Praise for Fundamentals of WiMAX

50 Chapter 2 • Overview of WiMAXrate, minimum tolerable rate, scheduling type, ARQ type, maximum delay, tolerated jitter, servicedata unit type and size, bandwidth request mechanism to be used, transmission PDU formationrules, and so on. Service flows may be provisioned through a network management system or createddynamically through defined signaling mechanisms in the standard. The base station isresponsible for issuing the SFID and mapping it to unique CIDs. Service flows can also be mappedto DiffServ code points or MPLS flow labels to enable end-to-end IP-based QoS.To support a wide variety of applications, WiMAX defines five scheduling services (Table 2.6)that should be supported by the base station MAC scheduler for data transport over a connection:1. Unsolicited grant services (UGS): This is designed to support fixed-size data packets at aconstant bit rate (CBR). Examples of applications that may use this service are T1/E1emulation and VoIP without silence suppression. The mandatory service flow parametersthat define this service are maximum sustained traffic rate, maximum latency, tolerated jitter,and request/transmission policy. 92. Real-time polling services (rtPS): This service is designed to support real-time serviceflows, such as MPEG video, that generate variable-size data packets on a periodic basis.The mandatory service flow parameters that define this service are minimum reserved trafficrate, maximum sustained traffic rate, maximum latency, and request/transmission policy.3. Non-real-time polling service (nrtPS): This service is designed to support delay-tolerantdata streams, such as an FTP, that require variable-size data grants at a minimum guaranteedrate. The mandatory service flow parameters to define this service are minimumreserved traffic rate, maximum sustained traffic rate, traffic priority, and request/transmissionpolicy.4. Best-effort (BE) service: This service is designed to support data streams, such as Webbrowsing, that do not require a minimum service-level guarantee. The mandatory serviceflow parameters to define this service are maximum sustained traffic rate, traffic priority,and request/transmission policy.5. Extended real-time variable rate (ERT-VR) service: This service is designed to supportreal-time applications, such as VoIP with silence suppression, that have variable data ratesbut require guaranteed data rate and delay. This service is defined only in IEEE 802.16e-2005, not in IEEE 802.16-2004. This is also referred to as extended real-time polling service(ErtPS).Although it does not define the scheduler per se, WiMAX does define several parametersand features that facilitate the implementation of an effective scheduler:• Support for a detailed parametric definition of QoS requirements and a variety of mechanismsto effectively signal traffic conditions and detailed QoS requirements in the uplink.9. This policy includes how to request for bandwidth and the rules around PDU formation, such aswhether fragmentation is allowed.