Mobile New Appl (202) 7:45 52 DOI 0.007/s036-0-0308-4 Mulicarrier-Based QAPM Modulaion Sysem for he Low Power Consumpion and High Daa Raes Jae-Hoon Choi & Heung-Gyoon Ryu & Xuedong Liang Published online: 5 April 20 # he Auhor(s) 20. his aricle is published wih open access a Springerlink.com J.-H. Choi : H.-G. Ryu (*) Deparmen of Elecronic Engineering, Chungbuk Naional Universiy, 36 763, Cheongju, Korea e-mail: ecomm@cbu.ac.kr J.-H. Choi e-mail: arcien@cbnu.ac.kr X. Liang Deparmen of Elecronic and Compuer Engineering, Universiy of Briish Columbia, Vancouver, Canada e-mail: xuedongl@ece.ubc.ca Absrac Low power consumpion and high daa rae are he mos imporan requiremens for he communicaion sysem. Especially, very low power consumpion modulaion mehod is required for he shor range communicaion sysems such as he medical implanable communicaion devices or capsule endoscope, and so on. For he higher daa rae, we like o combine he OFDM sysem ino he QAPM since he OFDM sysem has higher bandwidh efficiency han a single-carrier sysem. In his paper, we like o propose a QAPM (Quadraure ampliude posiion modulaion) mehod combined wih he orhogonal frequency-division muliplexing (OFDM) sysem. Nex, we analyze he performance of hree low-powerconsumpion modulaion schemes: he phase shif posiion modulaion (PSPM), phase silence shif keying (PSSK), and QAPM using orhogonal frequency-division muliplexing (OFDM) sysem in he muli-pah channel. hese schemes have lower bandwidh efficiency and he higher power efficiency han he exising phase-shif keying (PSK) and quadraure ampliude modulaion (QAM) schemes. I can be shown ha hey can achieve greaer power efficiency because every modulaion symbol has a zeroenvelope period as in pulse-posiion modulaion (PPM) echniques. Finally, we compare he performances of he PSPM, PSSK, and QAPM modulaion combined wih he OFDM sysem wih regard o bi error rae performance and hroughpu. Keywords PSPM. PSSK. QAPM. power efficiency. bandwidh efficiency. hroughpu. WBAN Inroducion Wih recen growh in he use of porable communicaion devices and neworked sensor sysems, communicaion sysems ha consume lile power have become more imporan. From among hese, WPAN and WBAN are acively sudies. he WPAN sysems are composed of shor range high daa rae communicaion sysem such as UWB and a sensor nework sysem such as Blueooh and Zigbee. A UWB sysem is required low ransmied power for in order o reduce inerference wih oher wireless devices. Also, he sensor nework sysems are required low power consumpion for he running ime. he WBAN sysems are composed of in-body and on-body sysems. And he inbody applicaions which inerconnec he implaned apparaus in he human body and he apparaus sicking on he human body suppor a wide range of medical applicaions []. herefore WBAN devices require a high degree of miniaurizaion and long operaion ime periods before mainenance. Because he sysem wih small sized baery inside he body and he baery is no easy o change. Sudies of low-power-consumpion communicaion sysems are based on he frequency-shif keying (FSK), pulseposiion modulaion (PPM), and pulse-widh modulaion (PWM) schemes [2, 3]. hese schemes are more power
