wherein the apparatus comprises a node that is deployed in a network to passively listen to detect imposter base stations for security purposes. ### Claim 10 (depends on 9) The apparatus of claim 9, wherein the apparatus comprises a stationary node. ### Claim 11 (depends on 1) The apparatus of claim 1, wherein the identifying comprises identifying the one or more silent periods during which a first base station refrains from at least certain downlink transmissions on at least some downlink resources. ### Claim 12 (depends on 1) The apparatus of claim 1, wherein the apparatus is configured to detect downlink transmissions based on one or more silent period patterns, each associated with a different first base station. ### Claim 13 (depends on 1) The apparatus of claim 1, wherein the apparatus is configured to detect downlink transmissions transmitted by one or more second base stations. ### Claim 14 (depends on 1) The apparatus of claim 1, wherein the apparatus comprises one of a plurality of first nodes configured to detect downlink transmissions based on the same silent period pattern associated with the same first base station. ### Claim 15 (depends on 1) The apparatus of claim 1, wherein the apparatus comprises one of a plurality of first nodes configured to detect downlink transmissions transmitted by the same second base station. ### Claim 16 (depends on 1) The apparatus of claim 1, wherein the at least one processor is further configured to notify one or more other nodes that are not configured with information identifying the one or more silent periods of the detection. ### Claim 17 An apparatus for wireless communications, comprising: at least one processor configured to: identify one or more silent periods during which the apparatus is to refrain from transmitting at least certain downlink transmissions on at least some downlink resources; randomly choose at least one of the one or more silent periods; refrain from transmitting the certain downlink transmissions on the at least some downlink resources during the one or more silent periods; and receive an indication that at least a first node detected, during the at least one of the one or more silent periods, one or more signals transmitted from a second base station; determine the second base station is posing as the apparatus based on the indication; and a memory coupled with the at least one processor. ### Claim 18 (depends on 17) The apparatus of claim 17, wherein the certain downlink transmissions comprise at least one of channel state information reference signal (CSI-RS), tracking reference signal (TRS), synchronization signal block (SSB), physical downlink control channel (PDCCH), or physical downlink shared channel (PDSCH) transmissions. ### Claim 19 (depends on 17) The apparatus of claim 17, wherein the at least one processor is further configured to send the first node an indication of the one or more silent periods. ### Claim 20 (depends on 19) The apparatus of claim 19, wherein the one or more silent periods are indicated by a pattern in a configuration; and wherein the apparatus generates the pattern. ### Claim 21 (depends on 20) The apparatus of claim 20, wherein the configuration is provided in an encrypted message. ### Claim 22 (depends on 20) The apparatus of claim 20, wherein the pattern indicates at least one of: a first set of slots corresponding to the one or more silent periods; or sets of downlink symbols, each within a slot of a second set of slots corresponding to the one or more silent periods, wherein the downlink symbols comprise symbols that can be determined as downlink semi-statically, semi-persistently or dynamically determined as downlink. ### Claim 23 (depends on 17) The apparatus of claim 17, wherein the certain downlink transmissions comprise at least one of a cell-specific signal or a user equipment (UE)-specific signal; wherein the cell-specific signal comprises at least one of: a synchronization signal block (SSB) that carries a same cell identifier (ID) as the apparatus; or a first physical downlink control channel (PDCCH); or a first physical downlink shared channel (PDSCH); and wherein the UE-specific signal comprises at least one of: a second PDCCH scrambled by a UE-specific identifier (ID); or a second PDSCH scheduled by a third PDCCH scrambled by a UE-specific ID. ### Claim 24 (depends on 17) The apparatus of claim 17, wherein: all of the one or more silent periods are randomly chosen by the apparatus. ### Claim 25 (depends on 24) The apparatus of claim 24, wherein the first node comprises a node that is deployed in a network to passively listen to detect imposter base stations for security purposes. ### Claim 26 (depends on 24) The apparatus of claim 24, wherein the first node comprises one of: a stationary node; a stationary user equipment (UE); or a mobile UE designed to roam a network to passively listen to detect imposter base stations in different locations. ### Claim 27 A method for wireless communications by a first node, the method comprising: identifying one or more silent periods during which at least a first base station is to refrain from at least certain downlink transmissions on at least some downlink resources; randomly choosing at least one of the one or more silent periods; detecting one or more downlink transmissions from a second base station during the one or more silent periods; determining the second base station is posing as the first base station based on the detection; and notifying a network entity of the detection. ### Claim 28 A method for wireless communications by a first base station, the method comprising: identifying one or more silent periods during which the first base station is to refrain from transmitting at least certain downlink transmissions on at least some downlink resources; randomly choosing at least one of the one or more silent periods; refraining from transmitting the certain downlink transmissions on the at least some downlink resources during the one or more silent periods; receiving an indication that at least a first node detected, during the at least one of the one or more silent periods, one or more signals transmitted from a second base station; and determining the second base station is posing as the first base station based on the indication.