A proportional fair scheduling algorithm based on QoS utility function in wireless networks

Transcription

1 Avalable onlne Journal of Chemcal and Pharmaceutcal esearch, 2014, 6(5): esearch Artcle ISSN : CODEN(USA) : JCPC5 A proportonal far schedulng algorthm based on QoS utlty functon n wreless networks Huang Zhao Mng Guang X Medcal Unversty 1st afflated Hosptal, Nannng, Guangx, Chna ABSTACT The traffc of multmeda servce n wreless network ncreases by exponental as the number of applcatons ncrease. Snce the weakness of proportonal far algorthm n meetng the Qualty of Servce (QoS) such as delay and packets loss, t s not so wdely used n modern wreless communcaton. Ths paper proposes a schedulng algorthm that based on QoS utlty functon n whch a parameter s ntroduced to mprove prorty mechansm for overcomng such weakness. Smulaton results show that our schedulng algorthm can meet the QoS requrements of real-tme traffc; and the whole system transmsson performance has been markedly mproved. Key words: Qualty of servce, Schedulng algorthm, Utlty functon, Proportonal far INTODUCTION Wth the rapd development of wreless network, the contradcton between wreless network resources and data servce demand ncreases sharp [1-5]. Wth the reason of wreless network resources not beng ncreased, wreless resource schedulng algorthm has become a progressve drecton [4-6]. Currently, the classc schedulng algorthms are manly ound schedulng (ound obn, ) algorthm [7], the maxmum Carrer to Interference schedulng (Max Carrer to Interference, Max C/I) algorthm [8], Proportonal Far schedulng (Proportonal Far, PF) algorthm [10]. algorthm takes turns to schedulng varous busness on tme slce, whch have the same schedulng prorty system n all busness, to guarantee equal opportunty for all busness dstrbuton system n the same amount of resources, such as tme or bandwdth. Then the users are n turn to schedulng accordng to some sort of agreement, untl after all the busness s scheduled to the next schedulng cycle. Max C/I algorthm s a knd of schedulng emphass on system throughput. It sorts descendng all users n the system accordng to the channel SN, system prorty schedulng SN of bg busness, untl the end of the schedulng. For user's largest farness, algorthm sacrfces the system throughput, however, Max C/I schedulng algorthm for maxmum system throughput and farness at the expense of the users. They are only n accordance wth a certan performance ndcators for schedulng, but gnorng the other performance ndcators, whch restrcts ther applcaton n the actual system. In order to mprove ths problem, PF schedulng algorthm was proposed by Jalal. The algorthm consders both the real-tme channel state of the busness and the farness between busness transmsson rate. The ntal tme of each busness prortes are attached to the same value, and schedulng s always prorty schedulng prorty every tme. But wth a good qualty busness channel contnuous schedulng, the average throughput wll ncrease, resultng n reducng ts schedulng prorty. It makes the orgnal low prorty users can get more chances of schedulng, ncreasng the farness of schedulng algorthm. Schedulng prorty of PF algorthm defned as: 1957

