www.advantech.com/products Online Download IEEE 802.15.4 IEEE802.15.4isdefinedand maintained by the IEEE organization.The standard intends to offer fundamental lower network layers of low-rate wireless personal area networks (WPANs) which focuses on low-data rates, low-power consumption ubiquitous wireless communication between devices. IEEE 802.15.4 conforming devices may use one of three possible unlicensed frequency bands for operation: ƒ ƒ 868.0-868.6 MHz: Europe, allows one communication channel. ƒ ƒ 902-928 MHz: North America, up to ten channels, extended to thirty. ƒ ƒ 2400-2483.5 MHz: worldwide use, up to sixteen channels. IEEE 802.15.4 defines the Wireless Medium Access Control (MAC) and Physical Layer (PHY) for WPANs only, upper layer stacks can be implemented by users for variety of applications. One example of the known protocols is ZigBee. M2M I/O Modules Overview Network Topologies Wireless Sensor Networks (WSN) can be built using a few or a lot of “nodes”. Each node can be connected to one or several sensors; the network topology is composed of three typical components, PAN Coordinator/Gateway, Router and End Device (or called End Node), which can be built to Star, Tree and Mesh network topologies. Three components of a wireless sensor network ƒ ƒ PAN Coordinator/Gateway A coordinator is the data collection center and also exists as a gateway to transfer and translate wireless data to other interfaces. ƒ ƒ Router A router enhances the wireless signal and a wireless router is used to select the optimal path for wireless communication between the coordinator and the end nodes. ƒ ƒ End Node/Device An end node is a wireless remote I/O for data acquisition. Data is acquired from sensors or devices which are then transmitted through it. The end node communicates with the coordinator directly or via a router to a coordinator. Three Network Topologies Comparison of Topologies Topology Star Tree Mesh Power Consumption Low Medium High Installation Fee Low Medium High Network Coverage Small Large Large Network Capability Small Large Large Reliability Low Low High ƒ ƒ Tree Topology Using a tree topology, the network can be extended through routers making it flexible enough to locate the end nodes in specified locations. Latency is increased with the number of routers hopping. ƒ ƒ Mesh Topology When routers connect to each other in a mesh topology they have the following benefits. 1. Wide network coverage. 2. Robust routing mechanism with self-healing. 3. Multi-hopping mechanism. But also the following limitations: 1. More power consumption than the other topologies. 2. Routing path and hop counts affect the latency and performance. ƒ ƒ Star Topology It‘s the simplest way to construct a network with a gateway and end nodes. The benefit of the topology is that it operates as a low-latency communication network. But has the limitation of low wireless signal coverage. Power & Energy Automation 8 5 4 4 10 Panel PCs 9 iDoor Technology Modules 8 Industrial monitors 7 Industrial IoT Gateways 6 Control Cabinet PCs High-Performance Control Panels Industrial Operator Panels 3 2 IntelligentMotionControl andMachineVision 1 11 Control IPCs 12 Remote DA&C Systems 13 Wireless IoT Sensing Devices 14 15 RS-485 I/O Modules 16 Thin-Client Terminals Industrial Ethernet Solutions 17 IP Gateway and Serial Device Servers iNetworking 18 19 WebAccess+ Solution Ethernet I/O Modules Chapter 14 Table of Contents Table of Contents