Performance Evaluation of the VoIP Services of the Cognitive Radio System, Based on DTMC

Transcription

1 J Inf Process Syst, Vol., No., pp.9~3, rch 24 pissn X eissn X Perfornce Evlution of the VoIP Services of the Cognitive Rdio Syste, Bsed on DTC Uy Hbib*, d. Iddul Isl**, nd. R. Ain* Abstrct In recent literture on trffic scheduling, the cobintion of the twodiensionl discrete-tie rkov chin (DTC) nd the rkov odulted Poisson process (PP) is used to nlyze the cpcity of VoIP trffic in the cognitive rdio syste. The perfornce of the cognitive rdio syste solely depends on the ccurcy of spectru sensing techniques, the iniiztion of flse lrs, nd the scheduling of trffic chnnels. In this pper, we only ephsize the scheduling of trffic chnnels (i.e., trffic hndling techniques for the priry user [PU] nd the secondry user [SU]). We consider the following three different trffic odels: the cross-lyer nlyticl odel, /G/() trffic, nd the IEEE 82.6e/ scheduling pproch to evlute the perfornce of the VoIP services of the cognitive rdio syste fro the contet of blocking probbility nd throughput. Keywords Cognitive Rdio, VoIP, DTC, Cross-lyer Anlyticl odel, /G/() Trffic, IEEE 82.6e/. INTRODUCTION The incresing dend for high dt rte wireless voice services over the Internet hs led to nuerous reserch inititives in the field of wireless couniction systes. The desired couniction syste should hve enhnced coputtionl intelligence long with higher ccess speeds, qulity of service ssurnce, nd the bility to successfully hndle ultiple users siultneously. The growing dend of users hs lso brought the need for the fleible nd efficient lloction of vilble spectru resources. Spectru regultory entities hve found tht spectru usge is currently concentrted over certin portion of the spectru nd tht ost of the licensed rdio frequency spectru is indequtely utilized []. Iproved utiliztion of the spectru is one of the key drivers for the developent of the cognitive rdio (CR), which ws first proposed by itol nd gure [2]. A CR cn use n unused licensed spectru s secondry user (SU), which ensures tht licensed priry users (PUs) re not interfered with by its trnsission. For the successful trnsission of secondry users, it is very iportnt to deterine the vcnt rdio frequency spectru of the PU, which is lso referred to s the spectru hole. While deterining the spectru hole, the probbility of flse lr should be inil nd the level of interference towrds the PUs should be t the cceptble level. If the CR detects tht the level of interference towrds the PUs hs eceeded the threshold level, it releses the spectru nd switches to nother spectru for trnsission. A CR syste cn support the ultiuser environent efficiently with liited nuber of spectru holes. To nuscript received Februry 27, 23; first revision April 8, 23 ; ccepted August 25, 23. Corresponding Author:. Ruhul Ain (rin@ewubd.edu) * Deprtent of Electronics nd Counictions Engineering, Est West University, Aftbngr, Dhk 22, Bngldesh (u.h.tithi@gil.co, idd@univ.edu) ** Deprtent of Coputer Science nd Engineering, Jhngirngr University, Svr, Dhk-342, Bngldesh 9 Copyright c 24 KIPS

