Advanced WLAN Optimization and Networking Techniques by Mustafa Ergen

1. Intelligent Wireless Local Area Networking Qualifying Exam Mustafa Ergen

2. Degrees • BS: Middle East Technical University, 2000 • MS: University of California Berkeley, 2002 • Selected Publications • Mustafa Ergen, Pravin Varaiya, “Admission Control and Throughput Analysis in IEEE 802.11,” ACM-Kluwer MONET Special Issue on WLAN Optimization at the MAC and Network Levels. • Mustafa Ergen, Sinem Coleri, Pravin Varaiya “QoS Aware Adaptive Resource Allocation Techniques for Fair Scheduling in OFDMA Based Broadband Wireless Access Systems,” IEEE Transactions on Broadcasting, Vol.:49: Dec. 2003 • Mustafa Ergen, Duke Lee, Ruchira Datta, Jeff Ko, Anuj Puri, Raja Sengupta, Pravin Varaiya, “Comparison of Wireless Token Ring Protocol with IEEE 802.11,” Journal of Internet Technology, Vol. 4 No. 4. • Sinem Coleri, Mustafa Ergen, Anuj Puri, Ahmad Bahai, “Channel Estimation Techniques Based on Pilot Arrangement in OFDM Systems,” IEEE Transactions on Broadcasting VOL. 48, NO. 3 September 2002, pp 223-229. • Xuanming Dong, Mustafa Ergen, Pravin Varaiya, Anuj Puri “Improving the Aggregate Throughput of Access Points in IEEE 802.11 Wireless LANs”, IEEE WLN, Bonn, Germany, October, 2003. • Mustafa Ergen, Duke Lee, Raja Sengupta, Pravin Varaiya “Wireless Token Ring Protocol-performance comparison with IEEE 802.11,” IEEE ISCC, Antalya, Turkey, July 2003. *Received Best Student Paper Award* • Sinem Coleri, Mustafa Ergen, Tak-Kuen John Koo, “Lifetime Analysis of a Sensor Network with Hybrid Automata Modeling,” ACM WSNA Atlanta, September 2002. • Mustafa Ergen, Anuj Puri, “MEWLANA-Mobile IP Enriched Wireless Local Area Network Architecture,” IEEE VTC, Vancouver September, 2002. • Mustafa Ergen, Sinem Coleri, Baris Dundar, Rahul Jain, Anuj Puri, Pravin Varaiya, “Application of GPS to Mobile IP and Routing in Wireless Networks,” IEEE VTC, Vancouver, Canada, September, 2002. • Sinem Coleri, Mustafa Ergen, Anuj Puri, Ahmad Bahai, “A Study of Channel Estimation in OFDM Systems,” IEEE VTC, Vancouver, Canada, September, 2002. • Mustafa Ergen, Sinem Coleri, Baris Dundar, Anuj Puri, Jean Walrand, Pravin Varaiya, “Position Leverage Smooth Handover Algorithm For Mobile IP,” IEEE ICN Atlanta, August, 2002. • Duke Lee, Sinem Coleri, Xuanming Dong, Mustafa Ergen, “FLORAX- Flow-Rate Based Hop by Hop Back-pressure Control for IEEE 802.3x,” IEEE HSNMC Jeju Island Korea July, 2002.

3. Outline • Introduction to IEEE 802.11 • 4 Markov models of DCF • Throughput Analysis • Different data rates • Unsaturated Traffic • Application: Admission Control • Application: Indoor Throughput • Next Generation WLANs • Adaptive Antenna • Multi-hop Networking • Positioning • Conclusion

4. Contribution • Joint Markov Model • 802.11+ Model • Unsaturated Model • Individual Throughput with Different Data Rates • 802.11a Performance Analysis • Admission Control • Indoor Throughput

