Praise for Fundamentals of WiMAX

2.4 MAC-Layer Overview 51Table 2.6 Service Flows Supported in WiMAXService Flow Designation Defining QoS Parameters Application ExamplesUnsolicited grant services (UGS)Real-time Polling service (rtPS)Non-real-time Polling service(nrtPS)Best-effort service (BE)Extended real-time Polling service(ErtPS)Maximum sustained rateMaximum latency toleranceJitter toleranceMinimum reserved rateMaximum sustained rateMaximum latency toleranceTraffic priorityMinimum reserved rateMaximum sustained rateTraffic priorityMaximum sustained rateTraffic priorityMinimum reserved rateMaximum sustained rateMaximum latency toleranceJitter toleranceTraffic priorityVoice over IP (VoIP) withoutsilence suppressionStreaming audio and video,MPEG (Motion Picture ExpertsGroup) encodedFile Transfer Protocol (FTP)Web browsing, data transferVoIP with silence suppression• Support for three-dimensional dynamic resource allocation in the MAC layer. Resourcescan be allocated in time (time slots), frequency (subcarriers), and space (multiple antennas)on a frame-by-frame basis.• Support for fast channel-quality information feedback to enable the scheduler to select theappropriate coding and modulation (burst profile) for each allocation.• Support for contiguous subcarrier permutations, such as AMC, that allow the scheduler toexploit multiuser diversity by allocating each subscriber to its corresponding strongestsubchannel.It should be noted that the implementation of an effective scheduler is critical to the overallcapacity and performance of a WiMAX system.2.4.3 Power-Saving FeaturesTo support battery-operated portable devices, mobile WiMAX has power-saving features thatallow portable subscriber stations to operate for longer durations without having to recharge.Power saving is achieved by turning off parts of the MS in a controlled manner when it is notactively transmitting or receiving data. Mobile WiMAX defines signaling methods that allow theMS to retreat into a sleep mode or idle mode when inactive. Sleep mode is a state in which theMS effectively turns itself off and becomes unavailable for predetermined periods. The periods