Fang Yang

Tsinghua University, Peping, Beijing, China

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Publications (52)19.34 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: The amplitude phase shift keying (APSK) constellation with Gray labeling (Gray-APSK) is able to achieve considerable shaping gains in comparison with the quadrature amplitude modulation (QAM) counterpart under both iterative and non-iterative scenarios. Nevertheless, the Gray-APSK constellation with the fixed radius cannot provide the optimal performance for every code rate of practical usage. In this paper, we propose a method based on the genetic algorithm to optimize the parameters of Gray-APSK constellations by maximizing the mutual information for the targeted code rate. Certain performance gains can be achieved via optimizing the radius of the Gray-APSK, as verified by both the average mutual information (AMI) analysis and the error performance evaluation.
    Wireless Communications and Mobile Computing Conference (IWCMC), 2013 9th International; 01/2013
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    ABSTRACT: This paper proposes a novel coded-modulation scheme using amplitude phase shift keying (APSK) constellations with Gray mapping for the broadband power line communication systems for the first time. In this scheme, three key techniques including the Gray-APSK constellation design, the bit mapping technique, and the method of simplified soft APSK demapper are jointly employed to enhance the error-control performance while ensuring low complexity. Simulation results over AWGN and power line channels show that the proposed scheme provides a remarkable receiving performance gain, compared to its counterpart specified in the G.hn standard.
    Communications (ICC), 2013 IEEE International Conference on; 01/2013
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    ABSTRACT: In this paper, an OFDM-based preamble is proposed for improving timing and frequency synchronization in the power line channel with narrowband interference (NBI) as well as transmitting several bits of transmission parameter signaling (TPS). In the time domain, an additional scrambling operation is applied to the cyclic extension of an OFDM training symbol to reduce the impact of NBI. Compared to the conventional Schmidl's and Minn's methods, the proposed preamble could provide even sharper correlation peak and achieve better timing detection in both AWGN and power line multipath channels under NBI, with a moderate complexity increase because more correlation and multiplication operations are required. Furthermore, the proposed preamble could also convey several bits of TPS via the variable distance of two training sequences allocated in the frequency domain. Better synchronization results can be achieved through analyses and simulations with the proposed method.
    Power Line Communications and Its Applications (ISPLC), 2013 17th IEEE International Symposium on; 01/2013
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    ABSTRACT: The previously proposed amplitude phase shift keying (APSK) with Gray labeling achieves a considerable shaping gain in comparison with conventional square quadrature amplitude modulation. In this letter, by reducing the number of points on the inner rings of Gray-APSK and introducing a non-equiprobable (NE) bit-to-symbol labeling, a novel NE-APSK constellation labeling is proposed. NE-APSK provides additional 0.1 dB shaping gain over Gray-APSK without any complexity increase, as illustrated by the mutual information analysis and verified by the bit error rate simulation.
    IEEE Communications Letters 01/2013; 17(6):1276-1279. · 1.16 Impact Factor
  • Fang Yang, Wenbo Ding, Jian Song
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    ABSTRACT: The power line quality has a significant impact on the reliability, delivery efficiency and safety of the power grids and the demands for monitoring the power line quality efficiently at a low cost in the power grid are constantly increasing. In this paper, a non-intrusive power line quality monitoring technique based on the power line communication (PLC) technologies is proposed. Through channel estimation in PLC system, the channel frequency response (CFR) can be obtained. We study the relationship between the CFR and the power line quality features, and find that the changes of certain key channel characteristics of the CFR including the positions and values of the peaks or valleys, the distances between the peaks or valleys and so on could be used to monitor the power line quality in a non-intrusive manner. The computer simulations are also carried out to verify the proposed method and the results show that this method could predict the power line changes well without additional devices and costs.
