Table 1.
Main symbols used in this paper.
| Symbols | Meaning |
|---|---|
| λl | Traffic generation probability at CoAP layer |
| αl,j | Busy channel probability of node l at the backoff stage j |
| Average busy channel probability for all backoff stages | |
| τl | Channel access probability of node l |
| Idle probability of node l | |
| c | Maximum number of CoAP retransmissions |
| m0 | Initial backoff exponent macMinBE |
| mB | Maximum backoff exponent macMaxBE |
| m | Maximum number of backoff macMaxCSMABackoffs |
| n | Maximum number of MAC retransmissions macMaxFrameRetries |
| ql | Probability of generating the first fragment or block of an update at node l |
| Sb | Backoff unit time aUnitBackoffPeriod |
| N | Number of nodes in the network |
| F | Number of 6LoWPAN fragments composing an update |
| B | Number of CoAP blocks composing an update |
| L | Fragment or block size |
| LACK | CoAP ACK size |
| LMAC ACK | MAC ACK size |
| Leq | Vulnerability window for the CCA |
| Pcoll,l | Collision probability of node l |
| Pframe,l | Probability that the transmission of a block, fragment or CoAP ACK for node l fails |
| Pcf,l | Probability for node l that the frame is discarded due to channel access failure |
| Pcr,l | Probability for node l of a frame to be discarded due to MAC retry limit |
| Pblock,l | Probability that a single block fails at node l |
| Pfrag,l | Probability that a 6LoWPAN fragmented update fails at node l |
| Perrblock,l | Probability that a block is retransmitted at node l |
| Perrfrag,l | Probability that a 6LoWPAN fragmented update is retransmitted at node l |
| Packblock,l | Probability that the transmission of the CoAP ACK relative to a block transmission fails |
| Packfrag,l | Probability that the transmission of the CoAP ACK relative to a 6LoWPAN fragmented update fails |
| Pfailblock,l | Probability that an update sent using blockwise transfer fails |
| Pfailfrag,l | Probability that an update sent using 6LoWPAN fragmentation fails |
| Rblock,l | End-to-end reliability for blockwise transfer |
| Rfrag,l | End-to-end reliability for 6LoWPAN fragmentation |
| Dfrag,l | Delay of a successful received 6LoWPAN fragmented update |
| Dblock,l | Delay of a successful received update using blockwise transfer |
| Dframe,l | Delay for successfully received frame |
| DACK,l | Delay for successfully received CoAP ACK |
| RTO | CoAP retransmission timeout |