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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Observation and understanding of the requirements of WLAN users and situational requirements will guide the development of
reasonable design goals. 500 users in a room who require simultaneous access to a single resource is a different design challenge
than 1000 or 1500 users who only occasionally use the wireless network. Also, be aware that user patterns can and do change
with time. This has been seen with the increase in the number of network clients per user. Monitoring network access and keeping
good statistics will allow wireless engineers to stay on top of user trends on the university campus. Good management platforms
such as Cisco WCS or Cisco Network Control System (NCS) are essential for managing the resulting network in real time
and monitoring trends in a proactive manner.
reasonable design goals. 500 users in a room who require simultaneous access to a single resource is a different design challenge
than 1000 or 1500 users who only occasionally use the wireless network. Also, be aware that user patterns can and do change
with time. This has been seen with the increase in the number of network clients per user. Monitoring network access and keeping
good statistics will allow wireless engineers to stay on top of user trends on the university campus. Good management platforms
such as Cisco WCS or Cisco Network Control System (NCS) are essential for managing the resulting network in real time
and monitoring trends in a proactive manner.
Access Point Placement and Coverage Strategies
Often one of the biggest challenges in a high-density environment is access and aesthetics. A large meeting hall is impressive
because of its size and a great deal goes into the aesthetics of the environment. The best approach to engineering a specific space
is to do a qualified sight survey. Once the APs are mounted, physical adjustments become a lot more complex, so it is best to test
while installing and make certain that the coverage that has been defined in the design is what is installed.
because of its size and a great deal goes into the aesthetics of the environment. The best approach to engineering a specific space
is to do a qualified sight survey. Once the APs are mounted, physical adjustments become a lot more complex, so it is best to test
while installing and make certain that the coverage that has been defined in the design is what is installed.
APs have evolved rapidly in short period of time. If an AP with external antenna capabilities is to be used, it is essential that an
antenna that was designed for that AP also be used. MIMO or 802.11n APs need MIMO antennas to perform properly. Even if HT
rates are not being counted on, the antenna and the radios are a system and the system is designed to perform with all of these
elements. A good overview of antennas and pattern information can be found in
antenna that was designed for that AP also be used. MIMO or 802.11n APs need MIMO antennas to perform properly. Even if HT
rates are not being counted on, the antenna and the radios are a system and the system is designed to perform with all of these
elements. A good overview of antennas and pattern information can be found in
Omnidirectional Antennas versus Directional Antennas for High-Density Coverage
Mounting APs or directional antennas directly overhead in an environment may not be acceptable to the building owners. There are
several ways to solve this problem and, depending on the environment and restrictions imposed, several methods may be used
together.
several ways to solve this problem and, depending on the environment and restrictions imposed, several methods may be used
together.
The best approach to engineering a specific space for a high-density WLAN is to first do a thorough, active site survey to determine
how and where the APs should be optimally installed. This will clarify what is possible in the space and provide a design to work
from. Any changes to the optimal placement imposed by restrictions will require another survey because the final throughput for the
space will likely change. If the environment and requirements neccesitate the use of directional antennas, remember that once the
APs are mounted, physical adjustments can become a lot more complex, depending on the mounting location. So it is best to test
them while they are being installing to ensure that the anticipated coverage results from what is installed.
how and where the APs should be optimally installed. This will clarify what is possible in the space and provide a design to work
from. Any changes to the optimal placement imposed by restrictions will require another survey because the final throughput for the
space will likely change. If the environment and requirements neccesitate the use of directional antennas, remember that once the
APs are mounted, physical adjustments can become a lot more complex, depending on the mounting location. So it is best to test
them while they are being installing to ensure that the anticipated coverage results from what is installed.
Omnidirectional Antennas
Use of an AP with attached low gain omnidirectional MIMO antenna is recommended if mounting is to be done on the ceiling of
a modest-sized auditorium (averaging 20 feet or lower) with no channel reuse required in 2.4 GHz or 5 GHz. Omnidirectional
antennas provide better ceiling-to-floor coverage, thereby reducing the likelihood that a packet traveling to or from the client has
bounced off some object (usually a wall or the ceiling) before reaching the receiving antenna. This reduces the opportunity for
multipath interference.
a modest-sized auditorium (averaging 20 feet or lower) with no channel reuse required in 2.4 GHz or 5 GHz. Omnidirectional
antennas provide better ceiling-to-floor coverage, thereby reducing the likelihood that a packet traveling to or from the client has
bounced off some object (usually a wall or the ceiling) before reaching the receiving antenna. This reduces the opportunity for
multipath interference.