User Manual

Chapter 6 Wireless LAN
NWA1120 Series User’s Guide
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6.10.1 Additional Wireless Terms
Table 24 Additional Wireless Terms
6.10.2 WMM QoS
WMM (Wi-Fi MultiMedia) QoS (Quality of Service) ensures quality of service in wireless networks. It
controls WLAN transmission priority on packets to be transmitted over the wireless network.
WMM QoS prioritizes wireless traffic according to the delivery requirements of the individual and
applications. WMM QoS is a part of the IEEE 802.11e QoS enhancement to certified Wi-Fi wireless
networks.
On APs without WMM QoS, all traffic streams are given the same access priority to the wireless
network. If the introduction of another traffic stream creates a data transmission demand that
exceeds the current network capacity, then the new traffic stream reduces the throughput of the
other traffic streams.
The NWA uses WMM QoS to prioritize traffic streams according to the IEEE 802.1q or DSCP
information in each packet’s header. The NWA automatically determines the priority to use for an
individual traffic stream. This prevents reductions in data transmission for applications that are
sensitive to latency and jitter (variations in delay).
TERM DESCRIPTION
Intra-BSS Traffic This describes direct communication (not through the NWA) between two wireless
devices within a wireless network. You might disable this kind of communication to
enhance security within your wireless network.
RTS/CTS Threshold In a wireless network which covers a large area, wireless devices are sometimes not
aware of each other’s presence. This may cause them to send information to the AP
at the same time and result in information colliding and not getting through.
By setting this value lower than the default value, the wireless devices must
sometimes get permission to send information to the NWA. The lower the value, the
more often the devices must get permission.
If this value is greater than the fragmentation threshold value (see below), then
wireless devices never have to get permission to send information to the NWA.
Preamble A preamble affects the timing in your wireless network. There are two preamble
modes: long and short. If a device uses a different preamble mode than the NWA
does, it cannot communicate with the NWA.
Fragmentation
Threshold
A small fragmentation threshold is recommended for busy networks, while a larger
threshold provides faster performance if the network is not very busy.
Roaming If you have two or more NWAs (or other wireless access points) on your wireless
network, you can enable this option so that wireless devices can change locations
without having to log in again. This is useful for devices, such as notebooks, that
move around a lot.
Antenna An antenna couples Radio Frequency (RF) signals onto air. A transmitter within a
wireless device sends an RF signal to the antenna, which propagates the signal
through the air. The antenna also operates in reverse by capturing RF signals from
the air.
Positioning the antennas properly increases the range and coverage area of a wireless
LAN.