17 LAN Access Point (the Internet) LAN(Local Area Network) LAN LAN LAN LAN (AP Access Point) IEEE 82.11b/g ( ) AP AP IEEE 82.11a/b/g (STA Station) AP

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1 LAN Access Point

2 17 LAN Access Point (the Internet) LAN(Local Area Network) LAN LAN LAN LAN (AP Access Point) IEEE 82.11b/g ( ) AP AP IEEE 82.11a/b/g (STA Station) AP STA AP STA LAN IEEE 82.11b LAN LAN AP

3 1 1 2 LAN MAC DCF PCF CSMA/CA RTS/CTS IEEE 82.11a IEEE 82.11b IEEE 82.11g AP MLT i

4 ii

5 1 (the Internet) LAN(Local Area Network) LAN LAN LAN LAN (AP Access Point) (STA Station) LAN AP STA [1] IEEE(Institute of Electrical and Electronics Engineering) IEEE 82.11b/g[2][3] 2.4 GHz 1 ( ) 2 MHz AP STA IEEE 82.11b/g 4 IEEE 82.11a[4] 8 AP IEEE 82.11a/b/g IEEE 82.11b 2.4 GHz ISM(Industrial Science and Medical band) ISM IC STA AP [5][6][7] [8][9] AP STA PER(Packet Error Rate) AP MLT(AP selection algorithm for Maximizing Local Throughput) MLT PER AP STA AP 1

6 AP STA 2 LAN

7 2 LAN IEEE LAN( LAN ) IEEE 82.11a/b/g LAN IEEE 82 IEEE MAC(Media Access Control) LAN presentation layer sesseion layer transport layer network layer IEEE82.1 Higher Level Layer Interface (HLLI) DATA LINK LAYER LLC MAC IEEE82.2 Logical Link Layer(LLC) IEEE82.11 CSMA/CA IEEE82.3 CSMA/CD PHYSICAL LAYER IrDA DS -SS FH -SS 82.1b DS-SS 1BASE-5 1BASE-2 1BASE-T 1 BASE Ethernet OSI Reference model Wireless LAN 1 BASE Ethernet 2.1: IEEE82.11 OSI. 2.2 IEEE LAN ( ) (WDS Wireless Distribution System WDS) 3 3

8 Ethernet Backbone Network AP Access Point AP Station Station Wireless Cell BSS Wireless Cell BSS ESS 2.2: 2.2 AP ( ) STA(STAtion ) AP (Ethernet) STA STA AP STA BSS(Basic Service Set ) STA AP BSS ESS(Extended Service Set ) AP LAN 4

9 station IBSS 2.3: 2.3 AP STA BSS IBSS(Independent BSS BSS) STA AP (WDS) 2.4 WDS WDS AP AP 2.5 IEEE LAN WDS 5

10 Ethernet backbone network AP AP AP AP 2.4: Ethernet backbone network AP Access Point AP AP AP Station Station 2.5: WDS 6

11 2.3 MAC LAN MAC AP STA DCF(Distributed Coordination Function ) PCF(Point Coordination Function ) DCF CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance ) RTS/CTS (Request To Send/Clear To Send) DCF DCF CSMA/CA IEEE DCF AP STA CSMA/CA STA PCF LAN DCF PCF PCF AP 7

12 PCF DCF CSMA/CA IEEE LAN DCF Ethernet CSMA/CD (Carrier Sence Multiple Access with Collision Detection ) CSMA/CA CSMA/CA CSMA/CA ( ) CSMA/CA 2.6 DIFS(Distributed Inter Frame Space) CW(Contention Window) CSMA/CA IFS(Inter Frame Space) SIFS(Short IFS) PIFS(PCF IFS) DIFS 3 IFS DCF DIFS ACK(ACKnowledment) SIFS DIFS SIFS ACK 8

13 DIFS DIFS PIFS Contention Window busy Data Frame SIFS time SIFS: highest priority, for ACK, CTS, polling response PIFS: medium priority, for time-bounded service using PCF DIFS: lowest priority, for asynchronous data service 2.6: CSMA/CA STA-A area STA-B area STA-A STA-B STA-C 2.7: LAN STA 2.7 STA A STA B STA B STA C STA A STA C STA A STA C STA B STA A STA C STA B STA A STA C STA 9

