Белая книга для Cisco Cisco Aironet 1250 Series Access Point
White Paper
© 2009 Cisco Systems, Inc. All rights reserved. This document is Cisco Public Information.
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productivity, resource utilization, and patient satisfaction (due to shorter wait times), all of which
leads to greater profitability.
Table 1.
Number of Video Streams per Wireless Technology
Video Stream Types (throughput required)
802.11g (22 Mbps)
802.11n (140 Mbps)*
Improvement Factor
HD (10 Mbps)*
2
14
7X
DVD (5 Mbps)**
4
28
7X
* In real-life network deployments, Cisco 802.11n solutions have maintained a consistent throughput peak of
185 Mbps. Unfortunately, when it comes to video streaming over Wi-Fi, contention reduces the available
throughput per 802.11n radio to roughly 140 Mbps.
** A typical DVD-quality video stream requires about 5 Mbps of throughput. A high-definition video stream
requires double the throughput—that is, about 10 Mbps.
8x More Users
The transformative nature of wireless networking drives—and also feeds—an insatiable appetite
for network-connected devices. Most of us today have at least one Wi-Fi-enabled device, but many
of us are starting to carry more than one—for example, a dual-mode phone, a laptop computer, a
digital camera, a gaming console, or a music device. We are also becoming accustomed to finding
an available network that we can connect those devices to while at home, at work, or on the go,
which in turn drives the need for ubiquitous network connectivity.
The proliferation of these network-connected devices is creating an undeniable need for high-
density deployments as more and more users connect to the same network with multiple devices
for different reasons. This need is only exacerbated in areas where people tend to congregate in
large numbers for business, education, entertainment, or other reasons.
The Cisco 802.11n solution has been particularly successful in higher education environments for
that same reason. Consider a large lecture hall where many students congregate during class and
are connecting to the wireless network with their laptop computers in order to download the
instructor’s presentation slides and notes or conduct parallel, online research on the discussion
topic of the day.
If we assume that this large lecture hall is equipped with three 802.11g access points today, the
students in the classroom and their connected devices would be sharing an available bandwidth of
22 Mbps by load balancing these users and devices across the three available access points. Now
suppose that all these students were required by the instructor to use a “blackboard” type of
application to download presentation notes transcribed onto slides in real time. The application
would require a consistent bandwidth of 5 Mbps in order to provide a good user experience, and
the result would be that only 12 students (four students per access point) would be able to use the
application effectively in the classroom.
Suppose we were to replace these three 802.11g access points with three next-generation,
802.11n access points. The system-level bandwidth in the classroom would increase substantially
and more than 96 students (32 users per access point) would be able to connect to their wireless
network and expect to have a consistent application experience.
In fact, a one-to-one replacement of access points is the most prevalent migration scenario to
802.11n for organizations that want to increase their deployment density. User density becomes
an even more complex problem to solve when network users are demanding different bandwidths
to run their specific applications. It is not hard to imagine how airport terminal or conference room