A Novel Space-Frequency Coding Scheme for Single Carrier Modulations

Single carrier frequency division multiple access (SC-FDMA) has been adopted as uplink multiple access scheme for 3GPP LTE as it combines the advantages of orthogonal frequency division multiple access (OFDMA) and the low envelope variation properties of single carrier (SC) transmission. Moreover, the classical transmit antenna diversity technique as space-time block code (STBC) and space-frequency block code (SFBC) can improve the uplink performance combination with SC-FDMA schemes. In this paper, a signal-to-interference-plus-noise ratio (SINR) performance analysis method of SC-FDMA is proposed for STBC and SFBC schemes, respectively. The closed-form SINR expressions based on the modified SC-preserved implementation structure and MMSE equalization for receivers are derived by channel frequency response and noise variance, considering inter-symbol interference. Moreover, it can be easily extended to multi-receive antennas. By simulation results it is shown that with proposed equivalent SINR, the BLock Error Rate (BLER) performance of MIMO-SC-FDMA over slow fading channel is well matched with that over AWGN channel.

The aim of paper is to design SCFDMA system using SFBC and receiver diversity which provides satisfactory performance over fast fading channel environment. The performance evaluation will be checked through MATLAB R2009b simulator. There are comparisons of performance among 1x1 SCFDMA system, 2x1 SCFDMA system using SFBC, 1x2 SCFDMA system using receiver diversity and 2x2 SCFDMA system using SFBC and receiver diversity. We describe design of SCFDMA system using transmitter diversity technique and receiver diversity technique. We have compared the performance of these systems with the conventional SCFDMA system. The main focus is on design of SCFDMA system using SFBC and receiver diversity which enables desired system to combat detrimental effects of fast fading.Keywords3rd Generation Partnership Project Long Term Evolution(3GPP-LTE)Binary Phase Shift Keying(BPSK)Discrete Fourier Transform(DFT)Inverse Discrete Fourier Transform(IDFT)Localized Frequency Division Multiple Access(LFDMA)Maximum Ratio Receiver Combining(MRRC)Multiple Input Multiple Output(MIMO)Orthogonal Frequency Division Multiple Access (OFDMA)Peak to average power ratio(PAPR)Single Carrier Frequency Division Multiple Access(SCFDMA)Space Frequency Block Code(SFBC)

Long Term Evolution (LTE) chose Single Carrier Frequency Division Multiple Access (SC-FDMA) for uplink communications due to lower signal envelope changes in SC-FDMA signal. This enables low peak to average power ratio (PAPR) in SC-FDMA in contrast to Orthogonal Frequency Division Multiple Access (OFDMA). High PAPR cannot be ignored as it reduces energy efficiency due to the requirement of large range linear power amplifiers. As the mobile devices are power restricted, there is a requirement to mitigate PAPR in the uplink SC-FDMA systems, especially for higher order modulations. Companding is an attractive technique to mitigate PAPR without any bandwidth extension. This paper suggests a companding transform using exponential function to mitigate PAPR in SC-FDMA systems. The suggested transform maintains the average signal power contrary to $\mu$ law companding. Simulation results demonstrate that exponential companding technique without any decompanding operation reduces PAPR by a significant value by maintaining the average signal power and BER performance.

Non-Gaussian noise is one of the most common noise models observed in wireless channels. This type of noise has severe impact on wireless systems detection devices. In this paper, the issue of OFDM and SCFDMA PAPR in non-Gaussian noise channel is addressed. Single carrier frequency division multiple access (SCFDMA) is developed form the Orthogonal Frequency Division Multiple access, (OFDM), and is a promising technique for high data rate uplink communications in the cellular systems. SCFDMA has similar throughput performance and essentially the same overall complexity as OFDM. One of the most important advantages of SCFDMA is the peak-to-average power ratio (PAPR), which is lower than that of OFDM. SCFDMA is employed in the uplink multiple access scheme in the Long Term Evolution (LTE) of cellular systems, and identified by the Third Generation Partnership Project (3GPP). In this paper, we show the performance differences of the OFDM and SCFDA system under different noise scenarios. The performance measure is the PAPR.

