A NOVEL THROUGHPUT AND PACKET DELAY ANALYSIS OF CONTROL SCHEME BASED ON A MARKOV CHAIN MODEL IN DENSE IEEE WLAN

Transcription

1 Inernaional Journal of Mechanical Engineering and echnology (IJME) Volume 8, Issue 7, July 207, , Aricle ID: IJME_08_07_068 Available online a h:// ISSN Prin: and ISSN Online: IAEME Publicaion Scous Indexed A NOVEL HROUGHPU AND PACKE DELAY ANALYSIS OF CONROL SCHEME BASED ON A MARKOV CHAIN MODEL IN DENSE IEEE 802. WLAN N.Vasudheva Reddy, V.Arun, A.V.Paramkusam Dearmen of Elecronics and Communicaion Engineering, MLR Insiue of echnology, Hyderabad, elangana, India N Paarao Insiue of Aeronauical Engineering4, Hyderabad, India ABSRAC Wireless comuer nework [] ha associaes wo or more devices using a wireless disribuion mehod ofen using sread-secrum or OFDM wihin a resriced area such as a camus or small building. he 802.a is anoher PHY exension o he 802. sandard. I oeraes a he frequency range of 5-GHz, i s unlicensed naional infrasrucure for informaion (UNII) band and i allows for daa raes of 6 54 Mbs. he aim of his aer is o analysis he erformance of IEEE 802. of hroughu and acke delay by using wo yes of algorihms i.e., Consan conenion window and Binary Exonenial Back-off. Key words: IEEE 802., Fragmenaion, Conenion window, Packe Delay. Cie his Aricle: N.Vasudheva Reddy, V.Arun, A.V.Paramkusam and N Paarao, A Novel hroughu and Packe Delay Analysis of Conrol Scheme Based on a Markov Chain Model in Dense IEEE 802. WLAN. Inernaional Journal of Mechanical Engineering and echnology, 8(7), 207, h:// INRODUCION here are currenly four secificaions in IEEE 802. family i.e., 802.b, 802.n, 802.a, 802.g, and 802.b. hey use he Eherne roocol and CSMA/CA (carrier sense mulile access wih collision avoidance insead of CSMA/CD) for ah sharing. In recen years he IEEE 802. [] family of WLAN sandards has emerged as he dominan echnology for broadband wireless access neworks. Alhough i suors relaively low ransmission raes comared o he wired echnologies he number of WLAN users coninues o grow dramaically mosly due o is flexibiliy and low cos. A saion can iniiae a ransmission when he backoff imer reaches zero. he back-off [2] [3] ime is uniformly chosen in he range (0, w-). Also h:// 604 edior@iaeme.com

2 N.Vasudheva Reddy, V.Arun, A.V.Paramkusam and N Paarao (w-) is known as Conenion Window (CW), which is an ineger wih he range CWmin and CWmax deermined by he PHY characerisics. Afer each unsuccessful ransmission, w is doubled, u o a maximum value 2mW, where W equals o (CWmin+) and 2mW equals o (CWmax+). Sauraion hroughu analysis of IEEE 802. WLAN using Fragmenaion In communicaion sysems, such as Eherne or acke radio, hroughu or nework hroughu is he average rae of successful daa delivery over a communicaion channel. he hroughu [7] is usually measured in bis er second (bi/s or bs), and someimes in daa ackes er second or daa ackes er slo. he sysem hroughu or aggregae hroughu is he sum of he daa raes ha are delivered o all he erminals in a nework. he ime o ransmi his acke is shown below ( Bis) ( Bi Sec) Daa DIFS + OVERHEAD + + SIFS + ACK Rae he average ime for correc ransmission o be received is given by () w + i ( ). i.. i PER -(-Pe) number of bis in he acke i i ( ). i.... ( ). i. w. + i. ( ). ( ) 2 ( ) + i ( ). i.. i. ( ) hroughu. i ( Bis Daa Daa ).( PER) sec w Using he above equaion, he hroughu can be derivedas (2) (3) (4) Binary Exonenial Backoff (BEB) algorihm In BEB [7], when a node over he nework has a acke o send, i firs senses he channel using a carrier sensing echnique. If he channel is found o be idle and no being used by any oher node, he node is graned access o sar ransmiing. Oherwise, he node wais for an inerframe sace and he back-off mechanism is invoked. A random back-off ime will be chosen in he range [0, CW-]. A uniform random disribuion is used here, where CW is he curren conenion window size. he following equaion is used o calculae he back-off ime (BO) Back-off ime (BO) (Rand() MOD CW) * a Slo ime (5) If he medium is found o be idle hen he back-off eriod is decremened by one ime slo. Back-off ime (BO) new (BO) old a Slo ime (6) If he ransfer fails, he node goes ino anoher back-off eriod. When going for anoher back-off eriod again, he conenion window size is exonenially increased wih a maximum of 023. h:// 605 edior@iaeme.com