    Power Line Communications and Its Applications (ISPLC), 2013 17th IEEE International Symposium on; 01/2013
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    ABSTRACT: In this paper, the spectrum notch technique which combines the time-domain windowing and training sequence (TS) redesigning for the time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) system is proposed. An improved frame structure with overlapping between adjacent frames for the dual pseudo noise padded (DPNP) TDS-OFDM system is put forward to make the spectral efficiency undiminished. The simulation results show that this method can deepen the notches in the power spectrum density (PSD) compared to the conventional TDS-OFDM system by about 7 to 8 dB without any spectrum efficiency cost, which could be in accordance with the -30dB spectrum notch requirements in the spectral mask defined in HomePlugAV 1.1.
    Wireless Communications and Mobile Computing Conference (IWCMC), 2013 9th International; 01/2013
  • Wenbo Ding, Fang Yang, Jian Song
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    ABSTRACT: In this paper, the out-of-band power suppression technique for the time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) system is proposed. The technique combines the time-domain windowing and training sequence (TS) redesigning, and could satisfy the spectral mask requirement for the digital television terrestrial broadcasting (DTTB) system without squared root raised cosine (SRRC) filter. An improved frame structure with overlapping between adjacent frames for the dual pseudo noise padded (DPNP) TDS-OFDM system is put forward to make the spectral efficiency undiminished. The simulation results show that the proposed method could lower the out-of-band power leakage by 6-10dB in the power spectrum density (PSD) compared to the conventional TDS-OFDM system without SRRC filter while achieving a similar spectrum shaping performance of conventional CP-OFDM. This technique will enhance the application of the TDS-OFDM in the broadband multimedia transmission areas.
    Broadband Multimedia Systems and Broadcasting (BMSB), 2013 IEEE International Symposium on; 01/2013
  • Xiao Zhou, Fang Yang, Jian Song
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    ABSTRACT: This contribution proposes a design method for training sequence (TS) defined as frequency-shift m-sequence (FSMS) and a novel transmit diversity scheme with FSMS padding as guard interval (GI) for the further evolution of time domain synchronous orthogonal frequency domain multiplexing (TDS-OFDM) systems. The good auto-correlation characteristic of FSMS can facilitate synchronization and channel estimation at the receiver. Due to the cross-correlation characteristics of FSMSs, the accuracy of channel estimation is affected by the mutual interference among the transmit antennas. To further improve the accuracy of channel estimation, the channel impulse response (CIR) should be estimated in an iterative manner to suppress the effects of the mutual interference and additive white Gaussian noise. Compared with the transmit diversity schemes based on the space-frequency coded TS and space-time coded TS for TDS-OFDM system, the proposed transmit diversity scheme with FSMS padding can provide diversity gain and superior system performance over time-varying and/or frequency-selective propagation conditions.
    IEEE Transactions on Broadcasting 01/2012; 58(2):317-324. · 2.09 Impact Factor
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    ABSTRACT: Single frequency network (SFN) is an attractive scheme for the digital television terrestrial broadcasting (DTTB) coverage with efficient utilization of the spectral resources. In this paper, a method featuring low complexity and low workload is proposed to estimate the reception quality under the SFN environment with the maximum delay spread of the artificial multipath no longer than the guard interval. Based on the analysis of error probability and channel capacity, this method supports an unambiguous prediction of the signal-to-noise ratio (SNR) threshold according to the parameters of received signals, which is thus meaningful for system evaluation. We applied this method to the digital television/terrestrial multimedia broadcasting (DTMB) systems, and carried out the laboratory measurements for performance verification. The predicted results show a satisfactory match with the measured results, validating the accuracy and effectiveness of the proposed method.
    IEEE Transactions on Broadcasting 01/2012; 58(4):629-636. · 2.09 Impact Factor
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    ABSTRACT: Automatic repeat request (ARQ) is a widely used technique in communication systems for transmission error control. In this paper, a Hybrid-ARQ (H-ARQ) scheme for LDPC coded system with low complexity and reduced additional transmission cost is proposed. This H-ARQ scheme exploit the unequal error protection (UEP) property in irregular LDPC coding and high-order quadrature amplitude modulation (QAM), where the bits with less protection are retransmitted with improved protection. Simulation results based on the power line communication (PLC) G.hn system demonstrate the advantage and flexibility of the proposed scheme over traditional H-ARQ scheme.
