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(IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 6, September 2010 PAPR Reduction Technique for LTE SC-FDMA Systems Using Root-Raised Cosine Filter Md. Masud Rana, Jinsang Kim and Won-Kyung Cho Deptartment of Electronics and Radio Engineering, Kyung Hee University 1 Seocheon, Kihung, Yongin, Gyeonggi, 449-701, Republic of Korea Email: mamaraece28@yahoo.com Abstract—Recently, mobile radio communications have de- rate transmission over mobile wireless channels. In OFDMA veloped rapidly due to the endless demand for broadband system, the entire channel is divided into many narrow sub- multimedia access and wireless connection anywhere, and any channels, which are transmitted in parallel, thereby increasing time. With the emergence of diverse fourth generation (4G) enabling technologies, signal processing has become ever in- the symbol duration and reducing the intersymbol-interference creasingly important for small power, small chip resources, (ISI) [4], [8]. Despite many beneﬁts of OFDMA for high speed and efﬁcient physical implementations of potential multimedia data rate services, it suffer from high envelope ﬂuctuation wireless communication systems. In this paper, we analytically in the time domain, leading to large PAPR. Because the derive the time and frequency domain single carrier-frequency high PAPR is detrimental to user mobile equipment (UE) division multiplexing (SC-FDMA) signals. Simulation results show that the SC-FDMA sub-carrier mapping scheme has a terminals, SC-FDMA has drawn great attention as an attractive signiﬁcantly lower peak-to average power ratio (PAPR) compared alternative to OFDMA for uplink data transmission. It can be to orthogonal frequency division multiplexing (OFDMA). In regarded as DFT-spread OFDMA (DFTS-OFDM), where time addition, the interleave FDMA (IFDMA) sub-carrier mapping domain data signals are transformed to frequency domain by scheme with root raised cosine ﬁlter reduced PAPR signiﬁcantly a DFT before going through OFDMA modulation. The main than localized FDMA (LFDMA) and distributed (DFDMA) sub- carrier mapping scheme. As a results, improves the mean power beneﬁt of DFTS-OFDM compared to OFDM scheme, is re- output from a battery driven terminal equipment and power duced variations in the instantaneous transmit power, implying ampliﬁer efﬁciency. the possibility for increased power-ampliﬁer efﬁciency, low- Index Terms—CCDF, IFDMA, OFDMA, PAPR, root-raised complexity high-quality equalization in the frequency domain, cosine, SC-FDMA. and ﬂexible bandwidth assignment [12]. In order to solve the high PAPR problem seen in the I. I NTRODUCTION uplink of OFDMA, research is now addressing techniques such The further increasing demand on high data rates in wireless as a SC-FDMA. The most of the previous work related to communication systems has arisen in order to support broad- 3GPP LTE uplink has been mainly focused on implementation band services. The third generation partnership project (3GPP) problems in the physical layer [2], [5], [9], [13]. In [10], [12] members started feasibility study on the enhancement of the proposed raised-cosine pulse shaping method that compare universal terrestrial radio access (UTRA) in December 2004, PAPR characteristics using the complementary cumulative to improve the mobile phone standard to cope with future distribution function (CCDF) for different subcarrier mapping. requirements. This project was called long term evolution PAPR reduction is of the most importance performance (LTE) [1]. parameter in case of high amplitude signals subject to non LTE uses single carrier frequency division multiple access linear power ampliﬁcation. This situation more and more occur (SC-FDMA) for uplink transmission and