2 Perfornce Evlution of the VoIP Services of the Cognitive Rdio Syste, Bsed on DTC overcoe the chllenge of the ultiple ccess control in the CR syste, n effective odultion strtegy nd trffic odel tht cn dpt to the tie vrying conditions of the rdio environent ssuring the relible couniction [3] need to be chosen. For future couniction systes, VoIP (Voice over IP) is one of the essentil technologies tht cn provide users with stisfctory voice services t lower cost. VoIP cn support s ny users s possible with stisfctory qulity of service. Therefore, the cobintion of VoIP technology with the CR syste hs the potentil to provide relible ultiedi wireless services with the efficient use of the liited rdio spectru. In this cse, the CR syste should be ble to support rel tie trffic with service stisfction. The voice cpcity of the CR syste nd the perfornce of the VoIP services lso needs to be investigted. Hence, in this pper we hve concentrted on the perfornce nlysis of VoIP services within CR syste by using different types of trffic odels. In the CR syste, VoIP services cn be odeled by choosing n efficient trffic odel nd odultion strtegy. In [4], the VoIP cpcity nd the perfornce of VoIP services hve been nlyzed using the queuing odel for the discrete-tie rkov chin (DTC) frework bsed on rkov odulted Poisson process (PP) trffic odel. However, the uthors hve concentrted ore on finding the iniu trget-detection nd flse lr probbilities. A cross-lyer nlyticl odel hs been proposed in [5] to ensure the qulity of service for the secondry CRs. In this pper, we consider the cross-lyer nlyticl odel for DTC bsed VoIP services in the CR syste. Furtherore, the trffic control schees for /G/() trffic discussed in [6, 7] hve been nlyzed in the contet of CR syste. Here, we lso investigte VoIP perfornce in the CR syste using the scheduling lgorith with n dptive ulti rte (AR) speech codec in IEEE 82.6e/[8]. In this pper, we hve de n effort to evlute the perfornce of the VoIP services in the CR syste for three different trffic odels nd to deterine n efficient trffic odel tht cn be ipleented for the DTC bsed secondry VoIP users of the CR syste [9, ]. The reinder of the pper is orgnized s follows: Section 2 outlines the VoIP trffic nd the syste odel long with the detils of the three trffic odels tht we consider for the CR syste, which re the cross-lyer nlyticl odel, /G/() trffic, nd the IEEE82.6e/ trffic scheduling odel. The results nd nlysis re presented in Section 3. Finlly, Section 4 concludes the pper. 2. SYSTE ODEL 2. VoIP Trffic using DTC VoIP trffic cn be odeled using the discrete-tie rkov chin (DTC) by considering the following two preters: () chnge in the nuber of queuing pckets in two dcent fres nd (b) chnge in the nuber of unoccupied chnnels between two dcent fres. Chnges in the bove two preters re epressed by trnsition tri s [4]: A, P AQ, A A, Q, L O L A A,Q Q,Q, () 2

3 Uy Hbib, d. Iddul Isl, nd. R. Ain where Q is the iu length of queue. Ech eleent A i, of the tri P is nother tri tht represents tht there re i pckets in the queue in the durtion of the current fre nd it will chnge to pckets in the net fre. The tri A i, is epressed in generlized for s: A i, B( B( i, )(, ) i,n )(, ) B B ( i, )(, ) ( i,n )(, ) L O L B B ( i, )(,N ) ( i,n )(,N ), (2) where ech eleent B ( i, )(,n ) of the tri A i, is nother tri of size 2 2 representing the chnge in the nuber of unoccupied chnnels fro to n when the nuber of pckets in the queue chnges fro i to. Here, N is the totl nuber of chnnels. Any eleent B ( i, )(,n ) of the tri A i, is evluted s: where: N ( i, )(,n ) U.D P k ( ( i k, )) Ps ( k c ), n B, (3) P,n in(, Nn ) N y P P P P (, n ) y Ny is the trnsition probbility tht indictes the nuber of unoccupied chnnels chnges fro (current fre) to n (net fre), which re derived fro the two-stte PP odel. Here, Ps ( k c ) represents the probbility tht node serves k pckets when the nuber of unoccupied chnnels is nd y n +. Fro the two-stte discrete tie PP odel, the digonl probbility tri D(k) nd the trnsition probbility tri U re epressed respectively s []: nd: ( λ T ) k λt f f e D ( k) k! (4) k λ2t f ( λ2t f ) e k! ( Λ R) Λ U, (5) where the trnsition rte tri R nd the Poisson rrivl rte tri Λ re epressed s follows: r r R (6) r2 r2 2

4 Perfornce Evlution of the VoIP Services of the Cognitive Rdio Syste, Bsed on DTC nd: λ Λ. (7) λ2 Here, λ nd λ 2 re the en rrivl rtes, r nd r 2 re the en soourn ties of the two-stte PP, nd T f is the fre durtion. Ech eleent of the D ( k ) tri provides the probbility of the rrivl of k pckets over fre durtion of T f. Now, the stedy probbility vector Π cn be obtined using the reltions Π pp Π p nd Π p e ; where e is vector where ll eleents re. The diension of the vector Π p is by 2 ( N + ) ( Q + ). The generl epression of the reltion Π P Π with e is derived s: p p Π p { P2( P) } { P3( P) } L { PN ( P) } { P ( P ) } { P ( P ) } L { P ( P ) } 2 { P ( P ) } { P ( P ) } { P ( P ) } N 2 NN 2N NN 32 3N 22 NN N2 L The probbility of k pckets witing in queue is found s: 22 π P P.. π2 22 π N PNN 2( N + ) p ( 2k( N + ) + i ) i π ( k ) π. (8) The stedy probbility vector of size by ( Q + ) is The en queue length is: The verge rrivl rte is: [ π ) π( )... π( Q )] Π. (9) ( Q Q vg i ( i ) i π. () N.A ρ v s i D( i ) e, () i where A is the iu nuber of pckets tht hve rrived fro node during the intervl [,Tf ] nd the vector s [ s, s2] is obtined fro the reltions su s nd s +s, where U is given by eqution (5). 2 22

