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TS004-2.0.0 Fragmented Data Block Transport

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LoRaWAN ® Fragmented Data Block Transport Specification TS004-2.0.0 ©2022 LoRa Alliance ® Page 17 of 32 The authors reserve the right to change specifications without notice. Where: 474 Bits 7:2 1:0 Param Bits RFU FragIndex Table 22: FragDataBlockReceivedAns Param bits The FragIndex field SHALL match the FragIndex field of the 475 FragDataBlockReceivedReq that is being acknowledged. 476 3.6 Data Fragment Message (DataFragment) 477 478 This message can be received by the end-device in a multicast or unicast downlink frame 479 and is used to carry a data block fragment. 480 481 The payload content is: 482 483 Size (octets) 2 0:MaxAppPl-3 DataFragment Field Index&N Table 23: Downlink Data Fragment payload MaxAppPl is the maximum LoRaWAN application payload size. 484 485 Bits 15:14 13:0 Index&N Fields FragIndex N Table 24: Downlink Data Fragment Index&N format If this message was received on a multicast address, the end-device SHALL check that the 486 multicast address used was enabled at the creation of the fragmentation session through the 487 McGroupBitMask field of the FragSessionSetupReq command. If not, the frame SHALL 488 be silently dropped. 489 490 is the fragment N over M of the session. 491 492 More than M fragments MAY actually be transmitted to add redundancy and packet loss 493 robustness. 494 495 N is the index of the coded fragment transported and is incremented starting from 1. 496 M is equal to the NbFrag parameter. 497 498 If a fragment is received multiple times by the end-device, only one occurrence SHALL be 499 kept and other identical fragments SHALL be silently discarded. 500 501 Once the data block has been reconstructed, the end-device SHALL drop any further 502 message using that FragIndex until the fragmentation session is first deleted and a new 503 fragmentation session is set up through the FragSessionSetupReq command. 504

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