46 Mobile New Appl (202) 7:45 52 Fig. PSPM consellaion efficien han phase-shif keying (PSK) and Quadraure ampliude modulaion (QAM), bu heir bandwidh efficiency is very poor. For his reason, hey require a high bandwidh. he phase silence shif keying (PSSK) modulaion scheme was proposed o address hese problems wih exising modulaion schemes [4]. I has beer bandwidh efficiency han FSK and beer power efficiency han PSK. hese characerisics are suiable for capsule-endoscopes, which require a communicaion sysem wih low power consumpion and a high daa rae [5]. he PSSK modulaion scheme deermines he symbol locaion by using he firs bi daa in a symbol period. herefore, his modulaion scheme ransmis boh symbols and zeros, like PPM. he PSPM modulaion scheme is an exension of he PSSK echnique. he bandwidh efficiency of PSPM is half ha of PSSK, bu is bi error rae (BER) performance is more han 5 db beer han ha of PSSK. Also, PSPM is more power efficien han PSK and PSSK because he modulaion level is lower. his modulaion scheme ransmis four PSK symbols of an orhogonal waveform. his modulaion uses wo bis o deermine he absence marking he posiion of he symbol s silence envelope. his characerisic is suiable for applicaions requiring low power consumpion. he QAPM modulaion scheme is an exension of he QAM echnique, unlike PSSK and PSPM [6, 7]. his mehod requires wice he bandwidh of QAM bu he same bandwidh as PSSK. However, is BER performance is 2~ 4 db beer han ha of QAM. Also, he power efficiency of he ransmier is improved by 3 db. In his paper, we propose a new QAPM mehod combined wih OFDM and analyze o compare he performance of low-power-consumpion modulaion schemes such as PSPM and PSSK using OFDM ransmission in he muli-pah channel. And his paper is organized as follow. Secion 2 describes he convenional mehod. And Secion 3 describes he proposed QAPM mehod combined wih he orhogonal frequency division muliplexing. Secion 4 presens he muli-pah channel model. Finally, he simulaion resuls are given in Secion 5. 2 PSPM and PSPM modulaion 2. PSPM modulaion scheme Figure is 6PSPM consellaion. he exising PSSK mehod ransmi 6PSSK modulaion by using wo orhogonal 8PSSK symbol, bu 6PSPM modulaion by using four orhogonal QPSK symbol. his mehod is wo bi deermines he silence-envelope posiion of he symbol, and (log 2 M)-2 bis deermine he phase of he symbol. herefore his mehod combine wo bi PPM and (log 2 M)-2 bi PSK. Figure 2 shows symbol duraion of PSPM. he symbol period of PSPM is decrease han exising PSSK, bu bandwidh is increase han exising PSSK. Fig. 2 PSPM symbol duraion 00 0 0 00 0 0 (a) PSK (b) PSPM
Mobile New Appl (202) 7:45 52 47 he M-ary PSPM for M 8 is represened as follows. D m ðþ ¼ X3 n¼0 A m;n að n=4 ( ; n < floor 4m=M A m;n ¼ ð Þ < n þ 0; oherwise Þ exp½jq m Š ð0 Þ; ðþ ð2þ a n ðþ ¼u ½ 0:25ðn ÞŠ u ½ 0:25nŠ; n ¼ ; 2; 3; 4 ð3þ Fig. 3 6PSSK consellaion Here, α n () is a uni sep funcion ha deermines he posiion of a symbol. If he α n () is zero, ransmied signal D m () is zero. Bu, if he α n () is one, ransmied signal D m () ise jq m. herefore, he ransmied signal s m () can be wrien using Eq., which reains he orhogonaliy of he symbol by A m,n. s m ðþ ¼ X3 n¼0 A m;n að n=4þe jq m ð4þ (a) PSK Fig. 4 6PSSK symbol duraion 0 0 /2 /2 (b) PSSK 2.2 PSSK modulaion scheme PSSK modulaion scheme is ransmiing wo PSK symbol of orhogonal waveform. As shown Fig. 3, he 6PSSK consellaion. he 6PSK is ransmiing 4-ary