14 2.3.5 RTS/CTS IEEE RTS/CTS RTS/CTS 2.8 STA 1 STA 3 STA 1 DIF S + Backoff STA 1 RTS AP RTS NAV(Network Allocation Vector) ACK RTS STA 2 NAV RTS AP SIFS CTS STA 1 STA 1 AP STA 3 CTS CTS RTS NAV STA 3 NAV STA 3 RTS/CTS STA AP STA AP AP AP ESSID AP STA AP Probe Request AP (Probe Response) AP Probe Response STA AP BSS Reassociate Request AP Probe Request STA AP Reassociate Request STA AP Reassociate Request 1

15 AP DIFS Backoff time CTS SIFS SIFS SIFS ACK RTS data frame STA STA NAV(RTS) NAV(CTS) STA STA2 exists within STA1 carrier sence area STA3 exists without STA1 carrier sence area. 2.8: RTS/CTS CSMA/CA 11

16 5.15 GHz 5.25 GHz 5.35 GHz before 34 ch 38 ch 42 ch 46 ch after 36 ch 4 ch 44 ch 48 ch 52 ch 56 ch 6 ch 64 ch modified channels additional channels 2.9: IEEE 82.11a IEEE IEEE IEEE 82.11a/b 23 IEEE 82.11g IEEE 82.11a IEEE 82.11a 5 GHz 54 Mb/s IEEE 82.11a GHz 2.9 IEEE 82.11a 5.15 GHz 5.25 GHz IEEE 82.11b IEEE 82.11b 2.4 GHz 11 Mb/s LAN IEEE 82.11b 2.1 ISM(Industrial Science and Medical band) ISM 12

17 ch GHz about 2 MHz GHz 2.1: IEEE 82.11b 2.1: IEEE 82.11b [Mb/s] [m] [m] 1 / IEEE 82.11b Mb/s 4 ( ) Mb/s CSMA/CA 5 Mb/s IEEE 82.11g IEEE 82.11g 2.4 GHz 54 Mb/s LAN IEEE 82.11b ISM 2.4 GHz IEEE 82.11b 54 Mb/s CSMA/CA 25 Mb/s 13

18 2.4.4 LAN 2.1 IEEE 82.11b/g 1 2 MHz IC ISM LAN [5][6] AP IEEE 82.11a/b/g AP [7] [1] AP STA AP 14

19 LAN IEEE 82.11b 11 Mb/s STA1 STA2 1,5 Byte UDP STA1 ( 3.1 attenuator) X r dbm STA1 ( 3.1 interference) X i dbm AP AP (anechoic chamber) AP X r dbm X i dbm STA2 (Frame Error Rate FER) STA interference Xi[dBm] anechoic chamber Xr[dBm] STA1 attenuator AP STA2 UDP transmitter receiver coaxial cable ethernet cable 3.1: STA1 ( 1 ) AP X r dbm X i dbm FER 3.2 FER X r = 9 dbm FER 3.2(1) X i = 4 dbm X r 15

20 FER X i = 4 dbm X r = 4 dbm FER X i = 4 dbm 1 X r = 4 dbm FER 3.3(1) 2 X r = 6 dbm 3.4(1) 3 X r = 8 dbm FER FER (1) RSSI-FER FER Xr [dbm] Xi [dbm] : 1 X r dbm X i dbm FER 16

21 (1) RSSI-FER FER Xr [dbm] Xi [dbm] 3.3: 2 X r dbm X i dbm FER (1) RSSI-FER FER Xr [dbm] Xi [dbm] 3.4: 3 X r dbm X i dbm FER 17

22 4 AP [8][9] AP MLT(AP selection algorithm for Maximizing Local Throughput) 3 STA AP MLT 4.1 MLT [8][9] STA AP MLT MLT MLT STA AP AP (4.1) P Packet Error Rate(PER) N AP STA W th = 1 P N + 1 (4.1) STA ( ) STA Search Interval AP 2. AP-1 AP-2 Backoff Time Re-Search 3. AP-2 Idle 4. AP-1 AP STA Search 5. AP Backoff Time 6. STA Idle Time Search Search Interval AP 18

23 Idle status (6) (3) (1) Search status (4) (2) Re-serch status (5) 4.1: [8][9] STA MLT AP AP STA 4.2 AP MLT PER (4.1) P STA 3 FER STA STA FER 3 3.2(1) FER 4.2(1) (a) 4.2(1) FER FER (b) FER 1 FER (c) 19

24 (2) (c) 1 (a) (1) (b) FER (1) (a) -1 Xr [dbm] error environment sharp error table (b) smooth error table (c) conservative error table 4.2: Xr dbm FER (a) FER FER STA FER 2

