Issue link: https://read.uberflip.com/i/1507762
Enabling CSMA for LoRaWAN TR013-1.0.0 ©2023 LoRa Alliance ® Page 8 of 18 The authors reserve the right to change specifications without notice. respectively. In both cases, the end-device state is set back to DIFS, and should perform the 217 next DIFS phase after configuring the radio to an unused channel pseudo-randomly, while 218 maintaining the same SF. 219 220 However, certain regulatory authorities, such as the [FCC], mandate equal use of all channels, 221 i.e., a channel that was utilized for transmission once should not be utilized again until all other 222 channels have been transmitted on. Therefore, when a CAD reports a busy channel during 223 either the DIFS or BO phase, the available channels for the end-device are limited to the 224 number of remaining unused channels (NumAvailableCh), where AvailableCh is the 225 list of those channels. Suppose an end-device has eight available channels and only one of 226 them has been used previously for a transmission. During the next transmission, the end- 227 device should only attempt to transmit on one of the seven remaining channels. 228 229 The end-device may restrict the number of channel hops per frame by setting the 230 MaxChanges parameter. Upon finding a busy channel, the end-device will channel-hop a 231 maximum number of MaxChanges times before defaulting to ALOHA. The list 232 AvailableCh is reset when all channels have been transmitted on. The variable 233 MaxChanges is reset for each new frame. Usage of MaxChanges is further discussed in 234 Section 4.2.1. 235 236 Another reason for adopting both the BO phase and the DIFS phase is when an application 237 requires prioritization of some end-devices. In a network where all end-devices use both BO 238 phase and DIFS phase, nodes that utilize lower BACKOFF_MAX values will receive an 239 advantage in capturing the channel. The reason for the prioritization is as follows. After 240 completing a successful DIFS phase, the random number of BO slots 241 (NumBackoff)assigned to the prioritized end-device will be lower than that assigned to a 242 non-prioritized end-device due to the lower BACKOFF_MAX value. Therefore, devices with 243 lower BACKOFF_MAX values are more likely to capture the channel faster as opposed to 244 others under the same CH/SF. 245 246