Correction: Suwannapong, C. et al. Congestion Control in CoAP Observe Group Communication. Sensors 2019, 19, 3433

The authors wish to make the following corrections to this paper [1]:

We have found two inadvertent errors in our paper published in this Sensors [1]:

1. In Section 3. of this paper [1], the sentence “Moreover, in each retransmission, the FPB (i.e., Fibonacci fib n, n = {1, 2, 3, 5}) was multiplied by the RTO_previous to determine the new RTO timer for the next retransmission.” This sentence should be modified to state: “Moreover, in each retransmission, the FPB (i.e., Fibonacci fib n, n = {1, 2, 3, 5}) was multiplied by the RTO_init to determine the new RTO timer for the next retransmission.”

2. In Section 3. of this paper [1], the following Algorithm 1 should be replaced with the Algorithm shown below it.

Algorithm 1. Fibonacci Pre-Increment Backoff

Initialize random value from [2 s, 4 s] to RTOinit Initialize Fibonacci to [1, 2, 3, 5] when transmitting CON  RTO = RTOinit  for i = 0 to (size of Fibonacci)-1    RTOprevious = RTO    if RTO expires without having received an ACK = RTO      RTO = RTOprevious * Fibonacci[i]      i = i+1    else  return transmission success return transmission fail endfor

Algorithm 1. Fibonacci Pre-Increment Backoff

Initialize random value from [2 s, 4 s] to RTOinit Initialize Fibonacci to [1, 2, 3, 5] when transmitting CON  RTO = RTOinit  for i = 0 to (size of Fibonacci)-1    if RTO expires without having received an ACK      RTO = RTOinit * Fibonacci[i]      i = i+1    else      return transmission success   endfor return transmission fail

The changes do not affect the scientific results. The manuscript will be updated, and the original will remain online on the article webpage, with a reference to this Correction. The authors would like to apologize for any inconvenience caused to the readers by these changes.