Due to the significant expansion and development of wireless sensor networks and the Internet of Things, many fields of research have been created in various fields, one of the most important of which is industrial wireless sensor networks. These systems require high reliability, and the slightest error can lead to heavy losses and costs. Many protocols and standards have been developed specifically for wireless and low-power industrial networks. The IEEE 802.15.4 standard is one of the standards specifically designed for industrial wireless networks. One of the functional modes of this standard is the time-slotted channel hopping (TSCH) which aims to reduce the destructive effect of external interference with the channel hopping method. Using a subset of high-quality radio channels can significantly increase packet retransmission and data loss. Because many technologies, such as Wi-Fi and Bluetooth, also operate in the 2.4 GHz frequency band, the chances of packets losing and missing are very high. In other words, the devices that use these protocols are considered as interference for TSCH-based networks and have a negative impact on the performance of these networks. In fact, making a good list and eliminating poor-quality radio channels is one of the techniques nowadays referred to as the blacklisting method. Thus, radio channels that are not efficient for any reason are removed from the hopping sequence list and are no longer used. Of course, not all radio channels can be removed from the network, so how you do this is very important. The network structure is also essential; For example, large-scale multi-hop networks with a tree topology are still one of the most challenging structures due to their structural complexity. In this study, a distributed local blacklist method based on TSCH called BLUE-TSCH is presented. In this way, each node can determine its own hopping sequence list based on the environmental conditions it feels around. This method uses two different hopping sequence lists in each node and uses one list to communicate with the children and another list to communicate with the parent node. Thus, each node is responsible for determining the hopping sequence lists to communicate with their children. Also, by providing a particular arrangement of radio channels, the problem of interference between two nodes that are next to each other and use a time slot for transmission can be avoided. In fact, this mechanism prevents the same radio channel from being selected by two nodes in the communication range of each other in a time slot and prevents packets from collisions and packet losses. In the field of discrete mathematics, the logic and theory of this algorithm are strengthened. On the other hand, the computational cost and time overhead of this mechanism is very low. This mechanism does not have a complex computational overhead and is easy to implement, and the only overhead is due to the updating of blacklists in the network; This issue is also managed by considering a special mechanism for updating, and only in certain cases is it necessary to update the network. The simulation uses the TSCH-Sim simulator, one of the newest simulators designed specifically for networks based on the TSCH protocol. To eva‎luate the performance of this method, Wi-Fi sources have been used as a source of interference generation, in different situations and scenarios, along with interference-free modes. Also, by designing a time-varying interference scenario, this mechanismʹs degree of adaptability and agility has been investigated. The simulation results show that BLUE-TSCH is highly adaptable to the interference conditions created and prevents network performance degradation. It also has good performance and efficiency, especially in large-scale multi-hop networks, and has improved the reliability of network data transmission compared to other methods.

مجيد نبي

حسين سعيدي، فرامرز هندسي