  Low Power Wide Area Networks (LPWANs) are gaining ground in the IoT landscape
and, in particular, for Industrial IoT applications. However, given the strict
duty cycle restrictions (e.g. 1% in SubGHz bands) and the limited power supply
of devices, requirements of some applications can not always be met. This paper
analyzes the potential of the combination of packet fragmentation -in the
direction of the IETF LPWAN working group- and negative group acknowledgement
(NACK) in LoRaWAN networks, a widespread LPWAN technology. Results show that
the proposed strategy can lead to significant gains in terms of goodput and
energy efficiency under congested situations.
