In the 802.11ac system, OFDM is used (Orthogonal Frequency Division Multiplexing), as as in 802.11a and 802.11n. Since the spaced subcarriers used to transmit data is equal in OFDM, the number of subcarriers in the 11ac signal depends on the bandwidth, shown in table below.
|
Bandwidth (MHz) |
Number of Subcarriers |
Subcarriers Transmitting Signal |
|---|---|---|
|
20 |
64 |
-28 to -1 and 1 to 28 |
|
40 |
128 |
-58 to -2 and 2 to 58 |
|
80 |
256 |
-122 to -2 and 2 to 122 |
|
160 |
512 |
-250 to-130, -126 to -6, 6 to 126 and 130 to 250 |
The frame format is shown in the Figure 1.
Figure 1. 80211ac WLAN Frame