Lynn's Industrial Protocols over IP

Thursday, November 09, 2006

City-wide WiFi - it's not Ethernet

One of my customers is struggling to IP-enable a few dozen Ethernet PLC via one of these new fangled city-wide WiFi systems that are all the rage now. Looked good on paper, but they can only keep the PLCs online for about 20 minutes at a time.

Why? Is the WiFi system defective? Of course not ... it is just behaving more like Wide-Area-Network than Local-Area-Network. I am not directly involved in this, but I'd wager the problem is neither the WiFi nor the PLC. The problem is the host software making Ethenet LAN assumptions about the system. I should offer to go out and do some latency tests; I'd wager the system has high and variable latency more like satellite or cellular.

So industrial control application developers beware, migrating your Ethernet-enabled, LAN-friendly applications to be true IP-enabled, WAN-friendly applications will become more important every time another city annouces the installation of a city-wide wireless infrastructure.

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