Wireless Reliability - Channel Bounding


Channel bounding has drastically increased the bandwidth of a BSS (Basic Service Set). With 128 Data subcarriers, transmissions can carry far more coded bits per burst. The issue is that this bounded channel increases the number of channels with noise on them. This means more overlap can occur between WLANs operating within the spectra. As a result of this, channel bounding is not advised in the 2.4 GHz because it will make non overlapping channels no longer independent due to the signal spilling into overlapping channels.

Figure 1

As shown in Figure 4, channels 11 and 6 are no longer independent channels because there is a device operating on channel 11 using 40MHz bounded channels, meaning 10 and 11 become bounded. This makes areas containing several APs in the 2.4 GHz band have really low SNR.

The same does not go for the 5GHz though. There 24 non-overlapping channels in the 5GHz band and each channel are equally spaced at 20MHz intervals.

Figure 2


The 802.11ac standard outlines a mandatory 80MHz channel width. This will eat up channels like nobody’s business, but since the spectra is designed for each channel to be separate, it will not compromise any more channels than those that it bounds together. As shown in Figure 5, an 80MHz bounded channel only takes up 4 of the 24 channels. This means there can be 6 independent BSSs (IBSS) operating simultaneously on separate channels using 80MHz. 802.11ac also has an optional 160MHz channel width that will take up 8 Channels, which only gives us 3 simultaneous IBBSs using 160MHz. This greatly reduces the reliability of the 5GHz band because 8 channels occupied by one BSS does not leave much for others. In a largely populated area with 10 or more WLANs overlapping, a crisis of spectra (much like that of the 2.4GHz band) will occur. This is due to the fact that there are multiple 160MHz BSSs operating. For this reason, 160MHz should stay optional and should, like in the 2.4GHz, not be used unless a larger spectrum is present.


802.11ad has up to 2GHz channel, but with such a large spectrum, overlapping WLANs are not an issue because there is so much space to spread out. Also with its reduced range, they would need to be in line of sight in order to overlap.


Channel bounding gives WLANs a big boost in speed, this speed really makes up for the cost in lost spectra. With the next generation of wireless ditching the 2.4GHz band, we no longer need to worry about shrinking space within the spectrum. When space in the 5GHz runs out, however, another low power home will be needed. This is because the 60GHz band is not viable for providing WLANs throughout homes.

To read more from Jackson Corson, check out his other blogs: Wireless Reliability and Wireless Reliability - Modulation