How to Choose a Wireless Industrial Ethernet Solution

Fear is often the biggest hurdle to overcome when looking at wireless networking as a way to reduce cabling costs, lower maintenance costs, introduce new ways to optimize applications, and maximize networking flexibility. This fear is based on valid concerns: What equipment do I need? Does the manufacturer understand my application? Who will be there for me if I need help?

These concerns must be addressed. The first step is to recognize that it takes more than wireless technology to make wireless communication work in harsh, demanding, cost-conscious, and ever changing industrial automation applications. From the perspective of the integrator or end user, communications expertise and comprehensive technical support are key considerations that distinguish ordinary wireless products from the robust wireless industrial communication solution that industrial users require.

If you are in the market to purchase wireless communication equipment, one thing you will quickly realize is that not all radios are created equal. There are some key questions to ask when shopping for a company to provide a solution for your wireless application.

1. What frequency ranges and power levels are acceptable in my country?
2. Is the radio easily programmable for both frequency and power?
3. Does the radio operate in a license-free bandwidth?
4. Which is better for my application, DSSS and FHSS?
5. How secure is the data transmitted over the radio?
6. What value added services does the company provide such as path studies and site audits?
7. What type of antenna do you need for your application?
8. What type of network selection and scalability does the radio have?
9. Is the product a true communications solution ?
10. Does it have industrial grade qualities?

What frequency ranges and power levels are acceptable in my country?

For North America , New Zealand and Australia , frequency ranges and power levels are usually no problem. As you can see in the charts, however, power and frequency levels vary widely.

"When developing industrial wireless Ethernet applications, particularly in Europe , it is imperative that the purchaser be aware of the regional variations in radio communications standards and regulations," says Kevin Zamzow , RadioLinx Product Manager for ProSoft Technology, Inc.

Operation of wireless industrial Ethernet within Europe still requires some adjustments either for frequency band, allowed effective radiated power, or both as the approval authority remains with each country.

"In France the indoor regulation is the same as the rest of Europe (maximum EIRP power of 100mW across the entire 2.400-2.4835 GHz frequency band)," says Francoise Mailharein, Application Engineer for ProSoft SARL in France . "However, outdoor use in France is restricted. With a maximum power of 100 mW frequencies must be between 2.400-2.454 GHz or with 10mW power at 2.454-2.483 GHz."

Editor's Note: Regulations regarding frequency ranges and power levels are constantly changing. If you choose to print the chart below, please notify me immediately so that we can verify any recent changes and/or additions.

Listed below are the frequency ranges and power levels per country:

Comparison of unlicensed bands in Europe and US suitable for wireless Ethernet

1 5.15 to 5.25 GHz in US 40 mW transmit power, 160 mW EIRP indoor only

2 5.25 to 5.35 GHz in US 200 mW transmit power, 800 mW EIRP indoor & outdoor

3 For omni-directional communications, for directional links 3 dBi of antenna gain may be added for each 1 dBm the radio transmit power is under the 30 dBm limit. For example, a 24 dBm (250 mW) radio may use up to 24 dBi of antenna gain for an EIRP of 64,000 mW.

Is the radio easily programmable for both frequency and power?

Many radios on the market today do not meet local country regulations due to either transmitting too much power or on frequencies not approved for unlicensed use. Therefore, it is important to determine whether or not the radio can be programmed to meet these regulations.

"We have made a huge effort to become intimately acquainted with the regulatory needs for European countries," says Alain Chevalin, General Manager ProSoft Technology in Europe . "Since our modems are programmable, it is easy for us to customize each network to meet the needs of different regulatory agencies."

Does the radio operate in a license-free bandwidth?

"The 2.4 GHz ISM band can be used and sold without license or on-going usage fees virtually anywhere in the world, whereas use of 900 MHz systems are much more restricted and cannot be used in Europe," says Mailharein.