5 Uy Hbib, d. Iddul Isl, nd. R. Ain The verge nuber of served VoIP pckets under spectru sensing sttistics T ( ) is: k v N N Q i k in(,k ) π ( k )p ( i )R( p, p ), (2) where R( pd, p f ) is the rtio of the nuber of successfully trnsitted pckets nd the nuber of scheduled pckets. The verge throughput is clculted s: s c d S k v l VoIP, (3) f where l VoIP is the length of the pcket dt unit (PDU) of the VoIP. Finlly, pcket-blocking probbility is clculted s: 2.2 VoIP Trffic under the Cross-Lyer Anlyticl odel kv β. (4) ρ A cross-lyer nlyticl odel of the Cognitive Rdio is proposed in [5]. The trffic preters of the PUs re the cll rrivl rte λ p, nd the cll terintion rte μ p. The blocking probbility of PU is evluted using the //N odel. Now, the probbility of chnnel is kept unoccupied by the PUs tht re sensed by the SU, which is epressed s: B ( η )( Pf ), (5) where P f is the probbility of flse lrs sensed by the SU nd η is the chnnel utiliztion fctor of the PUs, which is epressed s: Ap( Bp ) η, (6) n where Ap λp μ p is the offered trffic nd Bp is the blocking probbility of the PUs. The probbility of z chnnels being unoccupied nd correctly deterined s idle nd reining unoccupied during the spectru-sensing period cn be derived s: z ptp P( z ) ( B) λ e z, (7) where T p is the spectru-sensing period. Now, the probbility P( k c ) tht ppers s in Eqution (3) cn be epressed s: 23

6 Perfornce Evlution of the VoIP Services of the Cognitive Rdio Syste, Bsed on DTC P( k { P( N,A,k )} Y( ) ), (8) c s where: nd: P( N, A,k ) s k N As k, r N As r r Y ( ) P( n ). 2.3 Connection Oriented Pcket Switching of /G/() Trffic Let λ, h, V, nd y be the cll rrivl rte, en cll holding (connection) tie, dt speed, nd the dt ctivity rte for clss J, respectively. The input trffic lod nd the utiliztion ρ of the trnsission line re then given by: co λ, (9) J h nd: Lc ρco ( B ) λ hv y, (2) L c p respectively, where B is the cll blocking probbility, L c is the cell length (53 bytes for AT), L p is the pylod length (48 bytes for AT), nd c is the trnsission speed. We hve Erlng s loss forul: s B / s! J s i i, (2) i! where s is the nuber of virtul chnnels (VCs) ssigned to the trnsission line. According to [6,7] for the /G/ syste, we hve: * Π * * p Π + + p k + Πk ;,, 2,..., (22) k where p is the probbility tht clls rrive during the service tie. * The /G/() syste, Π for > + nd the eqution (22) tke the following recurrence for: 24

7 Uy Hbib, d. Iddul Isl, nd. R. Ain + + * * * * Π Π p Π p k Π k p ;,, 2,...,. (23) k Tking, * * C Π Π we get: Let, C C C C p p C p ;,, 2,...,. (24) + + k k k with C nd cobining the bove equtions, we obtin: C * Π Π P. (25) + C The cell loss rte is then: B P + P C C + C. + ρco C Here, the probbility P( k c ) cn be epressed s: with Y ( ) P( n ). P( k c ) Π ( k )Y( ), (26) 2.4 VoIP Trffic under IEEE 82.6e/ In VoIP trffic, there is lwys trdeoff between the efficient utiliztion of rdio resources nd the qulity of service. In the IEEE 82.6e/ odel, different lgoriths re prevlent for the scheduling of resources to support the tlk-spurt nd silent-period of user. One of the populr VoIP scheduling services under IEEE 82.6e/ is unsolicited grnt service (UGS), where bse sttion (BS) grnts constnt bndwidth (BW) to subscriber sttion (SS) during the entire service tie [,2]. Here, BS periodiclly ssigns grnt to SS, irrespective of the stte of the SS (i.e., its silent nd tlk-spurt sttes). During the silent-period ny lloction of BW is siply wste of the utiliztion of chnnel. Therefore, the UGS lgorith is inefficient for the cse of VoIP scheduling. The dptive ulti-rte (AR) speech codec under the IEEE 82.6e/ syste hs overcoe the bove-entioned wste of chnnel utiliztion. Here, speech fre of bits is generted periodiclly on every 2s during the tlk-spurt, while 4 bits of silence descriptor (SID) fres re generted every 6s during the silent-period. For further iproveent in the utiliztion of chnnel for VoIP service over AR speech codec, new lgorith is proposed in [8]. According to tht lgorith, SID is sent in rndo ccess ethod, insted of vi periodic trnsission during the silent-period. This is done to sve the BW of the uplink. When the stte of SS chnges fro the silent-period to tlk-spurt 25

