Integrating SIP and IEEE 802.11e to Support Handoff and Multi-grade QoS for VoIP Applications

1. Integrating SIP and IEEE 802.11e to Support Handoff and Multi-grade QoS for VoIP Applications Authors: Jen-Jee Chen, Ling Lee, and Yu-Chee Tseng High-Speed Communication and Computing Laboratory Department of Computer Science, National Chiao-Tung University, Taiwan

2. Outline • Introduction • Backgrounds • The Proposed QoS Mechanisms • Call Admission Control Algorithm • Resource Adjustment Algorithm • Simulation Results • Conclusions

3. Outline • Introduction • Backgrounds • The Proposed QoS Mechanisms • Call Admission Control Algorithm • Resource Adjustment Algorithm • Simulation Results • Conclusions

4. Introduction • User mobility and QoS are two important issues in mobile multimedia applications. • IEEE 802.11e supports: • Traffic differentiation • Simple admission control • IEEE 802.11e “CAN NOT” guarantee: • QoS when the QSTA handoffs to a new QAP. • Early resumption of resources as calls leave a QAP. • Resource is well utilized.

5. Introduction • Goal: • Guarantee QoS of each admitted VoIP calls. • Achieve early resumption of resources when handoff occurs. • Fairly distribute network resources. • Improve network utilization.

6. Outline • Introduction • Backgrounds • The Proposed QoS Mechanisms • Call Admission Control Algorithm • Resource Adjustment Algorithm • Simulation Results • Conclusions

7. Backgrounds • Original Handoff Procedure

8. Backgrounds • VoIP calls can be supported by different codec and packetization interval (PI). • Typical multimedia applications can tolerate little degrade in quality. Modifying the PI of a call can save resource. No paper discussed about dynamic QoS adjustment using adaptive PI. • Main Ideas: • Adjust the quality of the call according to the network conditions. Example: A call changes from a PI to another PI’, the difference of resource usage is: ( : data generation rate, : header overhead)

9. Outline • Introduction • Backgrounds • The Proposed QoS Mechanisms • Call Admission Control Algorithm • Resource Adjustment Algorithm • Simulation Results • Conclusions

10. The Proposed QoS Mechanisms • Two mechanisms: • CAC: accepts or rejects an arriving call according to the available resources and QoS requirements of the call. • RA: dynamically changes resource distribution among on-going calls for better resource utilization and fairness. • Assumptions: • VoIP calls support multi-level QoS, which correspond to a voice codec and a PI (packetization interval). Resource ↑ (codec, PI1) Level-1 • A call moves from level-i to level-j • (= changes PI from PIi to PIj) • i>j, resource required, =MT(j)-MT(i) • i<j, resource released, =MT(i)-MT(j) Level-2 (codec, PI2) Level-3 (codec, PI3) Level-4 (codec, PI4) Level-k (codec, PIk)

11. Characterizing The Resource of a QAP: • Btotal:the total resource of a QAP. • Bfree:the current free resource of the QAP. • Bth:the threshold of occupied resource. • Bdeg: the maximum available free resource of the QAP after degrading all existing calls to the lowest QoS level. • PIdef:the default PI for all new calls. • Walloc: the resource allocated to the request call New call isn’t admitted ! Bfree Bdeg Btotal Bth Used

12. Call Admission Control (CAC) Algorithm • When New Call Arrives • A. Resource Estimation at QAP • C. Resource Reservation at QAP • D. ADDTS Request by the Caller • E. ADDTS Response by the QAP • E. ADDTS Response by the QAP • According to the caller’s ADDTS request, the QAP can compute the • required MT. Each QAP keeps following variables. • ‧TXOPBudget[ACi], TxAdDn[ACi][TSID], TxAdUp[ACi][TSID], • TxAdDn[ACi], TxUsedDn[ACi] • Then, the QAP will reply an ADDTS response to the caller. INVITE A INVITE Ringing Ringing A. Resource Estimation at QAP Given codec, PI and physical rate, the QAP can compute Medium Time(MT) required for the call. For each codec, if Bdeg<MT, the QAP will remove the codec from the codec list. C OK OK Degrade Function ADDTS Request C. Resource Reservation ※The QAP decides to accept the call if: (1) MT(c,PImax,r)≦Bdeg and Bdeg> (Btotal – Bth) (2) MT(c,PImax,r)≦Bdeg, Bdeg≦(Btotal – Bth) with probability Pr ※ If the call is accepted: And if MT(c,PImax,r)>Bfree: the degrade function will be executed D E D. ADDTS Request by the Caller After deciding the PI and codec, the caller can send a bidirectional ADDTS request to the QAP by including a TSPEC element. ADDTS Response ACK ACK Communication

13. When Handoff Call Arrives Probe Request • Resource Estimation at QAP • QAP Selection at the Caller • C. Resource Reservation at QAP • D. ADDTS Request by the Caller • E. ADDTS Response by the QAP A Probe Request A Probe Response B A. Resource Estimation at QAP Given codec and PI, the QAP can compute Medium Time(MT) required for the call. For each codec, if Bdeg<MT, the QAP will remove the codec from the codec list. Probe Response • E. ADDTS Response by the QAP • According to the caller’s ADDTS request, the QAP can compute the • required MT. Each QAP keeps following variables. • ‧TXOPBudget[ACi], TxAdDn[ACi][TSID], TxAdUp[ACi][TSID], • TxAdDn[ACi], TxUsedDn[ACi] • Then, the QAP will reply an ADDTS response to the caller. Authentication Re-Association Request B. QAP Selection at the Caller After scanning channels, the caller will choose a target QAP based on various criteria, such as signal strength, best PI, best codec, etc. D. ADDTS Request by the Caller After deciding the PI and codec, the caller can send a bidirectional ADDTS request to the QAP by including a TSPEC element. C Degrade Function IAPP C. Resource Reservation ※The QAP decides to accept the call if: The requested MT(c,PImax,r) ≦Bdeg; otherwise, rejected. ※ If the call is accepted: And if MT(c,PImax,r)>Bfree: the degrade function will be executed Re-Association Response ADDTS Request D E ADDTS Response Communication

