SC-FDMA Scheme Research Articles

BER Evaluation in LTE SC-FDMA under Multipath Channels

Channel equalization is very essential step in Single Carrier Frequency Division Multiple Access (SC-FDMA) transmission for overcoming the inter-symbol interference (ISI). Also, to evaluate the data-link and network scheduling of LTE technique, a particular channel modelling is crucial. Due to the techniques’ complexity and requirement of high bandwidth for data transmission in literature, we motivated to perform a comparative analysis for BER reduction in SCFDMA scheme with and without equalizer. Therefor, in order to enhance efficiency of performance and functionality of network application, due to huge demand for lower delay, latency and higher speed by the modern users, BER reduction is a significant factor for enhancing signal quality. The substantial focus of this research is to improve the uplink signal of LTE technology by using two type of linear equalization methods such as zero forcing (ZF) and minimum mean square error (MMSE) at receiver part. Moreover, analysis of BER and SNR for SC-FDMA systems are obtained under several channel models and two different sub-mapping. This evaluation is performed for SC-FDMA in uplink by aid of adaptive modulation techniques like QPSK. Finally, for evaluating the channel equalization efficiency with SC-FDMA and for investigating the response of an uplink transmitter, MATLAB framework, is applied in this study. The results reveal that PAPR reduction does not have significant impact on BER performance.

Distributed Polar Coded Single Carrier-FDMA Based on Multilevel Construction Over Multipath Channels

A multilevel constructed polar coded single carrier frequency division multiple access (MLPC-SCFDMA) scheme is proposed and its bit-error rate performance over the multipath channels is examined. The multilevel construction of the polar code effectively divides the larger length polar code into two smaller length polar codes. This effective division of the polar codes have motivated the authors to efficiently transform the proposed scheme into coded-cooperative communication scheme. The relay’s contribution has always been given a supreme importance in the design of the any coded-cooperative communication system. Therefore, the authors have employed the use of re-transmission of the bad bit channels at the relay node. Moreover, in order to validate and compare its bit-error rate performance, the authors have also devised existing nested polar coded cooperative (NPCC) SCFDMA scheme over multipath channels. Numerical results based on Monte Carlo simulations demonstrate the superiority of multilevel constructed polar coded-cooperative SCFDMA scheme over traditional NPCC-SCFDMA scheme by gain of 0.2–0.3 dBs under similar conditions. This evident improved bit-error rate performance has occurred mainly because of an efficient re-transmission of the bad bit channels by polar sub-code placed at the relay node and the joint successive cancellation polar decoder efficiently utilized at the destination node. Moreover, the proposed multilevel constructed polar coded-cooperative SCFDMA scheme outperforms its corresponding multilevel polar coded SCFDMA (non-cooperative) scheme by the margin of 0.4 dBs under similar conditions.

MRC SC-FDMA scheme performance evaluation based on measurements at 30 GHz for 5G communications

Millimeter-wave band between 30-300 GHz frequencies combined with SC-FDMA are promoted to be a potential technology enabler for 5G mobile network in the uplink. So, in this paper an MRC SC-FDMA scheme based on measurement at 30 GHz is proposed for 5G system. Measurements were taken between three buildings under a non-line-of-sight (NLOS) scenario for a path length of 183m. The measured impulse response was used to evaluate the PAPR, the BER and the channel capacity. A MRC combiner is used to maximize the instantaneous SNR at the output of SIMO schemes. Simulation results show a PAPR gain of 3.3 dB for the MRC-ISC-FDMA over MRC OFDMA system. The MRC SIMO (1x3) provides a BER gain of 5.2 and 4.4 dB over the traditional ISC-FDMA and LSC-FDMA respectively. Moreover, channel capacity simulations corroborate the significant increases of capacity with the increasing of the number of antennas at the receiver (achievable date rate of 6.48 Gbps at SNR = 15 dB in SIMO 1 × 3 configuration). These results validate the viability of outdoor mm-waves link (30 GHz) under NLOS conditions for radio access transmission, where high transmission efficiency and data rates could be achieved. Hence, these results motivate the use of MRC SC-FDMA waveform for 5G mobile communications in the uplink.

