Efficient Resource Allocation Algorithm with Rate Requirement Consideration in Multicarrier-Based Cognitive Radio Networks

Transcription

1 Journa of Counications Vo. 0 No. January 05 Efficient Resource Aocation Agori wi Rate Requireent Consideration in uticarrier-based Cognitive Radio Networs Ling Zuang Lu Liu ai Sao Guangyu Wang and ai Wang Congqing ey Laboratory of obie Counication Congqing University of osts and eecounications Congqing Cina Eai: {zuanging saoai}@cqupt.edu.cn; {iuucqupt wcqupt}@63.co; wangguangy@cqupt.edu.cn Abstract In is paper we present an efficient downin resource aocation agori wi rate requireent consideration in uticarrier-based cognitive radio (CR) networs. e agori is divided into two steps aiing to axiize e downin capacity of e networ under e tota power e interference introduced to e priary users (Us) and e transission rate of e secondary users (SUs) constraints. e transission rate requireent is considered by ensuring e aocated nuber of subcarriers satisfies e required nuber of subcarriers for every SU wiin e subcarrier assignent step and turning e iniu transission rate resod constraints into e iniu power constraint on eac subcarrier wiin e power aocation step. Siuation resuts deonstrate at e proposed agori provides a good guarantee of transission rate requireent and prove at fiter ban uticarrier (FBC) as iger efficiency an orogona frequency division utipexing (OFD) in CR networs. Index ers Cognitive radio uticarrier rate requireent resource aocation I. INODUCION Spectru scarcity crisis exists for any wireess appications but investigations sow at any icensed frequency bands are far underutiized []. Cognitive Radio (CR) a tecnique first introduced by itoa [] is considered as a proising eod to sove e spectru efficiency probe in wic unicensed secondary users (SUs) are aowed to use e icensed frequency bands wiout causing a arfu interference to e icensed priary users (Us). e uticarrier tecnique is a ot topic in 5G counication systes [3] and as been suggested as a proising candidate for CR systes due to its fexibiity in aocating resources aong different SUs. Orogona frequency division utipexing (OFD) is e coon transission tecnique in current CR systes. Nevereess wi e arge side obes of its fiter frequency response e OFD-based CR syste suffers anuscript received October 0 04; revised January is wor was supported by Sino-Finand Cooperation roject (No. 08) and Congqing unicipa Education Coission roject (No. J400437). Corresponding auor eai: zuanging@cqupt.edu.cn. doi:0.70/jc fro considerabe aount of interference to e Us [4]. oreover inserting e cycic prefix (C) in eac OFD sybo decreases e syste tota capacity. As a candidate for e pysica ayer in e future 5G counications systes fiter ban uticarrier (FBC) can overcoe e spectra eaage probe wiout any C extension by decreasing e side obes of eac subcarrier wic eads to sa interference to e Us and ig efficiency [5]. In uticarrier-based CR systes e resource aocation probe is an attractive researc issue and any agoris ave been proposed wi different degree of success. In [6] e auor focused on axiizing e downin capacity of e CR syste wie eeping e interference induced to e U bands beow e prespecified resods but e tota power constraint was not considered and e optia soution obtained by e Lagrange eod ad a ig coputationa copexity. In order to reduce e copexity soe suboptia agoris were proposed to axiize e tota syste capacity under bo tota power and interference introduced to e Us constraints [7]-[9] but e copexity sti reained ig. In [7] two inds of subcarriers were considered e underay subcarriers and e overay subcarriers. e equa aount of power was aocated on eac underay subcarrier and e overay subcarriers were aocated power according to a adder profie. e proposed agori in [8] started wi an initia power aocation step were an initia power eve was aocated to e subcarriers according to four different criteria and en e subcarrier aocation probe was foruated as a utipe-coice napsac probe. In [9] based on e structure of soutions at were obtained roug e Lagrangian duaity a distributed agori was proposed wic ony required soe iited cooperation aong priary and secondary networs wie offering optiu perforance. In [0] an agori caed I agori was presented were e subcarriers were assigned based on e best canne gain criterion e interference constraints were converted into e axiu power constraint on eac subcarrier and e optiization probe was soved using e concept of e conventiona water-fiing wi ower copexity. However e iniu transission rate 05 Engineering and ecnoogy ubising 6

