Wireless Sensor Networks (W) play an important role in the Internet-of-Things (IoTs). There are several standard protocol stacks developed for communications in such networks. The IEEE 802.15.4 standard is one of the widely used technologies that provides physical and Medium Access Control (MAC) layers for low-power W. The new versions of this standard introduce a MAC operational mode, called Time Slotted Channel Hopping (TSCH), which has become a part of the IETF 6TiSCH standard protocol stack for IoT. This mode makes the network more reliable by alleviating the impact of cross-technology interference and multi-path fading. This is achieved by employing a channel hopping technique. Moreover, the Time Division Multiple Access (TDMA) nature of the TSCH mechanism leads to efficient and deterministic use of the RF channel resources in the WSN. However, the TSCH standard does not specify a scheduling mechanism for packets transmissions in the network; it is left for the upper layers in the protocol stack. Since the performance of the scheduling mechanism directly influences the performance of the TSCH-based networks, considerable research is being done to develop efficient scheduling mechanisms for these networks. The scheduling algorithms may be centralized or distributed. Although the centralized mechanism are able to provide optimum schedules, they are slow and impose a high traffic overhead to the network. In this thesis, a low-latency distributed scheduler, called LaDiS, is proposed. The main objective is to reduce the end-to-end latency of data packets and to provide low duty cycle in 6TiSCH-based networks. The 6TiSCH stack uses the RPL routing protocol. This protocol used some control packet exchanges to construct the routing tree. The proposed LaDiS scheduling algorithm schedules packet transmission timing of the nodes using the available RPL information and the required traffic of the nodes. Thus the communication overhead is very low and the scheduling is accomplished very fast. Moreover, the timeslots are dedicated to different node in such a way so that the timeslot of each parent node is after the timeslots of its children in the RPL tree. This leads to a very low end-to-end data delivery latency. On the other hand, it provides the possibility for the parent nodes to perform data aggregation and integration to reduce data traffic load in the network. LaDiS is implemented and tested in MATLAB as well as the Contiki operating system. The simulation results show that this mechanism outperforms the state of the art distributed schedulers with respect to end-to-end latency and data delivery ratio, while it is faster and imposes lower overhead. Therefore, it is a good option for W with stringent latency and reliability requirements. Key Words : Internet of Things (IoT), Wireless Sensor Networks (W), IEEE 802.15.4, Time Slotted Channel Hopping (TSCH), Distributed Scheduling, RPL