Wi-Fi Spectrum: ISM, U-NII, FCC Rules

Industrial wireless tutorials, Wi-Fi explanation: Wi-Fi is part of the 12 industrial, scientific, and medical (ISM) bands. Newer Wi-Fi standards allow for the bonding of multiple channels to allow up to 160 MHz wide channel combinations for faster data rates, multiple transceivers, and a theoretical throughput of up to 7 GBPS when the latest ratified Wi-Fi amendment, IEEE 802.11ac, is fully implemented.

07/16/2014


Figure 1: There are 12 industrial, scientific, and medical (ISM) bands. Of these, two are in use: the 26 MHz centered around 915 MHz, and the 100 MHz centered around 2.450 GHz. Currently, only the latter band is used for Wi-Fi. The former is used for deviWi-Fi operates within defined bands of frequencies as dictated by the Federal Communications Commission, specifically Part 15 of FCC rules. Wi-Fi operates in unlicensed frequency spectra, which means that anyone, within specified transmission power restrictions, can operate a transmitter within these bands.

There are 12 industrial, scientific, and medical (ISM) bands. Of these, two are in use: the 26 MHz centered around 915 MHz, and the 100 MHz centered around 2.450 GHz. Currently, only the latter band is used for Wi-Fi. The former is used for devices such as home automation (Zwave) and baby monitors. The 2.4 GHz band has a total of 14 channels, numbered 1-14. Channels 1-11 are allowed for use in the United States; 1-13 are used in Europe and Israel; 1-14 are used in Japan. Each channel is 22 MHz wide, with center frequencies of each channel separated by 5 MHz. As shown in Figure 1, only three channels do not overlap in the 11-channel model; therefore, only these channels can be used in a multi-channel architecture, or adjacent channel interference will render the network unusable.

As of this writing, there are 4 Unlicensed National Information Infrastructure bands (U-NII). There are a total of 23 U-NII channels available for use. 

4 bands within 5 GHz

The four bands in the 5GHz spectrum are:

  • U-NII-1 (lower) comprises four 20 MHz channels, 36-48 in the 100 MHz 5.150-5.250 GHz band.
  • U-NII-2A (lower middle) comprises four 20 MHz channels, 52-64 in the 100 MHz 5.250-5.350 GHz band.
  • U-NII-2C (upper middle) comprises 11 20 MHz channels, 100-140 in the 250 MHz 5.470-5.725 GHz band.
  • U-NII-3 (upper) comprises four 20 MHz channels, 149-161 in the 100 MHz 5.725-5.825 GHz band.

Figure 2: As of this writing, there are 4 Unlicensed National Information Infrastructure bands (U-NII) and 23 U-NII channels available for use. All four bands operate under power restrictions, with U-NII-1 being relegated to indoor use only. A recent ruleAll four bands operate under power restrictions, with U-NII-1 being relegated to indoor use only. A recent rule change effectively opened up this band for general use, removing the indoor-only stricture, and allowing transmit power to rise to 1 W from 50 mW. For comparison, U-NII-2A and 2C can operate up to 250 mW, and U-NII-3 can operate up to 1 W. Another change will be to add ISM channel 165, at the center frequency of 5.825 GHz, to the U-NII-3 band, bringing another 25 MHz into play. 

More Wi-Fi bands proposed

Proposed new bands are under consideration by the FCC to add even more bandwidth for Wi-Fi use. U-NII-2B will add 120 MHz bandwidth in the 5.350-5.470 band. U-NII-4 will add another 75 MHz in the 5.850-5.925 GHz band.

The 20 MHz wide channels are actually very narrow in terms of data throughput. Newer Wi-Fi standards allow for the bonding of multiple channels to allow up to 160 MHz wide channel combinations. This will have the effect, along with faster data rates and multiple transceivers, to allow a theoretical throughput of up to 7 GBPS when the latest ratified Wi-Fi amendment, IEEE 802.11ac, is fully implemented.

- Daniel E. Capano, owner and president, Diversified Technical Services Inc. of Stamford, Conn., is a certified wireless network administrator (CWNA). Edited by Mark T. Hoske, content manager, CFE Media, Control Engineering, mhoske@cfemedia.com.

ONLINE extras

www.controleng.com/blogs has other wireless tutorials from Capano on the following topics:

- What is wireless?

- Radio frequency basics

- Comparative modulation: Spread spectrum modulation terms and definitions for wireless networking

www.controleng.com/webcasts has wireless webcasts, some for PDH credit.

Control Engineering has a wireless page.



STEPHEN , NJ, United States, 07/16/14 01:08 PM:

Excellent explanation.
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Salary and career survey: Benchmarks and advice; Designing controls; Remote data collection, historians; Control valve advances; Hannover Messe; Control Engineering International
System integration: Best practices and technologies to help; Virtualization virtues; Cyber security advice; Motor system efficiency, savings; Product exclusives; Road to Hannover
Collaborative robotics: How to improve safety, return on investment; Industrial Internet of Things, Industrie 4.0: World views; High-performance HMI, Information Integration: OPC and OMG
This article collection contains several articles on the Industrial Internet of Things (IIoT) and how it is transforming manufacturing.
PLCs, robots, and the quest for a single controller; how OEE is key to automation solutions.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Getting to the bottom of subsea repairs: Older pipelines need more attention, and operators need a repair strategy; OTC preview; Offshore production difficult - and crucial
Digital oilfields: Integrated HMI/SCADA systems enable smarter data acquisition; Real-world impact of simulation; Electric actuator technology prospers in production fields
Special report: U.S. natural gas; LNG transport technologies evolve to meet market demand; Understanding new methane regulations; Predictive maintenance for gas pipeline compressors
click me