2 Journa of Counications Vo. 0 No. January 05 constraint for eac SU was not taen into consideration in e agoris proposed in [6]-[0]. In is paper an efficient resource aocation agori wi rate requireent consideration in downin uticarrier-based CR systes is presented to axiize e downin capacity of e CR syste wie eeping e tota power and e interference induced to e U bands beow e prespecified resods wi e consideration of e transission rate of e SUs constraints as we. e agori is divided into two pases and e iniu transission rate iit is considered in bo pases. e subcarriers to SUs assignent is perfored first according to e required nuber of subcarriers for every SU using e proposed RS agori. en e power is aocated to e different subcarriers using e proposed IR agori were e iniu transission rate constraints are transfored into e iniu power constraint on eac subcarrier and e optiization probe is soved efficienty wi e odified cap-iited water-fiing to reduce e coputationa copexity. e efficiency of e proposed agori wi be investigated in bo OFD and FBCbased CR systes. e rest of is paper is organized as foow. Section II presents e syste ode and foruates e probe. e subcarrier and power aocation agoris are deveoped in Section III. Siuation resuts are provided to evauate e perforance of e proposed agori in Section IV. Finay Section V concudes e paper. II. SYSE ODEL AND ROBLE FORULAION A. Syste ode Consider e downin of a utiuser uticarrierbased CR networ. e CR syste s frequency spectru is equay divided into subcarriers eac being assigned a f bandwid were L Us are in e icensed bands and e oers are e unicensed bands. A subcarriers are sared by SUs wic eans e SUs can use bo e unicensed bands and e icensed U bands. Assue at eac subcarrier goes under frequency fat fading gains and e instantaneous fading gains are perfecty nown at e CR syste. e transission rate of e subcarrier R e transit power eitted by e subcarrier and e canne gain are reated via e Sannon capacity forua and is given by R og were is e su of e additive wite Gaussian noise (AWGN) variance and e interference introduced by Us on e subcarrier wic is assued to be equa on eac subcarrier. In turn given a transission rate R e required transit power can be expressed as foows: () R () B. odeing of Interference to riary Users e interference of e U band introduced by e subcarrier wi unit transission power written as [4] db db IF can be IF g ( f ) df (3) were d is e spectra distance between e subcarrier and e center frequency of e U band is e bandwid occupied by e U g is e canne gain between e subcarrier and e U band ( f ) is e power spectru density (SD) of e subcarrier and can be written as B ( f ) H ( f ) (4) were H ( f ) is e frequency response of ( n ) wic denotes e saping fiter on e subcarrier. e expression of H ( f ) depends on e used uticarrier tecnique. If an OFD-based CR syste is assued e prototype fiter n ( ) can be cosen as e rectanguar window wi e eng C in nuber of sapes were is e nuber of subcarriers and C is e eng of e C in nuber of sapes. Hence we get H ( f ) rcos r f r (5) If an FBC-based CR syste is assued e prototype fiter can be cosen as n ( ) wi n 0... W were W N and N is e eng of eac poypase coponents (overapping factor). Assuing at (0) is zero and n ( ) ave even syetry around W ( ) [] we get W W W H ( f ) r cos r f r (6) C. robe Foruation e optiization objective is to axiize e tota capacity of e CR syste under e tota transit power e interference introduced to e Us and e transission rate of SUs constraints. e constrained optiization probe can be foruated as foows: subject to O: ax og. a (7) a 0 (8) 05 Engineering and ecnoogy ubising 7

3 Journa of Counications Vo. 0 No. January 05 a... (9) a (0) 0 () a IF I... L () a og R... (3) a were denotes e subcarrier aocation indicator i.e. a ony if e subcarrier is aocated to e SU. Inequaity (9) ensures at eac subcarrier can be aocated to one SU at ost. is e transit power on e subcarrier is e canne gain fro e base station to e SU on e subcarrier is e tota SUs power budget U and SU. I is e interference resod of e R is iniu transission rate iit of e III. DOWNLIN SUBCARRIER AND OWER ALLOCAION e optia soution for e cobinatoria optiization probe O as a ig coputationa copexity wic grows exponentiay wi e input size. e probe is soved in two steps to reduce e coputationa copexity were in e first step e