Uplink Scheduling and Power Allocation for M2M Communications in SC-FDMA-Based LTE-A Networks With QoS Guarantees

Providing diverse and strict quality-of-service (QoS) guarantees is one of the most important requirements in machine-to-machine (M2M) communications, which is particularly need for appropriate resource allocation for a large number of M2M devices. To efficiently allocate resource blocks (RBs) for M2M devices while satisfying QoS requirements, we propose group-based M2M communications, in which M2M devices are clustered based on their wireless transmission protocols, their QoS characteristics, and their requirements. To perform joint RB and power allocation in SC-FDMA-based LTE-A networks, we formulate a sum-throughput maximization problem, while respecting all the constraints associated with SC-FDMA scheme, as well as QoS requirements in M2M devices. The constraints in uplink SC-FDMA air interface in LTE-A networks complicate the resource allocation problem. We solve the resource allocation problem by first transforming it into a binary integer programming problem and then formulate a dual problem using the Lagrange duality theory. Numerical results show that the proposed algorithm outperforms traditional Greedy algorithm in terms of throughput maximization while satisfying QoS requirements, and its performance is close to the optimal design.

LTE-Advanced 환경에서 D2D 통신을 위한 송수신 기법

We treat device-to-device direct communication (D2D) by reusing cellular uplink resources in LTE-Advanced systems. Conventional schemes assume that D2D transmitter employs SC-FDMA scheme for the date transmission. In the conventional schemes, however, it is very difficult to reduce the interference between the users, D2D communication cannot be used when the interference caused by cellular uplink signal is high. In this paper, we propose D2D transmission scheme which employes MC-CDMA technology and D2D detection scheme which uses MMSE algorithm to reduce interference from the cellular uplink signal. Therefore, in the proposed scheme the D2D communication becomes possible even in the high interference scenario. Through simulation, we show that the proposed scheme has better BER performance than the conventional scheme.

Paper Performance Analysis of OFDM-IDMA and SC-FDMA-IDMA Scheme in Underwater Communication

The IDMA scheme based receiver complexity over multi-path channels is related to the channel length. OFDM-IDMA scheme was proposed as an alternative to plain IDMA over multi-path channels. OFDM-IDMA scheme inherits most of the merits of OFDM and IDMA scheme. The key advantage of OFDM-IDMA scheme is that MUD can be realized efficiently with complexity per user, independent of the channel length and the number of users, which is significantly lower than that of other alternatives. Single Carrier Frequency Division Multiple Access (SC-FDMA-IDMA) scheme structure is achieved by adding Discrete Fourier Transform (DFT) and inverse DFT (IDFT) blocks at the transmitter and receiver respectively, so SC-FDMA scheme is sometimes referred to as DFT-spread or DFT-precoded OFDMA scheme. The transmitter of SC-FDMA scheme uses different subcarriers to transmit information data as in OFDMA scheme. However SC-FDMA schemes transmit the subcarriers sequentially rather than in parallel. Due to addition of above blocks low PAPR is obtained which is important to increase cell coverage and to prolong the battery lifetime of mobile terminals. There are no major differences between the BER performance of SC-FDMA-IDMA and OFDM-IDMA schemes, but SC-FDMA- IDMA scheme has low PAPR than OFDM-IDMA scheme.

Performance of Frequency Domain DFE Using Subcarrier Allocation

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. 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). Simulation results show that equalization has been achieved for FD-LE and FD- DFE with distribution mapping. This structure can be used in the broadcasting uplink channels with SC-FDMA scheme.

Frequency-domain precoding for single carrier frequency-division multiple access

At present there is considerable interest in the use of single carrier frequency-division multiple access. This interest is justified by the inherent single carrier structure of the SC-FDMA scheme, which is more robust against phase noise and has a lower peak-to-average power ratio than orthogonal frequency-division multiple access. This consequently makes it more attractive for uplink transmission from low-cost devices with limited transmit power. SC-FDMA commonly makes use of frequency domain linear equalization in order to combat the frequency selectivity of the transmission channel. Frequency domain decision feedback equalization, composed of a frequency domain feed forward filter and a time domain feedback filter, outperforms LE due to its ability to cancel precursor echoes. Although these solutions suffer from error propagation, results show that DFE still offers a significant performance gain over conventional LE for uncoded SC-FDMA. In this article we show how precoding can be used on the uplink of the LTE standard to overcome the frequency selective nature of the radio channel. We propose a frequency domain implementation of Tomlinson- Harashima precoding and investigate the bit error rate and the PAPR performance for SCFDMA using ZF and MMSE THP.