Issue link: https://read.uberflip.com/i/1507762
Enabling CSMA for LoRaWAN TR013-1.0.0 ©2023 LoRa Alliance ® Page 11 of 18 The authors reserve the right to change specifications without notice. and assigns it to NumBackoff and enters the CSMA process. First device A follows DIFS 317 phase where it completes a successful DIFS slot and enters the BO phase immediately. 318 During the BO phase, device A decrements NumBackoff per each CAD reporting a clear 319 channel. When NumBackoff reaches zero, the frame is transmitted. 320 321 322 Figure 2: Two nodes contending for the same CH/SF combination 323 Figure 2 also illustrates the process where two end-devices, device A and device B, contend 324 for the same CH/SF. Note that, device A and device B start the CSMA process at 325 approximately the same time, and both complete a successful DIFS phase. When device B 326 performs DIFS, it detects a clear channel. Accordingly, device B then enters the BO phase, 327 but with NumBackoff=4. It starts decrementing NumBackoff with each successful CAD 328 and reports a failed CAD in its second BO window. This is because during device B's second 329 BO window, device A starts transmitting, which device B detects as a potential collision. As 330 per the state transition diagram, device B decrements MaxChanges by one, changes 331 channel randomly to one of the AvailableCh and transitions again to the DIFS state. 332 After completing a successful DIFS phase in the new channel, device B immediately 333 transitions to BO phase and resumes decrementing NumBackoff from three. When 334 NumBackoff reaches zero, device B transmits the frame. Upon transmission, the end- 335 device updates AvailableCh and NumAvailableCh. 336 337