daa of one phase symbol, bu 6PSSK ransmiing 4-ary daa of wo 8PSK orhogonal symbols. hus PSSK is one bi deermines he silence-envelope posiion of he symbol, and (log 2 M)- bis deermine he phase of he symbol. As shown Fig. 4, he PSK and PSSK symbol duraion. In Fig. 4(a), PSK symbol duraion is which is symbol period, Bu PSSK symbol duraion is /2 as Fig. 4(b). he symbol posiion of PSSK deermines using by he firs bi daa. his mehod is double porion of bandwidh more han ha of PSK, bu beween he Fig. 5 OFDM based QAPM sysem model
48 Mobile New Appl (202) 7:45 52 QAPM symbol 0 0 /2 /2 Zero symbol Sub-carrier Mapping (a) QAM (b) QAPM Fig. 8 6QAPM symbol duraion QAM symbol Fig. 6 QAPM subcarrier mapping s m ðþ ¼A m ðcos q m þ A m sin q m Þ aðþþb m ðcos q m þ sin q m Þ bðþ ð8þ symbols secure o hamming disance because M-ary PSSK is ransmiing M/2-ary PSK. he M-ary PSSK signal is represened as follows. s m ðþ ¼RefðA m aðþþb m bðþþ exp½jq m Šg ð0 Þ ð5þ Here, θ m =2πmod(m,0.5M)/0.5M; MOD (a, b) is he modulus afer a is divided by b, and is he symbol period. herefore, he phase θ varies as 4π/M. 8 >< ; 0 m M 2 A m ¼ >: 0; M 2 m M ð6þ aðþ ¼uðÞ u ð 0:5Þ; bðþ ¼að 0:5Þ ð7þ A m and B m are he posiion of he symbol in he symbol period, and α() and β() are uni sep funcions ha deermine he carrier frequency of he symbol. herefore, he ransmied signal s m () can be wrien using Eq. 8, which reains he orhogonaliy of he symbol by A m and B m. 3 Proposed sysem model 3. OFDM sysem model he Fig. 5 is block diagram of proposed sysem model. QAPM-OFDM ransmission sysem is using basic OFDM sysem. his sysem is ransmiing hrough IFF afer QAPM subcarrier mapping. Subcarrier mapping was shown in Fig. 6. A QAPM symbol consiss of QAM symbol and zero symbols. herefore subcarrier was arranged as shown Fig. 6. 3.2 QAPM modulaion scheme QAPM modulaion scheme is ransmiing wo QAM symbol of orhogonal waveform. As shown in Fig. 7, 6QAPM consellaion. 6QAM is ransmiing 4-ary daa of one symbol, bu 6QAPM ransmiing 4-ary daa of wo 8QAM orhogonal symbols. In Fig. 8(a), QAM symbol duraion is which is symbol period, bu QAPM symbol duraion is /2 as Fig. 8(b). he symbol posiion of QAPM deermines using he firs bi daa. his mehod is double porion of bandwidh more han QAM. he M-ary QAPM modulaion is represened as follows. D m ðþ ¼fðA I þ A J ÞA m aðþþða I þ A J ÞB m bðþg ð0 < Þ 8 >< ; 0 m M A m ¼ 2 >: M 0; 2 m M ð0þ ðþ Fig. 7 6QAPM consellaion aðþ ¼uðÞ u ð 0:5Þ; bðþ ¼að 0:5Þ ð2þ
Mobile New Appl (202) 7:45 52 49 Daa Daa Mapping QAM Modulaion A m α() Dm () α () R P m Compare A m QAM Demod P/S Converer Daa B m R 2 β () (a) QAPM demodulaion Fig. 9 QAPM modulaion and demodulaion β () (b) QAPM demodulaion. Here, A I is he in-phase ampliude, and A J is he quadraure ampliude. A m and B m are he posiion daa of he symbol in symbol period. As shown in Fig. 9(a), QAPM modulaion scheme will be process in 3-sep. A firs, he inpu daa is mapped ino QAPM daa as Fig. 6. Nex, his QAPM mapping daa is modulaed he QAM daa. Finally, a modulaion daa is modulaed he PPM using A m and B m as Fig. 3. he Fig. 9(b) shows he QAPM demodulaion scheme. he QAPM demodulaion scheme will be progress 3-sep as same modulaion scheme. R ðþ ¼ðD m ðþþnðþþ aðþ ¼A m ða I þ A J ÞþnðÞaðÞ R 2 ðþ ¼ðD m ðþþnðþþ bðþ ¼B m ða I þ A J ÞþnðÞbðÞ ð3þ A firs, we can deec he symbol posiion in period. he signal power compare R and R 2 ha we use o deec symbol posiion. ( max jr n j 2 ¼ R ) A m ¼ 0; P m ¼ r þ j r 2 ð4þ R 2 ) A m ¼ ; P m ¼ r 3 þ j r 4 If is R >R 2, han A m is 0. And if is R <R 2, han A m is. herefore QAPM signal be able o demodulaion by sum A m and QAM demodulaion daa. M-ary QAPM is one bi deermines he silence-envelope posiion of he symbol, and (log 2 M) bis QAM symbol. 