When devices want to join a WirelessHART network, they begin by listening for advertisements to join the network. Since the protocol utilizes channel hopping, the device while spend some time listening on each of the various channels. With an advertisement for the appropriate network, it also receives information on which channels the network uses. While waiting to join, it continues to update information on nearby devices on the network. When the device transmits a request to join, it also transmits a report on the signal levels of the neighbors it has identified. The network manager uses this information to provide the new device with routing information. It will also update neighboring devices. Keeping it current The network manager requests devices on the network send status information on their neighbors on a regular basis. If a device has dropped out of the network for some reason, the network manager can detect this disappearance through these reports. The network manager routinely optimizes the network and transmits new routing information to each device. In this way, devices may find themselves with a new set of neighbors to track. The buddy system – on steroids It’s a bit like the buddy system. When a group goes swimming, everyone pairs up with a buddy. Every so often, the leader asks everyone to hold up the hand of their buddy. If your buddy has drowned, you don’t have a hand to hold up. Of course the point is to notify the leader your buddy is drowning before it’s too late. Now imagine instead of one buddy, each swimmer had three, four, or more buddies to track. Anyone within site is a buddy. While you don’t get the same personal attention, the odds of detecting a problem increase. Additionally, if each swimmer only has one buddy a problem occurs if someone has to leave the pool. His buddy would be left alone. With multiple buddies this problem is avoided. While having kids in a swimming pool keep track of several other kids might be too much to ask of even the most responsible child, it is no problem for devices in a WirelessHART network. Once they detect other devices nearby, they will track the status of those neighbors and transmit the data to the network manager.