Single Carrier Frequency Division Multiple Access Research Articles

Peak-to-Average Power Ratio Reduction of Uplink Broadband Transmission Systems using Different Reduction Algorithms

Partial transmit sequence (PTS) and selective mapping (SLM), are two algorithms used for peak-to-average power ratio (PAPR) reduction in multicarrier transmissions. In this paper, these techniques are applied for single carrier transmission system enhancement. The advantage of these algorithms, that they have no effect on the bit error (BER) of the system. But it will increase the complexity of the system due to the need for additional inverse discrete fourier transform IDFT calculations, search complexity for optimum phase factor. These algorithms are implemented on a single carrier frequency division multiple access (SCFDMA) system. SC-FDMA is used in Long Term Evaluation (LTE) of 3rd Generation Partnership Project (3GPP) as a strong candidate for uplink multiple access scheme. Simulations show that the proposed system with these two algorithms introduces a significant PAPR reduction compared to conventional system. There is a tradeoff between the PAPR reduction and the transmitter complexity. Due to the need for additional IDFT blocks, the complexity increased and due to side information, data rate has small decrease. Different simulation parameters are used for these algorithms which provide a good indication for selection of optimum technique with optimum parameters.

Impact of the power amplifier on the performance of the single carrier frequency division multiple access system

Single-carrier frequency division multiple access (SC-FDMA) is a promising alternative to orthogonal frequency division multiple access (OFDMA) for uplink wireless communications in frequency-selective fading environments. In this paper, we investigate the impact of the power amplifier (PA) on the performance of the SC-FDMA system. The suitable saturation level thresholds of the PA that can be utilized in the SC-FDMA system are studied and determined through simulations for different modulation formats. Simulation results show that the saturation level of the PA has a significant effect on the bit error rate (BER) performance of the SC-FDMA system, especially with high order modulation formats.

Distributed Space-Time/Frequency Coding Schemes for Single-Carrier Frequency Division Multiple Access Systems

The single carrier-frequency division multiple access (SC-FDMA) system is a new system that was adopted in the standardization of the upcoming 3GPP long-term evolution (LTE). Designing diversity-achieving schemes for the SC-FDMA system is a challenging task. The codes adopted should not affect the peak-to-average power ratio (PAPR) among other constraints. In this paper, we consider the design of cooperative diversity schemes for SC-FDMA systems in the uplink direction. Specifically, two relay-assisted distributed space-time/frequency codes are proposed. The proposed distributed space-frequency code (SFC) achieves full spatial diversity in the uplink fast-fading channels, where a diversity of order three can be achieved. The proposed code keeps a low PAPR, which is a good feature of the system. A minimum mean square error (MMSE) decoder is used at the receiver of the destination node. Moreover, we propose a bandwidth-efficient distributed space-time code (STC) for slow-fading relay channels. A decode-and-forward (DF) protocol is used at the relay node, and the possibility of erroneous decoding is taken into account. Simulation results demonstrate the performance improvement of the proposed schemes.

Uplink single-carrier frequency division multiple access system with joint equalisation and carrier frequency offsets compensation

Similar to the orthogonal frequency division multiple access (OFDMA) system, the single-carrier frequency division multiple access (SC-FDMA) system also suffers from frequency mismatches between the transmitter and the receiver. As a result, in this system, the carrier frequency offsets (CFOs) disrupt the orthogonality between subcarriers and give rise to inter-carrier interference (ICI) and multiple access interference (MAI) among users. The authors present a new minimum mean square error (MMSE) equaliser, which jointly performs equalisation and carrier frequency offsets (CFOs) compensation. The mathematical expression of this equaliser has been derived taking into account the MAI and the channel noise. A low complexity implementation of the proposed equalisation scheme using a banded matrix approximation is presented here. From the obtained simulation results, the proposed equalisation scheme is able to enhance the performance of the SC-FDMA system, even in the presence of estimation errors.