orthogonal frequency due to the ever-growing demand in high spectral efﬁciency division multiple access (OFDMA) for downlink transmission advanced mobile telecommunications systems implying multi [6]. SC-FDMA is a promising technique for high data rate dimensional waveforms considerations for which the PAPR transmission that utilizes single carrier modulation and fre- is high. Pulse shaping is required for a single carrier sys- quency domain equalization. Single carrier transmitter struc- tem to bandlimit the transmit signal. This paper addresses ture leads to keep the peak-to average power ratio (PAPR) a theoretical analysis of the PAPR reduction of LTE SC- as low as possible that is reduced the energy consumption. FDMA systems when root-raised cosine (RRC) ﬁlter is used. SC-FDMA has similar throughput performance and essentially RRC is used as the transmit and receive ﬁlter in a digital the same overall complexity as OFDMA [3], [10], [12]. A communication system to perform matched ﬁltering. The highly efﬁcient way to cope with the frequency selectivity combined response of two such ﬁlters is that of the raised- of wideband channel is OFDMA. OFDMA is an effective cosine ﬁlter. In this paper, we analytically derive the time and technique for combating multipath fading and for high bit frequency domain SC-FDMA signals. Simulation results show 66 http://sites.google.com/site/ijcsis/ ISSN 1947-5500 (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 6, September 2010 One radio frame = 20 Slots = 10 Sub-frames = 10 ms that the SC-FDMA has a signiﬁcantly lower PAPR compared 1 Slot = 7 OFDM symbols = 0.5 ms 2 Slots = 1 Sub-frame = 10 ms to OFDMA system. In addition, we comparing the three forms of SC-FDMA sub-carrier mapping scheme and ﬁnd that the interleave FDMA (IFDMA) sub-carrier mapping with root 1 2 3 4 ….…… 15 16 17 19 20 raised cosine based pulse shapping method reduced PAPR Resource block: signiﬁcantly than localized FDMA (LFDMA) and DFDMA 12 sub-carriers 1 2 3 4 5 6 7 Short CP: =180 kHz 7 symbols x 12 sub-carriers sub-carrier mapping scheme. As a results, improves the mean Long CP: power output from a battery driven terminal equipment and Cyclic prefix 6 symbols x 12 sub-carriers power ampliﬁer efﬁciency. 7 OFDM symbols 1 resource element The rest of the paper is organized as follows. We describes Pilot the 3GPP LTE and LTE SC-FDMA system model in sec- tion II and III, respectively. In section IV, we describes the Fig. 2. LTE generic frame structure. different SC-FDMA sub-carrier mapping scheme. In section V, we describes the PAPR reduction technique for LTE SC- FDMA systems. In section VI, we simulated and compare blocks ﬁt in a carrier of 1.4 MHz and 100 resource blocks the proposed method with OFDMA for different sub-carrier ﬁt in a carrier of 20 MHz. Slots consist of either 6 or 7 mapping scheme. Finally, conclusions are made in section VII. OFDM symbols, depending on whether the normal or extended cyclic preﬁx (CP) is employed. The CP is added in front of II. 3GPP LTE each block. The details transmission scheme parameters of The main purposes of the 3GPP LTE are substantially the 3GPP LTE system are shown in Table I [7]. LTE uses SC- improved end-user throughputs, low latency, reduced user FDMA scheme for the uplink transmissions and OFDMA in equipment (UE) complexity, high data rate, and signiﬁcantly downlink transmission. improved user experience with full mobility. First 3GPP LTE TABLE I and LTE-advanced (LTE-A) speciﬁcation is being ﬁnalized LTE SYSTEM PARAMETERS within 3GPP release 9 and release 10, respectively [1]. Year 2005 2006 2007 2008 2009 2010 2011 2012 Trans. bandwidth (MHz) 1.25 2.5 5 10 15 20 Release 7 study phase (HSPA+) FFT size 128 256 512 1024 1536 2048 Occupied sub-carrier 76 151 301 601 901 1200 