Shigang Tang

Tsinghua University, Beijing, Beijing Shi, China

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Publications (12)4.17 Total impact

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    ABSTRACT: To efficiently support the transmission of terrestrial and mobile services within the same spectrum over the Digital Television Terrestrial Multimedia Broadcasting (DTMB) system, a flexible multi-service datacasting scheme in a backward compatible manner is proposed. Using this scheme, the conventional DTMB receivers work as usual by simply selecting the specific terrestrial DTV programs on the basis of the package identifier (PID) checking, while only the desired mobile service data are processed by the mobile receivers via the designed control signals. Both theoretical analysis and computer simulation show that, at acceptable spectral efficiency penalty, the proposed method not only supports the embedded transmission of multi-services with no reception performance degradation for the traditional terrestrial broadcasting service, but also flexibly provides much better mobile reception performance.
    IEEE Transactions on Broadcasting 01/2011; · 2.09 Impact Factor
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    ABSTRACT: To efficiently accommodate the terrestrial broadcasting service and the mobile service within the same spectrum over Chinese Digital Television Terrestrial Multimedia Broadcasting (DTMB) system, a novel multi-service datacasting scheme in a backward compatible manner is proposed in this paper. In this scheme, an equivalent QAM (E-QAM) mapping method is adopted for mobile services. Moreover, to reduce the impact of the larger peak to average power ratio (PAPR)caused by the E-QAM, a random constellation extension (RCE)technique is further proposed. Both theoretical analysis and computer simulation show that this scheme not only supports the normal reception of the traditional terrestrial broadcasting service in DTMB receivers, but also provides better mobile reception performance at acceptable spectral efficiency penalty.
    Proceedings of the 72nd IEEE Vehicular Technology Conference, VTC Fall 2010, 6-9 September 2010, Ottawa, Canada; 01/2010
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    ABSTRACT: Digital Television/Terrestrial Multimedia Broadcasting (DTMB) is announced as the Chinese Digital Television Terrestrial Broadcasting (DTTB) standard. In the conventional applications, all the transport streams (TS) from various programs are multiplexed in the level of TS packets. Therefore, all the programs should take the same interleaving, constellation mapping and channel coding, and hence the same quality of service (QoS). Moreover, due to the impact of convolutional interleaver, the receiver needs to be turned on all the time to obtain the designated data on the received signal. In this paper, the concept of physical sub-channel (PSC) for DTMB system is introduced and the method to support services with different QoS is addressed. Based on the two techniques, a novel approach to support multimedia services over DTMB system with the existing receivers untouched is proposed and evaluated by computer simulation.
    Broadband Multimedia Systems and Broadcasting (BMSB), 2010 IEEE International Symposium on; 01/2010
  • Shigang Tang, Ke Gong, Jintao Wang, Yu Zhang
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    ABSTRACT: Accurate channel estimation is essential for coherent single-carrier (SC) block transmission systems. In this paper, we propose novel iterative algorithms for estimating the channel impulse response (CIR) in SC block transmission systems by exploiting a unique word (UW) extension. The interference caused by the data to the UW is removed from the received signal by first equalizing the data using a previous channel estimate, and then subtracting the estimated interference signal from each received signal block. Erasure decision is used to improve the performance and the effects of error propagation is reduced. Simulation results show that the proposed channel estimation method brings good BER performance with fast convergence over frequency-selective slowly fading channels.
    Circuits and Systems for Communications, 2008. ICCSC 2008. 4th IEEE International Conference on; 06/2008
  • Shigang Tang, Kewu Peng, Ke Gong, Zhixing Yang
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    ABSTRACT: Novel channel estimation algorithm is presented in this paper for the recently proposed cyclic postfix based orthogonal frequency division multiplexing (OFDM) systems. Phase equalization with the erasure decision is used to reduce both the channel estimation error and the computational complexity. Simulation results show that the proposed channel estimation algorithm can effectively estimate the channel impulse response (CIR) and the performance of the proposed phase equalization with erasure decision is comparable with the minimal mean square error (MMSE) equalization but offers less computational complexity.
    Communications, Circuits and Systems, 2008. ICCCAS 2008. International Conference on; 06/2008
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    ABSTRACT: Accurate channel estimation is essential for coherent signal transmission. This paper presents a novel channel estimation algorithm for time-domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) systems with identical pseudo-noise (PN) sequence padding. Simple cyclic reconstruction and tail cancellation methods are proposed to estimate the channel impulse response (CIR). Phase equalization and partial hard decision on the received data symbols are used to improve the estimation performance. Simulation results show that the proposed channel estimation algorithm brings good BER performance (approaching the ideal case) with fast convergence (no iteration required) over frequency-selective slowly fading channels.
    Communications, 2008. ICC '08. IEEE International Conference on; 06/2008
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    ABSTRACT: Digital terrestrial multimedia/television broadcasting (DTMB), which is the recently released Chinese digital television terrestrial broadcasting (DTTB) standard, uses guard intervals padded with known pseudo-noise (PN) sequences for multi-carrier or single-carrier block transmission. Well designed synchronization algorithms are a prerequisite for achieving high-quality multimedia transmission. In this paper, a novel frame synchronization technique, which is robust to carrier frequency offset (CFO), is proposed for DTMB systems. This technique is derived through segmenting the local PN sequence into M contiguous blocks and performing multiple cross-correlations with the received signal. The metric for peak detection is defined as the non-coherent summation of the M cross-correlation magnitude outputs. Moreover, a low-complexity frame synchronizer based on segment-based full correlation for PN420 mode in DTMB system is proposed. It is shown through computer simulation that the proposed techniques generally outperform the conventional ones when CFO occurs, over both AWGN and frequency-selective fading channels. For a DTMB system using PN420 mode, the maximal allowed CFO to keep system still working normally of our proposed schemes are more than 3 times larger than that of the conventional method.