Use of 5 GHz systems, such as 802.11a, with its wider bandwidth than 2.4 GHz making it more line-of-sight, is more broadly allowed than 900 MHz, but still has some country-specific rules.

Which is better for my application, DSSS (Direct Sequence Spread Spectrum) or FHSS (Frequency Hopping Spread Spectrum)?

FHSS industrial modems typically enable the user to choose from a large number of hopping patterns (e.g. 150 or more), and within each data channel the modem will hop between a large number of frequency channels (e.g. 75 or more in the US ). With this flexibility, FHSS modems can be programmed to hop around virtually any electrical interference. For example, if transmission is blocked at one frequency, then the modem will automatically hop to the next frequency in the pattern, so reliable communication is maintained.

How secure is the data transmitted over the radio?

"Security is an important issue in any data network," says Scott Sibenac, Regional Manager for ProSoft. "With wireless communication you have the added worry of outside interference preventing your data from being received properly. ProSoft's RL-2400 Ethernet radio provides three levels of security for the customer:

• Inherent security in Frequency Hopping Spread Spectrum technology providing maximum protection against jamming, or unintentional interference typical of industrial automation environments.
• Encryption at the hardware level using ARC4, 128-bit technology. Without access to the encrypted data it is not possible to decipher the data.

• Proprietary architecture, which means third party radios cannot be used to circumvent the security of a RadioLinx network. Radios adhering to open standards, such as legacy 802.11b radios still using WEP (wired equivalent privacy), are vulnerable to would be hackers to gain access to encrypted data that passes over the air.
• For 802.11b, a,g radios, make sure products have the new TKIP (temporal key integrity protocol) encryption."

What value added services does the company provide such as path studies and site audits?

In order to insure the proper specification, ordering, and integration for your wireless network application, it is crucial that the radio company is familiar with the specifics of your application. Critical information that should be considered before purchasing a wireless network include:

• How far does data need to be transmitted?
• Are there any obstacles such as buildings or mountains impairing line-of-sight between radios?
• In what type of application will the radios be used, i.e. oil and gas pipeline, manufacturing plant, electric welding, etc.
• If it is determined that a path study or site audit is needed to insure the proper implementation and function of the wireless network, can the radio company provide this service?

What type of antenna do you need for your application?

The antenna you select depends on various factors that include antenna path, antenna mounting, cable type and loss, distance and so on. A variety of antennas are available such as:

• Whip antennas: The most commonly used antennas are normally connected directly to the radio. The articulating version bends in various directions. These antennas provide 2dBi gain and range in size from 2.5 inches to 5 inches long. Whip antennas receive and transmit radio waves in all directions.
• Collinear Array antennas: Typically composed of several linear antennas stacked on top of each other. The number of stacked elements increase the gain of this antenna which is typically between 5-10 dBi. Collinear Array antennas receive and transmit radio waves in all directions. A good choice for omni directional communication if either radio is moving.
• Yagi Array antennas: Composed of an array of linear elements, parallel to one another and attached perpendicular to and along the length of a metal boom. This type of antenna produces gain in the 6-15 dBi range. Yagi Array antennas transmit and receive radio waves from the direction they are aimed. Generally used for long-range links to fixed radios.
• Parabolic Reflector antennas: Consists of a parabolic shaped dish and a fee antenna located in front of the dish. Due to the parabolic shape, the reflector concentrates radiation into a norrow pattern, producing a high-gain beam. Typical gain values are in the 15-30 dBi range. Parabolic Reflector antennas transmit and receive radio waves from the direction they are aimed. Generally used for long-range links to fixed radios.

"The RadioLinx 2400 Ethernet modems provide two antenna ports for true antenna diversity," says Wallace Gastreich, Application Engineer for ProSoft Technology, Inc. "Antenna diversity increases the reliability of any wireless application, allowing the use of both a vertical and horizontal polarized antenna for rotating applications and allowing short and long range antenna combinations that effectively gather local data and transmit it up to 15 miles (24 kilometers) to a repeater or base station. RadioLinx' active antenna diversity also allows transmit/receive on both ports for optimum antenna selection."

