quality of service differentiation is per service flow. Each of the service flow
is having one of the scheduling types; best effort (BE), non-real time polling
service (nrtPS), real-time polling service (rt-PS), extended real-time polling
service (ert-PS) or unsolicited grant service (UGS).
WiMAX provides the five QoS classes through an architecture that is able to
process requests, perform access control and allocate the required radio
resources that are able to meet the requests that are accepted. The five QoS
classes are described as follows.
- UGS: this is designed to support real-time data streams that consist of fixed sized packets issued at periodic intervals, such as back haul and voice over IP (VoIP) without silence suppression.
- Ert-PS: this is designed for the extended real-time services of variable rates such as VoIP with silence suppression, interactive gaming, and video telephony.
- Rt-PS: this is designed to support real-time data streams of variable rates that are issued at periodic intervals, such as MPEG video, audio and video streaming, and interactive gaming.
- Nrt-PS: this is designed to support delay-tolerant data streams consisting of variable-sized data packets such as file transfer protocol (FTP), browsing, video download, and video on demand.
- BE: this is designed to support data streams for which there is no minimum service requirements, and no guarantee of timely delivery of packets such as E-mail and Internet browsing.
code points (DSCP). DSCP is a field in the header of IP packets used for
classifying packets entering the network in order to provide QoS guarantees.
From an IP transport perspective, the WiMAX network is divided into
multiple DSCP domains. One domain is between the base station and the
ASN gateway (ASN-GW) in every ASN termed as ASN DiffServ domain.
The second domain, CSN DiffServ domain, is between the ASN-GWs and
the HAs. The third domain is between the HAs and Internet or operator
service network.
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