subcarriers are assigned to e SUs and en e power is aocated to ese subcarriers in e second step. Once e subcarriers assignent is copete e utiuser uticarrier syste can be viewed virtuay as a singe user uticarrier syste wic aes e optiization probe coputationay siper. A. Subcarrier Assignent As proved in [] e CR syste can obtain e axiu transission rate in downin if e subcarriers are assigned to e SU wi e best canne gain on at subcarrier owever it wi ead to e situation at soe SUs cannot reac to e required transission rate. In is section we present a subcarrier assignent agori in wic e subcarriers are assigned by jointy considering e canne gain and e subcarrier requireent of eac SU. R og is e estiated nuber of subcarriers required for e SU were is e average power aocated to eac subcarrier of e SU is e average canne gain on eac subcarrier for e SU and is e AWGN variance. In e Requireentbased Subcarrier (RS) assignent agori referred to as RS agori e subcarriers are assigned successivey based on e best canne gain criterion in [] and if e nuber of subcarriers aocated to e SU satisfies e subcarrier requireent of at SU e subcarriers assignent for it wi stop. Wen e subcarrier requireent is et for every SU e reaining subcarriers are aocated according to e previous criterion. e ipeentation of e RS agori is described in abe I. B. ower Aocation By subcarrier assignent e vaues of e subcarrier aocation indicator a are deterined and ence for notation sipicity singe user notation can be used. e canne gain on e subcarrier is deterined as foows: a (4) It can be assued at eac subcarrier beongs to e cosest U band and ony introduces interference to it according to e fact entioned in [4] at ost of e interference of e U bands is caused by cognitive transission on e subcarriers wic are in e U bands as we as directy adjacent to e U bands. And ence e optiization probe O in (7) can be reforuated as foows: subject to O : ax og (5) (6) 0... (7) IF I... L (8) og R... (9) were denotes e set of e subcarriers beong to e U band and denotes e set of e subcarriers assigned to e SU.. Initiaize a 0. for to ABLE I: RS ALGORIH do a arg ax if et 0... end if end for 3. for to do end for a arg ax 05 Engineering and ecnoogy ubising 8

4 Journa of Counications Vo. 0 No. January 05 eore : e soution to e optiization probe O is given by IF were x ax(0 x) and L... (0) are e Lagrange utipiers for (6) (8) (9) respectivey. ree Lagrange utipies can be obtained based on interior point eod wi a copexity 3 O ( ) [3]. roof: See Appendix. e optia soution is coputationay copex so at it is unsuitabe for practica wireess counication systes and ence a ow copexity agori wi be proposed. If e tota power and e transission rate constraints are ignored appying e Lagrange utipier eod e optia soution can be written as IF IF IF were IF... () L is e Lagrange utipier for (8) and can be cacuated by substituting () into IF IF I to get IF I IF () Consider e optiization probe wose optiization goa is to iniize e tota transit power of e CR syste subject to e transission rate of e SUs constraints. According to () it can be foruated as subject to R O3: in (3) R R 0... (4) R R... (5) Appying e Lagrange utipier eod e optia soution can be written as R were... n n (6) is e Lagrange utipier for (5) and can be cacuated by substituting (6) into R R to get R n exp (7) erefore can be obtained by substituting (6) into (). In order to sove e optiization probe O e ower Interference Rate (IR) constrained agori referred to as IR agori is proposed. We can start by assuing at e axiu power wic can be aocated to a given subcarrier is deterined according to e interference constraints ony by using... L. () and () for every subcarrier By suc an assuption we can guarantee at e interference introduced to e U bands wi not exceed e prespecified resods. oreover assue at e initia iniu power wic can be aocated to a given subcarrier is deterined according to e transission rate constraints ony by using () (6) and (7) for every subcarrier.... e resuts at vioate e axiu power are deterined wi e upper bound and e iniu transission rate resod of eac SU is reduced by subtracting e transission rate at SU ave obtained so far. en use () (6) and (7) to update e iniu power of e subcarriers at did not vioate e axiu power e iniu power. is procedure is repeated unti does not vioate e axiu power on any of e subcarriers in e new iteration. By suc an assuption we can guarantee at e transission rate of e SUs wi not ower an e prespecified resods. Once e axiu power and e iniu power are deterined e tota power constraint is tested. If it is obvious at ere does not exist any soution to O e probe is studied except for e iniu power constraints [4]. oreover if en e soution is equa to e toerated axiu power aocated to eac subcarrier i.e.. In ost of e cases e foowing probe soud be soved: subject to WF O4 : ax og (8) WF WF (9) WF... (30) e probe can be soved efficienty using e odified cap-iited water-fiing. o begin wi e tota power budget is reduced by subtracting e 05 Engineering and ecnoogy ubising 9