    01/2012;
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    ABSTRACT: In this paper, a signaling-embedded preamble design is proposed for the orthogonal frequency division multiplexing (OFDM) system with transmit diversity. Utilizing the transmit diversity, two identical training sequences (TSs) are embedded in two OFDM symbols separately in discrete Fourier transform (DFT) domain and transmitted by two different antennas simultaneously. The relative distance between the two TSs in DFT domain could be varied in order to indicate several bits of signaling information for the receiver to acquire the transmission parameters signaling (TPS) quickly. Furthermore, the preamble can also be used for frame synchronization, carrier frequency offset (CFO) estimation, and coarse channel estimation. The computational simulations were carried out under both additive white Gaussian noise (AWGN) and multipath channels, and the results demonstrated the design works accurately on the preamble detection, CFO estimation and signaling demodulation under both static and dynamic channels.
    Wireless Communications and Mobile Computing Conference (IWCMC), 2012 8th International; 01/2012
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    ABSTRACT: A new specification for power line communication (PLC), named G.hn, has been developed recently for the existing-wire home networking. G.hn system specifies a coded modulation scheme based on quasi-cyclic low-density parity-check (QC-LDPC) codes and quadrature amplitude modulations (QAMs). In this paper, we present a bit mapping strategy to exploit the unequal error protection (UEP) property inherent in the irregular LDPC codes and high-order constellations, which can effectively improve the reliability of the whole coded modulation system with no penalty. The method to design the bit mapping scheme is also investigated via the analysis of extrinsic information transfer (EXIT) charts. Simulation results reveal that the appropriate bit mapping scheme can achieve considerable gains in the G.hn system.
    01/2012;
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    ABSTRACT: Due to the unequal error protection (UEP) property of both the irregular low-density parity-check (LDPC) code and the higher-order modulation, bit mapping is proposed as a joint optimization of the LDPC coded-modulation scheme. In this paper, we discuss the bit mapping optimization performed by employing an additional DEMUX following the given bit interleaver, and then apply it to the second generation digital video broadcasting system for cable (DVB-C2). The extrinsic information transfer (EXIT) chart technique is adopted to analyze the influence of bit mapping on the iterative decoding process. Based on the EXIT-chart analysis, an optimization method is proposed to design the DEMUX for performance improvement. As an example, we re-design the DEMUX for the DVB-C2 system with reduced DEMUX width. The superior performance of the optimized DEMUX is verified by the bit error rate (BER) simulation.
    Wireless Communications and Mobile Computing Conference (IWCMC), 2012 8th International; 01/2012
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    ABSTRACT: In the conventional digital television terrestrial multimedia broadcasting (DTMB) systems, all the transport streams (TS) from various programs are multiplexed in the level of TS packets, which have the same interleaving, constellation mapping, channel coding, and thus the same quality of service (QoS). Moreover, due to the convolutional interleaving mode, the receivers have to be turned on all the time to obtain the designated data until all the received signals are de-interleaved. In this paper, for DTMB systems, the concept of the physical sub-channel (PSC) in time-frequency domain is proposed, and the scheme to support services with different QoS requirements is also addressed. Based on these techniques, a novel approach to support multimedia services over DTMB systems in a backward compatible manner is proposed and evaluated by computer simulations.
    IEEE Transactions on Broadcasting 10/2011; · 2.09 Impact Factor
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    ABSTRACT: This paper presents a method to measure and predict the reception quality of the digital terrestrial/television multimedia broadcasting (DTMB) system in a single frequency network (SFN) environment. Measurement of the signal-to-noise ratio (SNR) threshold at several market commercial receivers was carried out in the laboratory. After analyzing the channel capacity loss produced by the multiple transmitter reception, a prediction model of SNR threshold is presented. Simulation results are also performed to verify the accuracy of the prediction method. This model and method could be adopted for SFN planning to ensure a good service quality in the SFN environment.
