Issue link: https://read.uberflip.com/i/1428350
LoRaWAN Remote Multicast Setup v1.0.0 Specification ©2018 LoRa Alliance™ Page 14 of 18 The authors reserve the right to change specifications without notice. 409 McGroupID is the identifier of the multicast group being used. 410 411 SessionTime is the start of the Class B window, and is expressed as the time in seconds 412 since 00:00:00, Sunday 6th of January 1980 (start of the GPS epoch) modulo 2^32. Note that 413 this is the same format as the Time field in the beacon frame. SessionTime MUST be an 414 integer multiple of 128. 415 416 TimeOut encodes the maximum length in BeaconPeriods (128seconds) of the multicast 417 fragmentation session (max time the end-device stays in classB before eventually reverting 418 to class A to save battery) 419 The maximum duration in second is 128*2 TimeOut (Example: TimeOut=8 corresponds roughly 420 to 9.1hours). 421 Attention: For classB TimeOut is expressed in BeaconPeriod 422 (128sec), whereas it is expressed in seconds for classC. This is 423 because a classB multicast session is heavily duty-cycled and is likely 424 to last a lot longer than a classC session. 425 This is a maximum duration because the end-device's application might decide to revert to 426 class A before the end of the session, this decision is application specific. 427 Periodicity encodes the classB ping slot periodicity for the multicast group. The encoding 428 format is the same than for the Periodicity field of the PingSlotInfoReq classB MAC 429 command defined in LoRaWAN. 430 431 DlFrequ: Encodes the frequency used for the multicast. This field is a 24 bits unsigned 432 integer. The actual channel frequency in Hz is 100 x DlFrequ whereby values representing 433 frequencies below 100 MHz are reserved for future use. This allows setting the frequency of 434 a channel anywhere between 100 MHz to 1.67 GHz in 100 Hz steps. 435 This field has the same meaning and coding as LoRaWAN NewChannelReq MAC command 436 'Freq' field. 437 In regions where the classB beacon is transmitted following a frequency hopping pattern, 438 DlFrequ=0 signals the end-device to use the default classB default frequency hopping 439 scheme. That scheme is defined in the classB section of the LoRaWAN specification. In that 440 case, Class B downlinks use a channel which is a function of the Time field of the last 441 beacon (see Beacon Frame content) and the multicast address McAddr. 442 Class B downlink channel = [ McAddr + floor ( Beacon_Time Beacon_period ) ] modulo NbChannel 443 • Whereby Beacon_Time is the 32-bit Time field of the current beacon period 444 • Beacon_period is the length of the beacon period (defined as 128sec in the 445 specification) 446 • Floor designates rounding to the immediately lower integer value 447 • McAddr is the 32-bit network address of the multicast group 448 • NbChannel is the number of channel over which the beacon is frequency hopping 449 450 451 DR: index of the data rate used for the classB multicast. Uses the same look-up table than 452 the one used by the LinkAdrReq MAC command of the LoRaWAN protocol. 453 454