SC-FDMA and OFDMA: An Efficient Wireless Image Transmission Schemes

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1 Journal of Control and Systems Engneerng 016, Vol. 4 Iss. 1, PP Frst onlne: 8 July 016 SC-FDMA and OFDMA: An Effcent Wreless Image Transmsson Schemes Fasal S. Al-Kamal 1, Abdullah A. Qasem, Samah A. Abuasbaa 3, Gehan A. Qasem Department of Electrcal Engneerng, Faculty of Engneerng and Archtecture, IBB Unversty, Yemen 1 fasalalkamal@yahoo.com; Abdullah.abdo013@gmal.com Abstract-Orthogonal frequency dvson multple access (OFDMA) and Sngle carrer frequency dvson multple access (SC-FDMA) systems are new systems, whch have become a preferred choce for current and future wreless communcatons. Ths s attrbuted to ther advantages such as the use of frequency doman equalzers. In ths paper, the ssue of the wreless mage transmsson over OFDMA and SC-FDMA systems s nvestgated over a frequency selectve channel for dfferent modulaton and subcarrers mappng schemes. Expermental results show that effcent wreless mage transmsson over OFDMA and SC-FDMA systems s possble. It s found that the nterleaved systems greatly enhance the clarty of the receved mage and ther performances are better than that of the localzed systems. Results also show that the SC-FDMA system provdes better performance than the OFDMA system when the 16QAM modulaton scheme s used and a worse performance than the OFDMA system when the QPSK modulaton scheme s used. Keywords- Image Transmsson; OFDMA; SC-FDMA; Subcarrers Mappng Schemes and Modulaton Schemes I. INTRODUCTION In these years, the demands for hgh data rates ncreased rapdly. Inter-symbol nterference (ISI) s the most challengng problems n wreless transmsson wth hgh data rates. ISI results from the tme dsperson caused by mult-path propagaton. It can cause an error and degrades the system performance. Based on ths fact, many new technques have emerged durng the last two decades such as the orthogonal Frequency Dvson Multple access (OFDMA) and the sngle Carrer Frequency Dvson Multple Access (SC-FDMA) systems. These systems have the ablty to overcome the ISI by the frequency doman equalzers (FDE) [1]. OFDMA systems suffer from several problems such as the hgh peak-to-average power rato (PAPR) and the hgh senstvty to carrer frequency offsets [, 3]. SC-FDMA has low PAPR and ts senstvty s lower than that n the OFDMA system [3]. In the fourth-generaton moble communcaton, SC-FDMA systems have been chosen as the uplnk transmsson technque as OFDMA systems have been chosen as the downlnk transmsson technque [4]. Due to nternet growth, wreless transmsson of the mages and vdeos can be easly performed over multpath channels. Image transmsson over multcarrer code dvson multple access (MC-CDMA) and orthogonal frequency dvson multplexng (OFDM) systems has attracted much attentons n the lterature [5-11]. However, to the best of the authors knowledge, the ssue of mage transmsson over OFDMA and SC-FDMA systems has not been adequately reported, nvestgated and compared. In [5-7], the ssue of mage transmsson over MC-CDMA system was studed. Performance evaluaton of mage transmsson over MC-CDMA system usng two nterleavng schemes was presented n [5]. An effcent mage transmsson based on the randomzaton and equalzer over the MC-CDMA system was suggested and nvestgated n [6]. Recently, an effcent wreless transmsson scheme based on the recent MC-CDMA system was proposed n [7]. Image transmsson over a space-tme coded OFDM system was suggested and dscussed n [8-10]. Chaotc nterleavng for robust mage transmsson wth LDPC coded OFDM was proposed n [11]. The man objectve of ths paper s to nvestgate the ssue of wreless mage transmsson over OFDMA and SC-FDMA systems for dfferent modulaton and subcarrers mappng schemes. In ths paper, the OFDMA and the SC-FDMA system models are derved. In addton, the peak-sgnal-to-nose-rato (PSNR) and the mean square error (MSE) performances of the receved mage over the OFDMA and the SC-FDMA systems are studed, compared and nvestgated for dfferent modulaton and subcarrers mappng schemes. The rest of ths paper s organzed as follows. Secton II derves the OFDMA and the SC-FDMA system models. Subcarrers mappng schemes are dscussed n Secton III. Secton IV explans the gray scale mage and gves the mage qualty metrcs. Secton V ntroduces the smulaton results. Fnally, Secton VI gves the paper conclusons. II. OFDMA AND SC-FDMA SYSTEM MODELS In ths secton, an OFDMA system wth K uplnk users over frequency selectve channels s dscussed, as shown n Fg. 1. A total of N subcarrers are consdered and M subcarrers are assgned for each user. d s the N 1 vector whch represents the modulated symbols of the th user. At the transmtter, the modulated symbols d are mapped. In ths paper, the nterleaved