4 Simulaion resuls Figure 0 shows he muli-pah channel model used in he simulaion [8]. Figure 0(a) shows he Pedesrian A channel model, which shows moderae fading and a shor delay ime. Figure 0(b) shows he Vehicular A model, which has a long delay ime and severe fading. We used his channel model in he simulaions. We also used a channelequalizing mehod such zero forcing. able shows he delay profiles of hese models. able 2 describes he OFDM simulaion environmen. We conduced he simulaions according o he IEEE 802.a sandard. Also, we ransmied 250,000 OFDM symbols for calculaing he hroughpu. Figure shows he simulaed low-power-consumpion modulaion in he AWGN channel. As shown in Fig. (a), Frequency domain channel response 4 3.5 3 2.5 2.5 0.5 0-0.5-0 0 20 30 40 50 60 subcarrier index (a) Pedesrian A model. Frequency domain channel response 4 3.5 3 2.5 2.5 0.5 0-0.5-0 0 20 30 40 50 60 subcarrier index (b) Vehicular A model. Fig. 0 Frequency response of muli-pah channel model
50 Mobile New Appl (202) 7:45 52 able Delay profile of muli-pah channel ap Pedesrian A Vehicular A Relaive delay (ns) Average power (db) Relaive delay (ns) Average power (db) 0 0 0 0 2 0 9.7 30.0 3 90 9.2 70 9.0 4 40 22.8 090 0.0 5 730 5.0 6 250 20.0 BER 0 0 0-0 -2 0-3 0-4 0-5 6QAPM-single 6QAPM-OFDM 6PSSK-single 6PSSK-OFDM 6QAM-OFDM 6PSK-OFDM 6PSPM-single 6PSPM-OFDM able 2 Simulaion environmen FF size 64 OFDM Sub-carrier 52 Daa Sub-carrier 48 Pilo carrier 4 Carrier separaion 0.325 MHz(=20 MHz/64) Symbol duraion 4 ms (=Daa :3.2 ms, CP : 0.8 ms) CP 6 Modulaion PSPM, PSSK, QAPM, PSK, QAM (6-ary, 32-ary) ransmi ime sec (250,000 symbol) Channel Pedesrian A Vehicular A BER 0-6 0 2 4 6 8 0 2 4 6 8 0 0 0-0 -2 0-3 0-4 0-5 0-6 (a) BER performance of 6-ary modulaion. 32QAPM-single 32QAPM-OFDM 32PSSK-sigle 32PSSK-OFDM 32QAM-OFDM 32PSK-OFDM 32PSPM-single 32PSPM-OFDM 0 2 4 6 8 0 2 4 6 8 20 (b) BER performance of 32-ary modulaion. Fig. BER performance in AWGN channel a a BER of 0 6, he BER performance a 6-ary PSPM is more han 5.6 db beer han ha of a 6-ary PSSK, and he BER performance of a 6-ary PSSK is more han 6 db beer han ha of PSK. he BER performance of a 6-ary QAPM is beer han ha of a 6-ary PSSK. hese resuls are consisen wih he simulaion resuls for a single-carrier sysem. Likewise, Fig. (b) shows ha 32-ary simulaion resuls are he same as hose of a single-carrier sysem. hese resuls show ha PSPM modulaion has he bes BER performance. able 3 described he power efficiency and bandwidh efficiency of modulaions in base-band. As shown in able 3, he bandwidh efficiency of PSPM is half han PSSK and QAPM because PSPM requires double porion of bandwidh more han ha of PSSK. Also, he bandwidh efficiency of PSSK and QAPM is half han PSK and QAM. Bu, BER performance of PSPM is beer han oher modulaion scheme. he duy gain is means symbol period o pulse-on duraion. herefore duy gain of PSPM is 