Release 8 work phase (LTE) Sampling frequency (MHz) 1.92 3.84 7.6815.36 23.04 30.72 Release Release 9 test specs No. of available PRBs 6 12 25 50 75 100 Release 10 (LTE User plane latency (ms) <5 advanced) PRB bandwidth (kHz) 180 Frame duration (ms) 0.5 Release 6 Core First First UE Initially Mass Sub-carrier bandwidth (kHz) 15 market HSPA uplink specs drafted test specs certification development Coverage (km) 5-30 Mobility (km/hr) 15-350 Peak data rates (Mbits/s) DL: 100, and UL: 50 Fig. 1. LTE release timeline. Antenna conﬁguration DL: 4x2, 2x2, 1x2, 1x1, and UL: 1x2, 1x1 Spectrum efﬁciency DL: 3-4 x HSDPA, and UL: 2-3 x HSUPA Rel.6 Control plane latency (ms) 100 (idle to active), and 50 (dormant to active) Speciﬁcally, the physical layer has become quite stable re- Radio resource DL: 3-4 fold higher than Rel.6 cently for a ﬁrst implementation. LTE supports multipule input multiput output (MIMO) with one, two, four, and eight antenna elements at base station (BS) and mobile terminal. Both closed III. LTE SC-FDAMA SYSTEM MODEL and open loop MIMO operation is possible. The target of LTE- The basic principle of a LTE SC-FDMA transmission sys- A is to reach and surpass the international telecommunication tem is shown in Fig. 3. union (ITU) requirements. One of the important LTE-A ben- At the transmitter side, a baseband modulator transmits the eﬁts is the ability to leverage advanced topology networks; binary input to a multilevel sequences of complex number optimized heterogeneous networks with a mix of macros with m1 (q) in one of several possible modulation formats including, low power nodes such as picocells, femtocells, ensures user quandary phase shift keying (QPSK), and 16 level-QAM. fairness, worldwide roaming, and new relay nodes [1]. These modulated symbols are perform a N-point discrete In 3GPP LTE, the basic unit of a transmission scheme is a Fourier transform (DFT) to produce a frequency domain radio frame which is ten msec long. They are divided into ten representation [3]: sub-frames, each sub-frame one msec long. Each sub-frame is N −1 further divided into two slots, each of half msec duration. Fig. 1 ∑ −j2πqn 2, shows the basic LTE generic frame structure [11]. The sub- s1 (n) = √ m1 (q)e N , (1) N q=0 carrier spacing in the frequency domain is 15 kHz. Twelve of these sub-carriers together (per slot) is called a resource where m1 is the discrete symbols, q is the sample index, j is block therefore one resource block is 180 kHz. Six resource the imaginary unit, and m1 (q) is the data symbol. The output 67 http://sites.google.com/site/ijcsis/ ISSN 1947-5500 (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 6, September 2010 Input data tones. Assume that the channel length of CP is larger than the Output data channel delay spread [8]. The transmitted symbols propagating through the radio Demodulation channel can be modeled as a circular convolution between the Modulation channel impulse response (CIR) and transmitted data blocks. R(k) m1(q) At the receiver, the opposite set of the operation is performed. Size-N IDFT The CP samples are discarded and the remaining N samples Size-N DFT s3(m) are processed by the DFT to retrieve the complex constellation s1(n) symbols transmitted over the orthogonal sub-channels. The Equalization received signals are de-mapped and equalizer is used to Subcarrier mapping compensate for the radio channel frequency selectivity. After Subcarrier demapping IDFT operation, the corresponding output is demodulated and s2(q) r(m) soft or hard values of the corresponding bits are passed to the Size-M IDFT Size-M decoder. Channel Noise DFT s(m) IV. SC-FDMA SUB - CARRIER MAPPING SCHEME Cyclic + There are two principal sub-carrier mapping modes- prefix(CP) X Remove CP insertion localized mode, and