Optimal Orthogonal Precoding for Power Leakage Suppression in DFT-Based Systems

A solution to the power leakage minimization problem in discrete Fourier transform (DFT) based communication systems is presented. In a conventional DFT based system, modulated subcarriers exhibit high sidelobe levels, which leads to significant out-of-band power leakage. Existing techniques found in the literature either do not achieve sufficient sidelobe suppression or suffer from significant spectral efficiency loss. Precoding can be seen as a general linear processing method for power leakage reduction, however, how to design the optimal linear precoder is still an open problem. In this paper, the power leakage suppression is first treated as a matrix Frobenius norm minimization problem, and then the optimal orthogonal precoding matrix design for the power leakage suppression is proposed based on singular value decomposition (SVD). By further exploiting the extra degrees of freedom in the precoding matrix, two kinds of optimized precoding matrices, one with multi-carrier property and the other with single-carrier property, are developed to take the advantages of orthogonal frequency division multiplexing (OFDM) and single carrier frequency division multiple access (SC-FDMA), respectively. Simulation results show that both the multi-carrier and the single-carrier precoding schemes achieve significant power leakage suppression, and have similar peak-to-average power ratio (PAPR) and bit-error-rate (BER) to those of OFDM and SC-FDMA systems, respectively.

Single-carrier Transmission Frequency-domain Equalization Based on a Wiener Filter for Broadband Wireless Communications

Recently, frequency-domain equalization for single-carrier transmission (SC-FDE) has been given much attention. For example, the enhanced mobile phone system, a SC-FDMA (Single-carrier frequency division multiple access) method using SC-FDE and multiple access will be adopted. However in previous research, there are many papers describing the features and advantages of SC-FDE based on a comparison of SC-FDE and orthogonal frequency-division multiplexing (OFDM) systems. In this technical note, we discuss single-carrier transmission equalization in the time-domain (SC-TDE) and SC-FDE in a unified way centered on the Wiener filter based on the minimum mean square error (MMSE) criterion. The reason to take up a Wiener Filter is that it is a basic filter based on the MMSE criterion. Also, we explain the basic principle of the SC-FDE and SC-FDMA in an organized and systematic way. Moreover, we point out the physical meaning of the Wiener solution in SC-FDE and relationship between SC-TDE and SC-FDE Wiener solutions. As a result, we show useful information and pointers, especially for when we want to replace existing SC-TDE technology with SC-FDE technology.

Iterative MMSE-FDE/MUI Cancellation and Antenna Diversity for Frequency-Domain Filtered SC-FDMA Uplink

Broadband single-carrier frequency division multiple access (SC-FDMA) uplink using frequency-domain square-root Nyquist filtering is considered. The peak-to-average power ratio (PAPR) of filtered SC signals can be reduced by increasing the filter roll-off factor α. Furthermore, an additional frequency diversity gain can be obtained by making use of the excess bandwidth introduced by the transmit root Nyquist filtering. However, if the carrier-frequency separation is kept the same as in the case of α = 0, the adjacent users' signal spectra overlap with the desired users' spectrum and the multiuser interference (MUI) is produced. In this paper, we propose two frequency-domain iterative MUI cancellation schemes which can achieve the frequency diversity gain through spectrum combining. The achievable bit error rate (BER) and throughput performances are evaluated by computer simulation.

Dual-Stage Detection Scheme for Ultra-Wideband Detect and Avoid

This paper discusses a dual-stage detection scheme composed of coarse detection stage and refined detection stage for the continuous detection operation of Ultra-Wideband (UWB) detect and avoid (DAA). The threshold factor for the probability of indefinite detection is first proposed and defined to combine the two stages. The proposed scheme focuses on the integration of two different detection schemes with different complexities in order to reduce total computational complexity. A Single-carrier Frequency Division Multiple Access (SC-FDMA) uplink system operating in a Time Division Duplex (TDD) mode is utilized to evaluate the proposed detection scheme. Simulation results indicate that the proposed scheme can make a tradeoff between the detection performance and the computational complexity by setting the probability of indefinite detection.

