Industrial environments are uniquely different from those in the office and home. High temperatures, airborne particulates, multiple obstacles and long distances separating equipment and systems present a special challenge in communicating with sensors, transmitters, and other data communication devices.
If one ever needed examples of how wireless can solve industrial network problems, connecting remote equipment sensors to central monitoring systems inside a steel mill would be ideal. The environment comprises excessive heat, heavy machinery, large distances, and high levels of EMI. Such things significantly shorten the lifespan of wires and network equipment. Conversely, a tank farm normally enjoys a much quieter and calmer life, but distance and cost issues show themselves when connecting to associated sensors and equipment.
These are two extreme cases, and, of course, the industrial world contains everything in between, in varying degrees of complexity.
The historic wireless perspective
Wireless I/O has had a rocky past and typically has not performed well enough to fulfil most industrial applications. There are, or more strictly speaking were, several reasons for this…
Signal echo. Typical open radio frequencies (900MHz and 2.4GHz) used within today’s wireless data communication applications have a reasonable penetration rate through office cubicles, dry walls, wood and other materials found in a home or office, but tend to bounce off larger objects, metals, and concrete. This bounce can redirect the data signal and return it to the original transmitter, causing an ‘echo’ or ‘multi-path’. First generation wireless systems easily became confused with this type of interference and would cancel transmission all together. The result was a state referred to as ‘radio null’ and prevented data communication.
Noise. The electromagnetic emissions created by large motors, heavy equipment, high power generation and usage, and other typical industrial machinery could create extremely high levels of electrical noise that interfered with early wireless equipment. In these noisy environments, transmitters and remote nodes were unable to hear each other, resulting in frequent data loss.
Channel sharing and interference. Radio frequency space became enormously crowded. FCC-approved frequency allocations were shared by many devices, including those used by WiFi (IEEE 802.11) and ZigBee (IEEE 802.15.4). The frequent result was data confusion as receivers and nodes gathered and sent information on the same channel as other devices in the area.
Industrial protocols not supported. The vast majority of early wireless devices were designed for home and inter-office use. Because of this, very few engineers were addressing the industrial protocols such as Modbus or the need to move from wireless to RS-232, 422 or 485 supports. Additionally, casing, circuitry, and connections were designed for lightweight usage and were inadequate for rugged industrial settings.
Distance. The sheer distances between central control systems and remote sensor and equipment constricted the use of early wireless systems in a true network mode.
Security. Early adoption of the IEEE 802.11 standards created a large number of security issues and continues to require a high level of counter-measures to ensure the safety of data and business systems. So, while the fundamental premise of wireless was a clear answer to many industrial data comms challenges, the reality was that unless the historic deficiencies could be overcome, wireless could not offer a viable solution.
New methods and technologies
Over time, this has changed, as new technologies have entered the picture. There are now many data communication solutions to historic problems. Here follows a snapshot of the options with some corresponding pros and cons. When looking for the optimum industrial wireless solution for your situation, carefully consider these factors. Several transmission and modulation schemes have been developed to counter the effects of echo, noise, and channel sharing. Here are two of the best to look for. But a note of cautions. All wireless transmitters, nodes and equipment on your network must support the same transmission scheme to operate properly.
FHSS (Frequency Hopping Spread Spectrum) – Data is transmitted on a single channel at a time, but the channel is rapidly and constantly changing or ‘hopping’. This scheme requires low bandwidth.
DSSS (Direct Sequence Spread Spectrum) – Data is transmitted simultaneously over every available channel, making it a bit more reliable in noisy environments, but is also bandwidth intensive. In addition to these transmission schemes, there are several design and development standards that play an essential role in establishing reliability, security, speed, distance and efficiency. Determining the best solution depends on the application and need. In outlining the various wireless options below, the pros and cons list are offered from a typical industrial environment perspective.
Wi-Fi (IEEE 802.11 b/g/n)
Pros – This standard forms the staple of home, business and office networking and is widely used for its high data transfer rate abilities (max throughput of up to 54Mbps with 12Mbps being typical).
