A new scheme combining a scalable transcoder with space time block codes （STBC） for an orthogonal frequency division multiplexing （OFDM） system is proposed for robust video transmission in dispersive fading channe...A new scheme combining a scalable transcoder with space time block codes （STBC） for an orthogonal frequency division multiplexing （OFDM） system is proposed for robust video transmission in dispersive fading channels. The target application for such a scalable transcoder is to provide successful access to the pre-encoded high quality video MPEG-2 from mobile wireless terminals. In the scalable transcoder, besides outputting the MPEG-4 fine granular scalability （FGS） bitstream, both the size of video frames and the bit rate are reduced. And an array processing algorithm of layer interference suppression is used at the receiver which makes the system structure provide different levels of protection to different layers. Furthermore, by considering the important level of scalable bitstream, the different bitstreams can be given different level protection by the system structure and channel coding. With the proposed system, the concurrent large diversity gain characteristic of STBC and alleviation of the frequency-selective fading effect of OFDM can be achieved. The simulation results show that the proposed schemes integrating scalable transcoding can provide a basic quality of video transmission and outperform the conventional single layer transcoding transmitted under the random and bursty error channel conditions.展开更多
Differential space-time coding was proposed recently in the literature for multi-antenna systems, where neither the transmitter nor the receiver knows the fading coefficients. Among existing schemes, double differenti...Differential space-time coding was proposed recently in the literature for multi-antenna systems, where neither the transmitter nor the receiver knows the fading coefficients. Among existing schemes, double differential space-time (DDST) coding is of special interest because it is applicable to continuous fast time-varying channels. However, it is less effective in fre- quency-selective fading channels. This paper’s authors derived a novel time-frequency double differential space-time (TF-DDST) coding scheme for multi-antenna orthogonal frequency division multiplexing (OFDM) systems in a time-varying fre- quency-selective fading environment, where double differential space-time coding is introduced into both time domain and fre- quency domain. Our proposed TF-DDST-OFDM system has a low-complexity non-coherent decoding scheme and is robust for time- and frequency-selective Rayleigh fading. In this paper, we also propose the use of state-of-the-art low-density parity-check (LDPC) code in serial concatenation with our TF-DDST scheme as a channel code. Simulations revealed that the LDPC based TF-DDST OFDM system has low decoding complexity and relatively better performance.展开更多
This paper proposes a time-domain clustered transmitter power adaptation scheme for orthogonal frequency division multiplexing (OFDM) system, which can significantly reduce the feedback amount during power adaptation ...This paper proposes a time-domain clustered transmitter power adaptation scheme for orthogonal frequency division multiplexing (OFDM) system, which can significantly reduce the feedback amount during power adaptation comparison with conventional frequency-domain adaptation schemes. It was found that the cluster size plays an important role on the adaptation performance, especially for the vehicular environment. Simulation results showed that using Lagrange interpolation to obtain an explicit curve of Doppler frequency vs cluster size yields good trade-off between the resulted bit error rate (BER) and the amount of feedback.展开更多
There are parallel channels which are not fully connected in practice, such as Frequency Division Multiplex (FDM or Orthogonal FDM) systems. Conventional space-time codes can be used for such parallel channels but not...There are parallel channels which are not fully connected in practice, such as Frequency Division Multiplex (FDM or Orthogonal FDM) systems. Conventional space-time codes can be used for such parallel channels but not the optimal. Based on the derivation of PEP expression for codes transmitted on parallel block fading channels, criteria of codes design for not fully connected channels are proposed and are compared with Tarokh's criteria for fully connected channel. New codes for such channels are provided by systematical and exhaustive search. Simulation results show that these codes offer better performance on parallel FDM channels than other known codes.展开更多
In multiple-input-multiple-output orthogonal-frequency-division-multiplexing （MIMO-OFDM） system, a rate-embedded differential space-time-frequency （DSTF） coding scheme was proposed. Both the conventional space-tim...In multiple-input-multiple-output orthogonal-frequency-division-multiplexing （MIMO-OFDM） system, a rate-embedded differential space-time-frequency （DSTF） coding scheme was proposed. Both the conventional space-time codes and coding techniques in frequency domain were employed to build high rate and low rate space-time-frequency message matrices. Then both types of message matrices were differentially transmitted alternately in the frequency domain. Consequently, the total transmission rate could be improved greatly. At receiver, a simple decision feedback differential detector （SDF-DD） was adopted to further enhance the total error performance with approximate DD complexity. Simulation results verified that the proposed scheme can implement high rate and high reliability differential transmission. Compared with the conventional DSTF coding schemes, the proposed scheme achieves higher spectral efficiency and much better error performance.展开更多
This paper presents a semi-blind tracking algorithm used for Multiple Phase Shift Keying based Orthogonal Frequency Division Multiplexing(MPSK-OFDM) system. By using special pream-bles to assist the decision of a feed...This paper presents a semi-blind tracking algorithm used for Multiple Phase Shift Keying based Orthogonal Frequency Division Multiplexing(MPSK-OFDM) system. By using special pream-bles to assist the decision of a feedback loop and to solve the problem of phase ambiguity,the tracking performance of the algorithm has been improved greatly. Only a few preambles are needed in the al-gorithm since the preambles are not used to estimate the frequency offset but used to provide the variation information of the phase due to the presence of frequency offset. Simulations verify that the algorithm has low SNR bound for tracking as well as high tracking accuracy and the tracking range is expanded to 30% of one subcarrier spacing.展开更多
文摘A new scheme combining a scalable transcoder with space time block codes （STBC） for an orthogonal frequency division multiplexing （OFDM） system is proposed for robust video transmission in dispersive fading channels. The target application for such a scalable transcoder is to provide successful access to the pre-encoded high quality video MPEG-2 from mobile wireless terminals. In the scalable transcoder, besides outputting the MPEG-4 fine granular scalability （FGS） bitstream, both the size of video frames and the bit rate are reduced. And an array processing algorithm of layer interference suppression is used at the receiver which makes the system structure provide different levels of protection to different layers. Furthermore, by considering the important level of scalable bitstream, the different bitstreams can be given different level protection by the system structure and channel coding. With the proposed system, the concurrent large diversity gain characteristic of STBC and alleviation of the frequency-selective fading effect of OFDM can be achieved. The simulation results show that the proposed schemes integrating scalable transcoding can provide a basic quality of video transmission and outperform the conventional single layer transcoding transmitted under the random and bursty error channel conditions.
