Cisco Cisco Catalyst 6500 6000 Series Services Maintenance Partition 白皮書
Wireless LAN Design Guide for High Density
Client Environments in Higher Education
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Directional Antennas
It is not always going to be possible to solve challenges in a high-density environment using strictly omnidirectional antennas. If
a WLAN requires channel reuse within the same floor space or if coverage is required for non-standard areas such as indoor or
outdoor arenas, mounting options for a usable design may be limited. Therefore directional antennas come in many coverage
patterns that are more suited to challenging environments where an omnidirectional will not be adequate.
a WLAN requires channel reuse within the same floor space or if coverage is required for non-standard areas such as indoor or
outdoor arenas, mounting options for a usable design may be limited. Therefore directional antennas come in many coverage
patterns that are more suited to challenging environments where an omnidirectional will not be adequate.
When an environment requires the use of directional antennas, the complexity of the design and the implementation both will go
up accordingly. It should, however, also be noted that outstanding results can be achieved.
up accordingly. It should, however, also be noted that outstanding results can be achieved.
Channel Reuse and Directional Antennas
If mounting on the ceiling in an auditorium with high ceilings greater than 25 feet, it is recommended that high gain directional
patch or Yagi style MIMO antennas be used because these antennas provide:
patch or Yagi style MIMO antennas be used because these antennas provide:
• Better ceiling to floor coverage, if mounted in the ceiling or on catwalks with antennas oriented in a direct downward direction.
This creates smaller cells of coverage directly beneath the APs and allows for better channel isolation between adjacent cells
while maintaining power levels and sensitivity in the direction of the covered clients.
while maintaining power levels and sensitivity in the direction of the covered clients.
• Coverage in larger venues with very high ceilings or perhaps where ceiling access is not available. Placing directional
antennas at mid level from the sides or from behind the coverage zone and using downtilt can provide controllable coverage
zones and better installation options in difficult environments.
zones and better installation options in difficult environments.
• A much narrower coverage lobe or beam, thus allowing smaller cells so the number of cells and channels for both 2.4 GHz
and 5 GHz can occupy a common room providing increased cell isolation and reducing CCI. This is critical in any environment
where the design solution requires channel reuse for either band.
where the design solution requires channel reuse for either band.
Directional antennas like omnidirectional antennas are classified by their 3 dB beamwidth in the horizontal and elevation planes.
But directional antennas typically have much higher gain than an antenna that is classified as omnidirectional. For example, the
AIR-ANT2460NP-R antenna, Table 7, has a 3 dB horizontal beamwidth of 80° and a 75° elevation plane. This is quite useful in
isolating the AP and antenna from surrounding energy and providing better coverage in the intended zone.
But directional antennas typically have much higher gain than an antenna that is classified as omnidirectional. For example, the
AIR-ANT2460NP-R antenna, Table 7, has a 3 dB horizontal beamwidth of 80° and a 75° elevation plane. This is quite useful in
isolating the AP and antenna from surrounding energy and providing better coverage in the intended zone.