Cons – Requires excessive overhead in terms of power consumption, software, processor resources, short range (160m max) and size of physical components, making it less than effective in most industrial situations.
Bluetooth (IEEE 802.15.1)
Pros – Bluetooth has gained popularity because of its small physical size and instant network setup. Three classes allow Bluetooth to move data anywhere from 3m to 100m distance. High power Bluetooth modules coming on to the market potentially extend link distance to over a kilometers.
Cons – Bluetooth has a relatively high duty cycle (especially in 2.0 and early versions), minimal data throughput (currently a maximum of 3Mbps is possible) and requires a fairly well defined line-of-site operation because of its low penetration qualities.
ZigBee (IEEE 802.15.4)
Pros – Relatively speaking, ZigBee is the new kid on the block, but there is much to recommend for the technology. It is far more power-friendly than Wi-Fi and Bluetooth due to its advanced sleep and sniff abilities. Additionally, it has high penetration ability, and operates with an even smaller physical footprint than Bluetooth.
Cons – ZigBee has a low data at rates – up to 720 kbps – and poor interoperability. Additionally, because it is relatively new, hardware developers are still refining and defining their systems.
Proprietary RF (non-standard)
Pros – Proprietary RF (PRF) provides an exact solution to meet specific needs. Modulation schemes, distances, throughput, casing, configurations, etc… can all be customized to the application. With PRF, interference issues virtually disappear because there is no longer a fight for the same channel sequences that standardized protocols and formats use. PRF tends to be more power-friendly as well since the protocol and hardware configuration can be tailored to the job. For this same reason, costs can actually be lower. PRF can operate in both the 900MHz and 2.4GHz frequencies, giving greater control over distance, penetration, and channel interference. Additionally, there are many PRF off-the shelf solutions that may meet specific needs, saving the time needed for customization.
Cons – PFR does not provide interoperability with any of the established wireless standards and is considered by some to create vendor lock-in.
If circumstances permit selection of an RF standard or off-the-shelf solution, then the options are fairly clear in terms of range, penetration, frequency, data rate, etc; there is a set base line to choose from. However, if the environment cannot be modified to fit these parameters, consideration will have to be given to proprietary RF.
The wireless advantage
•Low Costs – Wireless equipment represents a substantial saving over the cost of cabling, installation and configuration of wired networks.
•Longevity – Sensors, transmitters and receivers can be designed for the harsh environments, with many operating at temperatures between -40 to +85°C. Concerns about wires deteriorating or the need to install multiple signal boosters over long distances are eliminated.
•Swift deployment – Wireless systems can be set up for use almost instantly, modified and taken down, saving both time and engineering resource.
•Easy configuration – Many wireless systems are plug- and- play, self-configuring and self-repairing. Proprietary RF systems come with easy-to-use, free configuration software to make set-up and customization quick and easy.
Range considerations
Range is determined by four elements: Transmit power refers to the amount of power that is emitted from the antenna port of the radio device. Proprietary RF is regulated in the US for up to 1W. This provides substantial benefits when long ranges are needed, because the higher the transmit power, the stronger the signal and thus the further it can travel.
Receiver sensitivity is the complementary factor to transmit power. Sensitivity defines how well remote receivers can resolve the signal. Sensitivity is significantly affected by antenna type and hardware configurations. For maximum communication strength the fewer barriers along the line-of-sight between receiver and transmitter, the better. Frequency and transmit power levels have the most impact on how well the signal can negotiate physical and EMI line-of-sight barriers. The data rate and volume will also affect attainable range. Large data packets are more difficult to transmit than smaller packets and will typically reduce range. In general, the higher the higher the data rate, the shorter the attainable range.
Antenna considerations
Antenna selection will of course depend on the communication needs for the application. Directional aerials send and receive the signal most effectively from a single direction, although some leakage – and interference – can occur from directions other than the one for which the system is operationally aligned. However it extends the range for fixed links beyond that attainable with standard omni-directional antennas. Examples of directional aerials include Yagi, dish and panel arrays. Use would typically be for moving data from one single location to another single location. Omni-directional aerials come in various guises: vertical rods, ceiling domes and rubber ducks. They would be employed for transmitting data from a single location to multiple and possibly moving locations.