基金Project supported by the Hi-Tech Research and Development Pro-gram (863) of China (No. 2003AA123310) and the National Natural Science Foundation of China (No. 60272079)
文摘Differential space-time coding was proposed recently in the literature for multi-antenna systems, where neither the transmitter nor the receiver knows the fading coefficients. Among existing schemes, double differential space-time (DDST) coding is of special interest because it is applicable to continuous fast time-varying channels. However, it is less effective in fre- quency-selective fading channels. This paper’s authors derived a novel time-frequency double differential space-time (TF-DDST) coding scheme for multi-antenna orthogonal frequency division multiplexing (OFDM) systems in a time-varying fre- quency-selective fading environment, where double differential space-time coding is introduced into both time domain and fre- quency domain. Our proposed TF-DDST-OFDM system has a low-complexity non-coherent decoding scheme and is robust for time- and frequency-selective Rayleigh fading. In this paper, we also propose the use of state-of-the-art low-density parity-check (LDPC) code in serial concatenation with our TF-DDST scheme as a channel code. Simulations revealed that the LDPC based TF-DDST OFDM system has low decoding complexity and relatively better performance.
基金Project supported by the Hi-Tech Research and Development Pro-gram (863) of China (No. 2003AA123310), and the National Natural Science Foundation of China (No. 60332030)
文摘This paper proposes a time-domain clustered transmitter power adaptation scheme for orthogonal frequency division multiplexing (OFDM) system, which can significantly reduce the feedback amount during power adaptation comparison with conventional frequency-domain adaptation schemes. It was found that the cluster size plays an important role on the adaptation performance, especially for the vehicular environment. Simulation results showed that using Lagrange interpolation to obtain an explicit curve of Doppler frequency vs cluster size yields good trade-off between the resulted bit error rate (BER) and the amount of feedback.
基金Supported by the National Natural Science Foundation of China(No.60496311).
文摘There are parallel channels which are not fully connected in practice, such as Frequency Division Multiplex (FDM or Orthogonal FDM) systems. Conventional space-time codes can be used for such parallel channels but not the optimal. Based on the derivation of PEP expression for codes transmitted on parallel block fading channels, criteria of codes design for not fully connected channels are proposed and are compared with Tarokh's criteria for fully connected channel. New codes for such channels are provided by systematical and exhaustive search. Simulation results show that these codes offer better performance on parallel FDM channels than other known codes.
基金Supported by the High Technology Research and Development Programme of China （No. 003AA12331007） and the National Natural Science Foundation of China （No. 60332030, 60572157）.
文摘In multiple-input-multiple-output orthogonal-frequency-division-multiplexing （MIMO-OFDM） system, a rate-embedded differential space-time-frequency （DSTF） coding scheme was proposed. Both the conventional space-time codes and coding techniques in frequency domain were employed to build high rate and low rate space-time-frequency message matrices. Then both types of message matrices were differentially transmitted alternately in the frequency domain. Consequently, the total transmission rate could be improved greatly. At receiver, a simple decision feedback differential detector （SDF-DD） was adopted to further enhance the total error performance with approximate DD complexity. Simulation results verified that the proposed scheme can implement high rate and high reliability differential transmission. Compared with the conventional DSTF coding schemes, the proposed scheme achieves higher spectral efficiency and much better error performance.
基金the Natural Science Foundation of Jiangsu Province (BK2006701)the National Natural Science Foundation of China (No.60672079).
文摘This paper presents a semi-blind tracking algorithm used for Multiple Phase Shift Keying based Orthogonal Frequency Division Multiplexing(MPSK-OFDM) system. By using special pream-bles to assist the decision of a feedback loop and to solve the problem of phase ambiguity,the tracking performance of the algorithm has been improved greatly. Only a few preambles are needed in the al-gorithm since the preambles are not used to estimate the frequency offset but used to provide the variation information of the phase due to the presence of frequency offset. Simulations verify that the algorithm has low SNR bound for tracking as well as high tracking accuracy and the tracking range is expanded to 30% of one subcarrier spacing.