2 Journal of Control and Systems Engneerng 016, Vol. 4 Iss. 1, PP and the localzed subcarrers mappng schemes are assumed. More detals about the subcarrers mappng schemes are lsted n [, 3]. The mapped sgnal s gven as follows: T Ψ d (1) Ψ s the M N subcarrer mappng matrx of the th user. After that, the mapped sgnal s transformed nto the tme doman usng an M-pont nverse dscrete Fourer transform (IDFT). The tme-doman sgnal can be represented as 1 F M s the M-pont IDFT matrx. Fnally, a cyclc-prefx (CP) s added. t 1 1 FM T FM Ψ d () (a) Transmtter of the th user (b) Recever Fg. 1 Block dagram of the OFDMA system At the recever, the receved sgnal after the CP removal s wrtten as: K 1 C r H t n (3) H C s the M M crculant channel matrx of the th user and n s the nose vector. The crculant matrx expressed as follows [3]: H C can be H C 1 F Λ F (4) Λ s the frequency doman channel matrx and (4) n Equaton (3) and applyng the DFT, we get, F M s the M-pont DFT matrx. Now, substtutng Equatons () and R K 1 Λ T N (5) N s the DFT of n. The estmated symbols of the th user s gven as:

3 Journal of Control and Systems Engneerng 016, Vol. 4 Iss. 1, PP W s the N N equalzaton matrx of the th user. T dˆ W Ψ R (6) T Ψ s the N M subcarrers demappng matrx of the th user. Fnally, the demodulaton and the decodng processes are appled. In ths paper, the FDE based on the mnmum mean square error (MMSE) s used. Fg. descrbes the transcever structure of the SC-FDMA system. As shown n ths fgure, the block dagram of the SC- FDMA system s smlar to that of the OFDMA system n Fg. 1 except for addtonal DFT at the transmtter and IDFT blocks at the recever. So, an SC-FDMA system s defned as a DFT-precoded OFDMA system. A SC-FDMA system transmts the subcarrers n seral. So, SC-FDMA system has lower PAPR than the OFDMA system. It s easy to derve a SC-FDMA system model by replacng d by D n Equaton (1),, D s gven by: D F N 1 d (7) (a) Transmtter of the th user (b) Recever Fg. Block dagram of the SC-FDMA system At the recever sde, an N-pont IDFT s appled after the FDE process. Thus, the estmated symbols of the th user are gven by: dˆ T F W Ψ R (8) 1 M III. SUBCARRIERS MAPPING METHODS There are two methods to map the subcarrers among users [, 3]: the localzed mappng method and the dstrbuted mappng method. The former s usually referred to as localzed scheme, whle the latter s usually called dstrbuted scheme. In the localzed transmsson scheme, each user s data s transmtted wth consecutve subcarrers, whle n the dstrbuted scheme, the user s data s transmtted wth dstrbuted subcarrers. Because the nformaton symbols are spread across the entre sgnal band, the dstrbuted scheme s more robust aganst frequency-selectve fadng. Therefore, ths scheme can acheve more frequency dversty. For the localzed transmsson over a frequency-selectve fadng channel, both the multuser dversty and the frequency-selectve dversty can be accomplshed f each user s gven subcarrers wth favourable transmsson characterstcs