8 Perfornce Evlution of the VoIP Services of the Cognitive Rdio Syste, Bsed on DTC 26 Fig.. VoIP scheduling lgorith stte, the ccess technique is still intined s rndo during the trnsition tie since the durtion of this trnsition tie is unpredictble. Only during the tlk-spurt tie does the BS provide n lloction (grnt) to the SS, where the grnt size cn vry ccording to the required dt rte. Any SS cn use the reserved bit nd bndwidth-request (BR) field of the bndwidth request nd uplink sleep control (BRUSC) to pprise the BS bout the stte of the SS nd the required bytes. In this cse, SS need not to use generic-ac heder. The bove VoIP scheduling lgorith is depicted in Fig.. The AR speech codec nd the corresponding queuing ethod cn be odeled by one diensionl rkov chin, s shown in Fig. 2. Here, we consider the voice trffic to be eponentilly distributed with en on-tie of λ nd en off-tie of μ. Tking the length of the queue to be k, nd by pplying cut equtions on Fig. 2, we derive the stedy probbility sttes, blocking probbility, nd the probbility of entering the queue. The probbility stte is epressed s: < + ; )! ( )! N ( P ; P P 2 (27) where: y y )! y ( )! ( P. Wsted Resource BRUSC heder Grnt Size 6 sec 2 sec Grnt Size Polling Rndo ccess Silent Period (off) Tlk spurt (on) Rndo ccess Tie Silent Period (off)

9 Uy Hbib, d. Iddul Isl, nd. R. Ain The probbility of entering queue is: Q(,,,k ) k ( )! ( k ) y! y P. (28) λ (-)λ (-+2)λ (-+)λ (-)λ λ μ 2μ (-)μ μ μ μ Fig. 2. rkov chin of VoIP users for the on-off syste The en queue length is: Q k r rq(,,,r ) (29) nd the blocking probbility is epressed s: ( )! ( k) P!. (3) B(,,,k ) Bsed on the equtions (27)-(3), the probbility P( k c ) of Eqution (3) cn be epressed s: where: nd: { P(,k )S( k )} P( k c ), (3) P(, y ) P ( y ), k ( )! S( k ). P ( k ) ( k )!. The first ter indictes the probbility of occupncy of chnnels by the PU nd the second ter indictes the probbility tht k pckets eist in the queue. Finlly, we hve: r k r r + P ( k ) ( ). (32) r r k r 27

10 Perfornce Evlution of the VoIP Services of the Cognitive Rdio Syste, Bsed on DTC 3. RESULTS For ech of the trffic odels, we hve tken two sets of the tri P : one for the Q 3 nd nother is for Q. To for the tri P for Q 3, we tke 3 trices of A i, where the size of ech of A i, tri is 8 8. Thus, the size of the finl P tri becoes For Q, the size of the tri P becoes 8 8 with trices of A i,. Considering the totl nuber of chnnels N 3, we obtin the 2 2 tri B( i,n )(, ) nd tke soe typicl vlues of overloded network like: P. 6, P. 5, P. 75 nd P. 24. To get the digonl tri D(k) nd the trnsition probbility tri U, we ssue tht T f, λ. 656, λ , r. 2, nd r 2. 2 (considering n dverse condition of the network tht stys in n underloded nd overloded stte t 36% nd 64% of the observtion tie, therefore,.36 r /(r +r 2 ) nd.64 r 2 /(r +r 2 ) hence r.2 nd r 2.2) for the VoIP trffic under the cross-lyer nlyticl odel nd IEEE 82.6e/. For the VoIP trffic under the cross-lyer nlyticl odel nd /G/() trffic, we chose P f. 2, λ p 2 nd T p. For the VoIP trffic under cross-lyer nlyticl odel, we took A p 5 nd A s. 4. In the cse of /G/() trffic, we ssued tht A p 5, 35 Erls, s 44, λ, λ 2. 5, y. 5, y 2., V. 5, V 2, h, h 2 5, L c 53, nd L p 48. For VoIP trffic under IEEE 82.6e/, we took the nuber of users, 25,. 3, P d.85, nd 6. The stedy probbility stte vector Π obtined fro the P tri of the size for three different trffic odels of Section II is plotted in Fig. 3. The profile of the probbility sttes resebles to Poisson s pdf in repetitive nner in three different regions of chnnels. Aong the three cses, the IEEE 82.6e/ trffic odel shows the iu vrition of sttes. Fig. 3. The stedy probbility sttes of three trffic odels 28

