Document

LoRaWAN® Application Layer Clock Synchronization Specification v1.0.0

Issue link: https://read.uberflip.com/i/1428353

Contents of this Issue

Navigation

Page 6 of 12

LoRaWAN Application Layer Clock Synchronization v1.0.0 Specification ©2018 LoRa Alliance™ Page 7 of 13 The authors reserve the right to change specifications without notice. 3.1 PackageVersionReq & Ans 149 150 The PackageVersionReq command has no payload. 151 The end-device answers with a PackageVersionAns command with the following payload. 152 153 Field PackageIdentifier PackageVersion Size (bytes) 1 1 Table 2: PackageVersionAns 154 PackageIdentifier uniquely identifies the package. For the "clock synchronization package" 155 this identifier is 1. 156 PackageVersion corresponds to the version of the package specification implemented by the 157 end-device. 158 3.2 AppTimeReq & Ans 159 160 The AppTimeReq message is transmitted by the end-device to request a clock correction 161 from the application server. The message is meant to be transmitted periodically by the end- 162 device. The default periodicity is a function of the accuracy required by the application and 163 the maximum clock drift speed of the end-device. 164 This message SHALL only be transmitted a single time with a given DeviceTime payload, as 165 the network reception time stamp will be used by the application server to compute the 166 require clock correction. Therefore the "clock synchronization" package SHALL first 167 temporarily disable ADR and set NbTrans=1 before transmitting this message, then revert 168 the MAC layer to the previous state. 169 170 The AppTimeReq command has the following payload. 171 172 173 Field DeviceTime Param Size (bytes) 4 1 Table 3: AppTimeReq 174 Where: 175 176 Param Fields RFU AnsRequired TokenReq Size (bits) 3bits 1bit 4bits Table 4: Param fields 177 178 DeviceTime is the current end-device clock and is expressed as the time in seconds since 179 00:00:00, Sunday 6th of January 1980 (start of the GPS epoch) modulo 2^32. Note that this 180 is the same format as the Time field in the beacon frame. The time is captured immediately 181 before transmitting the radio packet. The processing delay between the clock time capture 182 and the transmission of the packet should be minimized. The intent is to provide second 183 accurate timing therefore the delay SHALL be < 250mSec. 184 185 TokenReq is a 4 bits counter initially set to 0. TokenReq is incremented (modulo 16) each 186 time the end-device receives and processes successfully an AppTimeAns message. 187 188

Articles in this issue

view archives of Document - LoRaWAN® Application Layer Clock Synchronization Specification v1.0.0