Hello, everyone!
Today, I would like to continue on the novel features ot the IEEE 802.11aa amendment.
Prioritization of intra-access categories.
Only 4 distinct access categories (ACs) which are substantially matched to 4 distinctive classes are allowed under the IEEE 802.11e amendment:
Video (VD)
Voice (VO)
Background (BK)
Best-effort (BE)
Table 1. Performance standards for various HD streaming applications are listed.
Nevertheless, there are numerous streaming services available, varying from basic video conferencing to HD streaming through IPTV systems, each with its own set of QoS needs (Table 1). In comparison to IEEE 802.11e, IEEE 802.11aa provides an additional scheduling layer to enable the potential to distinguish between various streams.
Each transmission queue connected with voice and video ACs is separated into a primary and alternate queue by IEEE 802.11aa. When the EDCA function for inter-AC collision resolution gives access to voice or video ACs, specialized scheduling rules can be used to determine which queue to fulfill.
IEEE 802.11aa uses the predefined mappings among user priority values and traffic types provided in the IEEE 802.1D standard to make managing service level agreements easier.
Figure 1: Prioritization of inter-AC traffics and stream classification.
Then it's only a matter of mapping traffic kinds to transmission queues and ACs (Figure 1). Lastly, the intra-AC diversification capability can be leveraged to provide traffic distinction that is more complicated than simple stream prioritization.
Many video applications, for example, employ Scalable Video Coding (SVC) techniques, which allow a video sequence to be partitioned into many layers of varying quality and rate. An SVC-based video stream often has a base layer that provides a basic degree of quality, as well as various enhancement layers that can only be decoded in conjunction with the base layer to help improve the overall video quality.
As a result, the various layers of a same encoded video stream can be readily assigned to multiple transmission queues to obtain differential QoS.
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