Cisco Cisco VPN Internal Service Module for ISR G2 Livre blanc
Wireless LAN Design Guide for High Density
Client Environments in Higher Education
10 © 2011 Cisco and/or its affiliates. All rights reserved.
Using legacy data rates as a nominal value, Table 3 shows the relationship between cell bandwidth and per
connection bandwidth.
connection bandwidth.
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A mixed cell containing both 802.11b and 802.11g traffic results in a throughput rate that is less than double that of 802.11b
alone and roughly half of 802.11g alone. A similar effect was seen when 802.11n and legacy 802.11a/g rates were compared.
Until the inclusion of 802.11n, all advances in Wi-Fi technology have come through incremental increases in encoding
technology. 802.11n changed the encoding and streamlined the logistics of bonding 20 MHz channels and increasing the
available channel bandwidth. In implementing new technology, it is also necessary to provide a mechanism that allows the
old and the new protocols to coexist. It is this mechanism that reduces the overall efficiency of the channel due to additional
overhead. An 802.11b modem was not designed to speak 802.11g. In order to avoid collisions, the 802.11b radios must be
informed that the channel is needed by 802.11g for a period of time.
alone and roughly half of 802.11g alone. A similar effect was seen when 802.11n and legacy 802.11a/g rates were compared.
Until the inclusion of 802.11n, all advances in Wi-Fi technology have come through incremental increases in encoding
technology. 802.11n changed the encoding and streamlined the logistics of bonding 20 MHz channels and increasing the
available channel bandwidth. In implementing new technology, it is also necessary to provide a mechanism that allows the
old and the new protocols to coexist. It is this mechanism that reduces the overall efficiency of the channel due to additional
overhead. An 802.11b modem was not designed to speak 802.11g. In order to avoid collisions, the 802.11b radios must be
informed that the channel is needed by 802.11g for a period of time.
In a high-density environment, every available efficiency must be taken advantage of to achieve the desired goal of maximum
throughput and access. Figure 5 shows the relationship of per frame air time (channel utilization), frame sizes, and data rates.
throughput and access. Figure 5 shows the relationship of per frame air time (channel utilization), frame sizes, and data rates.
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