2 Huang Zhao Mng J. Chem. Pharm. es., 2014, 6(5): r P[ ] = arg max( ) r as the nstantaneous channel sgnal-to-nose rato of the channel, busness [9] Update formula of [10]: (1) as the average throughput of the t c as the balance of tme parameters. (2) Although the PF algorthm s better than that of the algorthm and Max C/I, n recent years, a seres of mproved algorthm appeared that was shown n table 1. Table 1 the mproved PF algorthm algorthm name mprove drecton Schedulng prorty Parameter meanng schedulng algorthm of n The farness of the PF r Data rate control ndex P [ ] = a rg m a x ( ) n for the ndex parameter algorthm (DC) [11] schedulng algorthm of c The throughput of the r Adaptve proportonal far P [ ] = a rg m a x ( ) c for the ndex of control PF algorthm (APF) [12] parameters Based on the QoS of PF algorthm adapted to r proportonal far algorthm P [ ] = a rg m a x ( ) w w for the mnmum guarantee rate b b the busness rate [13] for the correspondng busness PF algorthm r M-LWDF algorthm [14] T adaptablty to busness P [ ] = a r g m a x ( ) tme delay T for the exstng delay, T T m ax for m a x the maxmum tme delay M-PF-1 algorthm [15] PF algorthm adaptablty to busness packet loss rate for the predcted values for packet loss rate, a as the ndex of control factors Although PF and mproved algorthm have good compromse on system throughput and farness, t s wdely used n the actual system. But, n recent years, as a result of multmeda servces as exponental growth n wreless networks, PF mproved algorthm can not meet the varous aspects of Qualty of Servce (QoS, Qualty of Servce) demand on busness. When there s a busness of QoS value close to the maxmum QoS threshold schedulng, prorty change trend s not obvous, so that the busness can not be tmely schedulng causng delay tmeout affect the Qualty of busness communcaton. So, n ths paper, some parameters based on the utlty functon of QoS factors, such as delay, packet loss rate and delay jtter busness QoS requrements collecton, are ntroduced n the schedulng prorty of PF algorthm. When the multmeda servce QoS factor s closed to the QoS threshold, the parameter can be rapdly ncreased busness opportuntes for schedulng, to ensure the qualty of the communcaton of multmeda busness. 2 A Proportonal Far Schedulng Algorthm Based on servce qualty utlty Functon PF algorthm can't guarantee well multmeda QoS requrements, manly does not take nto account QoS factors affect busness operaton. In order to mprove ths problem, ths paper ntroduced QoS n PF schedulng prorty factor parameters to ensure the QoS of multmeda busness communcaton requrements, establshed on the QoS factor parameters of the utlty functon model. Utlty functon s the characterzaton of the economc benefts of people occupes a certan assets of functon n economcs. The ntroducton to the wreless network s used to characterze wreless schedulng after receve the subjectve satsfacton degree functon. In general, the utlty functon on resource allocaton problem s a functon of Z [7].Therefore, ths artcle defned the t for the current busness QoS factor, and t ndcates the busness of the senstve degree of QoS. Therefore, when the task QoS factor s small, the emergency degree of task schedulng s small, beng remembered to 0 (mnmum of utlty functon); When the task QoS factor s close to or more than the current busness allowed maxmum QoS threshold, the emergency degree of task schedulng s hgh, beng remembered to b (maxmum of utlty functon). In bref, ths paper puts forward the followng utlty functon: 1958

3 Huang Zhao Mng J. Chem. Pharm. es., 2014, 6(5): α ( t c) e U ( t) = (3) α ( t c) 1 + e Among them, α shows the tlt of functon, and ts value represents the senstve degree of utlty functon on QoS requrements; c shows a turnng pont of functon, and ts value can tolerate maxmum QoS on behalf of the busness. Fgure 1 α for the nfluence of the U ( t ) Fgure 2 c for the nfluence of the U '( t ) From fgure 1, t shows that the larger s n the value of α, and the faster s n change when utlty functon n the QoS factors s close to the bggest busness of QoS threshold, whch can make the busness schedulng prorty ncreased dramatcally, to ensure the busness QoS demand; From fgure 2, t shows that the larger s the rght of extreme value pont of the value curve, the larger s n the maxmum tolerable by QoS, whch s easer to guarantee the QoS of the busness needs. In ths paper, based on the above reasons (PF - A) algorthm, PF - A algorthm of schedulng prorty s defned as: p[ ] = arg max f ( QoS, CSI ) r = arg max f ( Π ( U '( t), U '( d),..., U '( c)), ), = 1,2,..., N r as the nstantaneous channel sgnal-to-nose rato of the channel, busness. U '( x) as the dervatve of U ( x ), Π ( U '( t), U '( d),..., U '( c)) the product of the QoS factors account for the busness (4) as the average throughput of the QoS for the QoS requrements of the correspondng busnes, In ths paper, PF - A algorthm consderng the busness delay and packet loss rate and other QoS factors nfluence on task schedulng, task schedulng prorty values related to servce qualty utlty functon, the channel state. Fnally update expressons of formula (4) was as a prorty. At the tme delay and packet loss rate s close to the maxmum QoS value, the correspondng task schedulng prorty has ncreased dramatcally, so as to ensure the QoS requrements of the busness. To sum up, ths paper proposes the PF - A job schedulng algorthm steps are as follows: (1) Busness wll sent generate data to the respectve buffer, and change the schedulng prorty of the busness P[ ] 1 N = ; (2) accordng to the real-tme channel SN, formula (2) formula (3)respectvely update busness r U '( t ) (3) Accordng to the formula (4) calculatng schedulng prorty of the busness, accordng to the formula (5) calculatng the largest schedulng prorty, and accordng to the descendng order; (4) Schedulng prorty of the largest busness n turn untl after the allocaton of resources; (5) repeat steps (2) to (4), untl the schedule s complete. 3 Smulaton and analyss Ths paper use Matlab to smulaton experment, of whch the data model for the voce (VoIP) busness. VoIP 1959

