In recent years, LoRaWAN has been considered as one of the commonest low power area network technologies and has gained much attention due to the rapid growth of Internet of Things (IoT) market and applications. Its communication is characterized by very low power consumption, low cost, extensive network coverage and so on. However, LoRaWAN is faced with scalability challenge, which has affected its adoption. This challenge has attracted several research attentions and is far from over. Therefore, this paper performed a review on existing works, about 13 papers on LoRa/LoRaWAN were reviewed focusing on several challenges and solution methods for IoT applications. The analysis shows that LoRaWAN is effective for IoT deployment and confirmed the existence of scalability challenge which is still an open issue. Moreover, scalability issue often give rise to other challenges such as network coverage, capacity, and interference.