25 5 AP ns-2.27 LAN IEEE 82.11b 3 AP m 3 m AP AP1 AP2 AP3 4 STA m 3 m 5.1 Source AP STA TCP 1,5 Byte FTP Greedy AP (I) (II) MLT 2 STA 4.2 (a)(b)(c) 3 AP 5.1: TCP/Sack 1,5 Byte AP STA 11 Mb/s fixed 21

26 Flow : from Source to Station Traffic : TCP/Sack Packet size : 1,5 Byte Access Point Station Source 1Mb/s 1us Switch 1Mb/s 1us Wired Wireless 5.1: 1ch 6 [m] 7ch AP AP2 interference 3[m] 2ch AP1 AP3 14ch 3[m] area where STAs exit 5.2: 22

27 5.2 AP LAN STA STA balance index [1] balance index (5.1) β 1 1 N B i STA i N STA β = ( B i ) 2 N B 2 i (5.1) 23

28 AP STA (I) (II)MLT AP AP Kb/s STA 3 % (I) STA AP AP1 AP Kb/s STA (II) MLT AP AP1 STA (a)(b)(c) STA 3 Kb/s 6.1 balalnce index (a)(b)(c) 6.7 (a) Kb/s STA 5 % AP STA AP AP1 STA Kb/s STA 4.2(2) STA AP (b)(c) 6.11 Kb/s STA (b)(c) FER FER (b)(c) 24

29 6.1: AP balance index [Kb/s] balance AP index (I) (II) MLT (a) (b) (c) AP STA (a) STA AP (a) (b) (c) AP (c) FER (c) FER 25

30 .4 (I)radio.35 probability density function average throughput [Kb/s] 6.1: (I) AP.4.35 (I) radio AP (I) radio AP1 probability density function average throughput [Kb/s] 6.2: (I) [ AP] STA.4.35 (I) radio AP2 (I) radio AP3 probability density function average throughput [Kb/s] 6.3: (I) [ AP] STA 26

31 .4 (II)MLT.35 probability density function average throughput [Kb/s] 6.4: (II)MLT AP.4.35 (II) MLT AP (II) MLT AP1 probability density function average throughput [Kb/s] 6.5: (II) [ AP] STA.4.35 (II) MLT AP2 (II) MLT AP3 probability density function average throughput [Kb/s] 6.6: (II) [ AP] STA 27

32 .4 (a)sharp.35 probability density function average throughput [Kb/s] 6.7: (a).4.35 (a) sharp AP (a) sharp AP1 probability density function average throughput [Kb/s] 6.8: (a) [ AP] STA.4.35 (a) sharp AP2 (a) sharp AP3 probability density function average throuput[kb/s] 6.9: (a) [ AP] STA 28

33 .4 (b)smooth.35 probability density function average throughput [Kb/s] 6.1: (b).4 (c)conservative.35 probability density function average throughput [Kb/s] 6.11: (c) 29

34 6.2 (c) FER 6.12 (a) (c-1)x dbm FER X (b) X dbm (a) (b) (c-1) 1 FER (1) (1) -1 Xr [dbm] error environment (a) sharp error table (b) smooth error table (c-1) conservative error table with X dbm 6.12: (c-1)x dbm X 6.13 balance index X = 2.5 dbm (c-1) X X = 8. dbm 6.14 balance index (c) (b) X =. dbm Kb/s STA 5 % (c) X (1) 6.12(b) Kb/s LAN TCP 3

35 ISM [7] AP STA (b) (c) STA AP (c) STA Kb/s 8 dbm FER X = 8 dbm (b)(c) (b)(c) 31

36 throughput [Kb/s] (c-1)x dbm conservative max (c-1)x dbm conservative min (c-1)x dbm conservative ave (b)smooth max (b)smooth min (b)smooth ave plus X [dbm] 6.13: X dbm (b)(c) (b)smooth (c-1)x[dbm] conservative.94 balance index plus X [dbm] 6.14: X dbm (b)(c) balnce index 32

37 6.3 (b)(c) STA m 3 m( 6.15 ) 5 AP STA 1ch 6 [m] 7ch AP AP2 interference 3[m] 2ch AP1 AP3 14ch 3[m] area where STAs exit 6.15: (b)(c) STA (b)(c) Kb/s STA (c) STA AP STA (c) AP AP1 STA 2 % (c) STA AP (b) (c) AP STA 6.16 STA (c) AP (b)(c) AP (c) 33

38 6.2: AP STA STA [ ( )] AP AP AP1 AP2 AP3 (b) 8.1 (.2) 8.1 (.2) 11.9 (.29) 11.9 (.29) (c).7 (.1).3 (.1) 19.5 (.49) 19.4 (.49) 6.3: AP [Kb/s] AP (b) (c) (b) STA (b) 34

