Cisco Cisco Catalyst 6500 Series Network Analysis Module (NAM-3) White Paper
Wireless LAN Design Guide for High Density
Client Environments in Higher Education
6 © 2011 Cisco and/or its affiliates. All rights reserved.
What is ultimately going to effect the client devices more than any other factor is the degradation of signal-to-noise ratio
(SNR) through both co-channel and adjacent channel interference driven by co-located devices. Proper system engineering
can minimize the impact by maximizing proper spatial reuse but it cannot be eliminated in highly dense environments entirely.
Operating margins become more critical as space is condensed and a bad radio or behavior in the mix can have a large impact
within a cell. Client behavior under these conditions will vary widely and trends based on environment and event type have also
been reported. There is not much that can be done about the particular client mix or behavior. The design goal is to engineer the
network side as robustly as possible and to control and understand all variables.
(SNR) through both co-channel and adjacent channel interference driven by co-located devices. Proper system engineering
can minimize the impact by maximizing proper spatial reuse but it cannot be eliminated in highly dense environments entirely.
Operating margins become more critical as space is condensed and a bad radio or behavior in the mix can have a large impact
within a cell. Client behavior under these conditions will vary widely and trends based on environment and event type have also
been reported. There is not much that can be done about the particular client mix or behavior. The design goal is to engineer the
network side as robustly as possible and to control and understand all variables.
Within environments that qualify as high-density, there are also submodels built by use case. For example, in a high-density
environment such as a public venue or stadium, capacity is planned based on what percentage of users are likely to be active
on the network at any one time. In higher education there is a different model, where casual WLAN activity is one use case while
activity when a professor is lecturing may increase dramatically, up to 100 percent.
environment such as a public venue or stadium, capacity is planned based on what percentage of users are likely to be active
on the network at any one time. In higher education there is a different model, where casual WLAN activity is one use case while
activity when a professor is lecturing may increase dramatically, up to 100 percent.
Planning
The WLAN design process can begin in many ways but generally it begins with an expressed desire to provide connections to
a specific area where a number of users will participate in a focused activity. To evaluate what is possible, it is first necessary
to understand what is required as well as what is possible. There is generally a primary application that is driving the need
for connectivity. Understanding the throughput requirements for this application and for other activities that will take place
on the network will provide the designer with a per-user bandwidth goal. Multiplying this number by the number of expected
connections yields the aggregate bandwidth that will be required.
a specific area where a number of users will participate in a focused activity. To evaluate what is possible, it is first necessary
to understand what is required as well as what is possible. There is generally a primary application that is driving the need
for connectivity. Understanding the throughput requirements for this application and for other activities that will take place
on the network will provide the designer with a per-user bandwidth goal. Multiplying this number by the number of expected
connections yields the aggregate bandwidth that will be required.
The required per connection bandwidth will be used to drive subsequent design decisions.
Design Point #1: Establish and Validate a Per-Connection Bandwidth Requirement
How much bandwidth does each user require on average? In Table 1, the nominal throughput requirements for several popular
applications and use cases in a higher education setting are shown.
applications and use cases in a higher education setting are shown.
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Application by Use Case
Nominal Throughput
Web - Casual
500 kilobits per second (Kbps)
Web - Instructional
1 Megabit per second (Mbps)
Audio - Casual
100 Kbps
Audio - instructional
1 Mbps
On-demand or Streaming Video - Casual
1 Mbps
On-demand or Streaming Video - Instructional
2-4 Mbps
Printing
1 Mbps
File Sharing - Casual
1 Mbps
File Sharing - Instructional
2-8 Mbps
Online Testing
2-4 Mbps
Device Backups
10-50 Mbps