# US 12,120,709 B2 · RTT-aware scheduling of downlink transmissions to energy-constrained devices on low-power wide-area networks > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,120,709 B2 - Document ID: US12120709B2 - Status: Granted - Kind: B2 - Application number: 17/498,608 - Filed: 2021-10-11 - Published: 2023-04-13 - Granted: 2024-10-15 - Earliest claimed: 2021-10-11 - Assignees: Hughes Network Systems, LLC - Applicants: Hughes Network Systems, LLC - Inventors: Chi-Jiun Su - Web page: https://patentgrep.com/patent/US12120709B2 ## CPC - H04L 47/28: in relation to timing considerations - H04W 72/27: between access points - H04L 43/0864: Round trip delays - H04L 43/16: Threshold monitoring - H04W 28/0226: {based on location or mobility (handoff or reselection H04W36/00; mobile application services making use of the location of users or terminals H04W4/02)} - H04W 28/0231: {based on communication conditions (dynamic wireless traffic scheduling definition based on channel quality criteria H04W72/54)} - H04W 28/0247: {based on conditions of the access network or the infrastructure network (central resource management H04W28/16)} - H04W 72/0446: Resources in time domain, e.g. slots or frames - H04W 72/542: using measured or perceived quality - H04W 88/16: Gateway arrangements - H04L 41/142: using statistical or mathematical methods - H04L 43/0829: Packet loss - H04L 43/0876: Network utilisation, e.g. volume of load or congestion level - H04W 4/70: Services for machine-to-machine communication [M2M] or machine type communication [MTC] - H04W 24/02: Arrangements for optimising operational condition - H04W 24/08: Testing, {supervising or monitoring} using real traffic - Y02D 30/70: in wireless communication networks - 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) - Y02D: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE ## Abstract Some implementations of the disclosure relate to a backend server that is configured to perform operations including: determining one or more radio frequency (RF) gateways that are candidates for communicating with an end device over a RF link in a low-power wide-area network (LPWAN); obtaining, for each of the one or more RF gateways, a round trip time (RTT) of communications between the backend server and the RF gateway over a backhaul link; determining whether at least one of the one or more RTTs exceeds a threshold value; and when at least one of the one or more RTTs exceeds the threshold value, increasing a configured time interval between transmission of an uplink message by the end device and a downlink receive time slot in which the end device is configured to listen for a downlink message. ## Claims ### Claim 1 A backend server, comprising: one or more processors; and one or more non-transitory computer-readable storage medium storing instructions that, when executed by the one or more processors, cause the backend server to perform operations comprising: determining one or more radio frequency (RF) gateways that are candidates for communicating with an end device over a RF link in a low-power wide-area network (LPWAN), the end device being energy-constrained and configured to listen for downlink communications only during pre-specified time slots after uplink transmission by the end device; obtaining, for each of the one or more RF gateways, a round trip time (RTT) of communications between the backend server and the RF gateway over a backhaul link; determining whether at least one of the one or more RTTs exceeds a threshold value that is less than or equal to a configured time interval for the end device, the configured time interval corresponding to a time between transmission of an uplink message by the end device and a downlink receive time slot in which the end device is configured to listen for a downlink message, scheduled by the backend server, that is transmitted by the one or more RF gateways; and when at least one of the one or more RTTs exceeds the threshold value, increasing the configured time interval. ### Claim 2 (depends on 1) The backend server of claim 1, wherein obtaining for each of the one or more RF gateways, the RTT of communications between the backend server and the RF gateway over the backhaul link, comprises: passively measuring, using a transport layer network protocol, the RTT. ### Claim 3 (depends on 2) The backend server of claim 2, wherein passively measuring, at the backend server, using the transport layer network protocol, the RTT, comprises: reading, via an application programming interface (API) provided for the transport layer network protocol, real time values of protocol parameters or statistics corresponding to the RTT. ### Claim 4 (depends on 1) The backend server of claim 1, wherein obtaining for each of the one or more RF gateways, the RTT of communications between the backend server and the RF gateway over the backhaul link, comprises: passively measuring, using an application layer network protocol, the RTT. ### Claim 5 (depends on 4) The backend server of claim 4, wherein passively measuring, using the application layer network protocol, the RTT, comprises: transmitting a data packet from the backend server to the RF gateway; in response to transmitting the data packet, receiving an acknowledgement at the backend server from the RF gateway; and determining the RTT based on a transmission time of the data packet and a reception time of the acknowledgement. ### Claim 6 (depends on 1) The backend server of claim 1, wherein the end device is a battery powered device. ### Claim 7 (depends on 1) The backend server of claim 1, wherein increasing the configured time interval comprises: increasing the configured time interval such that the configured time interval is at least greater than a maximum RTT of the one or more RTTs. ### Claim 8 (depends on 7) The backend server of claim 7, wherein the operations further comprises: after increasing the configured time interval, deploying the end device in the LPWAN. ### Claim 9 (depends on 7) The backend server of claim 7, wherein determining one or more RF gateways that