Should we use a wireless connection?

Question:
Why should I use wireless connectivity when wires have worked for us in the past?

Answer:
Wired connections to sensors, actuators, equipment, controllers and computers work well in many situations. There are a number of situations, however, when wireless connections are more practical. Those situations include: The equipment to connect is already deployed or installed, and it would be expensive, difficult or interrupt operations to retrofit with wiring. The equipment to connect is at a facility controlled by someone else (e.g., the customer’s premises) and it will be a difficult process to negotiate the installation of wiring. Installing wiring would be intrusive, disruptive, complicated or unattractive. The equipment to connect is moveable or portable, and will probably be relocated periodically. The connection is an ad hoc connection or will be only needed temporarily. But the primary reason why wireless connections are increasingly being preferred to wired connections is because they are less expensive. Over time, the cost of wireless connectivity has declined dramatically, while the cost of materials and installation labor for wiring has increased. Wireless connections are now the lower cost approach in many situations.
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Question:
Is a wireless connection just as good as a wire? If not, how is it different?

Answer:
In many applications, a wireless connection is as good as a wired connection. Signals or data can be delivered over wireless connections reliably and quickly in a manner that is as good as using a wire. There are differences, however, between wired connections and wireless connections, and there are situations in which these differences are important. In general, wired connections can carry a significantly higher volume of data than a wireless connection. For example, the top data rate of an RS-232 serial connection is 115.2 Kbps, but a wireless connection must be carefully engineered to carry this much data, and many wireless connections can not handle this continuous data volume. Another difference is that wireless connections often introduce a slight latency in conveying data that is not present with wired connections. This latency may come from the “handshaking” protocol used by a wireless network to assure reliable data delivery, or from the time the radio is inactive to conserve battery power. This latency is usually measured in milliseconds and is unimportant in most applications. Finally, the range of wireless connections is not guaranteed and may vary due to local conditions (e.g., building walls and other obstructions). With wired connections, on the other hand, data can be communicated every time that a physical wire can be stretched between devices.

Both wired and wireless connections have reliability issues, but for different reasons. Wired connections can be interrupted when the wire is accidentally cut, or when it is inadvertently disconnected (for example, during maintenance, or during the installation of adjacent equipment). On the other hand, wireless connections can be interrupted if barriers to RF propagation are installed nearby, or by adjacent equipment that emits interfering signals.
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Question:
Can I substitute a wireless connection everyplace where I was using wire before? Should I?

Answer:
A wireless connection is a feasible alternative to a wired connection in most cases. There are some situations, however, when a wired connection must be used because a high volume of data is being transmitted, because the connection is used for real-time monitoring or control and any latency is intolerable, or because the communication is critical and absolute reliability is necessary (often with redundant communication paths). Even in the many situations when it is feasible to use a wireless connection in place of a wire, it is not always appropriate. The decision to use a wired or a wireless connection is often a decision on which alternative is the easiest and least expensive, and this should be evaluated on a case-by-case basis.
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Question:
How reliable is a wireless connection?

Answer:
Both wired and wireless connections have reliability issues, but for different reasons. Wired connections can be interrupted when the wire is accidentally cut, or when it is inadvertently disconnected (for example, during maintenance, or during the installation of adjacent equipment). On the other hand, wireless connections can be interrupted if barriers to RF propagation are installed nearby, or by adjacent equipment that emits interfering signals. In general, if two wireless devices are within range of each other and a connection can be established at all, then that connection will usually operate very reliably unless one of the devices moves or unless something significant changes in the environment that blocks or interferes with the radio signals.

Because of the nature of wireless propagation, however, most wireless networks use a sophisticated protocol when one device is communicating with another. That protocol is designed to avoid interruptions to the signals, and to recover from interruptions automatically when they do occur. Ethernet uses a similar protocol to provide reliable operation on its shared network.
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Question:
Isn’t a wireless connection susceptible to interruption from interference?

Answer:
Most wireless communications technologies can be subject to interference from other signals that make it difficult for wireless devices to recognize and receive radio signals meant for them. Most interference is intermittent, however, and not continuous. Consequently, most wireless networks use a sophisticated protocol when one device is communicating with another to detect when interference has occurred and to recover any lost or garbled data.
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Question:
Can I use wireless connections in situations where I already have some wired connections?

Answer:
You can combine wired connections and wireless connections in almost any monitoring and control application, as long as wireless is a feasible connection technology for the application (i.e., it can tolerate the data rate, latency, and coverage limitations of wireless connections). Mixed mode environments would occur if additional sensor connections are to be added inexpensively to an existing wired sensor application, or if a new system minimizes cost by using wired connections where cost effective and wireless connections where wiring costs are prohibitive. Some integration effort may be required, however, since most wireless connection nodes do not natively support the common wireline protocols. For example, wired connections in many industrial automation applications support common industry protocols (e.g., Modbus, Profibus, Canbus), but few wireless sensor networks support interfaces to these protocols.
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Question:
What do I do about equipment that is already deployed? Can I retrofit wireless connections in these cases?

Answer:
Wireless connections are an ideal means to connect sensors that are retrofitted to existing equipment since they avoid the considerable expense and disruption of installing wiring. As long as the application can tolerate data rate, latency, and coverage limitations of wireless, then wireless connections are usually the most cost effective means of adding communications to existing equipment.
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Question:
Can I use wireless connections in harsh environments?

Answer:
Wireless connectivity solutions can be used in harsh environmental conditions just as readily as wired connections. Whether the environmental stress comes from extreme temperatures, vibration, corrosive gases, or some other condition, a workable wireless solution can be designed. In some situations a wireless connectivity approach may be intrinsically safer than using the cabling and connectors of a wired connection, such as environments with high vibration or potentially explosive gases.
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