distribution mode. An example of SC- FDMA transmit symbols in the frequency domain for two Fig. 3. LTE SC-FDMA transceiver system model [6]. user, three sub-carrier per user and six sub-carriers in total is illustrated in Fig. 4 [6]. of the DFT is then applied to consecutive inputs of a size-M s1(1) s1(2) s1(3) inverse DFT (M >N) and where the unused inputs of the IDFT are set to zero. If they are equal (M=N), they simply cancel out and it becomes a conventional single user single carrier system with frequency domain equalization. However, if N is smaller than M and the remaining inputs to the IDFT are set to zero, the output of the IDFT will be a signal with ’single- (x) carrier’ properties, i.e. a signal with low power variations, and with a bandwidth that depends on N. The SC-FDMA is single- (y) carrier, not single frequency. The data signal of each user consists of a lot of frequency. DFT of SC-FDMA is used to ﬁlter the frequency items and maps them into IDFT to reform (z) single user waveform. This may justify the reduced peak-to- Zeros User 1 average power ratio (PAPR) experienced in the IDFT output. Complex weight User 3 The details description of the sub-carrier mapping mode are in User 2 section IV . PAPR is a comparison of the peak power detected Time domain Frequency domain over a period of sample occurs over the same time period. The PAPR of the transmit signal is deﬁned as [14]: Fig. 4. Multiple access scheme of SC-FDMA: (x) IFDMA mode, (y) max0<m<T |s(m)|2 DFDMA mode, and (z) LFDMA. P AP R = ∫ TN , (2) 1 |s(m)| dm 2 In distributed sub-carrier mode, the outputs are allocated TN 0 equally spaced sub-carrier, with zeros occupying the unused where T is the symbol period of the transmitted signal s(m). sub-carrier in between. While in localized sub-carrier mode, PAPR is best described by its statistical parameter, com- the outputs are conﬁned to a continuous spectrum of sub- plementary cumulative distribution function (CCDF). CCDF carrier [10], [12]. Except the above two modes, interleaved measures the probability of signal PAPR exceeding certain sub-carrier mapping mode of SC-FDMA (IFDMA) is another threshold [12], [14]. To further reduce the power variations special sub-carrier mapping mode. The difference between of the DFTS-OFDM signal, explicit spectrum shaping can be DFDMA and IFDMA is that the outputs of IFDMA are applied. Spectrum shaping is applied by multiplying the fre- allocated over the entire bandwidth, whereas the DFDMA’s quency samples with some spectrum-shaping function, e.g. a outputs are allocated every several sub-carriers. If there are root-raised-cosine function (raised-cosine-shaped power spec- more than one user in the system, different sub-carrier map- trum). The IDFT module output is followed by a CP insertion ping modes give different sub-carrier allocation [10], [12]. that completes the digital stage of the signal ﬂow. A CP is In order to accommodate multiple access to the system and used to eliminate ISI and preserve the orthogonality of the to preserve the constant envelope property of the signal, the 68 http://sites.google.com/site/ijcsis/ ISSN 1947-5500 (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 6, September 2010 elements of transmitted signal s(m) are mapped, by using the After IDFT operation, time domain signal can be described LFDMA or IFDMA sub-carrier mapping rule. as follows. Let m = Cq + c, where 0 ≤ c ≤ N − 1 and Here is output symbol calculation in IFDMA in time 0 ≤ c ≤ C − 1. Then time domain transmitted signal can be domain. The frequency samples after IFDMA sub-carrier represent as [12], [16]: mapping is [12], [16]: { M −1 1 ∑ 0≤n≤N −1 j2πml s1 (q/C) = 1 s(m) = s2 (q)e M s2 (q) = M 0 else l=0 N −1 ∑ where q = Cn, and C = M/N and it is the bandwidth 1 1 j2π(Cq+c)l expansion