ZyXEL NWA1123-NI User Guide - Page 89

Chapter 6 Wireless LAN 6.10.1 Additional Wireless Terms Table 24 Additional Wireless Terms TERM Intra-BSS Traffic RTS/CTS Threshold Preamble Fragmentation Threshold Roaming Antenna DESCRIPTION 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. 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. 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. A small fragmentation threshold is recommended for busy networks, while a larger threshold provides faster performance if the network is not very busy. 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. 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. 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). NWA1120 Series User's Guide 89