5 Journa of Counications Vo. 0 No. January 05 suation of e iniu power power power d e axiu is reduced by subtracting e iniu and e eigt of e container s botto power is increased by adding e iniu. en we execute e cap-iited waterfiing [4] and obtain e resut CWF. e fina soution WF of e probe O4 is e resut of e capiited water-fiing CWF pus e iniu power. e ipeentation of e IR agori is described in abe II. ABLE II: IR ALGORIH. Initiaize O U V W Q. Find e as foows: )... L ) R S sort IF O in decreasing order wi i being e sorted index n IF su O O I su IF 3) wie do i( n) O O \ i( n) su su i( n) IF su O I nn end wie IF 4) Set IF 3. Find e as foows: )... ) 4. if sort H n W in decreasing order wi j being e sorted index Hsu H expq Hsu W n W 3) wie n H j(n) do H H H W W \ j( n) expq H W nn su su j( n) su end wie 4) Set R n H V 5) Repeat if et R Q Q og \ V V W V and go to step ) end if unti U et end if 5. Let S and stop e agori S S execute e cap-iited water- WF CWF fiing and set WF e coputationa copexity of step in e proposed L IR agori is O( og ) ( og ) O. Step 3 as a copexity of O ( og ) O( og ax( ) ) were is e nuber of e iterations. Step 5 of e agori executes e odified cap-iited water-fiing wic as a copexity of O( og ) were is e nuber of e iterations. us e overa copexity of e agori is ower an O( og ) were 05 is estiated via siuation. Coparing to e coputationa copexity of e optia soution 3 O ( ) e proposed IR agori as uc ower coputationa copexity especiay for arge nuber of subcarriers. IV. ERFORANCE EVALUAION A. Siuation Configuration Siuations are perfored wi ALAB to evauate e perforance of e proposed agori. Consider a CR syste of L Us at eac as six subcarriers 3 SUs and N 3 subcarriers. e bandwid of subcarriers f is seected as 0.35 Hz 6 and e AWGN variance is 0. e canne gains and g are outcoes of independent identicay distributed Rayeig distributed rando variabes wi ean of. e OFD and FBC-based CR systes are evauated. e OFD syste is assued to ave a 6.67% of its sybo tie as e C. For FBC syste e prototype fiter coefficients are assued to be equa to HYDYAS coefficients wi overapping factor N 4 [5]. Furerore I I I and R R R R are 3 assued. e efficiency of e proposed agori wic consists of RS agori and IR agori is copared wi e I agori proposed in [0] wiout e step at ae e aocated power satisfy approxiatey e interference constraints. e I agori axiizes e downin capacity of e CR syste under ony two constraints e tota power and interference induced to e Us constraints. In e subcarrier assignent step it aways assigns e subcarriers based on e best canne gain criterion in order to obtain e igest transission rate. In e power aocation step it turns e interference constraints into e axiu power constraint on eac subcarrier and uses e concept of e conventiona water-fiing to sove e optiization probe. B. Siuation Resuts e capacity of e CR syste using proposed and I agoris for different interference resods wi 0.5 W and R 0 bit/s/hz is potted in Fig.. It 05 Engineering and ecnoogy ubising 0

6 Journa of Counications Vo. 0 No. January 05 can be observed at e capacity increases as e interference resod increases. e proposed agori is sigty inferior to e I agori. is is because in e subcarrier assignent step e subcarriers are aocated based on e requireent using e proposed agori in wic e subcarriers are not aways assigned to e SU wi e best canne gain unie e I agori wic ony taes e best canne gain into account to obtain e axiu capacity. e appearance of steep drop is due to e guarantee at eac SU can reac to e required transission rate in e power aocation step using e proposed agori wic is not e case in e I agori. e proposed agori transfors e iniu transission rate constraints into e iniu power constraint on eac subcarrier and en soves e optiization probe wi e odified cap-iited water-fiing so at it ay aocate e power to e subcarriers wi poor canne gain wic eads to e drop in capacity. In