Scheduling Algorithms for Super 3G Jean-Christophe Laneri Kungliga Tekniska Högskolan Radio Communications Laboratory Master Thesis Project Advisor: Hannes Ekström ( Ericsson Research) Examiner: Slimane Ben Slimane ( KTH) Master Thesis Presentation 1 Scheduling Algorithms for Super 3G 2006-03-23
Agenda Scheduling Algorithms for Super 3G � The Big Picture � Algorithms � Simulation Results � Conclusions Master Thesis Presentation 2 Scheduling Algorithms for Super 3G 2006-03-23
Super 3G Initial deployment in the 2009-2010 time perspective � Evolution of the 3GPP Radio Access Network (RAN) � Traffic carried on to of IP: Enhancements for packet-based services � Targets related to this work – High Peak & ’ cell-edge ’ data rates – Spectrum Efficiency improvement & Spectrum Flexibility – Improved Service Provisioning � Possible ways of enforcing these objectives which concern this project – Reduced number of Network Nodes – Differentiation of Services over a Shared Infrastructure – Physical Layer � Downlink: OFDM with frequency adaptation Master Thesis Presentation 3 Scheduling Algorithms for Super 3G 2006-03-23
Motivations and Problem Definition Providing Quality of Service over Shared Channels � Schedulers are used in order to – Divide the Resources between the users over Shared Channels – Provide Spectrum Efficiency – Fulfill Service Requirements We study Downlink Scheduling Algorithms within the following context � – Multi-user OFDMA environment (with frequency adaptation) – Services Differentiation – ‘Realistic’ Traffic Models � We aim at – Verifying if the QoS policy profiles can be enforced – Evaluating some scheduling algorithms characterized by different level of fairness (in terms of user data rates) – Investigating the tradeoffs between network capacity and user fairness Master Thesis Presentation 4 Scheduling Algorithms for Super 3G 2006-03-23
QoS Concept Realization of DiffServ for 3GPP access networks � Principle – Mark each packet at the network edge with a a Flow-Class Identifier (FC-ID) – FC-IDs permit to identify the QoS class of packets at each network node – Associate a Policy Profile to each FC-ID � FC-IDs are grouped into three categories – SIGnaling – Guaranteed Bit Rate: Policy Profile = [strict priority] – Best Effort: Policy Profile = [Committed Rate, Priority] Aggregate Cell Throughput Internet Access CR= 30% CR= 30% CR= 70% CR= 70% Corporate Access Video (Pr=2) VoIP (Pr=1) Allocated to Signaling Time Master Thesis Presentation 5 Scheduling Algorithms for Super 3G 2006-03-23
Scheduling Architecture Dividing the bandwidth between the FC-IDs BE Inter-FC-ID Scheduler GBR Inter-FC-ID Scheduler S3G Scheduler Master Thesis Presentation 6 Scheduling Algorithms for Super 3G 2006-03-23
Scheduling Framework Radio Resources, Algorithm Inputs and Design Parameters AR-process with Available at every tti 1 s memory Perceived User Throughputs Channel Estimate for all OFDM subbands FC-ID Policy Profiles Scheduler 20 MHz bandwidth GBR … <FC-ID><Priority><delay cst> 1 81 BE <FC-ID><CR><Priority> Allocation Algorithm Link Adaptation Scheduling Decision Estimate the transferable <user><FC-ID><Number of Bits> amount of bits given a scheduling allocation Master Thesis Presentation 7 Scheduling Algorithms for Super 3G 2006-03-23
Resource Allocation Algorithms (1/2) Dividing the bandwidth between the users: Intra-FC-ID � Maximum Signal to Interference Ratio (Max SIR) � Proportional Fair (PF) � Exponential Rule (ER) � Modified Exponential Rule (ER 2 ) � VoIP Scheduler (VoIP) Master Thesis Presentation 8 Scheduling Algorithms for Super 3G 2006-03-23