3 A Novel hroughu and Packe Delay Analysis of Conrol Scheme Based on a Markov Chain Model in Dense IEEE 802. WLAN he BEB algorihm uses he following equaion o increase he conenion window size. Back-off ime (BO) (Rand () MOD CW) * a Slo ime (7) Conenion Window scheme for WLANs he Consan conenion Window Algorihm is he modificaion of he IEEE 802. BEB algorihm, which is used o conrol he conenion window in he case of collisions, in order o rovide a beer hroughu. In case of collisions, he conenion window size is seleced beween [0 o CW] and CW is fixed for every rery. he value of CW is seleced beween CWmin and CWmax. 2. FRAGMENAION IN IEEE 802. Fragmenaion is he rocess of dividing a long frame ino shor frames. Fig. illusraes he fragmenaion rocess in IEEE 802. MAC. MSDU is assed down from he LLC layer, if he size of he MSDU is greaer han he fragmenaion hreshold and i is divided ino smaller fragmens. Each fragmen, namely an MPDU, becomes a MAC layer frame wih a MAC header. hen, a hysical layer convergence roocol (PLCP) header and a reamble are added o he MPDU. he resuling frame is called a PLCP roocol daa uni (PPDU), which is he frame ransmied by he hysical layer over he air. When he ransmission of a fragmen fails, he conenion rocess begins afer a DIFS idle ime eriod. he remaining fragmens are ransmied when he node seizes he channel again hrough he conenion rocess. he ransmission rocess for he fragmens of an MSDU is called a fragmen burs. Because he header of each MAC frame conains he informaion ha defines he duraion of he nex ransmission, he nodes ha overhead he header udae he NAV value for he nex fragmen ransmission. Figure Convenional fragmenaion rocess and imeline of daa ransmission wih rae Adaaion h:// 606 edior@iaeme.com

4 N.Vasudheva Reddy, V.Arun, A.V.Paramkusam and N Paarao HROUGHPU ANALYSIS he erformance of he wireless Communicaion nework can be evaluaed in erms of QOS arameers like hroughu [3], acke delay and acke delivery raio, acke dro ec. Le n be he fixed number of conending saions and τ be he robabiliy ha a saion ransmis he ackes. τ w. 2. ( 2 )(. ) m + ( ) ( ) + ( ) m (8) Where P is he robabiliy of collision W is he conenion window size and m is he rery limi. 2 τ CW + Where CW is he size of he conenion window. he robabiliy ha here is no ransmission in a given slo ime is: Pn ( τ ) n Probabiliy ha he channel is busy is given as Pb ( τ ) n Hence he oal ime ha he node sends in idle sae is Pb idle * sloime he ransmiing a acke Pr in an idle ime can be exressed as P c P r n ( τ ) he robabiliy of successful ransmission, Ps can be exressed as: P s nτ n ( τ ) ( τ ) n he hroughu considering he ransmission errors can be derived as S P s Ps ( Pfragerror ) L ( Pfragerror ) success + ( Ps ) collision + idle + PP s fragerror e Where L is he average acke ayload size (9) (0) () (2) (3) (4) (5) Packe Delay Analysis of IEEE 802. WLAN using Fragmenaion he delay erformance of IEEE 802. [][4] roocol can be done by aking he rery limis of a daa acke ransmission ino accoun. he acke dro robabiliy is defined, as he robabiliy ha a acke is droed when he rery limi is reached and i is equal o dro m+ (6) h:// 607 edior@iaeme.com

