# US 9,883,542 B2 · Method and device for performing link adaptation in wireless communication system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,883,542 B2 - Document ID: US9883542B2 - Status: Granted - Kind: B2 - Application number: 14/909,032 - Filed: 2014-07-29 - Published: 2016-07-07 - Granted: 2018-01-30 - Earliest claimed: 2013-07-30 - Assignees: LG Electronics Inc. - Applicants: LG Electronics Inc. - Inventors: Inkwon Seo; Seungmin Lee; Hanbyul Seo - Web page: https://patentgrep.com/patent/US9883542B2 ## CPC - H04W 76/14: Direct-mode setup - H04L 1/0001: {Systems modifying transmission characteristics according to link quality, e.g. power backoff (adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04)} - H04W 72/044: based on the type of the allocated resource - H04W 72/0473: {the resource being transmission power} - H04W 76/19: Connection re-establishment - H04W 76/23: Manipulation of direct-mode connections - H04W 92/18: between terminal devices - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract One embodiment of the present invention relates to a method by which a device-to-device (D2D) terminal performs link adaptation in a wireless communication system, the D2D link adaptation method comprising the steps of: performing measurement on a resource region to be used for D2D communication; and determining whether the measurement performance result satisfies a trigger condition, wherein if the trigger condition is satisfied for a first time with respect to the resource region, first link adaptation is performed, and if the trigger condition is satisfied for n times (n>=2) with respect to the resource region, second link adaptation is performed. ## Claims ### Claim 1 A method of performing link adaptation by a device-to-device (D2D) user equipment (UE) in a wireless communication system, the method comprising: performing measurement on a first resource region used for D2D communication; determining whether a result of the measurement satisfies a trigger condition, and performing different link adaptation according to a number of times the trigger condition is satisfied for the first resource region, wherein first link adaptation is performed if the trigger condition is satisfied one time, and wherein second link adaptation is performed if the trigger condition is satisfied at least two times. ### Claim 2 (depends on 1) The method of claim 1, wherein the first link adaptation comprises reporting a preferred resource region determined from the result of the measurement. ### Claim 3 (depends on 2) The method of claim 2, wherein the preferred resource region corresponds to a resource set having a smallest interference among a plurality of resource sets comprising a total resource region. ### Claim 4 (depends on 1) The method of claim 1, wherein the first link adaptation comprises at least power control, modulation and coding scheme (MCS) adjustment or resource adjustment. ### Claim 5 (depends on 1) The method of claim 1, wherein the second link adaptation comprises: transmitting a resource re-allocation request; and receiving a resource reallocation response or a D2D link failure (DLF) command in response to the resource re-allocation request. ### Claim 6 (depends on 5) The method of claim 5, wherein the resource re-allocation response comprises at least information indicating a second resource region different from the first resource region or additional transmit power assignment. ### Claim 7 (depends on 5) The method of claim 5, wherein the DLF command is transmitted when resource re-allocation or additional transmit power assignment is not available. ### Claim 8 (depends on 1) The method of claim 1, further comprising determining D2D link failure (DLF) if a number of times the second link adaptation is performed exceeds a predetermined number. ### Claim 9 (depends on 8) The method of claim 8, further comprising performing D2D communication after the DLF is determined until a confirm message for the DFL is received. ### Claim 10 (depends on 9) The method of claim 9, further comprising nullifying the DLF determination if a signal is successfully transmitted and received more than a predetermined number of times during a time period until the confirm message is received. ### Claim 11 (depends on 1) The method of claim 1, wherein the trigger condition corresponds to a signal-to-noise-plus-interference ratio (SINR) smaller than a predetermined value, receiving a NACK more than a predetermined number of times, not receiving a D2D signal for more than a predetermined number of times or receiving a NACK in response to transmission using a minimum coding rate. ### Claim 12 A device-to-device (D2D) user equipment (UE) in a wireless communication system, the UE comprising: a receive module configured to receive signals; and a processor configured to: perform measurement on a resource region used for D2D communications; determine whether a result of the measurement satisfies a trigger condition, and perform different link adaptation according to a number of times the trigger condition is satisfied for the resource region, wherein first link adaptation is performed if the trigger condition is satisfied one time, and wherein second link adaptation is performed if the trigger condition is satisfied at least two times. ### Claim 13 (depends on 12) The UE of claim 12, wherein the first link adaptation comprises reporting a preferred resource region determined from the result of the measurement. ### Claim 14 (depends on 13) The method of claim 13, wherein the preferred resource region corresponds to a resource set having a smallest interference among a plurality of resource sets comprising a total resource region. ### Claim 15 (depends on 12) The UE of claim 12, wherein the first link adaptation comprises at least power control, modulation and coding scheme (MCS) adjustment or resource adjustment. ### Claim 16 (depends on 12) The UE of claim 12, wherein the second link adaptation comprises: transmitting a resource re-allocation request; and receiving a resource re-allocation response or a D2D link failure (DLF) command in response to the resource re-allocation request. ### Claim 17 (depends on 16) UE of claim 16, wherein the resource re-allocation response comprises at least information indicating a second resource region different from the first resource region or additional transmit power assignment. ### Claim 18 (depends on 16) The UE of claim 16, wherein the DLF command is transmitted when resource re-allocation or additional transmit power assignment is not available. ### Claim 19 (depends on 12) The UE of claim 12, further comprising determining D2D link failure (DLF) if a number of times the second link adaptation is performed exceeds a predetermined number. ### Claim 20 (depends on 12) The UE of claim 12, wherein the trigger condition corresponds to a signal-to-noise-plus-interference ratio (SINR) smaller than a predetermined value, receiving a NACK more than a predetermined number of times, not receiving a D2D signal for more than a predetermined number of times or receiving a NACK in response to transmission using a minimum coding rate.