    Wireless Communications and Mobile Computing Conference (IWCMC), 2011 7th International; 08/2011
  • Source
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    ABSTRACT: The second-generation digital terrestrial television broadcasting standard adopts the so-called P1 symbol as the preamble for initial synchronization. The P1 symbol also carries a number of basic transmission parameters, including the fast Fourier transform size and the single-input/single-output as well as multiple-input/single-output mode, to appropriately configure the receiver for carrying out the subsequent processing. In this paper, an improved preamble design is proposed, where a pair of training sequences is inserted in the frequency domain, and their distance is used for transmission parameter signaling. At the receiver, only a low-complexity correlator is required for the detection of the signaling. Both the coarse carrier frequency offset and the signaling can simultaneously be estimated by detecting the aforementioned correlation. Compared with the standardized P1 symbol, the proposed preamble design significantly reduces the complexity of the receiver while retaining high robustness in frequency-selective fading channels. Furthermore, we demonstrate that the proposed preamble design achieves better signaling performance than the standardized P1 symbol despite reducing the numbers of multiplications and additions by about 40% and 20%, respectively.
    IEEE Transactions on Vehicular Technology 04/2011; · 2.06 Impact Factor
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    ABSTRACT: Signal space diversity (SSD) is a well-known power- and bandwidth-efficient diversity technique with constellation rotation and coordinate interleaving. This paper investigates issues of combining SSD with coded modulation systems (CMSs), e.g., bit-interleaved coded modulation (BICM) and its iterative version, BICM-ID. It demonstrates that the average mutual information (AMI) between the signal after rotated constellation mapping and the signal before or after the soft demapper varies with the rotation angle. A new criterion for determining the optimal rotation angle by maximizing such AMI is therefore proposed. Specific considerations of combining SSD with BICM (BICM-SSD) and BICM-ID (BICM-ID-SSD) are addressed. The demapper's extrinsic information transfer (EXIT) curve in traditional BICM-ID systems exhibits different slopes under different channels, which consequently prevents traditional BICM-ID systems from having simultaneously excellent performance under different channels. It is shown that such a different-slope problem can be simply mitigated by a proper use of SSD. Analysis and simulation show that the proposed BICM-ID-SSD systems hold a near-capacity performance under both additive white Gaussian noise (AWGN) and Rayleigh fading channels simultaneously.
    IEEE Transactions on Wireless Communications 03/2011; · 2.42 Impact Factor
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    ABSTRACT: Robust Physical Layer Signaling Transmission over OFDM Systems
    IEICE Transactions. 01/2011; 94-B:2900-2902.
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    ABSTRACT: To support the simultaneous transmission of multiple multimedia services with different quality of service (QoS) requirements within the same spectrum over digital television terrestrial broadcasting (DTTB) systems, datacasting approaches have been widely studied. In this paper, to improve the immunity to the fading in the mobile environment, a novel datacasting scheme for Chinese DTTB systems, namely digital television terrestrial multimedia broadcasting (DTMB), is proposed in a backward compatible manner. In this scheme, by taking advantage of the time-frequency domain physical sub-channel (PSC), the modulation method of the multi-dimensional rotated BPSK constellation mapping using the signal space diversity (SSD), which are backward compatible with DTMB systems, are addressed together with the iterative demapping and decoding technique. Simulations over Rayleigh channels show that the proposed scheme efficiently improves the mobile reception performance of newly-introduced services at acceptable complexity penalty meanwhile without any degradation in the existing DTMB receivers for terrestrial services.
    Proceedings of the 7th International Wireless Communications and Mobile Computing Conference, IWCMC 2011, Istanbul, Turkey, 4-8 July, 2011; 01/2011
  • IEEE ISIT; 01/2011