Design of SCFDMA System Using MIMO

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.

In this paper, the parameters estimation for the interference rejection combining (IRC) technique with the inter-cell interference (ICI) and narrowband interference (NBI) in single-carrier frequency-division multiple access (SC-FDMA) systems is considered. Due to the characteristics of the interferences in uplink SC-FDMA systems is quite different from that in downlink orthogonal frequency-division multiple access (OFDMA) systems, the traditional autocorrelation matrix estimation and channel estimation schemes, which refine the estimation in both the time and frequency domain, can not be employed in SC-FDMA systems directly. Therefore, a simple but effective autocorrelation matrix estimation scheme is suggested in this paper, besides, an EVD-based channel estimation which can filter out the energy of the interference plus noise with low complexity is proposed. Simulation results display the effectiveness of the autocorrelation matrix estimation and the advantage of the EVD-based channel estimation with the ICI and NBI in SC-FDMA systems.

Single carrier frequency division multiple access (SC-FDMA) has not only utilized the single carrier modulation., frequency-domain equalization., and the most features of OFDMA., but also., it has an outstanding feature. It is the lower PAPR due to its single carrier structure. However., localized frequency division multiple access (LFDMA) still needs more PAPR reduction., since the pulse shaping does not affect much its PAPR performance. In this paper., we propose a scheme that's utilizing the selective mapping technique., which consider a distortionless PAPR reduction scheme in multicarrier systems. Afterwards, we numerically discuss the PAPR characteristics using the complementary cumulative distribution function (CCDF) of PAPR. The results demonstrate that SC-FDMA signals, which use Time Domain-Selective Mapping (TD-SLM)., indeed have a significant reduction in PAPR compared to those., which do not use it. For long term, we also prove numerically that the only thing affecting the PAPR performance is the number of phases, whereas, the phases' values themselves do not affect the P APR performance at all.

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 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.

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.

Single-carrier frequency division multiple access (SC-FDMA) has been adopted as a possible air interface for future wireless networks. It combines most of the advantages of orthogonal frequency division multiple access and the low peak to average power ratio (PAPR) of single carrier (SC) transmission. Existing transmit antenna diversity techniques such as space-time block coding and space-frequency block coding are incompatible either with the system constraints or with the SC nature of SC-FDMA. We propose a novel space-frequency flexible coding scheme compatible with SC-FDMA and we prove its good performance both in terms of PAPR and bit error rate (BER) on frequency selective multiple input multiple output channels.

Single carrier-frequency division multiple access (SC-FDMA) has been adopted as the uplink transmission standard in fourth generation cellular network to enable the power efficiency transmission in mobile station. Since multiuser multiple-input multiple-output (MU-MIMO) is a promising technology to fully exploit the channel capacity in mobile radio network, this paper investigates the uplink transmission of SC-FDMA systems with orthogonal space frequency block codes (SFBC). Two linear multiuser MIMO (MV-MIMO) receivers, orthogonal SFBC (OSFBC) and minimum mean square error (MMSE), are derived for the scenarios with limited number of users or adequate receive antennas at base station.

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

For the 3G-LTE (Long Term Evolution) up-link, SC-FDMA (single carrier frequency division multiple access) system was adopted by the 3GPP (Third Generation Partnership Project) as standard method. However, similar to the other OFDM-based systems, SC-FDMA system is also very sensitive to frequency synchronization errors, especially in the uplink communications, where different users always have different CFOs (Carrier Frequency Offset). When multiple CFOs exist, the orthogonalities between the subcarriers are lost. ICI (Inter Carrier Interference) as well as MAI (Multi-Access Interference) are generated to degrade the quality of received signals. A novel suppression method based on block type pilots is proposed to overcome the interferences simultaneously. It is confirmed that the proposed suppression algorithm can significantly improve the performance by simulation results.

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.

Carrier frequency offset (CFO) and phase noise are challenging problems in single carrier frequency division multiple access (SC-FDMA) system. In this study, the authors have studied single-carrier space frequency block coding (SC-SFBC) to reduce the peak to average power ratio (PAPR) of the multiple-input multiple-output (MIMO) SC-FDMA signal, in which Alamouti SFBC will change the signal spectrum structure, break the single-carrier property and increase PAPR. Also, the authors propose a joint algorithm to suppress the inter-carrier interference (ICI) caused by phase noise and CFO. Conventional methods are to estimate phase noise and CFO in other algorithms, which are pretty difficult and complicated to obtain accurate estimation results. Unlike the conventional works, the novelty of the authors proposed algorithm is that it directly calculates the interference components and then reconstructs the ICI matrix. Thus, it avoids the degrading interactions between phase noise and CFO estimations. The proposed algorithm exploits block-type pilot, which is a common pilot pattern in SC-FDMA communications and is used in other wireless communication standards. Simulation results show that the suppression performance keeps smooth while phase noise and CFO varies, and BER performance degradation can be significantly reduced in 3 dB.

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.

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.