Forum

The IEEE Std 802.11a-1999 amendment, ratified 16 Sept 1999, added Clause 17 OFDM PHY (operating in the 5 GHz band) to the IEEE 802.11 standard. Operating channel frequencies are defined in section 17.3.8.3. Table 88 shows the three FCC U-NII bands (lower, middle, and upper) that we have all become familiar with on certification exams.

The IEEE Std 802.11h-2003 amendment, ratified 29 Dec 2003, added to Table 88 (aka Table 94) a 5.47 - 5.725 GHz unnamed band between the middle and upper bands, but only for the CEPT (European Conference of Postal and Telecommunications) regulatory domain. This amendment also deleted the first paragraph of text following the table.

The IEEE Std 802.11j-2004 amendment, ratified 23 Sept 2004, deleted Table 88 and companion Figure 119 and replaced the text of section 17.3.8.3.3 with: "The set of operating channel numbers by regulatory domain is defined in Annex J. As shown in Figure 117, no subcarrier is allocated on the channel center frequency." The former Table 88 became multiple tables in Annex J, one for each regulatory domain. Table J.1 for the USA is essentially the same as the original table published in 1999, although the familiar FCC names "U-NII, lower, middle, upper" are gone, the three familiar channel sets remain. Table J.2 for Europe (CEPT) is essentially the same as the table published in 2003, including the channels corresponding to 5.47 - 5.725 GHz.

According to Cisco: "In February 2004, the FCC released a revision to the regulations covering 5 GHz channel usage. This revision added 11 channels, bringing the available channels capacity to 23 channels. In order to use the 11 new channels (ed. in Europe?), however, radios must comply with two features that are part of the 802.11h specification-Transmitter Power Control (TPC) and Dynamic Frequency Selection (DFS)." Also: "... the initial FCC regulations limited the use of the UNII-1 band to "integral" (permanently attached) antennas. With the October 2004 update of the FCC regulations, this regulation was removed, permitting the use of external antennas on all 23 channels in the 5 GHz bands." I have not searched the FCC documents that confirm these assertions, but I am willing to (mostly) believe Cisco.

Since February 2004 the question has been heard, "When will the IEEE amend 802.11 to include the extra eleven channels for OFDM PHY?" The answer is, "They were included automatically."

The IEEE Std 802.11a-1999 amendment, section 17.3.8.3.1 says, "The OFDM PHY shall operate in the 5 GHz band, as allocated by a regulatory body in its operational region. Spectrum allocation in the 5 GHz band is subject to authorities responsible for geographic-specific regulatory domains (e.g., global, regional, and national). The particular channelization to be used for this standard is dependent on such allocation, as well as the associated regulations for use of the allocations. These regulations are subject to revision, or may be superseded."

The IEEE P802.11-REVma/D8.0 Aug 2006 draft revision of 802.11 has an Annex J Table J.1 table of 5 GHz bands in the USA. It shows five classes of channel sets as follows.

Class 1: 36, 40, 44, 48 -- the FCC's lower U-NII band
Class 2: 52, 56, 60, 64 -- the FCC's middle U-NII band
Class 3: 149, 153, 157, 161 -- the FCC's upper U-NII band
Class 4: 100, 104, 108, 114, 116, 120, 124, 128, 132, 136, 140 -- the FCC's new? band
Class 5: 165 -- the FCC's ISM band!

That makes a total of not 23 but 24 channels! The mystery channel 165 is centered at 5.825 GHz, the upper edge of the FCC's upper U-NII band but squarely within the FCC's 5.725 - 5.850 GHz ISM band.

I hope this helps. Thanks. /criss