39 .4 (b)smooth.35 probability density function average throughput [Kb/s] 6.16: (b).4 (c) conservative.35 probability density function average throughput [Kb/s] 6.17: (c) 35

40 6.4 AP AP AP ISP(Internet Service Provider) AP 6.18 AP AP3 1 AP1 AP2 2 5 m 5 m AP1 AP3 1 2 STA 2 4 STA 6.18 STA (b) AP (I) (II) MLT 5 1ch AP1 25[m] AP Interferance AP2 5[m] 7ch 14ch 2ch AP3 25[m] 5[m] Network1: AP, AP3, 2 STAs Network2: AP1, AP2, 2 STAs 6.18: STA (I)(II)

41 6.2 Kb/s STA (b) AP Kb/s STA 3 Kb/s 6.4 (1)(2) AP STA (b) AP (b).4 (1)radio.35 probability density function average throughput [Kb/s] 6.19: (I) AP 37

42 .4 (2)MLT.35 probability density function average throughput [Kb/s] 6.2: (II)MLT AP.4 (b) smooth.35 probability density function average throughput [Kb/s] 6.21: (b) 38

43 6.4: AP [Kb/s] AP (1) (2) MLT (b)

44 7 LAN IEEE 82.11a/b/g AP STA AP IEEE 82.11b STA AP AP STA STA LAN AP [11][12] LAN AP 4

45 (PCC) (B) ( 17771) NICT JGN2 41

46 [1] M Cesana, D Maniezzo, P Bergamo, M Gerla Interference Aware (IA) MAC: an Enhancement to IEEE82. 11b DCF, Proceedings of IEEE Vehicular Technology Conference-VTC 23 Fall 23 [2] IEEE WG Part11: Wireless LAN Medium Access Control(MAC) and Physical Layer(PHY) specification Higher-Speed Physical Layer Extension in the 2.4 GHz Band, IEEE82.11 Std. Sep 1999 [3] IEEE WG Part11: Wireless LAN Medium Access Control(MAC) and Physical Layer(PHY) specification Amendment 4: Further Higher Data Rate Extention in the 2.4 GHz Band, IEEE82.11 Std. Sep 23 [4] IEEE WG Part11: Wireless LAN Medium Access Control(MAC) and Physical Layer(PHY) specification Higher-Speed Physical Layer Extension in the 5 GHz Band, IEEE82.11 Std a Sep 1999 [5] Masami Kato, Hirotsugu Okura, Kiyoshige Ito and Shuji Tasaka Experimental Assessment of Media Synchronization Quality in IEEE 82.11b under Bluetooth Interference, in Proc IEEE PIMRC 23 Sep. 23 [6] Yasushi Matsumoto Masanobu Nakatsuka Takahide Murakami Katsumi Fujii and Akira Sugiuchi Reduction of Microwave Oven Interference in DS-SS WLAN Systems by Using Adaptive Filters, International symposium on Electromagnetic Compatibility Sep 24 [7] IEEE 82.11b LAN, P B [8] Yutaka Fukuda Takamitsu Abe and Yuji Oie Decentralized Access Point for Wireless LANs, In the Proceedings Of WTS 24 SA3 May 24. [9] Yutaka Fukuda and Yuji Oie Decentralized Access Point Selection Architecture for Wireless LANs -Deployability and Robustness-, Proceedings of the IEEE VTC24-Fall, Los Angeles, 42

47 CA September 26-29, 24 [1] Dah-Ming Chiu and Raj Jain Analysis of the Increase and Decrease Algorithmes for Congestion Avoidance in Computer Network Computer Network and ISDN Systems vol 17 pp [11] Kamal Jain Jitendra Padhye Venkata N.Padmanabhan Inpact of Interference on Multihop Wireless Network Performance, MobiCom 3 Sep [12] Hung-Yu Wei Samrat Ganguly Rauf Izmailov Zygmunt J.Hass Interference-Aware IEEE WiMax Mesh Networks, Proceedings of IEEE Vehicular Technology Conference-VTC 25 Spring May 25 43

18 LAN AP (AP, Access Point) LAN (STA, Station) (RSSI, Received Signal Strength Indicator) AP AP STA AP LAN AP STA LAN AP LAN LAN STA AP LAN (Local Ar

LAN AP 19 2 16 18 LAN AP (AP, Access Point) LAN (STA, Station) (RSSI, Received Signal Strength Indicator) AP AP STA AP LAN AP STA LAN AP LAN LAN STA AP LAN (Local Area Network) AP (Access Point) 1 1 2