Issue link: https://read.uberflip.com/i/1464683
LoRaWAN
®
Fragmented Data Block Transport
Specification TS004-2.0.0
©2022 LoRa Alliance
®
Page 28 of 32
The authors reserve the right to change
specifications without notice.
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Figure 2: 32x32 matrix A built during decoding process
A.3 Performance of the Coding Scheme 724
725
As described in Gallager's thesis, parity check codes have a non-zero statistical overhead, 726
independent of the coded word length. In our case, the word length used is M. The actual 727
overhead depends on the way the parity check matrix is built. To be able to reconstruct the 728
uncoded fragments, the receiver must receive at least M linearly independent coded 729
fragments. In other words, the parity check matrix reconstructed by the receiver based on 730
the fragments received must be of rank M. 731
732
This condition is ideally fulfilled as soon as M coded fragments have been received. But 733
sometimes, those first M fragments that are received are not all independent and the 734
resulting matrix rank is