11 Uy Hbib, d. Iddul Isl, nd. R. Ain.9.8 Blocking Probbility Offered Trffic ) Q 3 IEEE 82.6e/ /G/() Cross lyer Blocking Probbility Offered Trffic b) Q IEEE 82.6e/ /G/() Cross lyer Fig. 4. Vrition of blocking probbility ginst offered trffic: ) Q 3, b) Q Considering the bove preters, the vrition of the blocking probbility ginst offered trffic is plotted in Fig. 4(). The IEEE 82.6e/ odel revels the best perfornce tht stisfies the bsic concept of pcket trffic. A siilr nlysis is lso shown in Fig. 4(b) considering Q, which cn support ore offered trffic, s visulized in Fig. 4(b). The perfornce of the cross-lyer nlyticl odel hs iproved with wider rgin. Finlly, considering Q 3 the throughput is plotted ginst the length of the PDU for three cses in Fig. 5(). Aong these three cses, throughput is found iu for the IEEE 82.6e/ cse. Fig. 5(b) shows the profile for Q, where the throughput is incresed significntly for ll of the trffic cses with n increent in the queue length..9.8 Blocking Probbility IEEE 82.6e/ /G/() Cross lyer Blocking Probbility IEEE 82.6e/ /G/() Cross lyer Offered Trffic Offered Trffic ) Q 3 b) Q Fig. 5. Vrition of the throughput ginst the length of PDU: ) Q 3, b) Q 29

12 Perfornce Evlution of the VoIP Services of the Cognitive Rdio Syste, Bsed on DTC 4. CONCLUSION To eet the dend of wireless voice services, ore dynic nd fleible technologies need to be designed to ensure the efficient utiliztion of spectru resources. One such syste odel cn be designed bsed on the DTC trffic odel to nlyze the VoIP trffic on the CR syste. In this pper, we hve nlyzed the perfornce of VoIP services using three different trffic odels in ters of throughput, stedy probbility sttes, nd blocking probbility. By copring the VoIP perfornce under the cross-lyer nlyticl odel, /G/(), nd the IEEE82.6e/ trffic odel, we showed tht the IEEE82.6e/ trffic odel outperfors other cses in ters of blocking probbility nd throughput when we tke Q 3 nd the cross-lyer odel yields the best if we consider Q. For ll three cses throughput is incresed with the increent of the queue length. Therefore, we cn conclude tht the reltive perfornce of the three trffic odels is sensitive to the length of the queue (i.e., Q ). It should be entioned here tht the proper detection of PU nd the iniiztion of flse lrs, which is nother spect of the CR syste nd tht is relted to the fding condition of the wireless chnnel nd the detection techniques, is beyond the scope of this pper. REFERENCES [] FCC Spectru Policy Tsk Force, FCC Report of the Spectru Efficiency Working Group, Nov. 22 [Online] Avilble: [2] J. itol III nd G. Q. guire, Cognitive rdio: king softwre rdios ore personl, IEEE Personl Counictions, vol. 6, no. 4, pp. 3-8, Aug [3] S. Hykin, Cognitive rdio: brin-epowered wireless counictions, IEEE J. Select. Ares Coun., vol. 23, pp. 2-22, Feb. 25. [4] Howon Lee nd Dong-Ho Cho, Cpcity iproveent nd nlysis of VoIP service in cognitive rdio syste, IEEE trnsctions on Vehiculr Technology, vol.59, no.4, pp , y 2. [5] Yki Y. ihov, Cross-lyer QoS Provisioning in Cognitive Rdio Networks, IEEE Counictions Letters, vol. 6, no. 5, pp , y 22. [6] H. Akiru nd K. Kwshhi, Teletrffic-Theory nd Applictions, London, U.K. Springer- Verlg, 993. [7] Hruo Akiru, rion R. Finley nd Kyoko Yori, A Prcticl Diensioning ethod for AT Systes, IEEE Trnsctions on Counictions, vol. 47, no. 2, pp.3-35, Feb [8] Sung-in Oh, Sunghyun Cho, Je-Hyun nd Jonghyung Kwun, VoIP Scheduling lgorith for AR speech codec in IEEE 82.6e/ syste, IEEE Counictions Letters, Vol. 2, No. 5, pp , y 28. [9] J. O. Neel, Anlysis nd Design of Cognitive Rdio Networks nd Distributed Rdio Resource ngeent Algoriths, Doctor of Philosophy, Virgini Polytechnic Institute nd Stte University, Blcksburg, VA, Sept. 26. [] J. itol, Cognitive Rdio: An Integrted Agent Architecture for Softwre Defined Rdio, Doctor of Technology, Royl Inst. of Technology (KTH), Stockhol, Sweden, y 2. [] J. So, Perfornce nlysis of VoIP services in the IEEE 82.6e OFDA syste with inbnd signling, IEEE trnsctions on Vehiculr Technology, vol.57, no.3, pp , y 28. [2] S. Oh, S. Cho, J. Ki, nd J. Kwun VoIP Scheduling Algorith for AR Speech Codec in IEEE 82.6e/ Syste, IEEE Counictions Letters, vol. 2, no. 5, pp , y 28. 3

