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Chapter 19: Quality Of Service (QoS)
Understanding QoS
Psion Teklogix 9160 G2 Wireless Gateway User Manual 187
Quality of Service ( QoS ) provides you with the ability to specify parameters on multiple
queues for increased throughput and better performance of differentiated wireless traffic like
Voice-over-IP (VoIP), other types of audio, video, and streaming media, as well as tradi-
tional IP data over the 9160 G2 Wireless Gateway.
The following sections describe how to configure Quality of Service queues on the 9160 G2
Wireless Gateway.
19.1 Understanding QoS
A primary factor that affects QoS is network congestion due to an increased number of
clients attempting to access the air waves and higher traffic volume competing for band-
width during a busy time of day. The most noticeable degradation in service on a busy,
overloaded network will be evident in time-sensitive applications like Video,
Voice-over-IP
(VoIP), and streaming media.
Unlike typical data files which are less affected by variability in QoS, Video, VoIP and
streaming media must be sent in a specific order at a consistent rate and with minimum
delay between
Packet transmission. If the quality of service is compromised, the audio or
video will be distorted.
19.1.1 QoS And Load Balancing
By using a combination of load balancing (see Chapter 18: “Load Balancing”) and QoS
techniques, you can provide a high quality of service for time-sensitive applications even on
a busy network. Load balancing is a way of better distributing the traffic volume across
access points. QoS is a means of allocating bandwidth and network access based on trans-
mission priorities for different types of wireless traffic within a single access point.
19.1.2 802.11e And WMM Standards Support
QoS describes a range of technologies for controlling data streams on shared network con-
nections. The IEEE 802.11e task group is in the process of defining a QoS standard for
transmission quality and availability of service on wireless networks. QoS is designed to
provide better network service by minimizing network congestion; limiting
Jitter , Latency ,
and Packet Loss ; supporting dedicated bandwidth for time-sensitive or mission critical ap-
plications, and prioritizing wireless traffic for channel access.
As with all IEEE
802.11 working group standards, the goal is to provide a standard way of
implementing QoS features so that components from different companies are interoperable.