Fig. e capacity acieved using e proposed agori is not as idea as at acieved using e I agori. e reason is at in e proposed agori e subcarriers ay be assigned to e SUs wi poor canne gain owing to e subcarrier requireent of eac SU wiin e subcarrier assignent step and e power is probaby aocated to e subcarriers wi poor canne gain on account of e iniu power constraint on eac subcarrier wiin e power aocation step. Fig. aso sows at e capacity of FBC-based CR syste is iger an at of OFD-based CR syste because e side obes of e subcarrier s SD in FBC syste are saer an at in OFD one wic introduces ess interference to e U bands. Anoer reason is e inserted C in OFD-based CR syste wic can reduce e syste capacity. e significant advantage in e capacity of FBC-based CR syste over e OFDbased one recoends e FBC as a candidate for e pysica ayer in e future CR systes. By sacrificing a itte syste capacity e proposed agori as a good guarantee of transission rate requireent as sown in Fig. wic pots e transission rate of a specific SU versus e required transission rate of e SU wi 0.5 W and I 0 W for different agoris. It can be noted at e practica transission rate of e SU varies wi e transission rate requireent and aways stricty satisfies it in e proposed agori wie it reains constant regardess of e transission rate requireent in e I agori. is is because in e proposed agori wi e cange of e required transission rate bo e assignent of e subcarriers to SUs in e first step and e aocation of e power to subcarriers in e second step wi vary wic eads to a different transission rate. Fig. 3 iustrates e transission rate per SU versus SU index wi 0.5 W I 0 W and R 0 bit/s/hz using different agoris. We can observe at a ree SUs can satisfy its transission rate requireent in 05 Engineering and ecnoogy ubising e proposed agori. Nevereess in e I agori ony SU can acieve e required transission rate since ere are not any efficient transission rate requireent assurance scees in it. ore subcarriers and power are aocated to SU in virtue of its better canne gains wic resuts in at e transission rate of SU is uc iger an e required transission rate and e oer two SUs cannot reac to it. Fig.. Capacity of secondary users versus interference resod for OFD and FBC-based CR systes. Fig.. ransission rate versus required transission rate of a specific secondary user for OFD and FBC-based CR systes. Fig. 3. ransission rate per secondary user versus secondary user index for OFD and FBC-based CR systes.

7 Journa of Counications Vo. 0 No. January 05 Fig. 4 sows e instantaneous transission rate of a specific SU over tie for different agoris wi 0.5 AENDIX ROOF OF HEORE e probe O can be considered as a convex optiization probe wic can be soved using e Lagrange utipier eod [3] and e Lagrange function can be written as W I 0 W and R 0 bit/s/hz. In bo agoris e instantaneous canne gains are exacty e sae. It can be noted at e proposed agori eeps e instantaneous transission rate above R 0 bit/s/hz a e tie wiin is observation period wie e I agori cannot. is deonstrates at e proposed agori can acieve a better guarantee of transission rate requireent an e I agori. L og L IF I R og (3) were L and... are e Lagrange utipiers. According to e conditions we ave arus-un-ucer () Fig. 4. Instantaneous transission rate of a specific secondary user for OFD and FBC-based CR systes. L IF 0 V. CONCLUSION Eiinate fro (3) and rewrite e conditions as foows: In is paper an efficient resource aocation agori wi rate requireent consideration for downin in uticarrier-based CR networs is proposed. e proposed agori axiizes e tota downin capacity of e uticarrier-based CR networs wie respecting e avaiabe power budget and guaranteeing at no excessive interference is introduced to e U bands and eac SU can acieve e required transission rate. e iniu transission rate iit is considered in bo subcarrier assignent and power aocation steps. In e subcarrier assignent step e subcarriers are aocated to e SUs based on e required nuber of subcarriers for every SU using e proposed RS agori. In e power aocation step e proposed IR agori is perfored were e iniu transission rate constraints are converted into e iniu power constraint on eac subcarrier and e odified cap-iited water-fiing is executed to sove e optiization probe efficienty. Siuation resuts prove at e proposed agori as a significant advantage in e strict guarantee of transission rate requireent over e I agori wi a itte expense of e syste capacity. ey aso deonstrate at e capacity of FBC-based CR syste is ore an OFD-based one and recoend FBC as a candidate for transission in CR networs. In our future wor we pan to extend e appications of 5G in CR networs. 05 Engineering and ecnoogy ubising (3) 0... IF... (33) IF If IF e second condition in (33) ods if 0 wic ipies IF oreover if IF 0 (34) we assue wic ipies IF and vioates e ird condition in (33). us e ony possibe soution in is case is 0. erefore e optia soution can be written as foows:

8 Journa of Counications Vo. 0 No. January 05 if IF IF 0 if IF wic is equa to IF ACNOWLEDGEN (35) (36) is wor was supported by Sino-Finand Cooperation roject (No. 08) and Congqing unicipa Education Coission roject (No. J400437). REFERENCES [] Spectru oicy as Force Federa Counication Coission Wasington DC 00. [] J. itoa and G. Q. aguire Jr Cognitive radio: aing software radios ore persona IEEE ersona Counications vo. 6 no. 4 pp. 3-8 Aug [3] 5G Wavefor Candidate Seection 5GNOW 03. [4]. Weiss J. Hienbrand A. ron and F.. Jondra utua interference in OFD-based spectru pooing systes in roc. 59 IEEE Veicuar ecnoogy Conf. ian 004 pp [5] B. Farang-Boroujeny OFD versus fiter ban uticarrier IEEE Signa rocessing agazine vo. 8 no. 3 pp. 9- ay 0. [6] L. ang Q. Cen G. Wang X. Zeng and H. Wang Opportunistic power aocation strategies and fair subcarrier aocation in OFD-based cognitive radio networs eecounication Systes vo. 5 no. 4 pp Apr. 03. [7] G. Bansa. J. Hossain V.. Bargava and. Le-Ngoc Subcarrier and power aocation for OFDA-based cognitive radio systes wi joint overay and underay spectru access ecanis IEEE rans. on Ve. ecno. vo. 6 no. 3 pp. - ar. 03. [8] S.. Aafou and G. L. Stuber Interference-aware radio resource aocation in OFDA-based cognitive radio networs IEEE rans. on Ve. ecno. vo. 60 no. 4 pp ay 0. [9] D.. Ngo and. Le-Ngoc Distributed resource aocation for cognitive radio networs wi spectru-saring constraints IEEE rans. on Ve. ecno. vo. 60 no. 7 pp Sep. 0. [0]. Saat and F. Bader Coputationay efficient power aocation agori in uticarrier-based cognitive radio networs: OFD and FBC systes EURASI Journa on Advances in Signa rocessing vo. 00 pp [] L. G. Batar D. S. Wadauser and J. A. Nosse Out-of-band radiation in uticarrier systes: A coparison uti-carrier Spread Spectru pp ay 007. [] J. Jang and. B. Lee ransit power adaptation for utiuser OFD systes IEEE Journa on Seected Areas in Coun. vo. no. pp Feb [3] S. Boyd and L. Vandenberge Convex Optiization Cabridge U..: Cabridge University ress 009. [4] N. apandreou and. Antonaopouos Bit and power aocation in constrained uticarrier systes: e singe-user case EURASI Journa on Advances in Signa rocessing vo. 008 pp [5] FBC ysica Layer: A rier HYDYAS 00. Ling Zuang is an associate professor since 00 in e Coege of Counication and Inforation Engineering Congqing University of osts and eecounications (CU) Cina. Se received er.d. degree in 009 in Contro eory and Contro Engineering fro e Congqing University er.s. in 003 in Counication and Inforation Syste and er 4-year B.S. degree in 000 in Counication Engineering fro CU. Her ain researc interests are cognitive radio counications and networing uticarrier oduation tecnique for obie counication uti-rate digita signa processing and fiter ban eory. Lu Liu was born in Hunan rovince Cina in 990. Se received e B.S. degree fro CU in 0. Currenty se is woring on er.s. degree in Congqing University of osts and eecounications. Her researc interests are cognitive radio counications and networing uticarrier oduation tecniques for obie counication and fiter ban eory. ai Sao is an Associate rofessor since 0 in e Coege of Counication and Inforation Engineering CU. His ain researc interests are fiter ban eory uticarrier oduation tecnique for obie counication and reated topics. Guangyu Wang is a rofessor in e Coege of Counication and Inforation Engineering CU. He received a.d. degree in 999 in Eectrica Engineering fro e ie University Gerany an Sc degree in 988 in eecounication Engineering fro Beijing University of osts and eecounications Cina and a 4-year BS degree in 985 fro CU. His ain researc interests incude ig-speed signa processing and uti-rate fiter ban eory. ai Wang was born in Cina in 989. He received is B.S. degree fro Hubei University of Arts and Science Cina in 0. Currenty e is woring on is.s. degree in CU. His researc interests are uticarrier oduation tecniques for obie counication and uti-rate digita signa processing. 05 Engineering and ecnoogy ubising 3