An Efficient Receiver for Preamble Detection in LTE SC-FDMA Systems with an Antenna Array

In this letter, we propose an efficient low complexity receiver for the preamble detection in single-carrier frequency division multiple access (SC-FDMA) systems with an antenna array. The proposed low complexity receiver is derived using a digital mixer and a multistage decimation filter. The signals for each receive antenna are non-coherently combined. Simulations performed in various channel environments validate that the proposed receiver attains a high detection performance equivalent to the full frequency domain approach which provides the optimal performance, while being quite low in computational complexity.

ICI problem and compensation in MIMO SC‐FDMA system with SC‐SFBC scheme

AbstractIn this paper, we address the ICI (intercarrier interference) problem and compensation in MIMO (multiple input multiple output) SC‐FDMA (single carrier frequency division multiple access) system that exploits SC‐SFBC (single carrier‐space frequency block coding) scheme. Recently, SC‐FDMA technique has received more attention due to the low PAPR (peak to average power ratio) property. However, SC‐FDMA system is sensitive to phase noise and CFO (carrier frequency offset) which is unavoidable in wireless communication systems. Phase noise and CFO introduce CPE (common phase error) as well as ICI into the received signal and seriously degrade the system performance. Therefore, analysis and suppression of these interferences are of great importance. In this paper, we analyze the interferences in MIMO SC‐FDMA system with SC‐SFBC. Then a new ICI estimation and suppression method is proposed to suppress the interferences. Instead of directly estimating the CFO and phase noise, which is pretty difficult and complex, this algorithm exploits block‐type pilots, which is a common pilot pattern in wireless communication systems, such as LTE standard, to estimate the interferences. After that the interferences are suppressed by the inverse matrix method. Simulation results show that the system performance is significantly improved. Copyright © 2010 John Wiley & Sons, Ltd.

MMSE Beamforming for SC-FDMA Transmission over MIMO ISI Channels

We consider transmit beamforming for single-carrier frequency-division multiple access (SC-FDMA) transmission over frequency-selective multiple-input multiple-output (MIMO) channels. The beamforming filters are optimized for minimization of the sum of the mean-squared errors (MSEs) of the transmitted data streams after MIMO minimum mean-squared error linear equalization (MMSE-LE), and for minimization of the product of the MSEs after MIMO MMSE decision-feedback equalization (MMSE-DFE), respectively. We prove that for SC-FDMA transmission in both cases eigenbeamforming, diagonalizing the overall channel, together with a nonuniform power distribution is the optimum beamforming strategy. The optimum power allocation derived for MMSE-LE is similar in spirit to classical results for the optimum continuous-time transmit filter for linear modulation formats obtained by Berger/Tufts and Yang/Roy, whereas for MMSE-DFE the capacity achieving waterfilling strategy well known from conventional single-carrier transmission schemes is obtained. Moreover, we present a modification of the beamformer design to mitigate an increase of the peak-to-average power ratio (PAPR) which is in general associated with beamforming. Simulation results demonstrate the high performance of the proposed beamforming algorithms.

PAPR in 3rd Generation Partnership Project Long Term Evolution: An Overview to Find the Impact

Third Generation Partnership Project Long Term Evolution (3GPP LTE) has adopted orthogonal frequency division multiple access (OFDMA) as the downlink and single-carrier frequency division multiple access (SC-FDMA) as the uplink for the multiple access scheme. SC-FDMA is adopted in the uplink due to its low peak-to-average-power ratio (PAPR). To reduce the PAPR in OFDMA, several techniques have been used in the literature. Many researches are still going on to find the impact of different parameters on PAPR in SC-FDMA. To further reduce the PAPR in SC-FDMA, techniques used to reduce the PAPR in OFDMA can be a potential choice. In this paper, we investigate some existing papers and find the opportunity to build a platform for further reduction in the PAPR in SC-FDMA environment.