factor of the symbol sequence. If N = M/C = s1 (l)e CN (6) CN l=0 and all terminals transmit N symbols per block, the system can handle C simultaneous transmissions without co-channel if c = 0, then interference. After M-point IDFT operation (M > N ), time N −1 domain signal can be described as follows. Let m = N c + q, 1 1 ∑ j2πql s(m) = [ s1 (l)e N ] where 0 ≤ c ≤ C − 1 and 0 ≤ q ≤ N − 1. The time domain C N l=0 IFDMA transmitted signal can be express as [12], [16]: 1 M −1 = m1 (q) (7) 1 ∑ j2πmq C s(m) = s2 (q)e M ∑N −1 −j2πlp M q=0 Since m1 (q) = m1 (p)e N , and if c ̸= 0, then p=0 N −1 ∑ 1 N −1 N −1 1 ∑ ∑ j2πmn = s1 (n)e N −j2πlp j2π(Cq+c)l NC s(m) = [ m1 (p)e N ]e CN n=0 NC p=0 N −1 l=0 1 1 ∑ N −1 N −1 ∑ ∑ j2π(N c+q)n = s1 (n)e N 1 CN n=0 = m1 (p)e(j2π(q−p)/N +c/CN )l NC N −1 l=0 p=0 1 1 ∑ j2πqn N −1 ∑ = [ C N s1 (n)e N ]. (3) 1 1 − ej2π(q−p) ej2πc/C) = m1 (p) n=0 NC p=0 1 − e(j2π(q−p)/N +c/CN ) The square backed [.] of the above equation represent the N- N −1 ∑ point IDFT operation. The above equation can be rewritten 1 1 − ej2πc/C = m1 (p) as NC p=0 1 − e(j2π(q−p)/N +c/CN ) 1 N −1 s(m) = m1 (q), C (4) 1 1 ∑ m1 (p) ∑N −1 = (1 − ej2πc/C ) (8) 1 j2πqn where m1 (q) = N n=0 s1 (n)e N is the N-point IDFT C N n=0 1 − e(j2π(q−p)/N +c/CN ) operation. Therefore in case of IFDMA, every output symbol is So, the time domain LFDMA sub-carrier mapping signal has simple a repeat of input symbol with a scaling factor of 1/C in exact copies of input time signals with a scaling factor of 1/C time domain. When the sub-carrier frequency allocation starts in the N-multiple sample positions and in between values are from f th sub-carrier i.e. q = Cn + f then the frequency sum of all the time input symbols in the input block with samples after IFDMA sub-carrier mapping is { different complex-weighting (CW) [12]. s1 (q/C − f ) = 1 0≤n≤N −1 Here is output symbol calculation in DFDMA in time s2 (q) = 0 else domain. The frequency samples after DFDMA sub-carrier and the time domain transmitted signal can be express as mapping is [12], [16]: N −1 { 1 1 ∑ j2πqn j2πmf s1 (q/C) = 1 0 ≤ n ≤ N − 1 ˜ s(m) = [ s1 (n)e N ]e M s2 (q) = C N n=0 0 else 1 j2πmf where 0 ≤ c ≤ C − 1, q = Cn, and 0 ≤ C ≤ C. Let ˜ = e M m1 (q). (5) C m = N q + c where 0 ≤ c ≤ C − 1 and 0 ≤ q ≤ N − 1and Thus, when the sub-carrier frequency allocation starts from 0 ≤ q ≤ N − 1. The time domain DFDMA transmitted signal f th instead of zero then there is an additional phase rotation can be express as [12], [16]: of ej2πmf /M . M −1 Here is output symbol calculation in LFDMA sub-carrier 1 ∑ j2πml mapping in time domain. After DFT operation the frequency s(m) = s2 (q)e M M l=0 domain sub-carrier mapping signal can be written as { N −1 1 1 ∑ 0≤l ≤N −1 j2π(Cq+c)l s1 (l) = 1 = s1 (l)e CN Cl ˜ (9) s2 (q) = 0 N ≤l ≤M −1 CN l=0 69 http://sites.google.com/site/ijcsis/ ISSN 1947-5500 (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 6, September 2010 TABLE II if c = 0 and according to the previous procedure, we obtain THE SYSTEM PARAMETERS FOR SIMULATIONS 1 ˜ s(m) = m1 (Cq) (10) System parameters Assumptions C ∑N −1 −j2πlp System bandwidth 5M Hz Since m1 (q) = p=0 m1 (p)e N , if c ̸= 0 and according Number of sub-carriers 512 to the previous procedure, we obtain Data block size 16 Roll of factor 0.0999999999 N −1 1 ∑ Oversampling factor 4 1 ˜ m1 (p) 104 s(m) = (1 − ej2πCc/C ) ˜ ˜ (11) Number of iteration C N n=0 1 − e(j2π(Cq−p)/N +Cc/CN ) Sub-carrier mapping schemes DFDMA, IFDMA, LFDMA Modulation data type Q-PSK and 16-QAM So, the time domain symbols of DFDMA sub-carrier mapping Spreading factor for IFDMA 32 Spreading factor for DFDMA 31 have the same structure as those of LFDMA sub-carrier mapping. V. PAPR REDUCTION TECHNIQUE FOR LTE SC-FDMA exceeded with probability less than 0.1 percentile PAPR. The