Long Term Evolution (LTE) has adopted Single Carrier Frequency Division Multiple Access (SCFDMA) technique for uplink and Orthogonal Frequency Division Multiple Access (OFDMA) for downlink. SCFDMA is often called as Discrete Fourier Transform (DFT) spread OFDMA. In this paper, Wavelet based SCFDMA is proposed for analyzing Bit Error Rate (BER) performance. Analysis is carried out using different wavelets and different modulation schemes under AWGN channel. This analysis will show that the reduction in BER takes place by using wavelet transform in SCFDMA. Thus wavelet based SCFDMA provides better BER performance than that of DFT based SCFDMA.

Single carrier-frequency division multiple access (SC-FDMA) utilizes single carrier modulation at the transmitter and frequency domain equalization at the receiver. It has almost similar performance and essentially the same overall structure of an orthogonal frequency division multiple access (OFDMA) system with low peak to average power ratio (PAPR). Recently, the SC-FDMA has drawn great attention as an attractive alternative to OFDMA, in the uplink communications where lower PAPR greatly benefits the mobile terminal in terms of manufacturing cost as well as transmit power efficiency. Such power efficiency can provide considerable performance improvements in future wireless communication networks. This article outlines the basic principles of SC-FDMA systems with different types of sub-carrier mapping schemes. Simulation results demonstrate the performance of different sub-carrier mapping schemes under ideal and pedestrian channel condition.

Quadrature Orthogonal Frequency Division multiple access (Q-OFDMA) has been renowned as a promising technique which provides a solution to the high PAPR (Peak to average power ratio), sensitivity to carrier frequency offset (CFO) problem and design complexity as introduced by the normal OFDMA systems. Exploiting this Q-OFDMA systems on the Multi-Input Multi-Output (MEMO) architecture, leads to a remarkable improvement in achievable rates. A critical part of this technology is to design the full-rate diversity codes for two transmit and two receive antennas. This paper endeavours to identify key factors and trade-offs issues associated with designing Q-OFDMA systems. We proposed a Space Time Block Codes and spatial multiplexing technique as well as low complexity detection methods for more than 2×2 antennas at the cost of low complexity. This performs well for different fading channel environments and improves the overall system performance such as diversity gain, SNR (Signal to Noise Ratio), Coding gain and BER (bit error rate. The proposed scheme can be easily applied in OFDMA and Single-Carrier Frequency Division Multiple Access (SC-FDMA) by adjusting the parameters of Q-OFDMA.

The Long Term Evolution (LTE) standards are generated by the Third Generation Partnership Project (3GPP) for the Fourth Generation (4G) wireless communication systems. The Fourth Generation (4G) wireless communication standards use new physical layer signaling techniques in their physical layer. Single Carrier Frequency Division Multiple Access (SC-FDMA) and Orthogonal Frequency Division Multiple Access (OFDMA) are the two major signaling techniques used in LTE. OFDMA is used in the downlink of the Fourth Generation (4G) wireless communication systems for its high spectral efficiency and SC-FDMA is used in the uplink of the Fourth Generation (4G) wireless communication systems for its high power efficiency. The main objective of this paper is to design and implement the reliable and energy efficient architecture for LTE uplink system using FPGA. IFDMA is the most energy efficient subcarrier mapping scheme of SC-FDMA multiple access scheme. In IFDMA, the data symbols subcarrier mapping is not one to one instead each subcarrier carries a part from each data symbol transmitted at that time instant. The reason for the selection of IFDMA subcarrier mapping along with SC-FDMA multiple access scheme for LTE uplink comes mainly from its advantage to provide a low peak to average power ratio (PAPR) for the transmitted waveform. This results in less power consumption in the mobile station during uplink transmission. The reliability of the system is improved using interleaving process by avoiding packet loss. Convolution codes are less complex and are used to provide error free transmission. The enhancement of energy efficiency is done using the convolution coded IFDMA. The chosen energy efficient architecture must be more power efficient and support high data rates, which is the main requirement for the mobile user. The proposed reliable and energy efficient architecture for LTE uplink system is implemented using Xilinx system generator tool.