4 Huang Zhao Mng J. Chem. Pharm. es., 2014, 6(5): busness s composed of sudden perods and the quet perod n wreless network, whch QoS factors s less than 300 ms for tme delay and packet loss rate s less than 3%. So, ths artcle proposed n the utlty functon U '( t ) c =300, = 1,2,..., N,n the packet loss rate of the utlty functon U '( d ) c =0.03, = 1,2,..., N and breakng perod can produce 9.3 KBPS voce data at the same tme, but slence does not produce data [8]. Based on the lterature [8], sudden perod and quet perod are expressed wth two state markov process, whch they are ndependent and the converson process obey the exponental dstrbuton at the same tme, rate parameters of a =2.841, respectvely, b = Fgure 3 VoIP busness model The nstablty of the wreless channel wll brng transmsson delay and delay jtter. To make t easer to measure the tme delay, the wreless channel model s wth FSMC channel. FSMC channel state s only allowed n the adjacent state transtons. S0 for no channel nose, S 1 for channel nose stronger state, S2 strongest state to channel nose. Based on lterature [8] = 0.09, = 0.3. Fgure 4 wreless channel model In order to verfy the advantages of PF - A algorthm n real-tme busness servce (VoIP servce) n ths paper, the PF algorthm and PF - A algorthm based on servce qualty utlty functon are comparson the performance n 5 aspects of the overall performance from farness, system throughput, delay, packet loss rate, and the schedulng algorthm Fgure 5, fgure 6 and fgure 7 and fgure 8 statstcs of several schedulng algorthm of farness, throughput, delay and packet loss rate. Fgure 5 shows when the schedulng perod s more than 100, FA values are greater than 0.9, whch shows that farness s of PF - A algorthm s acceptable, although slghtly smaller than other PF algorthm. Fgure 6 shows that PF - A throughput s hgher than PF algorthm, PF - A system throughput ncrease 3.7% of the algorthm. Fgure 7 shows that PF, DC, APF three algorthms can not meet the requrement of the VoIP mnmum delay (300 ms), and the maxmum delay of PF - A algorthm s less than 300 ms, meetng the demand of VoIP busness the mnmum delay. It proves that PF - A algorthm sutable for VoIP busness wth delay lmt. Fgure 8 four schedulng algorthm can be obtaned the average packet loss rate s respectvely: 0.62% (PF), 0.64% (DC), 0.63% (APF), 1.34% (PF - A). Although PF - A algorthm of packet loss rate s greater than other PF algorthm, but also meet the mnmum requrements of VoIP busness (less than 3%). It proves that PF - A method s applcable to a packet loss lmt of VoIP busness. 1960