SYSTEMS PAPR calculation using various sub-carrier mapping schemes In case of high amplitude signals subject to non linear for SC-FDMA and OFDMA system is shown in Fig. 5. The power ampliﬁcation, PAPR reduction is one of the most modulation scheme used for the calculation of PAPR is QPSK. importance performance parameter. This situation more and It can be seen that SC-FDMA sub-carrier mapping schemes more occur due to the ever-growing demand in high spectral efﬁciency telecommunications systems implying multi dimen- 0 sional waveforms considerations for which the PAPR is high. 10 In a single-carrier communication system, pulse shaping is required to bandlimit the signal and ensures it meets the spectrum mask. In this paper, a root raised cosine (RRC) ﬁlter −1 is used to pulse shape the SC-FDMA signals. RRC is used 10 as the transmit and receive ﬁlter in a digital communication system to perform matched ﬁltering. The combined response Pr(PAPR>PAPRo) of two such ﬁlters is that of the raised-cosine ﬁlter. The raised- −2 cosine ﬁlter is used for pulse-shaping in digital modulation 10 Proposed DFDMA Existing DFDMA due to its ability to minimize intersymbol interference (ISI). Proposed LFDMA Existing LFDMA Its name stems from the fact that the non-zero portion of the Proposed IFDMA frequency spectrum of its simplest form β = 1 (called the Existing IFDMA OFDMA −3 roll-off factor) is a cosine function, ’raised’ up to sit above 10 the f (horizontal) axis. The RRC ﬁlter is characterized by two values; β, and Ts (the reciprocal of the symbol-rate). The impulse response of such a ﬁlter can be given as: −4 10 1 − β + 4β/π, t = 0 1 2 3 4 5 6 7 8 9 10 11 √ β/ 2[(1 + 2/π) sin(π/β4) + (1 − 2/π) cos(π/β4)], PAPRo dB h(t) = t = ±T /β4 sin[πt/Ts (1−β)]+4βt/Ts cos[πt/Ts (1+β)] s Fig. 5. Comparison of CCDF of PAPR for SC-FDMA with OFDMA using πt/Ts [1−(4βt/Ts )2 ]) , else QPSK. It should be noted that unlike the raised-cosine ﬁlter, the impulse response is not zero at the intervals of ±Ts . However, gives lower PAPR values as compared to OFDMA scheme. the combined transmit and receive ﬁlters form a raised-cosine In addition, the root raised cosine pulse shaping method has ﬁlter which does have zero at the intervals of ±Ts . Only in lower PAPR than the case of existing pulse shapping method the case of β = 0, does the root raised-cosine have zeros at by more than 3dB. Due to the complex-weighting of LFDMA ±Ts . and DFDMA equation would increase the PAPR. Due to the phase rotation it is unlikely that the LFDMA samples will VI. PERFORMANCE ANALYSIS all add up constructively to produce a high output peak after The performance of the aforementioned PAPR reduction pulse shaping. But it is shown that LFDMA has a lower PAPR technique is explored by performing extensive computer sim- than DFDMA when pulse shaping is applied. Another PAPR ulations. All simulation parameters of the LTE SC-FDMA simulation using various sub-carrier mapping schemes for LTE systems are summarized in Table II [6]. SC-FDMA systems is shown in Fig. 6. The modulation scheme The CCDF)of PAPR, which is the probability that PAPR used for the calculation of PAPR is 16-QAM. It show that is higher than a certain PAPR value PAPR0, is calculated by IFDMA has lowest value of PAPR at 7.8dB which is 6.7dB in Monte Carlo simulation. We compare the PAPR value that is case of QPSK as modulation technique. Finally, we conclude 70 http://sites.google.com/site/ijcsis/ ISSN 1947-5500 (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 6, September 2010 [3] B. Karakaya, H.Arslan, and H. A. Cirpan, ”Channel estimation for LTE 0 10 uplink in high doppler spread,” Proc. WCNC, pp. 1126-1130, April 2008. [4] J. Berkmann, C. Carbonelli, F.Dietrich, C. Drewes, and W. Xu, ”On 3G LTE terminal implementation