If one ever needed examples of how wireless can solve industrial network problems, connecting remote equipment sensors to central monitoring systems inside a steel mill would be ideal. The environment comprises excessive heat, heavy machinery, large distances, and high levels of EMI. Such things significantly shorten the lifespan of wires and network equipment. Conversely, a tank farm normally enjoys a much quieter and calmer life, but distance and cost issues show themselves when connecting to associated sensors and equipment.
These are two extreme cases, and, of course, the industrial world contains everything in between, in varying degrees of complexity.
The historic wireless perspective
Wireless I/O has had a rocky past and typically has not performed well enough to fulfil most industrial applications. There are, or more strictly speaking were, several reasons for this…
Signal echo. Typical open radio frequencies (900MHz and 2.4GHz) used within today’s wireless data communication applications have a reasonable penetration rate through office cubicles, dry walls, wood and other materials found in a home or office, but tend to bounce off larger objects, metals, and concrete. This bounce can redirect the data signal and return it to the original transmitter, causing an ‘echo’ or ‘multi-path’. First generation wireless systems easily became confused with this type of interference and would cancel transmission all together. The result was a state referred to as ‘radio null’ and prevented data communication.
Noise. The electromagnetic emissions created by large motors, heavy equipment, high power generation and usage, and other typical industrial machinery could create extremely high levels of electrical noise that interfered with early wireless equipment. In these noisy environments, transmitters and remote nodes were unable to hear each other, resulting in frequent data loss.
Channel sharing and interference. Radio frequency space became enormously crowded. FCC-approved frequency allocations were shared by many devices, including those used by WiFi (IEEE 802.11) and ZigBee (IEEE 802.15.4). The frequent result was data confusion as receivers and nodes gathered and sent information on the same channel as other devices in the area.
Industrial protocols not supported. The vast majority of early wireless devices were designed for home and inter-office use. Because of this, very few engineers were addressing the industrial protocols such as Modbus or the need to move from wireless to RS-232, 422 or 485 supports. Additionally, casing, circuitry, and connections were designed for lightweight usage and were inadequate for rugged industrial settings.
Distance. The sheer distances between central control systems and remote sensor and equipment constricted the use of early wireless systems in a true network mode.
Security. Early adoption of the IEEE 802.11 standards created a large number of security issues and continues to require a high level of counter-measures to ensure the safety of data and business systems. So, while the fundamental premise of wireless was a clear answer to many industrial data comms challenges, the reality was that unless the historic deficiencies could be overcome, wireless could not offer a viable solution.
New methods and technologies
Over time, this has changed, as new technologies have entered the picture. There are now many data communication solutions to historic problems. Here follows a snapshot of the options with some corresponding pros and cons. When looking for the optimum industrial wireless solution for your situation, carefully consider these factors. Several transmission and modulation schemes have been developed to counter the effects of echo, noise, and channel sharing. Here are two of the best to look for. But a note of cautions. All wireless transmitters, nodes and equipment on your network must support the same transmission scheme to operate properly.
FHSS (Frequency Hopping Spread Spectrum) – Data is transmitted on a single channel at a time, but the channel is rapidly and constantly changing or ‘hopping’. This scheme requires low bandwidth.
DSSS (Direct Sequence Spread Spectrum) – Data is transmitted simultaneously over every available channel, making it a bit more reliable in noisy environments, but is also bandwidth intensive. In addition to these transmission schemes, there are several design and development standards that play an essential role in establishing reliability, security, speed, distance and efficiency. Determining the best solution depends on the application and need. In outlining the various wireless options below, the pros and cons list are offered from a typical industrial environment perspective.
Wi-Fi (IEEE 802.11 b/g/n)
Pros – This standard forms the staple of home, business and office networking and is widely used for its high data transfer rate abilities (max throughput of up to 54Mbps with 12Mbps being typical).
Cons – Requires excessive overhead in terms of power consumption, software, processor resources, short range (160m max) and size of physical components, making it less than effective in most industrial situations.
