A single carrier frequency division multiple access (SC-FDMA), is a technique that has a similar performance and essentially the same overall complexity as those of orthogonal frequency division multiple access (OFDMA). The main advantage of SC-FDMA over OFDMA is its lower peak-to-average power ratio (PAPR). In this paper, an enhancement of a SC-FDMA by decreasing the PAPR is addressed. An efficient repeated clipping and filtering (RCF) algorithm is applied to a SC-FDMA system, which results in a significant PAPR reduction. System performance remains the same after applying the RCF algorithm. Simulations show the proposed scheme provides a bit error as that of the conventional system. That is, due to the selection of the optimum clipping ratio (CR). For more accurate validation, simulations of the conventional system and the proposed system have been performed using different types of channels. The proposed scheme provides a PAPR reduction by a gain of approximately 4 dB with a slight increase of complexity.
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 (SC-FDMA) system. SC-FDMA is used in Long Term Evaluation (LTE) of 3 rd 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.
This paper proposes, a DFT-based OFDMA with phase modulation (DFT-OFDMA-PM) system. One main advantage of the phase modulated system is the constant envelope (CE) resulted signal, i.e, 0 dB PAPR, the second advantage is the ability to improve the diversity of multipath channels. These advantages have been exploited in the proposed system of this paper. The performance of the proposed system in terms of the bit error rate (BER) is studied and investigated and compared to the previously proposed DCT-OFDMA-PM system and the conventional OFDMA system without PM via computer simulation. The key parameter that affects the performance of the PM systems, the modulation index, is also studied and the optimum value is selected using exhaustive simulation scenarios. Moreover, the PAPR is also simulated for the proposed system and compared to the conventional system. Simulation results show the significant improvement of the proposed system in terms of PAPR and BER when compared to the conventional system. The simulation results for the proposed system show the effectiveness of the proposed system for wireless broadband communications.
A single carrier frequency division multiple access (SC-FDMA), is a technique that has a similar performance and essentially the same overall complexity as those of orthogonal frequency division multiple access (OFDMA).In this paper, a strong "energy compaction" property of discrete cosine transform (DCT) is exploiting to enhance the performance of SC-FDMA system. A new SC-FDMA system for uplink wireless transmissions is proposed. The proposed system is based on DCT prior to the OFDMA modulation at the transmitter and reverse operation performed at the receiver. The proposed discrete cosine fourier transform (DCFT) SC-FDMA signal is compared with that of the DFT SC-FDMA and OFDMA signals in terms of bit error rate (BER) and peak-to average power ratio (PAPR). Moreover, the proposed system is compared to a recently introduced DCT SC-FDMA system. Simulation results show that the proposed DCFT SC-FDMA provides a significant improvement in BER performance than the DFT SC-FDMA, OFDMA and DCT SC-FDMA. There is a BER improvement of a gain up to 7 dB compared to OFDMA, 5 dB when compared to DFT SC-FDMA and 3 dB when compared to DCT SC-FDMA. In addition, it is found that the PAPR of the DCFT SC-FDMA signals is lower than that of OFDMA signals. Moreover, the proposed system complexity is comparable with the traditional DCT SC-FDMA.
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