The development of network technologies has prompted sensor folks to consider alternatives that reduce costs and complexity and improve reliability. Early sensor networks used simple twisted shielded–pair (TSP) implementations for each sensor. Later, the industry adopted multidrop buses (e.g., Ethernet). Now we’re starting to see true web-based networks (e.g., the World Wide Web) implemented on the factory floor.
Figure 1. In point-to-point network topologies, each sensor node requires a separate twisted shielded–pair wire connection. The cost is high, configuration management is difficult, and nearly all the information processing is done by the host.

As wireless sensors become real commodities on the market, new options or new arguments for old options are causing professionals to consider network strategies once ruled out. Let’s look at the three classic network topologies (point-to-point, multidrop, and web), assess their strengths and weaknesses, and look at how the rules have changed now that wireless systems are coming online.

In addition, to build functional sensor networks, you’ll probable have to integrate hardware and software from multiple vendors (see the sidebar “Network Questions,”). So along with everything else, you have to come to terms with standards and protocols—those that exist, those that are emerging, and those needed to ensure interoperability on the factory floor.