Bluetooth (IEEE 802.15.1)
Pros – Bluetooth has gained popularity because of its small physical size and instant network setup. Three classes allow Bluetooth to move data anywhere from 3m to 100m distance. High power Bluetooth modules coming on to the market potentially extend link distance to over a kilometers.
Cons – Bluetooth has a relatively high duty cycle (especially in 2.0 and early versions), minimal data throughput (currently a maximum of 3Mbps is possible) and requires a fairly well defined line-of-site operation because of its low penetration qualities.
ZigBee (IEEE 802.15.4)
Pros – Relatively speaking, ZigBee is the new kid on the block, but there is much to recommend for the technology. It is far more power-friendly than Wi-Fi and Bluetooth due to its advanced sleep and sniff abilities. Additionally, it has high penetration ability, and operates with an even smaller physical footprint than Bluetooth.
Cons – ZigBee has a low data at rates – up to 720 kbps – and poor interoperability. Additionally, because it is relatively new, hardware developers are still refining and defining their systems.
Proprietary RF (non-standard)
Pros – Proprietary RF (PRF) provides an exact solution to meet specific needs. Modulation schemes, distances, throughput, casing, configurations, etc… can all be customized to the application. With PRF, interference issues virtually disappear because there is no longer a fight for the same channel sequences that standardized protocols and formats use. PRF tends to be more power-friendly as well since the protocol and hardware configuration can be tailored to the job. For this same reason, costs can actually be lower. PRF can operate in both the 900MHz and 2.4GHz frequencies, giving greater control over distance, penetration, and channel interference. Additionally, there are many PRF off-the shelf solutions that may meet specific needs, saving the time needed for customization.
Cons – PFR does not provide interoperability with any of the established wireless standards and is considered by some to create vendor lock-in.
If circumstances permit selection of an RF standard or off-the-shelf solution, then the options are fairly clear in terms of range, penetration, frequency, data rate, etc; there is a set base line to choose from. However, if the environment cannot be modified to fit these parameters, consideration will have to be given to proprietary RF.
The wireless advantage
•Low Costs – Wireless equipment represents a substantial saving over the cost of cabling, installation and configuration of wired networks.
•Longevity – Sensors, transmitters and receivers can be designed for the harsh environments, with many operating at temperatures between -40 to +85°C. Concerns about wires deteriorating or the need to install multiple signal boosters over long distances are eliminated.
•Swift deployment – Wireless systems can be set up for use almost instantly, modified and taken down, saving both time and engineering resource.
•Easy configuration – Many wireless systems are plug- and- play, self-configuring and self-repairing. Proprietary RF systems come with easy-to-use, free configuration software to make set-up and customization quick and easy.
Range considerations
Range is determined by four elements: Transmit power refers to the amount of power that is emitted from the antenna port of the radio device. Proprietary RF is regulated in the US for up to 1W. This provides substantial benefits when long ranges are needed, because the higher the transmit power, the stronger the signal and thus the further it can travel.
Receiver sensitivity is the complementary factor to transmit power. Sensitivity defines how well remote receivers can resolve the signal. Sensitivity is significantly affected by antenna type and hardware configurations. For maximum communication strength the fewer barriers along the line-of-sight between receiver and transmitter, the better. Frequency and transmit power levels have the most impact on how well the signal can negotiate physical and EMI line-of-sight barriers. The data rate and volume will also affect attainable range. Large data packets are more difficult to transmit than smaller packets and will typically reduce range. In general, the higher the higher the data rate, the shorter the attainable range.
Antenna considerations
Antenna selection will of course depend on the communication needs for the application. Directional aerials send and receive the signal most effectively from a single direction, although some leakage – and interference – can occur from directions other than the one for which the system is operationally aligned. However it extends the range for fixed links beyond that attainable with standard omni-directional antennas. Examples of directional aerials include Yagi, dish and panel arrays. Use would typically be for moving data from one single location to another single location. Omni-directional aerials come in various guises: vertical rods, ceiling domes and rubber ducks. They would be employed for transmitting data from a single location to multiple and possibly moving locations.
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