Multimedia Internet of Things: A Comprehensive Survey <s> A. EXISTING WORK ON M-IoT APPLICATIONS IN THE CONTEXT OF PHY-MAC PROTOCOLS 1) INDUSTRIAL APPLICATIONS <s> Industrial applications of wireless sensor networks require timeliness in exchanging messages among nodes. Although IEEE 802.15.4 provides a superframe structure for real-time communication, a real-time message-scheduling algorithm is still required to schedule a large number of real-time messages to meet their timing constraints. We propose a distance-constrained real-time offline message-scheduling algorithm which generates the standard specific parameters such as beacon order, superframe order, and guaranteed-time-slot information and allocates each periodic real-time message to superframe slots for a given message set. The proposed scheduling algorithm is evaluated and analyzed extensively through simulations. In addition, a guaranteed time service is implemented in a typical industrial sensor node platform with a well-known IEEE 802.15.4-compliant transceiver CC2420 and ATmega128L to verify the feasibility of the guaranteed time service with the schedule generated by the proposed scheduling algorithm. Through experiments, we prove that the real system runs accurately according to the schedule calculated by the proposed algorithm. <s> BIB001 </s> Multimedia Internet of Things: A Comprehensive Survey <s> A. EXISTING WORK ON M-IoT APPLICATIONS IN THE CONTEXT OF PHY-MAC PROTOCOLS 1) INDUSTRIAL APPLICATIONS <s> The IEEE 802.15.4 protocol offers great potential for industrial wireless sensor networks, especially when operating in beacon-enabled mode over star or cluster-tree topologies. However, it is known that beacon collisions can undermine the reliability of cluster-tree networks, causing loss of synchronization between nodes and their coordinator. For this reason, this paper proposes a Multichannel Superframe Scheduling (MSS) algorithm, a novel technique that avoids beacon collisions by scheduling superframes over different radio channels, while maintaining the connectivity of all the clusters. The paper describes the MSS algorithm and addresses the advantages it provides over the time-division superframe scheduling. Analytical results are shown which provide a quantitative estimation of how the schedulability space is improved, while simulation results show that the proposed technique increases the number of schedulable clusters and the maximum cluster density. Finally, this paper proves the feasibility of the proposed approach describing a working implementation based on TinyOS. <s> BIB002
The IEEE 802.15.4 standard has been identified as a suitable technology for industrial applications owing to the features it offers in this domain such as support for a peer-to-peer topology and beaconing in the MAC protocol. The different beacon intervals for the IEEE 802.15.4 superframes leads to a scheduling problem in the network. Toscano and Bello BIB002 present a solution for the scheduling problems in the multichannel networks. The key concept underlying the Multichannel Superframe Scheduling (MSS) algorithm is utilizing the maximum superframe duration to determine the length of the timeslice and to schedule all the superframes within the same timeslice on different channels BIB002 . The experimental results reveal the beacons are perfectly aligned, and through the tracking of the parents, the synchronization is maintained. This is not feasible in the time-division approach. Chen et al.  present a case for the use of IEEE 802.15.4 in the industrial scenario. The experimental evaluation of the standard is carried out in the OMNET++/INET framework that tests the large scale deployment of the nodes in an industrial setup. The node energy efficiency and the goodput support the argument for industrial applications. The Time Division Multiple Access (TDMA) approach is used with the Guaranteed Time Slot (GTS) that enhances reliability. The authors in BIB001 also propose a GTS based real-time messaging service in the industrial environment. Kim et al. in [272] allow a periodic synchronization of the node network clocks using Enhanced Beacons (EBs). The synchronization allows efficient scheduling in the proposed Time Slotted Channel Hopping (TISH) mode. The overall result is the reduction in energy consumption and traffic collisions compliant with industrial standards. 