    IEEE Transactions on Broadcasting 04/2008; · 2.09 Impact Factor
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    ABSTRACT: This study proposes an iterative channel impulse response (CIR) estimation scheme for multicarrier block transmission with known symbol padding, in the context of the time-domain synchronous OFDM (TDS-OFDM) system. It is shown that the TDS-OFDM still fulfils the circular convolution relationship even if pseudo-noise (PN) sequence is used as guard interval. While conventional methods perform the channel estimation based on the cyclic prefix reconstruction or residual intersymbol interference cancellation in the time domain, by processing the data part and the known symbol padding in one TDS-OFDM block separately, the new proposal uses the one- tap frequency-domain equalization to separate the data part and the known symbol padding and the CIR can be estimated in an iterative manner. In a typical example for 3780-point FFT based TDS-OFDM system with 16QAM constellations, the mean square error (MSE) of of the proposed channel estimator can be reduced to about 10<sup>-5</sup>/2 after two iterations when the channel signal-to-noise ratio (SNR) is larger than 8 dB, without the initial CIR estimation. The BER performance of a QPSK TDS-OFDM system shows that the signal-to-noise-ratio (SNR) degradation based on the proposed channel estimator is less than 0.3 dB compared with the lower bound for both Brazil A and B channels.
    Global Telecommunications Conference, 2007. GLOBECOM '07. IEEE; 12/2007
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    ABSTRACT: As one of the most common linearization techniques, adaptive digital predistortion minimizes the difference between the input signal of the predistorter and the feedback signal from the power amplifier. The loop delay between these two signals must be controlled precisely so that the convergence of the predistorter should be assured. In this paper a novel two-stage loop delay correction scheme is presented. In the first stage, the integer delay between the input signal and the feedback signal is estimated based on the cross-correlation of them. In the second stage, the fractional delay between these two signals are corrected by a delay lock loop (DLL) circuit, in which a novel timing error detector used as the discriminator is proposed. The proposed loop delay correction scheme is applied to an adaptive digital predistorter in an orthogonal frequency-division multiplexing (OFDM) system. Simulation results show that the proposed loop delay correction method eliminates the loop delay perfectly, so that nearly optimal power spectral density (PSD) performance is achieved and a high degree of linearization is realized.
    Wireless Communications and Networking Conference, 2007.WCNC 2007. IEEE; 04/2007
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    ABSTRACT: The implementation of OFDM system suffers from the effect of phase noise generated by local oscillator (LO), which disturbs the orthogonality between subcarriers and causes intercarrier interference (ICI). In this paper, the symmetric conjugate-negative property of the ICI weighting function is found. Based on that, the ICI self-cancellation of symmetric data-conjugate method is studied to suppress phase noise. The carrier-to-interference ratio (CIR) improvement by this method is shown to be larger than 22 dB in flat fading channel. For a BER of 10<sup>-3</sup>, this method can tolerate a phase noise standard deviation of 7 deg in flat fading channel. Moreover, this method could offer frequency diversity gain in frequency selective channels. Both analytical and numerical results show that this method outperforms the conventional schemes
    Personal, Indoor and Mobile Radio Communications, 2006 IEEE 17th International Symposium on; 10/2006
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    ABSTRACT: The implementation of OFDM system suffers from the effect of phase noise and IQ imbalance, which disturb the orthogonality between subcarriers and cause intercarrier interference (ICI). When treated separately, effective algorithms, such as the ICI self-cancellation scheme, exist for suppression of phase noise as well as IQ imbalance. However, with both effects present, such algorithms do not lead to effective suppression. In this paper, we propose a novel technique to jointly combat the IQ imbalance and phase noise at baseband. An IQ imbalance estimation and compensation module, which is robust against phase noise, is added in the ICI self-cancellation based OFDM system. After the IQ imbalance has been compensated in the time domain, the ICI self-cancellation scheme of data-conjugate method is used to suppress the phase noise and the residual IQ imbalance. This scheme has a fast convergence and a nearly optimal BER performance even for large IQ imbalance in AWGN channel. In multipath channel, even for large IQ imbalance, this joint suppression scheme offers frequency diversity gain and as a result, the BER performance surpasses that of the conventional OFDM system without IQ imbalance and phase noise
    Communications, Circuits and Systems Proceedings, 2006 International Conference on; 07/2006
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    ABSTRACT: The distributed radio transmission scheme can improve signal coverage, as the single frequency network (SFN) for DTV broadcasting. However, the propagation characteristics of the distributed transmission in SFN have to be studied carefully for they are different from conventional single transmission cases. In this paper, the field measurement carried out in a rural SFN with two synchronized transmitters is reported. It is found that, on the one hand, the radio signal coverage of the distributed transmission scheme has been distinctly improved with the total transmitted power by multi-transmitters as same as compared single transmitter system; and, on the other hand, the power delay profile (PDP) has shown rather different features than the single transmission cases, in which there are long delay "echoes" and could not be modeled simply by exponential decays because of the existence of distributed transmitters. The parameter called "transmission gain" has been introduced in order to extend the concept of "path gain" to the distributed transmission cases and, the tapped delay line is used to model the average PDP in the distributed transmission cases
    Vehicular Technology Conference, 2006. VTC 2006-Spring. IEEE 63rd; 06/2006