What type of network selection and scalability does the radio have?

Many wireless modems offer the user the ability to select from a number of networks and broadcast modes. On ProSoft Technology's RL-2400 modems for example, the user can select from a simple point-to-point network, a point-to-multipoint broadcast network, a Modbus addressed network with 255 modems, or an Ethernet network with 2000 radios. If the network has to be increased, it is straightforward to add the new remote or repeater modems without having to reconfigure the existing network. Moreover, the user can physically overlap networks of the same or different types by selecting different channels for modem operation.

Is the product a true communications solution ?

When choosing a company to provide you with a wireless network, look for communications expertise. A true communication solution provider should be able to take the guesswork out the decision. They should be able to knowledgeably explain the "jargon" that is the origin of so many difficulties for a new radio user or to someone lacking protocol expertise, demystifying the terminology. (Frequently asked questions include: What is license-free...ISM...usable bandwidth...FHSS...802.11b? What is the difference between DNP 3.0 and IEC 60870-5-101 protocols? Do different Ethernet protocols work the same way over wireless, such as Modbus TCP/IP, PROFIBUS DP or IEC 60870-5-104?).

The company should be a communication solutions provider. This is critical because it means that from the President on down, you are dealing with people that understand the importance of both the physical and protocol layers of any wireless communication solution. Good questions to ask include:

• Do they have a deep understanding of industrial automation applications from a practical level?
• Is the solution backed by technical support at both the hardware and the communications level and are each of these dimensions met with equal commitment and expertise?

Does it have industrial grade qualities?

Is the hardware truly industrialized? Look at the form factor, temperature and power ratings, industrial certifications, networking flexibility, noise immunity and security. Look for quality configuration, networking and diagnostics tools that can mean huge savings in implementation, operation and maintenance costs. Is it DIN rail mounted and have readily available industrial power (12 or 24 VDC)?

Evaluating your solution options using these criteria will help you choose the wireless network that is right for your application.

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1 The European Commission (EC) has been promoting harmonization of radio communications standards, particularly through Directive 1999/5/EC of the European Parliament and of the Council of 9 March 1999 on radio equipment and telecommunications terminal equipment and the mutual recognition of their conformity (R&TTE Directive). The EC, via a March 20 th Recommendation, continues to encourage member state to allow general use of Radio Local Area Networks, R-LAN (such as 2.4 GHz Wi-Fi) with only general authorizations to promote use of R-LAN for public access to the Internet via wireless coverage areas known as ?hotspots?. The European Radiocommunications Office (ERO http://www.ero.dk ) is the permanent office, which supports the European Radiocommunications Committee (ERC) of the European Conference of Postal and Telecommunications Administrators (CEPT ? www.cept.org ). The ERO develops radio communications policies and coordinates frequency, regulatory and technical radio issues for member countries.

The standard for 2.4 GHz wireless communications in the European Union (and adopted by many countries outside of the EU) is maintained by the European Telecommunications Standards Institute (ETSI http://portal.etsi.org ) and the most recent version is ETS 300.328 V1.4.1 (2003-04) for "Data transmit transmission equipment operating in the 2,4 GHz ISM band and using spread spectrum modulation techniques". Changes in the new version include removal of the minimum bit rate of 250 kbits/s and inclusion of new wide band technologies. Additional standards for wireless Ethernet networks, such as 802.11b for 2.4 GHz DSSS WLAN, are set by IEEE http://grouper.ieee.org/groups/802/11 . Recent or soon to be released IEEE specifications include 802.11g for 2.4 GHz WLAN to 54 Mbits/s and 802.11i security enhancements. For countries harmonized to EN 300 328, 13 channels of 802.11b are allowed vs. 11 in the USA and 14 in Japan .