4 Journal of Control and Systems Engneerng 016, Vol. 4 Iss. 1, PP The dstrbuted FDMA scheme wth equdstance between occuped subcarrers throughout the whole band s called the nterleaved scheme. An example system wth 3 users, 1 subcarrers, and 4 subcarrers allocated per user s llustrated n Fg. 3. In ths paper, the LFDMA denotes the localzed SC-FDMA system, the IFDMA denotes the nterleaved SC-FDMA system, the LOFDMA denotes the localzed OFDMA system and the IOFDMA denotes the nterleaved OFDMA system. Fg. 3 Subcarrers mappng schemes for multple users (3 users, 1 subcarrers, and 4 subcarrers allocated per user) [] A. Gray Scale Image IV. GRAY SCALE IMAGE AND IMAGE QUALITY METRICS Furthermore, a gray scale mage s assumed, composed of a range of gray shades. The darkest shade n the gray scale represents black and the lghtest shade s whte. The dfferent shades aggregate to a pxel value, whch are represented by decmal values. So, the gray scale mage s represented by a matrx of decmal values between 0 and 55. Each ndvdual pxel n the gray scale mage s represented by a decmal value. B. Image Qualty Metrcs In ths paper, the PSNR and the MSE metrcs are used to evaluate the qualty of the receved mage. A lower PSNR ndcates that the qualty of the reconstructon mage s low. Therefore, a hgher PSNR s requred. The PSNR can be expressed as [5, 7]: PSNR(dB) fmax 10log MSE (9) f max s the maxmum pxel value n the mage. The MSE s defned as follows [5, 7]: M s number of pxels and I o and M M 1 1( I (, j) I (, j)) MSE J o r (10) M I r are the transmtted and the receved mages, respectvely. V. SIMULATION RESULTS Ths secton s devoted to nvestgatng and evaluatng the ssue of wreless mage transmsson over OFDMA and SC- FDMA systems for dfferent modulaton and subcarrers mappng schemes. N = 64, M = 56 and K = 4 are used. MMSE equalzaton and perfect channel estmaton are assumed. The channel model used n ths paper s the vehcular A model [1]. A convolutonal code wth rate 1/ s consdered. The Cameraman and the Lena mages of sze 56 x 56 are transmtted for each user, whch are shown n Fg

5 Journal of Control and Systems Engneerng 016, Vol. 4 Iss. 1, PP A. PSNR Performance (a) Cameraman mage (b) Lena mage Fg. 4 Cameraman and Lena mages In ths subsecton, the PSNR performance of the receved mage over the OFDMA and the SC-FDMA systems for QPSK and 16QAM s studed. The PSNR values are tabulated n Tables 1 and for QPSK and 16QAM, respectvely. Fgs. 5 and 6 show the varatons of the PSNR of the receved mage wth a SNR for the SC-FDMA and the OFDMA systems at dfferent modulaton and subcarrers mappng schemes. It s clear that the OFDMA system gves better PSNR values than the SC- FDMA system for QPSK. Ths s attrbuted to the hgh spectral effcency of the OFDMA and to ts robustness aganst multpath channel. For 16QAM, the PSNR performance of the SC-FDMA system s better than that of the OFDMA system. Results also show that the IOFDMA system gves the best PSNR performance for QPSK and that the IFDMA system gves the best PSNR performance for 16QAM. Ths results that because the nterleaved systems are more robust aganst the burst errors than the localzed schemes. TABLE 1 PSNR VALUES OF THE RECEIVED CAMERAMAN IMAGE OVER THE OFDMA AND THE SC-FDMA SYSTEMS WHEN THE QPSK IS USED SNR (db) OFDMA SC-FDMA IOFDMA LOFDMA IFDMA LFDMA TABLE PSNR VALUES OF THE RECEIVED CAMERAMAN IMAGE OVER THE OFDMA AND THE SC-FDMA SYSTEMS WHEN THE 16QAM IS USED SNR (db) OFDMA SC-FDMA IOFDMA LOFDMA IFDMA LFDMA

6 PSNR (db) PSNR (db) Journal of Control and Systems Engneerng 016, Vol. 4 Iss. 1, PP IOFDMA LOFDMA IFDMA LFDMA QPSK SNR(dB) Fg. 5 PSNR aganst SNR of the receved mag over the IOFDMA, the LOFDMA, the IFDMA and the LFDMA systems when the QPSK s used 16QAM 60 IOFDMA 50 LOFDMA IFDMA LFDMA SNR(dB) Fg. 6 PSNR aganst SNR of the receved mag over the IOFDMA, the LOFDMA, the IFDMA and the LFDMA systems when the 16QAM s used B. MSE Performance In ths subsecton, the MSE performance of the receved mage over the IOFDMA, the LOFDMA, the IFDMA and the LFDMA systems s nvestgated and compared for both QPSK and 16QAM, respectvely. The MSE values are tabulated n Tables 3 and 4 for QPSK and 16QAM, respectvely. Fgs. 7 and 8 show the varatons of the MSE n the receved mage wth a SNR for the IOFDMA, the LOFDMA, the IFDMA and the LFDMA systems at dfferent modulaton schemes. For QPSK, t s clear that the transmtted mage usng the IOFDMA system gves lower MSE values than other systems. However, for 16QAM, t s clear that the transmtted mage usng the IFDMA system gves lower MSE values than other systems. TABLE 3 MSE VALUES OF THE RECEIVED CAMERAMAN IMAGE OVER THE OFDMA AND THE SC-FDMA SYSTEMS WHEN THE QPSK IS USED SNR (db) OFDMA SC-FDMA IOFDMA LOFDMA IFDMA LFDMA