5 A Novel hroughu and Packe Delay Analysis of Conrol Scheme Based on a Markov Chain Model in Dense IEEE 802. WLAN he average lengh of a slo ime is [ slo ] ( ). σ ( ) s E. r r s r s c (7) Where E[X] is he average number of slo imes required for successfully ransmiing a acke and is given by E [ X ] ( 2 )(. cw + ) +. cw. ( 2 ) 2. ( 2 )(. ) m able Simulaion Parameers Descriion Value Slo ime 20 µs SIFS 0 µs DIFS 50 µs PLCP Preamble 44 µs PLCP Header 48 µs Minimum Conenion Window 3 Maximum Conenion Window 023 Channel bi rae U o 54 Mbs PHY header 24 Byes MAC header 28 Byes RS 44 Byes ACK 38 Byes Proagaion delay, δ 2 µs (8) 3. SIMULAION ANALYSIS Figure 2 Conenion windows vs. sauraion hroughu h:// 608 edior@iaeme.com

6 N.Vasudheva Reddy, V.Arun, A.V.Paramkusam and N Paarao Fig 2 los he conenion window versus sauraion hroughu a differen nodes. When he number of nodes increases, he hroughu decreases, bu by roerly adjusing he conenion window, he maximum hroughu can be achieved. Figure 3 Number of nodes versus hroughu (fragmen size 256 byes, BER 0-6 ) Figure 4 Number of nodes versus hroughu (fragmen size 52 byes, BER 0-6 ) Here, he number of saions is varied and uses he acke size of 2000 byes and fragmen size of 256 byes is aken in Fig.3 and 52 byes in Fig.4. he robabiliy of collision increases wih increase in number of conending nodes and hence he hroughu decreases. Bu he hroughu can be increased by selecing he roer conenion window even he number of nodes increases. Here, he oimal conenion window size is 300. If he conenion window is se a 500, he hroughu is beer bu i doesno work if he numbers of nodes are less han 20. h:// 609 edior@iaeme.com

7 A Novel hroughu and Packe Delay Analysis of Conrol Scheme Based on a Markov Chain Model in Dense IEEE 802. WLAN he BER is aken as 0-4 and he variaion of hroughu wih conending nodes are loed in Fig. 5 and Fig.6. In his case also, he oimal conenion window size is 300 and he oimal fragmen size is 52 byes as given below. Figure 5 Number of nodes versus hroughu (fragmen size 256 byes, BER 0-4 ) Figure 6 Number of nodes versus hroughu (fragmen size 52 byes, BER 0-4 ) h:// 60 edior@iaeme.com

