Harmonizing global 802.11a spectrum, Part 2

As a follow-up to my Q&A with Intel’s Jayne Stancavage, who sits on the Wi-Fi Alliance board, this time we’ll discuss some of the more technical and standards-oriented issues surrounding worldwide harmonization of the 5-GHz spectrum band for 802.11a LANs.

Stancavage and I have been talking on the eve of the World Radiocommunication Conference (WRC), to begin June 9. The WRC takes place every three to four years with the goal of coordinating spectrum-allocation and frequency-usage regulation on a global basis.

Wexler: What are some of the technical conditions that are currently out of sync around the world as regards the 5-GHz spectrum band for 802.11a use?

Stancavage: Europe allows the use of an extra 255 MHz of spectrum in the “mid-band” of 5.47 to 5.725 GHz. In addition, because of its own concerns about interference with military radar, Europe has imposed power limits – known as transmit power control, or TPC – and dynamic frequency selection (DFS) requirements on the use of that spectrum. The European Telecommunications Standards Institute requires that 802.11a LAN products built for use in Europe conform to these specifications.

Wexler: How does one know if a product complies?

Stancavage: The European requirements are described in an emerging extension to the 802.11 standard called 802.11h. 802.11h is currently in the final stages of approval by the IEEE.

Wexler: In its own WRC proposal, is the U.S. asking for similar limits in the 5-GHz mid-band?

Stancavage: Yes. The U.S. DFS threshold limits are -64 dBm for 200-milliwatts to 1-watt of radio LAN output power. For less than 200-milliwatts of output power, the proposed U.S. DFS limit is  -62 dBm.

Wexler: What do these thresholds represent?

Stancavage: They describe the strength, or “loudness,” of a signal beyond which the wireless LAN must move to another, distant channel so as not to interfere with military radar.

Wexler: If the U.S. spectrum proposals get the green light at the WRC, what will be the impact on the wireless LAN industry?

Stancavage: The current proposal represents a strong win-win compromise. It addresses the U.S. Department of Defense’s concerns for protecting its radar, as well as industry concerns about self-interference that would have resulted from earlier DFS thresholds. Overall, the strides toward globally harmonizing regulation of 802.11a operation would provide additional broadband wireless spectrum and consistency in product specs, usage, and economies of scale around the world.