7 MSE Journal of Control and Systems Engneerng 016, Vol. 4 Iss. 1, PP e e e e e e e e e e e-005 TABLE 4 MSE VALUES OF THE RECEIVED CAMERAMAN IMAGE OVER THE OFDMA AND THE SC-FDMA SYSTEMS WHEN THE 16QAM IS USED SNR (db) OFDMA SC-FDMA IOFDMA LOFDMA IFDMA LFDMA e e e e e e e e e QPSK LOFDMA IOFDMA IFDMA LFDMA SNR(dB) Fg. 7 MSE aganst SNR of the receved mag over the IOFDMA, the LOFDMA, the IFDMA and the LFDMA systems when the QPSK s used

8 MSE Journal of Control and Systems Engneerng 016, Vol. 4 Iss. 1, PP QAM IOFDMA LOFDMA IFDMA LFDMA SNR(dB) Fg. 8 MSE aganst SNR of the receved mag over the IOFDMA, the LOFDMA, the IFDMA and the LFDMA systems when the 16QAM s used C. Clarty Investgaton To nvestgate the clarty of the receved mages over OFDMA and SC-FDMA systems, the receved mages at a SNR= 5 db are selected and shown n Fg. 9 when the QPSK s used. It s clear that the qualty of the receved mages usng the IOFDMA and the LOFDMA systems s better than that of the IFDMA and the LFDMA systems. To show the clarty of the receved mages over the OFDMA and the SC-FDMA systems, the receved mages at a SNR= 5 db are selected and shown n Fg. 10 when the 16QAM s used. It s clear that the qualty of the receved mages usng the IFDMA and the IOFDMA systems s better than that of the LFDMA and LOFDMA systems. It s also shown that the clarty of the receved sgnal usng the LFDMA s better than that usng the LOFDMA system. (a) IOFDMA System (b) LOFDMA System (c) IFDMA System (d) LFDMA System Fg. 9 The receved Cameraman mages usng the OFDMA and SC-FDMA systems for QPSK and SNR= 5 db

9 Journal of Control and Systems Engneerng 016, Vol. 4 Iss. 1, PP (a) IOFDMA System (b) LOFDMA System (c) IFDMA System (d) LFDMA System Fg. 10 The receved Cameraman mages usng the OFDMA and SC-FDMA systems for 16QAM and SNR= 5 db The performances of the OFDMA and SC-FDMA systems are also tested wth another gray scale mage, Lena mage, and the receved mages at a SNR= 5 db are shown n Fg. 11 when the QPSK s used. It s found that the clarty of the receved mages usng the OFDMA and the SC-FDMA systems s hgh and both systems are able to transmt gray scale mages over a frequency selectve channel. (a) IOFDMA System (b) LOFDMA System (c) IFDMA System (d) LFDMA System Fg. 11 The receved Lena mages usng the OFDMA and SC-FDMA systems for QPSK and SNR= 5 db - 8 -