are candidates for communicating with the end device over the RF link in the LPWAN, comprises: determining a geographical location of the end device; and determining that the geographical location is within a coverage area where each of the one or more RF gateways is capable of receiving uplink transmissions form the end device. ### Claim 10 (depends on 1) The backend server of claim 1, wherein the operations further comprise: scheduling, based at least on the one or more RTTs, one or more downlink receive time slots of the end device for a first RF gateway of the one or more RF gateways to transmit a downlink message to the end device; and transmitting the downlink message from the backend server to the first RF gateway that sends the downlink message to the end device during the one or more downlink receive time slots. ### Claim 11 (depends on 10) The backend server of claim 10, wherein determining the one or more RF gateways that are candidates for communicating with the end device over the RF link in the LPWAN, comprises: determining a plurality of RF gateways that forwarded, to the backend server, a same uplink message from the end device; determining the one or more RF gateways from the plurality of RF gateways by determining that each of the one or more RF gateways: meets an RF signal quality metric threshold of an RF signal received over the RF link from the end device; and meets a link quality metric threshold of communications over the backhaul link with the backend server. ### Claim 12 A method, comprising: determining, at a backend server, one or more radio frequency (RF) gateways that are candidates for communicating with an end device over a RF link in a low-power wide-area network (LPWAN), the end device being energy-constrained and configured to listen for downlink communications only during pre-specified time slots after uplink transmission by the end device; obtaining, at the backend server, for each of the one or more RF gateways, a round trip time (RTT) of communications between the backend server and the RF gateway over a backhaul link; determining, at the backend server, whether at least one of the one or more RTTs exceeds a threshold value that is less than or equal to a configured time interval for the end device, the configured time interval corresponding to a time between transmission of an uplink message by the end device and a downlink receive time slot in which the end device is configured to listen for a downlink message, scheduled by the backend server, that is transmitted by the one or more RF gateways; and in response to determining that at least one of the one or more RTTs exceeds the threshold value, increasing, at the backend server, the configured time interval. ### Claim 13 (depends on 12) The method of claim 12, wherein obtaining for each of the one or more RF gateways, the RTT of communications between the backend server and the RF gateway over the backhaul link, comprises: passively measuring, at the backend server, using a transport layer network protocol or an application layer network protocol, the RTT. ### Claim 14 (depends on 12) The method of claim 12, wherein: the end device is a battery powered device. ### Claim 15 (depends on 14) The method of claim 14, wherein increasing, at the backend server, the configured time interval comprises: increasing the configured time interval such that the configured time interval is at least greater than a maximum RTT of the one or more RTTs. ### Claim 16 A backend server, comprising: one or more processors; and one or more non-transitory computer-readable storage medium storing instructions that, when executed by the one or more processors, cause the backend server to perform operations comprising: determining a first plurality of radio frequency (RF) gateways that forwarded to the backend server an uplink message transmitted by an end device over a RF link in a low-power wide-area network (LPWAN), the end device being energy-constrained and configured to listen for downlink communications only during pre-specified time slots after uplink transmission by the end device; determining one or more RF gateways of the plurality of RF gateways that are eligible to send a downlink message to the end device over the RF link; obtaining, for each of the one or more RF gateways, a round trip time (RTT) of communications between the backend server and the RF gateway over a backhaul link; determining whether any of the one or more RTTs exceeds a threshold value that is less than or equal to a configured time interval, the configured time interval corresponding to a time between transmission of the uplink message by the end device and a first downlink receive time slot of one or more downlink receive time slots in which the end device is configured to listen for a downlink message; in response to determining that none of the RTTs exceeds the threshold value, scheduling, based at least on the one or more RTTs, the one or more downlink receive time slots of the end device for a first RF gateway of the one or more RF gateways to transmit a downlink message to the end device; and transmitting the downlink message from the backend server to the first RF gateway to send to the end device during the one or more downlink receive time slots. ### Claim 17 (depends on 16) The backend server of claim 16, wherein: scheduling, based at least on the one or more RTTs, one or more downlink receive time slots of the end device for the first RF gateway of the one or more RF gateways to transmit the downlink message to the end device, comprises: determining, based at least on the one or more downlink receive time slots, a schedule time interval before sending the downlink message to arrive at the RF gateway from the backend server; and transmitting the downlink message from the backend server to the first RF gateway, comprises: transmitting, after the schedule time interval, the downlink message from the backend server to the first RF gateway. ### Claim 18 (depends on 16) The backend server of claim 16, wherein the end device is a battery powered device.