The Realities of Dealing with Wireless Mesh Networks
Mesh networking is the hot new thing, whether it’s of the wired or wireless type. Mesh-networked wireless sensor systems promise an easy way to deploy nodes in various physical environments, and while this topology does offer operational performance improvements over its counterpart topologies, there are inherent limitations that you should understand before adopting this information delivery method.
The most recent addition to the wireless networking family revolves around an ad hoc distribution of network nodes. This situation, typified by a mesh network shown in Figure 2, imposes an additional requirement on the individual nodes: They must agree to pass on messages from their nearest neighbors.
n some applications information may be completely inside the mesh network (e.g., a light switch activating a light); in other applications, information must be presented to “the outside.” The ZigBee Alliance nomenclature defines a network coordinator that may be the natural choice for presenting this information to the rest of the world, but other devices with a long-haul or broadband network link may fill this role as well. We’ll call this device the “data gateway.” The sources of the information, i.e., the sensors and radio transceivers, are referred to as “end devices.” The routers serve as repeaters. Notice that if each end device communicates directly with the data gateway, the “mesh” reverts to the classic star topology.
In a real-world mesh network, the network provides each node with multiple data transmission paths, forming a mesh. Each node communicates its existence as well as other information with its neighbors, allowing various algorithms to determine the best way to transmit end-device data to the network coordinator. Some networks communicate this information on demand, when a message needs to be sent, while others maintain it actively. In either case, transmission of network information takes up bandwidth, reducing the maximum bandwidth available to the sensor.
The most recent addition to the wireless networking family revolves around an ad hoc distribution of network nodes. This situation, typified by a mesh network shown in Figure 2, imposes an additional requirement on the individual nodes: They must agree to pass on messages from their nearest neighbors.
n some applications information may be completely inside the mesh network (e.g., a light switch activating a light); in other applications, information must be presented to “the outside.” The ZigBee Alliance nomenclature defines a network coordinator that may be the natural choice for presenting this information to the rest of the world, but other devices with a long-haul or broadband network link may fill this role as well. We’ll call this device the “data gateway.” The sources of the information, i.e., the sensors and radio transceivers, are referred to as “end devices.” The routers serve as repeaters. Notice that if each end device communicates directly with the data gateway, the “mesh” reverts to the classic star topology.
In a real-world mesh network, the network provides each node with multiple data transmission paths, forming a mesh. Each node communicates its existence as well as other information with its neighbors, allowing various algorithms to determine the best way to transmit end-device data to the network coordinator. Some networks communicate this information on demand, when a message needs to be sent, while others maintain it actively. In either case, transmission of network information takes up bandwidth, reducing the maximum bandwidth available to the sensor.
posted by DC at 12:48 AM
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