8 N.Vasudheva Reddy, V.Arun, A.V.Paramkusam and N Paarao Figure 7 Number of nodes versus Delay he acke delay analysis for various nodes using BEB and Consan conenion window algorihms is loed in Fig 7. he acke delay reduces by roerly selecing conenion window size in consan backoff algorihm. If he conenion window is seleced as 300, one can ge he minimum acke delay which is very imoran. 4. CONCLUSION Simulaion resuls shows ha he acke delay increases and hroughu decreases in BEB comared o Consan backoff algorihm. he oimal fragmen size and oimal conenion window are deermined o achieve he maximum hroughu for he secified BER. REFERENCES [] IEEE Sd 802., Par : Wireless LAN Medium Access Conrol (MAC) and Physical Layer (PHY) Secificaions, IEEE, 999. [2] Q. Ni,. Li,. urlei, and Y. Xiao, AFR arial MAC roosal for IEEE 802.n, 2004, IEEE n. [3] P. Leieri and M. B. Srivasava, Adaive frame lengh conrol for imroving wireless link hroughu, range, and energy efficiency, in Proc. IEEE INFOCOM, 998, [4] G. R. Canieni, Q. N. C. Baraka, and. urlei, Performance analysis under finie load and imrovemens for mulirae 802., Elsevier Com. Commun. J, 28(0), , Jun [5] RAPPAPOR.S.: Wireless communicaions: rinciles and racice (Prenice Hall, 2002, 2nd edn.) [6] MARCUM J. I.: able of Q funcions. U.S. Air Force Projec RAND Res. Memo. M-339, ASIA Documen AD 6545, RAND Cororaion, Sana Monica, CA, January 950. [7] Yusun Chang; Lee, C.; Kwon, B.; Coeland, J.A, Dynamic Oimal Fragmenaion for Goodu Enhancemen in WLANs, ridencom 2007,.-9, 2-23 May [8] PAPOULIS A., PILLAI S.U.: Probabiliy, random variables, and sochasic rocesses (McGraw-Hill, 2002, 4h edn.) [9] ELLAMBURA C., BHARGAVA V.K.: Unified error analysis of DQPSK in fading channels, Elecron. Le, 994, 30, [0] D. Qiao; S. Choi, Goodu enhancemen of IEEE 802.a wireless LAN via link adaaion, IEEE Inernaional Conference on Communicaions, 200. h:// 6 edior@iaeme.com

9 A Novel hroughu and Packe Delay Analysis of Conrol Scheme Based on a Markov Chain Model in Dense IEEE 802. WLAN [] J. del P. Pagon, S. Choi, Link Adaaion Sraegy for IEEE 802. WLAN via Received Signal Srengh Measuremen, IEEE Inernaional Conference on Communicaions, -5 May [2] Liljana Gravrilovska, Vladimir Aanasovski, Influence of Packe Lengh on IEEE 802.b hroughu Performance in Noisy Channels, Proceedings of s Inernaional MAGNE WorkshoD6.2.5, Shangai, China, -2 November 2004, ISBN [3] H. Wu, Y. Peng, K. Long, S. Cheng and J. Ma, Performance of Reliable ransor Proocol over IEEE 802. Wireless LAN: Analysis and Enhancemen, IEEE INFOCOM [4] G. R. Canieni, Q. Ni, C. Baraka, and. urlei, Performance Analysis under Finie Load and Imrovemens for Mulirae 802., Elsevier Comuer Communicaions Journal, Vol. 28, Issue 0, June 2005, [5] M. Heusse, F. Rousseau, R. Guillier and A. Duba, Idle Sense: An Oimal Access Mehod for High hroughu and Fairness in Rae Diverse Wireless LANs, SIGCOMM [6] Chaiali K.Dhande and P.M.Mahajan, Evaluaing Neural Nework and Hidden Markov Model Classifiers For Handwrien Word Recogniion, Volume 4, Issue 6, November - December, 203,. 7-23, Inernaional Journal of Elecronics and Communicaion Engineering & echnology. [7] Kulkarni U. Vasanrao, Fahd N. Al-Wesabi and Adnan Z. Alsakaf, Hybrid Zero- Waermarking and Markov Model of Word Mechanism and Order wo Algorihm For Conen Auhenicaion Of English ex Documens, Volume 4, Issue 3, May-June (203), , Inernaional Journal of Comuer Engineering and echnology [8] G. Bianchi. Performance Analysis of he IEEE 802. Disribued Coordinaion Funcion, IEEE Journal on Seleced Area in Comm. V8, N3, , h:// 62 edior@iaeme.com