6 db, duy gain of PSSK and QAPM are 3 db. Figure 2 shows he simulaed BER performance of he low-power-consumpion modulaion schemes in he mulipah channel. he resuls for he Pedesrian A channel model are he same as hose for he AWGN channel. Figure 2(a) shows he resuls of 6-ary modulaion in a muli-pah channel. he resuls of he Pedesrian A model are 5~6 db beer han hose of he Vehicular A model because he channel model delay ime is longer han he CP. he BER performance shows he same characerisics. Figure 2(b) shows he resuls of 32-ary modulaion in he muli-pah channel. A 32-ary PSPM has he bes BER performance. Figure 3 shows he resuls of a hroughpu simulaion of each modulaion scheme in he muli-pah channel. Figure 3(a) shows he resuls of 6-ary modulaion; he hroughpu of a 6-ary PSPM requires half he bandwidh of a 6-ary PSSK or a 6-ary QAPM. Figure 3(b) shows
Mobile New Appl (202) 7:45 52 5 able 3 Power efficiency and bandwidh efficiency (Bandwidh=20 MHz) Modulaion level PSPM PSSK QAPM PSK QAM 6 32 6 32 6 32 6 32 6 32 Bi rae (Mbps) 0 2.5 20 25 20 25 40 50 40 50 Symbol Period (ns) 50 50 50 50 50 50 50 50 50 50 Pulse-on duraion (ns) 2.5 2.5 25 25 25 25 50 50 50 50 Duy gain (db) 6 6 3 3 3 3 0 0 0 0 Eb/N0 (0^-6) 7.2.3 2.5 8.3 2 3.5 8.3 23 4.3 6.3 he resuls of 32-ary modulaion. he hroughpu of a 32- ary PSPM is half ha of a 32-ary PSSK wih a high signalo-noise raio (SNR). However, he hroughpu of a 32-ary PSPM in he Vehicular A channel model is beer han ha of a 32-ary PSSK a an SNR of 0~ db because PSPM modulaion is less affeced by he channel. 5 Conclusions In his paper, we propose a QAPM mehod combined wih OFDM and analyze he performance of low-power- BER 0 0 0-0 -2 0-3 0-4 6PSPM-AWGN 6PSPM-PedA 6PSPM-VehA 6PSSK-AWGN 6PSSK-PedA 6PSSK-VehA 6QAPM-AWGN 6QAPM-PedA 6QAPM-VehA ransmi Bi (Bi/s) 2.4 x 07 2.2 2.8.6.4.2 6PSPM-PedA 6PSPM-VehA 6PSSK-PedA 6PSSK-VehA 6QAPM-PedA 6QAPM-VehA 0-5 BER 0-6 0 2 4 6 8 0 2 4 6 8 20 22 0 0 0-0 -2 0-3 0-4 (a) BER performance of 6-ary modulaion. 32PSPM-AWGN 32PSPM-PedA 32PSPM-VehA 32PSSK-AWGN 32PSSK-PedA 32PSSK-VehA 32QAPM-AWGN 32QAPM-PedA 32QAPM-VehA ransmi Bi (Bi/s) 0.8 0 2 4 6 8 0 2 4 6 8 x 0 7 3 2.5 2.5 (a) hroughpu performance of 6-ary modulaion. 32PSPM-PedA 32PSPM-VehA 32PSSK-PedA 32PSSK-VehA 32QAPM-PedA 32QAPM-VehA 0-5 0-6 0 2 4 6 8 0 2 4 6 8 20 22 (b) BER performance of 32-ary modulaion. Fig. 2 BER performance in muli-pah channel 0.5 0 2 4 6 8 0 2 4 6 8 (b) hroughpu performance of 32-ary modulaion. Fig. 3 hroughpu performance in muli-pah channel
52 Mobile New Appl (202) 7:45 52 consumpion modulaion schemes such as PSPM and PSSK using OFDM ransmission in a muli-pah channel. In an AWGN channel, he resuls of low-power-consumpion modulaion show he same characerisics as a single-carrier sysem. Likewise, he simulaion resuls of he Pedesrian A model show similar performance o ha of an AWGN cannel. However, he BER performance and hroughpu performance deeriorae in he Vehicular A channel model because he delay ime for his model is longer han he CP. he hroughpu of PSPM modulaion is half ha of PSSK and QAPM, bu PSPM modulaion is less affeced by he channel. And we can see ha hroughpu of QAPM modulaion is beer han PSSK. herefore we can design he low power consumpion ransmission sysem using PSPM and QAPM o mee he sysem requiremens. And we