Quality of Service

In the wireless world, QoS is used to make sure the most important traffic will have priority over less sensitive traffic.

Voice traffic is sensitive to delays in audio delivery (latency) and to variations in the timing of the audio delivery (jitter). Voice over wireless is especially challenged because it is a shared medium. For the best user experience, all audio traffic must be tagged with the appropriate QoS markings on the wired infrastructure and be allocated to the appropriate wireless priority queue. The recommendations described here focus on wireless prioritization, as it is typically more constricted.

Tip: An important thing to remember about Quality of Service (QoS) is that it is only important if there is contention on the media. Traffic metering lights on freeway entrances are a type of quality of service. When there is no traffic on the freeway there is no need to restrict traffic coming on. When the freeway is very busy, the metering lights are used to restrict the cadence of adding more traffic. This restriction prevents the freeway from coming to a standstill.

Wireless prioritization is usually done at the SSID level. Vocera recommends that all voice only applications, such as the Vocera Badge, be allocated to the voice SSID.

Mixed use devices, such as smartphones running Vocera Collaboration Suite (VCS), should use an SSID with highest priority. Because the smartphone can only associate to one SSID, it cannot send voice packets to the voice SSID and other packets to a lower priority SSID. It allows VCS voice packets to have higher priority over other data traffic. The data packets from VCS will not impact voice quality on the voice only SSID.

All other data applications in the environment should use an SSID with Best Effort priority. Data applications typically use TCP and HTTP, which have protocol layer redundancy. Latency and jitter that would seriously impact a voice application have no discernable effect on data applications.

The Background priority should be used for traffic that is least important to business. While Guest access is important to patient and family satisfaction, it is less important than most business traffic. Care should be taken to provide a balance for guest access to the wireless network.