The 802.11a Standard

• 802.11 was adopted in July 1997 as a worldwide standard.
  • Supports 1 and 2 Mbps operation at 2.4 GHz band

  • Physical layers: DSSS, FHSS and Infrared

• 802.11b high rate extension adopted in 1999
  • Supports 5.5 Mbps and 11 Mbps at 2.4 GHz

  • CCK modulation, bandwidth compatible with DSSS

• 802.11a specs approved at the beginning of year 2000
  • Supports up to 54 Mbps at 5 GHz band

  • Uses OFDM modulation

Frequency Allocations

Following is a summary of the frequency allocations for this standard.

• Modulation: OFDM

• Uses 52 subcarriers: 48 data + 4 pilots

• Convolutional coding rate: 2/3

• The carries can be BPSK, QPSK, 16QAM or 64QAM modulated. The RF bandwidth is approximately 16.6Mhz.

• OFDM frame duration: 4ms with guard interval: 0.8ms

• Data rate: 6, 9, 12, 18, 24, 36, 48, 54Mbps (6, 12 and 24Mbps mandatory)

OFDM Signal Spectrum

Following are examples of OFDM Signal Spectrum.

Generating an 802.11a Frame Using ADS

Select Tutorial: Understanding the 802.11a Frame Format.