Issue link: https://read.uberflip.com/i/1428383
LoRaWAN 1.0.3 Specification ©2018 LoRa™ Alliance Page 15 of 72 The authors reserve the right to change specifications without notice. 4 MAC Message Formats 359 All LoRa uplink and downlink messages carry a PHY payload (Payload) starting with a single- 360 octet MAC header (MHDR), followed by a MAC payload (MACPayload) 1 , and ending with a 361 4-octet message integrity code (MIC). 362 363 Radio PHY layer: 364 Preamble PHDR PHDR_CRC PHYPayload CRC* Figure 5: Radio PHY structure (CRC* is only available on uplink messages) 365 PHYPayload: 366 MHDR MACPayload MIC or 367 MHDR Join-Request MIC or 368 MHDR Join-Response MIC Figure 6: PHY payload structure 369 MACPayload: 370 FHDR FPort FRMPayload Figure 7: MAC payload structure 371 FHDR: 372 DevAddr FCtrl FCnt FOpts Figure 8: Frame header structure 373 Figure 9: LoRa message format elements 374 4.1 MAC Layer (PHYPayload) 375 376 Size (bytes) 1 1..M 4 PHYPayload MHDR MACPayload MIC Table 1: PHY payload format 377 The maximum length (M) of the MACPayload field is region specific and is specified in 378 Chapter 6. 379 4.2 MAC Header (MHDR field) 380 381 Bit# 7..5 4..2 1..0 MHDR bits MType RFU Major 382 The MAC header specifies the message type (MType) and according to which major version 383 (Major) of the frame format of the LoRaWAN layer specification the frame has been encoded. 384 1 Maximum payload size is detailed in the Chapter 6.