Resource Allocation Algorithms (2/2) Dividing the bandwidth between the users: Intra-FC-ID � Fair Throughput Smaller average Larger throughput throughput User 7 User 5 User 9 User 3 User 2 User 6 � While users in U1 = {7,5,2} have data to receive – Iterate over U1, giving the best available chunk � While users in U2 = {6,9,3} have data to receive – Iterate over U2, giving the best available chunk Master Thesis Presentation 9 Scheduling Algorithms for Super 3G 2006-03-23
Scenarios & Performance Measures Algorithms Validation and Realistic Traffic Evaluation � Scenarios – Fully Loaded System � (Infinite source – only PHY/MAC is simulated) – File Transfer � (10 MB fixed file size, PHY/MAC/RLC/IP/TCP simulated) – Web-Browsing � (500 kB fixed file size, PHY/MAC/RLC/IP/TCP simulated) – Voice Over IP � (32 B frame every 20 ms, PHY/MAC/RLC/IP/UDP/RTP simulated) � Performance Measures – Cell Throughput (Information bits) – Link Utilization (Percentage of used chunk) – User Throughput Fairness (Jain fairness index) – Mean User Throughput – VoIP capacity: 90 % of the users with a delay below 50 ms Master Thesis Presentation 10 Scheduling Algorithms for Super 3G 2006-03-23
Simulation Results QoS Concept Verification for the Best Effort Policies 15.55 % � GBR service is emulated BE traffic gets a varying CR=30 % percentage of the resources. Percentage of Allocated Resources 36.3 % � Two BE FC-IDs, with CR=70 % Committed Rates of 70 % and 30 % 48.15 % Emulated BE Policies are enforced! � GBR Time (s) Master Thesis Presentation 11 Scheduling Algorithms for Super 3G 2006-03-23
Simulation Results Full Buffer Scenario (PHY/MAC only-100 users–400 s) � Traffic belonging to one BE FC-ID Is simulated. Fair Throughput Fairness = 0.899 � Tradeoff between Cell Maximum SIR and User Throughputs Fairness = 0.121 Proportional Fair Fairness = 0.435 ER 2 Fairness = 0.245 ER Fairness = 0.418 100Mbps 1Mbps 10Mbps Master Thesis Presentation 12 Scheduling Algorithms for Super 3G 2006-03-23
Simulation Results File Transfer (PHY/MAC/RLC/IP/TCP-10 MB files-20 min) Mean Throughput Fairness Cell Throughput Link Utilization Arrival Rate (users/s) Arrival Rate (users/s) Fair Throughput Maximum SIR Proportional Fair Modified ER Master Thesis Presentation 13 Scheduling Algorithms for Super 3G 2006-03-23
Simulation Results Web Browsing (PHY/MAC/RLC/IP/TCP-500 kB pages-20 min) � Web-Effect: users with low serving time (high SIR) monopolize the system � Traffic with interactive characteristic � Conclusion: – A fair scheduler could be profitable Master Thesis Presentation 14 Scheduling Algorithms for Super 3G 2006-03-23
Simulation Results VoIP (PHY/MAC/RLC/IP/UDP-32 B frames-20 min) Delay Constraint: 90% of the received 90 th percentile of the packet delays 50 ms delay tolerance packets with a delay under 50 ms Fair Throughput VoIP Max SIR Number of Users Master Thesis Presentation 15 Scheduling Algorithms for Super 3G 2006-03-23
Conclusions and Future Works QoS Concept Validated – Service Specific Scheduler Conclusions � – Policy Profiles can be enforced – Proposed schedulers validated with the Full-Buffer Scenario – Impact of realistic traffic: service-dependent scheduling algorithms � Radio oriented method for background downloads � Fair approach for interactive scenarios � Delay aware scheduler for conversational services – QoS concept well suited for this type of differentiation Future Works � – Controlling the scheduling decision as a function of what the users perceive (fairness, mean throughput) and load. – Resources Allocation for more than one tti Master Thesis Presentation 16 Scheduling Algorithms for Super 3G 2006-03-23
Master Thesis Presentation 17 Scheduling Algorithms for Super 3G 2006-03-23
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