Open standard wireless systems
The present situation of open wireless systems and standards in use is reminiscent of an earlier time when wired networks first became viable. Many old timers out there remember the "thick yellow hose" of the first commercial Ethernet systems; this was called 10base5. 10base5 allowed 10 MPS throughput, and it used baseband modulation and was limited to 500 m end-to-end. This illustrates how early systems were implemented and tested in the field and formed a basis that became Ethernet. There were other systems in use, and many were proprietary. Each system had good and bad points. Fortunately, the good points were incorporated into modern systems and became enhancements to the overall technology. This situation is unfolding in the steady deployment of wireless systems. Below are several examples of open standard wireless systems.
The system most widely deployed after Wi-Fi is Bluetooth. Bluetooth was never envisioned as a high-speed data communication network technology. Instead, it was designed to provide low bandwidth, short range, and low-rate connectivity for discrete devices such as mobile phones and associated headsets. This made mobile technology less obtrusive by eliminating the annoying wiring between the phone and the headset.
All hands-free mobile applications rely on Bluetooth. With the development of the Bluetooth Audio extension, much more personal entertainment functionality was afforded the user. Bluetooth adheres to the IEEE 802.15.4 open standard. Bluetooth is a frequency hopping technology; the communication channel frequency changes regularly according to an agreed upon algorithm. Bluetooth also operates in the 2.4 GHz frequency spectrum and has presented interference problems to Wi-Fi systems that operate in the same area. As Wi-Fi slowly migrates to the 5 GHz spectrum, Bluetooth will eventually have the spectrum to itself.
Wireless highway addressable remote transducer (WiHART) is the wireless implementation of the wireline HART protocol. WiHART also adheres to the IEEE 802.15.4 open standard, but only at the lower two layers of the OSI model. At layers 3-7, proprietary protocols and algorithms still prevail. This is another example of the evolution of a technology. The HART protocol allows for the monitoring and configuration of remote instrumentation, eliminating the need to go to the device to perform these functions. Of course, this system will only work with HART-capable instrumentation, so some capital expenditure will be necessary; however, the utility and economy resulting from this conversion is, in a word, astonishing.
Z-Wave is a wireless technology that operates in the 900 MHz spectrum and is used exclusively in the home automation market. At this writing, practically all of the home automation/home awareness systems use Z-Wave for control and monitoring while using Wi-Fi or Bluetooth for wireless user interface. Z-Wave evolved as a result of disparate and often proprietary home wireless systems operating in the 27 MHz and 433 MHz spectrums. These systems were geared towards a low price point, resulting in low quality and low security systems. They also used proprietary protocols and were not feature rich. The systems were not interoperable and were easily compromised.
Z-Wave has become the de facto wireless standard in home awareness/automation (A/A) because of widespread support and interoperability by and between vendors. It also offers backwards compatibility with previous versions. Z-Wave operates in the 900 MHz spectrum and creates a mesh network. Each Z-Wave node acts as a repeater and has a line-of-sight (LOS) range approaching 100 feet. For the typical household, this range is more than adequate. Outside of that range, signals can be repeated up to four times, greatly expanding the system’s reach. Z-Wave communicates at low data rates, between 9.6 and 100 KBPS. A Z-Wave gateway is required in order to control the system, and most systems will interface with a router via 802.3 Ethernet or 802.11 wireless, allowing control and monitoring from anywhere via mobile applications.
Based on IEEE 802.15.4, ZigBee is another wireless technology geared towards the home A/A market. ZigBee is capable of providing a wireless interface with many different devices, from home A/A to home entertainment device controls. The technology is geared towards low-rate communication devices, topping out at 250 KBPS. It has a range of about 35 feet, comparable to Bluetooth, but where Bluetooth allows a maximum of seven devices to pair, ZigBee allows 65,000. ZigBee is a mesh network and operates in the 900 MHz and 2.4 GHz spectrums. ZigBee also requires a gateway ("hub"). Both Z-Wave and ZigBee use 128-bit, advanced encryption standard (AES) symmetric encryption for system security. It showed promise because it is designed to expand the functionality of Bluetooth by allowing many more devices to associate. However, the biggest obstacle to adoption seems to be the lack of operability between vendors.
Worldwide interoperability for microwave access (WiMAX) is a family of communication standards based around the IEEE 802.16 standard, also known as metropolitan area networks (MAN). WiMAX was originally conceived as an alternative to wired DSL and cable service for "last mile" or for monitoring of smart grids. WiMAX can provide Internet service wirelessly across large geographic areas from fixed WiMAX stations. WiMAX requires the use of gateway devices at the subscriber location, which will interface with or contain an integrated Wi-Fi access point or router. The original specification called for operation in the 10 to 66 GHz range. The updated standard added support for the 2 to 11 GHz spectrum. The maximum range for WiMAX is 30 miles, with optimum speeds of 10 MBPS being attained at a range of 1 to 6 miles. WiMAX is a long-range system as compared to the other systems considered here. It also uses both licensed and unlicensed spectrum as opposed to Wi-Fi and the others, which operate solely in unlicensed spectrums. WiMAX is used throughout the world, but a movement toward long-term evolution (LTE) has caused several networks to be shut down.
At this writing, ISA 100.11a is the last iteration of a wireless instrumentation communication standard being promoted by the International Society for Automation (ISA). ISA 100.11a is similar in many ways to WiHART, and various comparisons of these two competing technologies can be found. ISA 100.11a uses IPV6 (6LoWPAN) and is based upon the IEEE 802.15.4 standard, but then deviates from the standard in several ways. The Datalink layer incorporates a "noncompliant" MAC structure that will not support universal interoperability between devices from different vendors, as is the case with WiHART. Users have many options that must be carefully configured on each device in order to allow interoperability. For instance, while WiHART specifies and strictly enforces operational parameters (to ensure interoperability), ISA 100.11a allows users to configure parameters to values unique to that network and its constituent devices. ISA 100.11a does not specify an encryption method or application layer interface, and routing between devices is optional.
It is apparent this standard was intended for implementing proprietary networks, allowing each vendor to tweak operational parameters to allow only a single vendor to communicate. Interoperability was not considered in the development of this standard unless it is within a single-vendor implementation. In the unlikely event that different vendors would cooperate, then it is possible that different vendors could play well together. But this runs counter to conventional marketing philosophy. The standard requires an intimate knowledge of the various configurable parameters, and all wireless devices on the network must be configured identically.
Several vendors offer ISA 100.11a functionality, but, again, all communicating devices must conform to the same network configuration; in this sense, the standard is not open. However, it can be argued that this standard is "customizable" in the sense that it can be made to operate in a mixed radio frequency (RF) environment because it can be made incompatible with every other device operating in the same spectrum.
– Daniel E. Capano, owner and president, Diversified Technical Services Inc. of Stamford, Conn., is a certified wireless network administrator (CWNA); firstname.lastname@example.org. Edited by Chris Vavra, production editor, CFE Media, Control Engineering, email@example.com.
www.controleng.com/blogs has other wireless tutorials from Capano on the following topics:
Understanding RFI and EMI’s effects
WLAN troubleshooting best practices
Wireless intrusion detection and protection systems
www.controleng.com/webcasts has wireless webcasts, some for PDH credit.
Control Engineering has a wireless page.