standard, algorithms, complexities and challenges,” Proc. Int. Con. on Wireless Communications and Mobile Computing, pp. 970-975, August 2008. −1 [5] A. Ancora, C. Bona, and D.T.M. Slock, ”Down-sampled impulse response 10 least-squares channel estimation for LTE OFDMA,” Proc. Int. Con. on Acoustics, Speech and Signal Processing, Vol. 3, pp. 293-296, April 2007. [6] M. M. Rana, M. S.Islam, and A. Z. Kouzani, ”Peak to average power ratio analysis for LTE aystems,” Proc. Int. Con. on Communication Software Pr(PAPR>PAPRo) and Networks, pp. 516-520, February 2010. Proposed DFDMA −2 10 [7] A. Ancora, C. B. Meili, and D. T. Slock, ”Down-sampled impulse Existing DFDMA response least- squares channel estimation for LTE OFDMA,” Proc. Int. Proposed LFDMA Con. on Acoustics, Speech, and Signal Processing, April 2007. Existing LFDMA [8] L. A. M. R. D. Temino, C. N. I Manchon, C. Rom, T. B. Sorensen, and Proposed IFDMA P. Mogensen, ”Iterative channel estimation with robust wiener ﬁltering in Existing IFDMA LTE downlink,” Proc. Int. Con. on Vehicular Technology Conference, pp. −3 10 1-5, September 2008. OFDMA [9] J. Zyren, ”Overview of the 3GPP long term evolution physical layer,” Dr. Wes McCoy, Technical Editor, 2007. [10] H. G. Myung, J. Lim, and D. J. Goodman, ”Single carrier FDMA for uplink wireless transmission,” IEEE Vehicular Technology Magazine, vol. 1, no. 3, pp. 30-38, September 2006. −4 10 2 3 4 5 6 7 8 9 10 11 [11] M. Noune and A. Nix, ”Frequency-domain precoding for single carrier PAPRo dB frequency- division multiple access,” IEEE Commun. Magazine, vol. 48, no. 5, pp. 86-92, May 2010. [12] H.G. Myung, J. Lim, and D. J. Goodman, ”Peak to average power ratio for single carrier FDMA signals,” Proc. PIMRC, 2006. Fig. 6. Comparison of CCDF of PAPR for SC-FDMA with OFDMA using [13] S. Maruyama, S. Ogawa, and K.Chiba, ”Mobile terminals toward LTE 16-QAM. and requirements on device technologies,” Proc. Int. Con. on VLSI Circuits, pp. 2-5, June 2007. [14] S. H. Han, and J. H. Lee, ”An overview of peak to average power ratio reduction techniques for multicarrier transmission,” IEEE Transction on that the higher values of PAPR by using 16-QAM which is Wireless Communications, April 2005. undesirable because they cause non linear distortions at the [15] H. G. Myung, ”Introduction to single carrier FDMA,” Proc. Int. Con. transmitter. on European Signal Processing (EUSIPCO), Poznan, Poland, September 2007. [16] A. Sohl, and A. Klein, ”Comparison of localized, interleaved and block- VII. C ONCLUSIONS interleaved FDMA in terms of pilot multiplexing and channel estimation,” The efﬁciency of a power ampliﬁer is determined by the Proc. Int. Con. on PIMRC, 2007. PAPR of the modulated signal. In this paper, we analysis different sub-carrier mapping scheme for LTE SC-FDMA systems. We derive the time and frequency domain signals of different sub-carrier mapping scheme, and numerically compare PAPR characteristics using CCDF of PAPR. We come to the conclusion that the IFDMA sub-carrier mapping with RRC pulse shaping method has lowest PAPR values compare to the other sub-carrier mapping methods. As a results, im- proves the mean power output from a battery driven terminal equipment and power ampliﬁer efﬁciency. Therefore, SC- FDMA is attractive for uplink transmissions since it reduces the high PAPR seen with OFDMA. ACKNOWLEDGMENT This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (20100017118). R EFERENCES [1] Q. Li, G. li, W. Lee, M. Il. Lee, D. Clerckx, and Z. li, ”MIMO techniques in WiMAX and LTE: a feature overview,” IEEE Commun. Magazine, May 2010. [2] E. Dahlman, S. Parkvall, J. Skold, and P. Beming, ”3G evolution HSPA and LTE for mobile broadband,” Academic Press is an Imprint of Elsevier, 2007. 71 http://sites.google.com/site/ijcsis/ ISSN 1947-5500