10 Journal of Control and Systems Engneerng 016, Vol. 4 Iss. 1, PP VI. CONCLUSIONS In ths paper, the ssue of wreless mage transmsson over OFDMA and SC-FDMA systems has been studed and nvestgated for dfferent gray scale mages. Smulatons have been shown that the qualty of the receved mage over the IOFDMA system s better than that over the LOFDMA, the IFDMA and the LFDMA systems when the QPSK s used. Also, results show that the clarty of the receved mage over the IFDMA and the IOFDMA systems s better than that over the LFDMA and the LOFDMA systems when the 16QAM s used. Ths ndcates that the IOFDMA and the IFDMA systems are more sutable schemes to transmt wreless gray scale mages over a frequency selectve channel. REFERENCES [1] R. Nogueroles, M. Bossert, A. Donder, and V. Zyablov, Improved performance of a random OFDMA moble communcaton system, n Proc. of IEEE VTC1998, vol. 3, pp , May [] H. G. Myung and D. J. Goodman, Sngle carrer FDMA a new ar nterface for long term evaluaton, John Wley & Sons, Ltd., 198 pages, ISBN: , December 008. [3] F. E. Abd El-Same, F. S. Al-Kamal, A, Y. Al-nahar, and M. I. Dessouky, SC-FDMA for moble communcatons, CRC Press, 38 pages, ISBN: , July 013. [4] 3rd generaton partnershp Project, TR techncal specfcaton group rado access network; physcal layer aspects for evolved unversal terrestral rado access (UTRA) (Release 7), Secton 9.1, 006. [5] S. Jndal and D. Agarwal, Performance evaluaton of mage transmsson over MC-CDMA system usng two nterleavng schemes, n Proc. of ICACCI014, 014, pp [6] E. M. El-Bakary, E. S. Hassan, O. Zahran, S. A. El-Doll, and F. E. Abd El-Same, Effcent mage transmsson wth mult-carrer CDMA, Wreless Personal Communcatons, Sprnger, vol. 69, ss., pp , March 013. [7] A. F. Al-Junad and F. S. Al-kamal, Effcent wreless transmsson scheme based on the recent DST-MC-CDMA, Wreless Networks, Sprnger, vol., ss. 3, pp , Aprl 016. [8] Y. Sun and Z. Xong, Progressve mage transmsson over space-tme coded OFDM-based MIMO systems wth adaptve modulaton, IEEE Trans. On Moble Computng, vol. 5, ss. 8, pp , 006. [9] W. Wang, Space tme codng MIMO-OFDM SAR for hgh-resoluton magng, IEEE Trans. On Geoscence and Remote Sensng, vol. 49, ss. 8, pp , 011. [10] M. Shayeganna, A. Hajshrmohammad, S. Muhadat, and M. Tork, Space tme codng MIMO-OFDM SAR for hgh-resoluton magng, IET Image Processng, vol. 7, ss. 1, pp , 013. [11] N. F. Solman, Y. Albagory, M. A. Elbendary, W. Al-Hanafy, E. M. El-Rabae, S. A. Alshebel, and F. E. Abd El-Same, Chaotc nterleavng for robust mage transmsson wth LDPC coded OFDM, Wreless Personal Communcatons, vol. 79, ss. 3, pp , Dec [1] 3rd generaton partnershp project, 3GPP TS techncal specfcaton group rado access network; user equpment (UE) rado transmsson and recepton (FDD) (Release 7), Secton B.., Sep Fasal S. Al-Kamal has receved the B.Sc. degree n electroncs and communcatons engneerng from the faculty of engneerng, Baghdad Unversty, Baghdad, Iraq, n 001. He has receved the M.Sc., and PhD degrees n communcaton engneerng from the faculty of electronc engneerng, Menoufa Unversty, Egypt, n 008 and 011, respectvely. He joned the teachng staff of the department of electrcal engneerng, faculty of engneerng and archtecture, Ibb Unversty, Yemen n 011. He has served as a head of the electrcal department, Ibb Unversty from Oct. 013 to Oct He s a co-author of many papers n natonal and nternatonal conferences and journals and one textbook. Hs research areas of nterest nclude CDMA systems, OFDMA systems, sngle carrer FDMA (SC- FDMA) system, MIMO systems, nterference cancellaton, synchronzaton, channel equalzaton, channel estmaton and mage processng. Abdullah A Qasem has receved the B.Sc. degree n electroncs and communcatons engneerng from the faculty of engneerng, Ibb Unversty, Yemen n 01. Currently, He s workng as a demonstrator at the department of electrcal, faculty of engneerng and archtecture, Ibb Unversty, Yemen. Hs research area of nterest ncludes mage processng over wreless systems, sngle and multcarrer systems. Samah A. Abuasbaa s an undergraduate student. She s currently studyng n the fnal year n the electrcal department (communcatons engneerng dvson) n the faculty of engneerng and archtecture, Ibb Unversty, Yemen. Her research area of nterest ncludes wreless communcaton systems. Gehan A. Qasem s an undergraduate student. She s currently studyng n the fnal year n the electrcal department (communcatons engneerng dvson) n the faculty of engneerng and archtecture, Ibb Unversty, Yemen. Her research area of nterest ncludes wreless communcaton systems