# A Survey on Adaptive Data Rate Optimization in LoRaWAN: Recent Solutions and Major Challenges
## 6 Conclusions  
The LoRa specification does not state the way the NS should instruct end nodes pertaining to data rate adaptation. This has resulted in a gap in terms of ADR implementation as vendors keep their implementations private. Because of this, new ADR schemes are always still developing. Considering the strength and weaknesses of existing ADR schemes paves way for more efficient and effective algorithms. This paper reviewed the ADR schemes that have been proposed in the public domain and classified the solutions. We discussed the impact of the ADR solutions on the performance of LoRaWAN networks. There are numerous ADR schemes that have been proposed in literature that used different techniques to accomplish desired optimization goals depending on the objective of the scheme responding to specific performance needs and applications. The study revealed that although the transmission parameters are standard, the methods and considerations for ADR to improve network performance are countless. We identified the gaps in literature and propose future work on ADR optimization. Although existing solutions achieved promising performances, they are not optimal, therefore there it is essential to find efficient solutions. To this end, ADR algorithms can be improved to increase the energy efficiency and performance of energy-constrained end nodes. Conceptualization, A.M.A.-M. and G.P.H. ; methodology, R.K. and A.M.A.-M.; writing--original draft preparation, R.K.; writing--review and editing, G.P.H., A.M.A.-M. and R.K.; visualization, R.K.; supervision, G.P.H. and A.M.A.-M.; project administration, A.M.A.-M. and G.P.H. ; funding acquisition, G.P.H. All authors have read and agreed to the published version of the manuscript. This research received no external funding. The authors declare no conflict of interest. Appendix A* _[PERSON] et al. (2019)_ [PERSON] _LoRa and LoRaWAN-A Technical Overview_; White Paper; LoRa Alliance: Boston, MA, USA, 2019. * _[PERSON] et al. (2018)_ [PERSON] [PERSON]; [PERSON]; [PERSON] [PERSON] Security risk analysis of LoRaWAN and future directions. _Futur. Internet_**2018**, _11_, 3. [CrossRef]
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