Cooperative diversity schemes for uplink single-carrier FDMA systems

Single-carrier frequency division multiple access (SC-FDMA) is considered as a promising technique that is adopted in the uplink for the upcoming 3GPP long term evolution (LTE). This is because it keeps most of the advantages of OFDMA in addition to low peak to average power ratio (PAPR). Designing diversity achieving schemes for SC-FDMA is a challenging task. The code should not affect the PAPR among other constraints. In this paper, we propose cooperative diversity schemes for SC-FDMA systems. Specifically, distributed space-time/frequency codes are proposed. The proposed distributed space-frequency code (DSFC) takes into account the low PAPR which is the feature of the system. Both decode-and-forward (DAF) and amplify-and-forward (AAF) protocols are considered. Erroneous decoding at the relay node is taken into account. Moreover, we propose a bandwidth efficient distributed space-time code (DSTC) for slow fading relay channels with DAF. Analytical and simulation results indicate that the proposed schemes achieve full diversity at the expense of small performance loss compared to the proposed codes in the literature.

Interpolation-Based SC-FDMA Transmitter with Localized Resource Allocation

This paper introduces a practical implementation of a single carrier frequency division multiple access (SC-FDMA) transmitter with localized resource allocation based on rate conversion using interpolation. This implementation provides a significant reduction in computational complexity when the size of resource allocation is relatively smaller than the total number of subcarriers, which is a valid assumption for multiuser systems. The optimization of design parameters for the proposed transmitter is discussed along with an analysis for the condition of mode selection between two different implementations: the interpolation-based SC-FDMA and the conventional SC-FDMA.

An Efficient Receive-Diversity-Combining Technique for SC-FDMA-Based Cooperative Relays

In this correspondence, an efficient receive-diversity-combining technique is proposed for single-carrier frequency-division multiple access (SC-FDMA)-based cooperative relay systems when discrete Fourier transform (DFT) spreading sizes for mobile stations and relay stations are different. The proposed technique is composed of an adjustment block for the DFT spreading size, a phase rotation block, a resource reallocation block, a channel phase compensation block, a receive-diversity-combining block, a channel gain compensation block, and a resource de-allocation block. The proposed technique is shown to provide a high diversity gain in multipath channel environments with a relatively small computational complexity.

Carrier Frequency Offsets Problem in DCT‐SC‐FDMA System: Investigation and Compensation

The Single‐Carrier Frequency Division Multiple Access (SC‐FDMA) system is a well‐known system, which has recently become a preferred choice for uplink channels. In this system, the Carrier Frequency Offsets (CFOs) disrupt the orthogonality between subcarriers and give rise to Intercarrier Interference (ICI), and Multiple Access Interference (MAI) among users. In this paper, the impact of the CFOs on the performance of the Discrete Cosine Transform (DCT) SC‐FDMA (DCT‐SC‐FDMA) system is investigated. Then, a new low‐complexity joint equalization and CFOs compensation scheme is proposed to cancel the interference in frequency domain. The Minimum Mean Square Error (MMSE) equalizer is utilized in the proposed scheme. A hybrid scheme comprising MMSE equalization, CFOs compensation, and Parallel Interference Cancellation (PIC) is also suggested and investigated for further enhancement of the performance of the DCT‐SC‐FDMA system with interleaved subcarriers assignment. For simplicity, this scheme will be referred to as the MMSE+PIC scheme. From the obtained simulation results, it is found that the proposed schemes are able to enhance the system performance, even in the presence of the estimation errors.

