Issue link: https://read.uberflip.com/i/1428383
LoRaWAN 1.0.3 Specification ©2018 LoRa™ Alliance Page 65 of 72 The authors reserve the right to change specifications without notice. transmission happens on a new frequency channel, but can also happen at a different data 1676 rate (preferable lower) than the previous one. It is strongly recommended to adopt the 1677 following re-transmission strategy. 1678 The first transmission of the "confirmed" frame happens with a data rate DR. 1679 1680 Transmission nb Data Rate 1 (first) DR 2 DR 3 max(DR-1,0) 4 max(DR-1,0) 5 max(DR-2,0) 6 max(DR-2,0) 7 max(DR-3,0) 8 max(DR-3,0) The Data Rate max(a,b) stands for maximum of a and b values. 1681 If after a recommended 8 transmissions, the frame has not been acknowledged the MAC layer 1682 should return an error code to the application layer. 1683 Note: For each re-transmission, the frequency channel is selected 1684 randomly as for normal transmissions. 1685 Any further transmission uses the last data rate used. 1686 For example if an end-device sends a "confirmed" frame first using DR5 and has to retransmit 1687 3 times (twice at DR5 then twice at DR4), the next frame transmitted will use DR4 1688 Other example, if an end-device sends a "confirmed" frame first using DR5 and does not 1689 receive an acknowledge after 8 transmissions (2 at DR5, 2 at DR4, … , 2 at DR2), and the 1690 application of this end-device re-initiates a "confirmed" transmission a little later, the first two 1691 transmission will be tentatively at DR2, then switch to DR1, then to DR0. 1692