Читать книгу Industry 4.0 Vision for the Supply of Energy and Materials - Группа авторов - Страница 37

It was approved in 2002 and designed for short-range, low-power, and low-cost connectivity in WPAN applications. IEEE 802.15.1 is established on Bluetooth v1.1 foundation specifications that govern Bluetooth technology [79]. There are two main variations of this technology: classic Bluetooth and Bluetooth low energy (BLE). Classic Bluetooth supports devices with high demand of small transmission and low energy consumption, whereas BLE is ideal for applications that require communication of small quantities of data on an occasional or periodic basis.

Bluetooth classic. The Bluetooth PHY layer is adapted from the IEEE 802.15.1 standard and operates in the frequency band of 2.4 GHz. Its transmission technique exploits frequency hopping spread spectrum (FHSS). This results in the reduction of interference from nearby systems sharing the same frequency band (ISM band) and increases system robustness. Bluetooth defines two types of network topologies, namely, piconet and scatternet. Piconet is a single-hop topology that enables communication between one master node and multiple slave nodes. A scatternet topology is a cluster of Bluetooth piconets overlapping in space and time; there is only one master node, while a slave node could operate as slave in different piconets. Bluetooth MAC layer mainly focuses on establishing physical connections between the master and slaves, synchronizing network nodes with the master node’s clock, packet transmission on physical channels, and device management for energy-saving modes [80].

Bluetooth low energy (BLE). A smart variation of the IEEE 802.15.1 standard, also known as Smart Bluetooth, BLE supports industrial wireless communication [81]. It is designed for short-range communication and, compared with classic Bluetooth, has much smaller latency, lower energy consumption, and increased range with higher data rates [49]. BLE adopts master–slave architecture, and role of a device (as master or slave) is defined in its MAC layer. To decrease channel sensitivity to interference and multipath fading, BLE employs TDMA-based MAC protocol and frequency hopping [82]. Additionally, the center frequency of channels has been assigned in a way to minimize interference with IEEE 802.11 channels [57]. Even though there are options to increase BLE’s data rate at the expense of range, the limited range of BLE makes it inept for extensive IIoT deployments. To address this problem, a Bluetooth mesh network is introduced to increase the number of relaying neighbors, making it applicable to industrial use cases such as alerting and logging systems [83]. Recently most wearables are equipped with BLE interfaces. Overall, considering its low power consumption, BLE could be utilized as a practical and effective wireless technology for IoT applications that require short-range communication [68, 81].