Saturday, November 6, 2010


These frameworks employ more than one type of scheduler for the various traffic classes of WiMAX.
WRR has been adopted for rtPS and nrtPS traffic classes, whereas simple RR has been employed for BE. It does not consider the ertPS traffic class and nor does it specify clearly whether or not GPSS is used.
Based on priority scheduling and dynamic bandwidth allocation, a QoS architecture for WiMAX. The contention slot allocator has been proposed to be used by the BS to dynamically adjust the ratio of the bandwidth allocated to the contention and reservation slots. WRR has been used as an upstream scheduler at the BS. At the SS level, there are two levels of scheduler, viz., (1) strict priority scheduling for distribution of allocated bandwidth among various classes and (2) schedulers for each of four classes. At the first level of scheduling at SS, the Multiclass Priority Scheduler has been suggested; whereas, at the second level of scheduling at the SS IWFQ has been proposed for higher priority, WRR for middle priority, and first-in-first-out (FIFO) for lower priority traffic classes of WiMAX. No experimental or simulation results have been presented.

A scheduling framework has been proposed, which is based on a centralized mechanism similar to the GPC mode of operation. The proposed UL packet scheduler requires three modules at the BS: an information module, a scheduling database module, and a service assignment module. The information module performs the following functions: retrieving the queue size information for each connection from bandwidth request messages, determining the number of packets that have arrived from an rtPS connection in the previous time frame by using arrival service concept, determining rtPS packets’ arrival time/deadlines and updating the scheduling database, queueing information from nrtPS, and BE request messages are directly passed to the scheduling database. The proposed scheduling database module will provide scheduling information to all of the connections; whereas the service assignment module determines UL-MAP by using information in the scheduling database. A strict priority scheduler is used for allocation of bandwidth from UGS, rtPS, nrtPS, and BE. Further, it has been proposed that there is no scheduler for UGS, EDF for rtPS, WFQ for nrtPS, and FIFO for BE. 

Deficit fair priority queueing (DFPQ) has been proposed for the first layer of scheduling at SSs. It has been derived from the DRR discipline. At the second layer of scheduling, EDF has been proposed for rtPS, WFQ for nrtPS, and WRR for BE. Some simulation results have also been presented. It is not clear whether GPSS or GPC has been employed for this work. However, the idea of DFPQ can be easily adopted for other advanced scheduling frameworks involving WiMAX.

A multiclass uplink fair scheduling structure (MUFSS), to support delay and bandwidth requirements of IEEE 802.16 QoS. The BS adopts modified WRR, but these details are not provided. At the SS, a modified WFQ has been suggested for UGS and rtPS classes; whereas, modified WRR and FIFO have been suggested for nrtPS and BE classes. Although MUFSS can provide guarantees for delay sensitive real-time traffic, it has less throughput overall and higher processing time.
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