14. Resource Adjustment (RA) Algorithm • Goal: re-allocate resources to calls for better resource utilization and fairness. • The RA algorithm is triggered by: • Departure of calls or call termination: • The upgrade algorithm will be called. • Transmission rate change of existing calls • A call changes to higher rate: decrease its required MT, the upgrade algorithm will be called. • A call changes to lower rate: increase its required MT, the degrade algorithm will be called.

15. Degrade Algorithm degrade(c, p, r) • t_PI = p; • while (not all calls are reserved by PImax) do • let X be the call with the smallest PI in the system; in case of tie, the one with the lowest physical rate is selected; • change X’s PI to next(X.PI); • Bfree= Bfree + MT(X.codec, X.PI, X.rate) – MT(X.codec, next(X.PI), X.rate); • if(Bfree≧ MT(c, t_PI, r)) then • return(t_PI); • else if (there is no call with PI smaller than or equal to t_PI) then • t_PI = next(t_PI); • end if; • end while; • return(PImax);

16. Example of Degrade Algorithm Physical Rate (Mbps) 11 5.5 2 Degrade 2 1 2 1 5.5 2 5.5 2 Required MT (11M,5.5M,2M,1M) Bfree=0 R1 arrives (Rate=1Mbps)

17. Example of Degrade Algorithm 11 5.5 2 2 1 1 11 5.5 2 2 1 1 Degrade 5.5 2 5.5 2 5.5 2 Bfree=0 Bfree=0 R2 arrives (Rate=1Mbps)

18. Example of Degrade Algorithm 11 5.5 2 1 11 5.5 2 1 11 5.5 2 2 1 1 Degrade 2 1 1 2 1 1 5.5 2 5.5 2 5.5 2 5.5 2 Bfree=0 Bfree=0 Bfree=0 R3 arrives (Rate=5.5Mbps)

19. Example of Degrade Algorithm 11 5.5 11 5.5 2 1 11 5.5 2 2 1 1 2 1 1 5.5 2 2 1 1 1 5.5 2 5.5 2 5.5 2 5.5 2 Bfree=0 Bfree=0 Bfree=0 Bfree=1

20. The Upgrade Algorithm upgrade() • while (TRUE) do • let X be the call with the largest PI in the system; in case of tie, the one with the highest physical rate is selected; • if Bfree ≧ MT(X.codec, prev(X.PI), X.rate) – MT(X.codec, X.PI, X.rate) then • change X’s PI to prev(X.PI); • Bfree = Bfree – MT(X.codec, prev(X.PI), X.rate) + MT(X.codec, X.PI, X.rate); • else • return; • end if; • end while;

21. Example of Upgrade Algorithm 11 5.5 2 1 11 5.5 2 1 One departs (Rate=2Mbps) Bfree=5.5 11 2 Upgrade 5.5 5.5 11 5.5 Upgrade Upgrade 5.5 11 1 5.5 5.5 Bfree=0 One departs (Rate=1Mbps) Bfree=2 Bfree=0 Bfree=1.5

22. Outline • Introduction • Backgrounds • The Proposed QoS Mechanisms • Call Admission Control Algorithm • Resource Adjustment Algorithm • Simulation Results • Conclusions

23. Simulation Results • Environment: • We use Poisson process to simulate both new and handoff calls with rate . • The communication channel is error-free. No RTS/CTS is used. • BI is set to 500 ms. • We choose G.726 with rate 32 kbps as voice source. • Define the offered network load . • The simulation for each case runs for one million arrivals to reach steady state.

24. Simulation-1 • Influence of CAC and RA • Compared with “CAC-only” and “no-CAC-no-RA” mechanisms. • In our method, the PI is adaptive according to network condition. In other cases, the PIs are fixed. Proposed mechanism No-CAC-no-RA (PI=20) CAC-only (PI=20) Proposed mechanism

25. New call blocking rate and handoff call dropping rate under different offered loads. Proposed mechanism

26. Simulation-2 • Influence of Request Probability (Pr) • Larger Pr will benefit new calls, but hurt handoff calls. • The suggested value of Pr could range from 0.2 to 0.6.

27. Simulation-3 • Influence of Traffic Characteristic • We change the percentage of handoff calls while keep the offered load unchanged. • Our scheme is quite insensitive to this change, unless the offered load is very high.

28. Outline • Introduction • Backgrounds • The Proposed QoS Mechanisms • Call Admission Control Algorithm • Resource Adjustment Algorithm • Simulation Results • Conclusions

29. Conclusions • Contribution: • We propose the CAC and RA mechanisms. • Fairly distribute network resource. • Significant decreased blocking rate for new calls, less dropping rate for handoff calls and better utilization of bandwidth. • Successfully achieve early resumption of resources as calls leave a QAP.