13 Uy Hbib, d. Iddul Isl, nd. R. Ain Uy Hbib Uy Hbib received the B.Sc. degree in Electronics nd Telecouniction Engineering fro North South University, Dhk, Bngldesh, in 2 nd hs copleted the.s. degree in Telecouniction Engineering fro Est West University, Dhk, Bngldesh, in 22. She is now working s Lecturer t the Deprtent of Electronics nd Counictions Engineering t Est West University, Dhk, Bngldesh. She hs nuber of reserch ppers in ournls nd conferences. Her reserch interests include dynic spectru ccess, power, nd perfornce nlysis of Cognitive Rdio nd Wireless Counictions systes. d. Iddul Isl d. Iddul Isl hs copleted his B.Sc. nd.sc Engineering in Electricl nd Electronic Engineering fro Bngldesh University of Engineering nd Technology, Dhk, Bngldesh in 993 nd 998 respectively nd hs copleted his Ph.D degree fro the Deprtent of Coputer Science nd Engineering, Jhngirngr University, Dhk, Bngldesh in the field of network trffic engineering in 2. He is now working s Professor t the Deprtent of Coputer Science nd Engineering, Jhngirngr University, Svr, Dhk, Bngldesh. Previously, he worked s n Assistnt Engineer in Sheb Teleco (Pvt.) LTD (A oint venture copny between Bngldesh nd lysi, for obile cellulr nd WLL), fro Sept.994 to July 996. Dr. Isl hs very good field eperience in instlltion of Rdio Bse Sttions nd Switching Centers for WLL. His reserch field is network trffic, wireless counictions, wvelet trnsfor, OFDA, WCDA, dptive filter theory, ANFIS nd rry ntenn systes. He hs ore thn hundred reserch ppers in ntionl nd interntionl ournls nd conference proceedings.. R. Ain. R. Ain received his B.S. nd.s. degrees in Physics fro Jhngirngr University, Dhk, Bngldesh in 984 nd 986 respectively nd his Ph.D. degree in Pls Physics fro the University of St. Andrews, U. K. in 99. He is Professor of Electronics nd Counictions Engineering t Est West University, Dhk, Bngldesh. He served s Post-Doctorl Reserch Associte in Electricl Engineering t the University of Albert, Cnd, during He ws n Alender von Huboldt Reserch Fellow t the -Plnck Institute for Etrterrestril Physics t Grching/unich, Gerny during Dr. Ain wrded the Coonwelth Postdoctorl Fellowship in 997. Besides these, he hs lso received severl wrds for his reserch, including the Bngldesh Acdey of Science Young Scientist Awrd nd the University Grnts Coission Young Scientist Awrd for the yer 996. He is eber of the IEEE. 3