Uplink Scheduling with Quality of Service in IEEE Networks Juliana Freitag and Nelson L. S. da Fonseca State University of Campinas, Sao Paulo, Brazil IEEE Global Telecommunications Conference, GLOBECOM '07. Mei-Jhen Chen

Outline Introduction Introduction A scheduling Mechanism A scheduling Mechanism Simulation Experiments Simulation Experiments Conclusions Conclusions

Introduction To support a wide variety of multimedia applications, the IEEE standard defines four types of service flows, each with different QoS requirements. Each connection between the SS and the BS is associated to one service flow. UGS (Unsolicited Grant Service) rtPS (real time Polling Service) nrtPS (non-real time Polling Service) BE (Best Effort)

Introduction (cont.) A signaling mechanism for information exchange between the base station (BS) and subscriber stations (SSs) was defined. allow the SSs to request bandwidth to the BS Bandwidth allocation is provided on demand When an SS has backlogged data, it sends a bandwidth request to the BS. The BS allocates time slots to the SS. Each frame is divided in two parts the downlink subframe and the uplink subframe

Introduction (cont.) different scheduling mechanisms have been proposed not all of them comply with the IEEE standard Authors introduce a BS uplink scheduling algorithm which allocates bandwidth to the SSs based on the QoS requirements of the connections. The proposed policy is fully standard-compliant and it can be easily implemented in the BSs.

A Scheduling Mechanism According to the IEEE standard the BS uplink scheduler provides grants (time slots) at periodic intervals to the UGS flows to send data. Periodic grants are also given to rtPS and to nrtPS flows to request bandwidth. the uplink scheduler must guarantee that the delay and the bandwidth requirements of rtPS and nrtPS flows are met. The BS executes the uplink scheduler during each frame, and it broadcasts the schedule in the UL-MAP message in the downlink subframe.

A Scheduling Mechanism low priority queue intermediate queue high priority queue

A Scheduling Mechanism

A Scheduling Mechanism -CheckDeadline low priority queue intermediate queue high priority queue current_time = 8ms Frame_duration = 5ms UGS request rtPS request nrtPS request BE request Server UL-MAP deadline = 18ms 13ms 20ms frame[i] : 2 1 2

A Scheduling Mechanism -CheckMinimumBandwidth low priority queue intermediate queue high priority queue current_time = 8ms Frame_duration = 5ms UGS request rtPS request nrtPS request BE request Server UL-MAP BWmin : granted_BW_tmp : backlogged_tmp : Priority[i] = backlogged_tmp[CID] – (granted_BW_tmp[CID]-BWmin[CID])

Simulation Experiments -assumption NS-2 250x250 meter area a BS ： located at the center the SSs ： uniformly distributed The frame duration ： 5 ms the capacity of the channel ： 40 Mbps

Simulation Experiments -assumption Each SS has only one traffic flow. four types of traffic Voice “ on/off ” ： a mean of 1.2 s and 1.8 s During “ on ” periods, packets of 66 bytes are generated every 20 ms Video real MPEG traces FTP a hybrid Lognormal/Pareto distribution an area of 0.88 with a mean of 7247 bytes the tail is modeled with a mean of bytes WEB exponential distribution with a mean of 512 KBytes.

Simulation Experiments -assumption UGS The interval between data grants is 20 ms since the BS rtPS The interval is 20 ms the delay requirement is 100 ms nrtPS the interval of the nrtPS service 1 s. minimum bandwidth requirement of 200Kbps BE not have any QoS requirement

Simulation Experiments - experiment 1 Whether the BS is able to allocate bandwidth to connections in the same service level in a fair way, regardless the number of connections in the network. one BS the number of SSs varies between 10 and 30 Each SS has one nrtPS connection that generates FTP traffic with rate of 600 Kbps.

Simulation Experiments - experiment 1 Fig. 2. Throughput of each SS

Simulation Experiments - experiment 2 whether or not the increase of the UGS traffic load degrades the QoS level of services with lower priority. one BS and 81 SSs 6 rtPS connections 20 nrtPS connections 20 BE connections the number of active UGS connections varies from 15 to 35.

Simulation Experiments - experiment 2 Fig. 3. Delay of UGS and rtPS connections

Simulation Experiments - experiment 2 Fig. 4. Throughput of nrtPS and BE connections

Simulation Experiments - experiment 3 the impact of the load increase of the rtPS service on the performance of other service classes. one BS and 62 SSs 15 UGS connections 20 nrtPS connections 20 BE connections the number of active rtPS connections varies from 1 to 7

Simulation Experiments - experiment 3 Fig. 5. Delay of UGS and rtPS connections

Simulation Experiments - experiment 3 Fig. 6. Throughput of nrtPS and BE connections

Simulation Experiments - experiment 4 whether the increase of the BE traffic load influences or not the QoS level of services which has higher priority. one BS and 70 SSs. 15 UGS connections 5 rtPS connections 15 nrtPS connections the number of active BE connections varies from 10 to 35.

Simulation Experiments - experiment 4 Fig. 7. Delay of UGS and rtPS connections

Simulation Experiments - experiment 4 Fig. 8. Throughput of nrtPS and BE connections

Conclusions An uplink scheduling mechanism for IEEE networks was introduced. The proposed solution supports the four service levels specified by the standard and considers their QoS requirements for scheduling decisions. The complexity of the proposed mechanism is O(k + rlogr) k : number of slots in the uplink subframe r : the number of rtPS and nrtPS bandwidth requests in the intermediate queue

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