Although you can use directional antenna and have an AP-to-AP distance longer than
250 feet (76.2 meters), for seamless roaming, we recommend that you have an AP-to-AP
distance no more than 250 feet.
Note
Wireless Propagation Characteristics
Table 29: Comparison of 2.4-GHz and 5-GHz Bands, on page 89
provides a comparison of the 2.4-GHz and
5-GHz bands.
The 2.4-GHz band provides better propagation characteristics than 5 GHz, but 2.4 GHz is an unlicensed band
and has historically been affected with more noise and interference to date than the 5-GHz band. In addition,
because there are only three backhaul channels in 2.4 GHz, co-channel interference would result. Therefore,
the best method to achieve comparable capacity is by reducing system gain (that is, transmit power, antenna
gain, receive sensitivity, and path loss) to create smaller cells. These smaller cells require more access points
per square mile (greater access point density).
Table 29: Comparison of 2.4-GHz and 5-GHz Bands
5-GHz Band Characteristics
2.4-GHz Band Characteristics
20 channels
3 channels
No co-channel interference
More prone to co-channel interference
Higher power
Lower power
Higher SNR requirements given higher data rates
Lower SNR requirements given lower data rates
Worse propagation characteristics than 2.4 GHz but
less susceptible to noise and interference
Better propagation characteristics than 5 GHz but
more susceptible to noise and interference
Not as widely available in the world as 2.4-GHz.
Licenses in some countries.
Unlicensed band. Widely available throughout the
world.
2.4 GHz has more penetration capability across the obstacles due to a larger wavelength. In addition, 2.4 GHz
has lower date rates which increases the success of the signal to reach the other end.
CleanAir
The 1550 series leverages 802.11n technology with integrated radio and internal/external antennas. The 1550
series access points are based on the same chipset as the present CleanAir capable Aironet 3500 APs. In other
words, the 1550 series access points are capable of doing CleanAir.
With the 7.2.103.0 release, 3600 series access points can mesh with each other and can also provide CleanAir
functionality.
Cisco Mesh Access Points, Design and Deployment Guide, Release 7.3
OL-27593-01
89
Site Preparation and Planning
Wireless Propagation Characteristics