can know ha a QAPM scheme could be idenified as a more good a modulaion scheme han he PSSK scheme. Acknowledgemen his research was suppored by Basic Science Research Program hrough he Naional Research Foundaion of Korea (NRF) funded by he Minisry of Educaion, Science and echnology (No. 200 0007567) Open Access his aricle is disribued under he erms of he Creaive Commons Aribuion Noncommercial License which permis any noncommercial use, disribuion, and reproducion in any medium, provided he original auhor(s) and source are credied. References. Chen M, Gonzalez S, Vasilakos A, Cao H, Leung V (20) Body area neworks: a survey, ACM/Springer Mobile Neworks and Applicaions (MONE), April 20 2. Long C, Reddy S, Pamari S, He L, Karnik (2006) Powerefficien pulse widh modulaion DC/DC converers wih zero volage swiching conrol. In: Proc. Low Power Elecronics and Design, ISLPED 06., pp. 326 329, Oc. 2006 3. Cho SH, Chadrakasan AP (2004) A 6.5-GHz energy efficien BFSK modulaor for wireless sensor applicaions. IEEE J Solid- Sae Circui 39:73 739 4. Kim DK, Lee HS (2009) Phase-silence-shif-keying for powerefficien modulaor. IEICE rans Communicaion, Vol. E92-B, No.6, June. 2009 5. Oh JY, Kim JH, Lee HS (200) PSSK modulaion scheme for high daa rae implanable medical device. IEEE rans Informaion echnology Biomedicine 4:634 640 6. Choi JH, Ryu HG (20) A QAPM (Quadraure Ampliude Posiion Modulaion) for low power consumpion communicaion. Wireless Pervasive Compuing, 20. ISWPC 20., Feb. 20 7. Choi JH, Ryu HG (20) Design of QAPM modulaion sysem wih high power efficiency and SIMULINK evaluaion. Advanced Communicaion echnology, 20. ICAC 20., Feb. 20 8. 3GPP SGR-0-0030, Furher resuls on CPICH Inerference Cancellaion as A means for Increasing DL Capaciy, Inel Corporaion, Jan. 200 Jae-Hoon Choi was born in Dae-Jun, Republic of Korea, in 985. He received he B.S. degree in he deparmen of elecronics, Chungbuk Naional Universiy in Augus 2003 and 200, respecively. He is currenly working oward M.S degree a he Deparmen of Elecronic Engineering, Chungbuk Naional Universiy, Repurblic of Korea. He research ineress include digial communicaion sysem, wireless body area nework and in-body communicaion sysem. Heung-Gyoon Ryu (M 88) was born in Seoul, Republic of Korea in 959. He received he B.S. and M.S. and Ph.D. degrees in elecronic engineering from Seoul Naional Universiy in 982, 984 and 989. Since 988, he has been wih Chungbuk Naional Universiy, Korea, where he is currenly Professor of Deparmen of Elecrical, Elecronic and Compuer Engineering in Chungbuk Naional Universiy. And he worked as direcor of RICIC (research insiue of compuer, informaion communicaion cener) in Chungbuk Naional Universiy from March 2002 o Feb 2004. His main research ineress are digial communicaion sysems, communicaion circui design and communicaion signal processing. Xuedong Liang is a Posdocoral Research Fellow a he Deparmen of Elecrical and Compuer Engineering, he Universiy of Briish Columbia. He received his Ph.D degree in he Deparmen of Informaics, Universiy of Oslo in 2009. His research ineress are in he areas of wireless communicaion proocols, cooperaive communicaions, game heory and is applicaions, resource allocaion and opimizaion, QoS provisioning, formal modeling and validaion of wireless neworks.