5. Introduction to IEEE 802.11

6. 802.11 MAC Meta-States

7. Idle Procedure

8. Backoff Procedure

9. VCS: NAV Update Procedure

10. Frame Sequence and Retry Procedure (RTS + CTS) is treated the same as (Data + Ack) with frame length < aRTSThreshold

11. IEEE 802.11 DCF Time Scale of DCF Function Saturation Throughput • OPNET Simulation • FHSS • 1Mbps Channel • Saturation Throughput • Packet Size 1000bytes • Inter-arrival time 0.005 • Load 1.6 Mbps • Observation time • Determination of discrete events • Construction of Markov model • Saturation throughput RTS/CTS w/o RTS/CTS SIFS SLOT DIFS EIFS time

12. 4 Markov Models of DCF

13. Joint Model All stations are dependent

14. Independent Model Each station has its own independent channel, but with same parameter p(n)

15. Markov Model Analysis Case I Case II Probability of Tx after/before Tx 802.11b 802.11+ CWmin=16 CWmax=1024 1/20 • Assumption: • Saturation Throughput • Limitless Retry • Everybody hears everybody • Case I: No consecutive Transmission

16. t : Probability of Transmission of a STA p: Probability of Channel Busy n: Number of Stations Ptr: Probability of Transmission in Medium Ps: Probability of Successful Transmission in Medium EP: Packet Size Ts: Duration of Successful Transmission Tc Duration of Collision s: Duration of Slot Time S: Throughput Ptr: Probability of Transmission Ps: Probability of Successful Transmission from model EP: Packet Size Ts: Duration of Successful Transmission Tc Duration of Collision s: Duration of Slot Time given by the PHY layer

17. Independent Markov Model • No freeze in backoff Definition b0a: Probability of being in state 0a t : Transmission occurs if STA is at 0a p: Channel Busy if there is one station at 0a but me Ptr: Transmission if there is at least one STA at 0a Ps: Successful Transmission if there is one STA at 0a • Freeze in backoff Assumption: constant and independent collision probability

18. Joint Markov Model • n=2 • STA a and STA b • # states = 4n • Dependent STAs in 802.11+ • Ptr=p0a0b+p0a1b+p0a2b+p0a3b+p1a0b+p2a0b+p3a0b :At least one Zero State • Ps=p0a1b+p0a2b+p0a3b+p1a0b+p2a0b+p3a0b: Only one Zero State

19. Throughput analysis

20. One level backoff • Independent of access mechanism • Independent of PHY layer • FHSS used • 802.11+ Joint Markov Model exactly • approximates Simulation OPNET Simulation: Ptr= ( #Total ACK rcvd + #Collision)/( #Back-off slot+ #Total ACK rcvd+ #Collision) Ps= (#Total ACK rcvd)/(#Back-off slot + #Total ACK rcvd + #Collision) Verification of the simulation Simulation Time = SLOT * #Back-off slot+ Ts* #Total ACK rcvd+ Tc #Collision)

21. FHSS Data Rate 1Mbps Saturation Throughput Throughput 802.11+ Joint Markov Model exactly approximates Simulation Verification of Duration Values from Simulation Throughput Mbps n Ts=0.0088sec Tc=0.0088sec for FHSS T+s=Tdata+SIFS+d+Tack+DIFS+d T+c=Tdata+d+EIFS Tbs=Tdata+SIFS+d+Tack+DIFS+d+SLOT Tbc=Tdata+d+DIFS+SLOT Basic Access Mechanism Ts=0.0087sec Tc=0.0007sec T+s=Trts+SIFS+d+Tcts+SIFS+d+Tdata+SIFS+d+Tack+DIFS+d T+c=Trts+d+EIFS Tbs=Trts+SIFS+d+Tcts+SIFS+d+Tdata+SIFS+d+Tack+DIFS+d+SLOT Tbc=Tdata+d+DIFS+SLOT RTS/CTS Access Mechanism

22. Multi Level Back-off 802.11b • FHSS • Data Rate 1Mbps • Saturation Throughput • W=16 • m=7 • CWmin=16 • CWmax=1024 • Retry Count = 255 802.11+ Basic Ts=0.0088s Tc=0.0088s RTS/CTS Ts=0.0090s Tc=0.0007s

