Xiaohu Youl

Bio: Xiaohu Youl is an academic researcher from Southeast University. The author has contributed to research in topics: Frequency-division multiple access & Bit error rate. The author has an hindex of 1, co-authored 1 publications receiving 37 citations.

Performance Analysis of Frequency Domain Equalization in SC-FDMA Systems

Abstract: The performance of linear receivers for detection of the single carrier frequency division multiple access transmission over frequency-selective fading channels is investigated in this work. Firstly, the cumulative distribution functions (CDF) of output signal to interference plus noise ratios (SINR) with zero forcing frequency domain equalization (ZF-FDE) and minimum mean squared error frequency domain equalization (MMSE-FDE) are derived by employing the numerical inversion of Laplace transforms. Next, based on the CDFs of the output SINRs, the approximate average bit error rate expressions as functions of the average receive signal to noise ratio for Gray-coded quaternary phase shift keying constellations are obtained. Finally, analytical and Monte Carlo simulated results are compared, and they perfectly agree for both ZF-FDE and MMSE-FDE.

SC-FDMA Versus OFDMA: Sensitivity to Large Carrier Frequency and Timing Offsets on the Uplink

Abstract: In this paper, we present a comparison between the sensitivity of SC-FDMA and OFDMA schemes to large carrier frequency offsets (CFO) and timing offsets (TO) of different users on the uplink. Our study shows the following observations: 1) In the ideal case of zero CFOs and TOs (i.e., perfect synchronization), the uncoded BER performance of SC-FDMA with frequency domain MMSE equalizer is better than that of OFDMA due to the inherent frequency diversity that is possible in SCFDMA. Also, because of inter-symbol interference in SC-FDMA, the performance of SC-FDMA with MMSE equalizer can be further improved by using low-complexity interference cancellation (IC) techniques. 2) In the presence of large CFOs and TOs, significant multiuser interference (MUI) gets introduced, and hence the performance of SC-FDMA with MMSE equalizer can get worse than that of OFDMA. However, the performance advantage of SC-FDMA with MMSE equalizer over OFDMA (due to the potential for frequency diversity benefit in SC-FDMA) can be restored by adopting multistage IC techniques, using the knowledge of CFOs and TOs of different users at the receiver.

Performance enhancement of SC-FDMA systems using a companding technique

Abstract: In this paper, a companding technique is proposed to effectively reduce the peak-to-average power ratio (PAPR) in single-carrier frequency division multiple access (SC-FDMA) systems. By companding the samples with large amplitudes, while enhancing those with small amplitudes, a significant reduction in the PAPR can be achieved. The performance of the proposed SC-FDMA with companding system is studied and compared with that of the standard SC-FDMA system. Simulation results show that the SC-FDMA with companding system has a lower PAPR when compared with the conventional SC-FDMA system, while the complexity of the system slightly increases. Results also reveal that the companding coefficient must be chosen carefully in order to limit the PAPR without introducing degradations into the bit error rate performance.

Multisatellite Cooperative Random Access Scheme in Low Earth Orbit Satellite Networks

Abstract: Multisatellite cooperative random access (MSC-RA) scheme is proposed in low earth orbit (LEO) satellite networks. In the scheme, a packet structure based on single carrier interleaved frequency division multiple access (SC-IFDMA) is designed to overcome the effect of users’ propagation delays on the received signals at satellite nodes, which ensures the synchronization of received signals. The transmission model from multiple terminals to multiple satellite nodes in a slot can be equivalent to a virtual multi-input multioutput model, and MSC detection is employed to decode multiple collided packets. The MSC detection can be applied to slotted ALOHA (SA), contention resolution diversity slotted ALOHA (CRDSA), CRDSA-3, and irregular repetition slotted ALOHA (IRSA) protocols, which are dubbed MSC-SA, MSC-CRDSA, MSC-CRDSA-3, and MSC-IRSA, respectively. At the gateway station, the MSC detection and iterative interference cancellation processing are alternately conducted for multiple collided packets at satellite nodes. The performance of these MSC-RA schemes is evaluated via mathematical analysis and computer simulation in terms of throughput, stability and energy efficiency. Simulation results show that MSC-SA, MSC-CRDSA, MSC-CRDSA-3, and MSC-IRSA schemes significantly outperform conventional ones, and the MSC-CRDSA scheme is superior to MSC-SA, MSC-CRDSA-3 and MSC-IRSA schemes.

BER Analysis for Zero-Forcing SC-FDMA Over Nakagami-m Fading Channels

Abstract: In this paper, we present an analytical study of the bit error rate (BER) for single-carrier frequency-division multiple access (SC-FDMA) transmission over frequency-selective fading channels when zero-forcing frequency-domain equalization is applied. SC-FDMA, which can be described as a precoded version of orthogonal frequency-division multiple access (OFDMA), is regarded as a promising candidate for next mobile communication systems due its favorable envelope characteristics and low peak-to-average-power ratio (PAPR), compared with that of OFDMA. We focus on Nakagami-m fading channels and provide a method to calculate BER values with a single numerical computation. We provide a closed-form expression for the BER with binary phase-shift keying (BPSK) and square M-ary quadrature amplitude modulation (M-QAM) under the assumption of independence among channel frequency responses for allocated subcarriers.

Error Probability Analysis of Interleaved SC-FDMA Systems Over Nakagami- $m$ Frequency-Selective Fading Channels

Abstract: In this paper, we present an analytical study of the average bit error probability (ABEP) for interleaved single-carrier frequency-division multiple-access (SC-FDMA) systems over independent but not necessarily identically distributed Nakagami-m fading channels with fading parameters {m} being integers when either zero-forcing (ZF) or minimum-mean-square-error (MMSE) frequency-domain equalization (FDE) is applied. Under the assumption of independence among channel frequency responses (CFRs) at the allocated subcarriers for a specific user, accurate and closed-form numerical ABEP computations of the generalized hierarchical M -ary pulse amplitude and square/rectangular M-ary quadrature amplitude modulations for both ZF-FDE and MMSE-FDE are developed by exploiting the derived statistics of the equalized noise, including the probability density function and cumulative distribution function. More importantly, the ABEP derivation is based on the real distribution of the CFRs without applying the widely used Nakagami-m approximation of the CFRs in previous literature, resulting in a more accurate ABEP analysis.