Single carrier frequency division multiple access (SC-FDMA) which utilizes single carrier modulation at the transmitter and frequency domain equalization at the receiver is a technique that has similar performance and essentially the same overall structure as those of an OFDMA system. One prominent advantage over OFDMA is that the SC-FDMA signal has lower peak-to-average power ratio (PAPR). SC-FDMA has drawn great attention as an attractive alternative to OFDMA, especially in the uplink communications where lower PAPR greatly benefits the mobile terminal in terms of the transmit power efficiency. SC-FDMA is currently a working assumption for the uplink multiple access scheme in 3GPP Long Term Evolution (LTE). To achieve low PAPR, a novel scheme, SC-OFDMA with super frame using intermediate mapping (SF-IFDMA), is proposed in this paper. In our proposed scheme, B frames with N subcarriers will be combined into one super frame, then SC-OFDM technique is applied to reduce the PAPR of the super frame, the super frame with lowered PAPR will finally be divided into B OFDM frames for the transmission. The combining and dividing process is equivalent to the concatenation process. The proposed scheme requires no side information and can significantly reduce PAPR while maintaining small number of subcarriers.

Single-carrier frequency-division multiple-access (SC-FDMA) has been adopted in the uplink of the LTE standard due to its lower peak-to-average-power ratio (PAPR) compared to orthogonal frequency-division multiple access (OFDMA). Recent activities in the LTE-advanced (LTE-A) standardization have focused on effective uplink transmit diversity schemes with low PAPR [1] but without considering the performance degradation due to Doppler despite the fact that LTE-A is required to support high mobility. In this paper, we present an open-loop space-frequency block coding (SFBC) scheme for the SC-FDMA uplink and demonstrate its robustness to high Doppler and large multipath delay spread while enjoying full spatial diversity, low PAPR and practical decoding complexity by a suitable design of the frequency span of each SFBC codeword. In this paper, we study the design tradeoffs involved in SFBC design for mobile SC-FDMA.

We propose a simple and flexible peak-to-average power ratio (PAPR) reduction scheme for coded single carrier frequency division multiple access (SC-FDMA) signals in the uplink of the Long Term Evolution (LTE). The proposed scheme is based on the introduction of few bit errors to modify the few complex modulated symbols of each data SC-FDMA symbol in a sub-frame, which cause peaks of the output signal samples to be larger than a predetermined threshold value. In addition, the effect on the bit error rate (BER) performance of the few deliberately corrupted bits can be greatly mitigated by using the channel decoding at the receiver. Computer simulations show that the proposed scheme can reduce the PAPR of SC-FDMA signals effectively with almost the same BER as the conventional SC-FDMA signals when the signal-to-noise ratio (SNR) is below 35 dB.

Orthogonal frequency division multiple access (OFDMA) and Single Carrier Frequency Division Multiple Access (SC-FDMA) are the two major multiple access schemes for 4G wireless communications. In long term evolution (LTE) the downlink multiple access scheme is based on OFDMA and the uplink multiple access scheme is based on SC-FDMA. In this letter, we derive the fundamental performance difference between OFDMA and SC-FDMA, and present the general performance comparison between them. Analytical results show that OFDMA performance upper bounds SC-FDMA in the sense of capacity. The conclusion is further confirmed by numerical results.

A low complexity iterative equalization technique for OFDMA and SC-FDMA uplink systems with Tx-Rx IQ imbalance and CFO under doubly selective channels

Single-Carrier Frequency Division Multiple Access (SC-FDMA) has been selected as the uplink transmission scheme in the 3GPP Long Term Evolution standard. SC-FDMA has reduced sensitivity to phase noise and a lower Peak-to-Average Power Ratio (PAPR) compared to Orthogonal Frequency Division Multiple Access. In this paper we propose joint Tomlinson-Harashima Precoding and transmit power allocation for SC-FDMA. We derive the optimum power allocation for SC-FDMA transmission for both Zero-Forcing (ZF) and Minimum Mean-Square Error (MMSE) LE receivers in order to maximize the achievable data rate subject to constant transmit power. Although this improves the system's performance and offers a 1-2 dB improvement over Frequency-Domain Decision Feedback Equalization (FD-DFE), when the proposed transmit power allocation scheme is combined with decision feedback equalization the system incurs a performance degradation due to error propagation. In this paper we propose a joint implementation of the derived power allocation scheme with THP. Here we show that the system's performance is further improved over both FD-LE and FD-DFE when transmit power allocation is applied.

Blind selective mapping for single-carrier frequency division multiple access system