23. Different (Mixed) data rates

24. Individual Throughput with Different Data Rates N=8 D=4 [1 2 3 4 5 6 7 8 ] :Station ID [R1R2R1R3 R4R1 R4R1 ] :Data Rates [Ts1Ts2Ts1Ts3 Ts4Ts1 Ts4Ts1] :Succ. Dur. [Tc1Tc2Tc1Tc3 Tc4Tc1 Tc4Tc1] :Coll. Dur. n1=4, n2=1, n3=1, n4=2 • Throughput distributes evenly among STAs • ni is the number of stations with data rate i • D is the total number of data rate choices • E[Ts] is Average • E[Tc] is highest of the STA in collision

25. Verification in 802.11b Simulation Scenario Start: 5 Stations with 1 Mbps Data Rate Step: 1 Station shift to 11 Mbps Stop: 5 Stations with 11 Mbps Data Rate Throughput of all stations is the same! Throughput Individual Throughput

26. Unsaturated case

27. New Model: Unsaturated Traffic • Modifications • Operation in non-saturated load • Different Data Rates, • Modified in IEEE 802.11a TrafficIntensity

28. 802.11a OFDM Packet Format

29. Probability of Transmission Probability of Collision Throughput w/o RTS/CTS DR=54Mbps Throughput with RTS/CTS DR=54Mbps

30. Analysis Throughput with Different Data Rates not mixed l=0.1 Throughput with Offered Load DR=54Mbps Throughput with Constant total load l=1/n

31. Admission Control

32. Throughput fixed station same SNR Fairness Constraint Time=N Time=N

33. Admission Control: w/o Mobility Total Throughput Individual Throughput Data Rates are fixed Without RTS/CTS l=0.2 With RTS/CTS gap will be smaller

34. Admission Control: w/o Mobility Probability of being selected Number of Stations selected at time t Data Rate vs Throughput Fairness Constraint

35. Admission Control: with Mobility Total Throughput Individual Throughput Data Rates are changed in every iteration

36. Admission Control: with Mobility Probability of being selected Number of Stations Selected at time t Data Rate vs Throughput Fairness Constraint

37. Indoor Throughput

38. Indoor Throughput Access Point Coverage Determination Signal Power (RSSI Map) • Access Point Coverage gives the number of • Mobiles attached per AP Signal Power gives the data rate of each mobile • Client model (power level 1-30mW) • Omni-directional antennas • APs (power level 1-100mW) • Model the interference between the APs and the mobiles

40. Performance Total Throughput: 5 AP Individual Throughput: 5 AP Throughput: 50 STAs Data Rate vs Throughput: 5 AP

41. Future work

42. Intelligent Network • Problems • Coverage • Throughput • Security • Interference • Power Efficiency • Applications • WLAN • Mesh Networks • UWB

43. Adaptive Antenna: Infrastructure BSS: Only AP has AA, RTS/CTS/ACK omni directional • Rate Adaptation Mechanism • Decrement with timeout • Increment with received ACK • Power: 1mW • 10mW in direction • (45o, 90o, 180o, 360o) • 0.01mW out of direction

44. Adaptive Antenna Ad hoc All STAs have Adaptive Antenna Infrastructure Only AP have Adaptive Antenna

45. Multi Hop Networking : Motivation • The smaller the range the higher the throughput

46. Multi Hop Networking: Algorithm Operation in PCF

47. Positioning • Outdoor • GPS • Cellular Networks • Indoor • WLAN • UWB • Motivation • Location Aware Applications • Wireless Security

48. Hybrid Method for Positioning • Hybrid Method • Achieve the accuracy of fingerprinting with less data collection effort, • Error bound,

49. Conclusion • Markov Model • Independent Markov Model • Joint Markov Model • Different Data Rates • (Un) Saturated Traffic • Application: Admission Control • Application: Indoor Throughput • Next Generation WLANs • Adaptive Antenna • Multi-hop Networking • Positioning

50. Appendix • 802.11a* • Slot 9 • SIFS 16 • PIFS 25 • DIFS 34 • EIFS 96 • 802.11* • Slot 50 • SIFS 28 • DIFS 128 • EIFS 384 *msec