5 Huang Zhao Mng J. Chem. Pharm. es., 2014, 6(5): Fgure 5 farness Fgure 6 through put Fgure 7 tme delay Fgure 8 packet loss probablty Although through the above experments demonstrated that PF -a algorthm s sutable for the specfc QoS requrements of VoIP busness, the algorthm s at the expense of the system's farness and packet loss rate. The same as the mproved algorthm, the QoS optmzaton goal s better than the orgnal algorthm, but n other ways worse than the orgnal algorthm. So, ths paper ntroduce parameter Q to represent the overall performance of the schedulng algorthm, and through the analytc herarchy process (AHP) to fnd the reasonable optmum value, drect descrpton so as to acheve the purpose of schedulng algorthm performance. In order to better descrbe the overall performance of the schedulng algorthm, ths paper defnes: delay (8) Q = ( a* T + b* C + c* FA ) Q as the overall performance of the schedulng algorthm, T delay as the busness tme delay, C as the system throughput, FA as system tables farness, a b c as weght coeffcent In ths paper, the AHP s appled to the optmal soluton, the steps are as follows: (1) accordng to the demand of the actual system, the most mportant s the nfluence of tme delay of the system, so the tme delay of mportance to 1; Secondly, attaches great mportance to the throughput, the throughput of mportance for 3; Fnally, t s farness, farness of mportance for (2)To construct judgment matrx, 1 5 A =

6 Huang Zhao Mng J. Chem. Pharm. es., 2014, 6(5): (3)To calculate weght busness: a =0.6522,,b = , c = (4)Consstency check.to calculate CI : CI =0 ⅱ. To fnd I : I =0.58 ⅲ. To calculate C : C == CI I weght coeffcents of the busness s acceptable. =0,C < 0.10,So the consstency of judgment matrx s reasonable, the (5) Computng algorthm the overall performance Q Fgure 9 shows the algorthm overall performance curve, from whch, the overall performance of the proposed PF - A algorthm parameters Q than PF and APF algorthm and farly wth the DC method, but stablty than DC algorthm. Fgure 9 Algorthm performance CONCLUSION Ths paper proposes a PF - A algorthm based on servce qualty of the utlty functon, and the smulaton results show that the algorthm can meet the VoIP busness through the utlty functon to solve tme delay and packet loss rate, the specfc QoS requrements such as algorthm. Of course, the algorthm s also at the expense of the other propertes such as part of the equty. The examples show that the PF - A algorthm through custom optmal solutons, can look for QoS satsfacton wth the best compromse between system losses. Acknowledgements Ths study s subsdzed by (Guangx A-48) Scentfc and Technologcal Development Gudance Plan, And It s also subsdzed by Guangx Medcal Unversty Teach eform Plan(2012XJGW07) EFEENCES [1]Dongfeng Yuan; Haxa Zhang; Yanbo Ma. Wreless communcaton cross-layer desgn: from theory to applcaton, People's posts and telecommuncatons publshng house, BeJng,2010: [2]Yuhu Zeng; Guangx Zhu; Wemn Wu. Journal of Chnese Computer Systems, 2012,33(5): [3] Chen Le and Lu Jun. esearch on QoS servce based PF schedulng algorthm for LTE systems. STU DY ON OPTICAL COM M UNICATIONS, 2012,173(5): [4] Xan Yong-ju, Tan Feng-chun,and Xu Chang-bao, et al. The Journal of Chna Unverstes of Posts and Telecommuncatons,2011,18(4): [5] Drouch, E. IEEE Transactons on,2012,61(2): [6]Feng Hu-fang,Zhao Lang,and Chen Yuan-yuan. Applcaton esearch of Computers, 2012,2013(1): [7] Hu Yng,Huang Yong-mng,and Yu Fe.Energy-effcent Optmzaton Based User Schedule and esource Allocaton Algorthm, Journal of Electroncs & Informaton Technology, 2012,34(8): [8] Marques, A. G.;Lopez-amos, and L. M.;Gannaks, G. B.. IEEE Transactons on Vehcular Technology, 2012,61(6):

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