Carrier Frequency Offsets Problem in DCT-SC-FDMA System: Investigation and Compensation

The Single-Carrier Frequency Division Multiple Access (SC-FDMA) system is a well-known system, which has recently become a preferred choice for uplink channels. In this system, the Carrier Frequency Offsets (CFOs) disrupt the orthogonality between subcarriers and give rise to Intercarrier Interference (ICI), and Multiple Access Interference (MAI) among users. In this paper, the impact of the CFOs on the performance of the Discrete Cosine Transform (DCT) SC-FDMA (DCT-SC-FDMA) system is investigated. Then, a new low-complexity joint equalization and CFOs compensation scheme is proposed to cancel the interference in frequency domain. The Minimum Mean Square Error (MMSE) equalizer is utilized in the proposed scheme. A hybrid scheme comprising MMSE equalization, CFOs compensation, and Parallel Interference Cancellation (PIC) is also suggested and investigated for further enhancement of the performance of the DCT-SC-FDMA system with interleaved subcarriers assignment. For simplicity, this scheme will be referred to as the MMSE+PIC scheme. From the obtained simulation results, it is found that the proposed schemes are able to enhance the system performance, even in the presence of the estimation errors.

Frequency Domain Decision Feedback Equalization for Uplink SC-FDMA

Single carrier frequency division multiple access (SC-FDMA) is one well-known scheme, which has recently become a preferred choice for uplink channels. Due to the usage of single carrier, the performance of SC-FDMA systems degrades in deep frequency selective fading channels. In this paper, we propose a structure of equalizer based on frequency domain decision feedback which could be used for multi-user SC-FDMA systems. Specific parameters of the equalizer are analyzed as well. This algorithm is applicable to various carrier allocations in multi-user systems such as localized allocation, distributed allocation, and frequency-hopping (FH) allocation. To reduce the complexity, it is not necessary to derive the inversion of matrix, which is required in the traditional decision feedback equalizer for single carrier frequency domain equalization (SC-FDE-DFE). It is shown by the simulation results that perfect performance could be achieved under all kinds of situations for multi-user systems. This structure can be used in the broadcasting uplink channels with SC-FDMA scheme.

A Time Slicing Adaptive OFDM System for Mobile Multimedia Communications

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Multi-Symbol Encapsulated-Orthogonal Frequency Division Multiplexing (MSE-OFDM) is an adaptive OFDM system which was proposed earlier to meet the overwhelming needs of spectrum-efficient wireless communication systems. In this technique, one cyclic prefix (CP) is used for multiple OFDM symbols. The motivation for MSE-OFDM is to mitigate two major inherited disadvantages of OFDM system at the same time i.e., the sensitivity to carrier frequency offset (CFO) and high peak to average power ratio (PAPR). In this paper, we propose a new time slicing technique where the cyclic prefix is replaced with the precoded pseudo-random sequence for MSE-OFDM system. Therefore it is possible to multiplex multiple data streams using this technique with dynamic data rates for mobile multimedia communications. It also overcomes disadvantages with other techniques such as high sensitivity to frequency offset inherited with Orthogonal Frequency Division Multiple Access (OFDMA) system and complex equalization problem with conventional Single Carrier-Frequency Division Multiple Access (SC-FDMA). Therefore this technique can be used for both uplink and downlink transmissions of mobile multimedia communications with variable data rates. With those inherent advantages of proposed time slicing technique which is compatible to DVB-H standard, power saving for mobile receivers is enabled and therefore extended battery life can be guaranteed which is very important for the mobile users. </para>

An interference self-cancellation technique for SC-FDMA systems

A new interference self-cancellation (ISC) method for Single Carrier-FDMA (SC-FDMA) systems is proposed to mitigate the inter-user interference caused by frequency offset or Doppler effect. By transmitting a compensation symbol at the first symbol location in each resource block, the energy leakage can be significantly suppressed. With little bandwidth and power sacrifice, the proposed method can greatly improve the system robustness against frequency offset. Simulation results show that the signal-to-interference ratio (SIR) can be improved by 7 dB on average for the entire system band, and up to 11.7 dB for an individual user.