Many common multimedia signal processing, including cropping, filtering, and perceptual coding, make watermark signal fading-like modification. A scheme that applies transmit diversity technique to improve robustness ...Many common multimedia signal processing, including cropping, filtering, and perceptual coding, make watermark signal fading-like modification. A scheme that applies transmit diversity technique to improve robustness of digital watermarking is presented. First, the scheme decomposes the original image using wavelet pyramid algorithm and chooses the middle-frequency band for transmission channel that the watermark will be embedded into. Then the watermark is pseudo-randomly permuted. The scheme makes use of space-time coding and differential detection technique to embed and extract watermark. The extracting process has access to neither the original image nor channel state information. Experimental results demonstrate that the scheme improves the performance of robust watermarking.展开更多
The paper investigates closed-loop transmit diversity (CLTD) systems with antenna selection technique. The expected received signal-noise-ratio (RxSNR) of the proposed systems is analyzed and compared with CLTD sy...The paper investigates closed-loop transmit diversity (CLTD) systems with antenna selection technique. The expected received signal-noise-ratio (RxSNR) of the proposed systems is analyzed and compared with CLTD systems. An algorithm is proposed for determining the number of increased transmit antennas in terms of a reduced RF chains without performance degradation. Since a feedback channel is bandwidth-limited, we present a method of quantizing transmit-weight vectors. Simulation results demonstrate advantage of the proposed systems with full and quantized feedback information. Quantized feedback has less effect on the proposed systems than CLTD systems.展开更多
This paper investigates the transmission scheme of the orthogonal time frequency space(OTFS)system with multiple antennas.Previous works have studied the multi-antenna transmitter diversity scheme with the ideal pulse...This paper investigates the transmission scheme of the orthogonal time frequency space(OTFS)system with multiple antennas.Previous works have studied the multi-antenna transmitter diversity scheme with the ideal pulse shaping in OTFS systems assuming the wireless channels of two consecutive frames duration are invariant.However,the ideal pulse shaping can not be realized in practice and the channel varies rapidly in two consecutive frames in the high-speed mobility scenarios.To this end,we redesign the multi-antenna transmitter diversity scheme to ensure its practicability in the rectangular-pulsebased OTFS systems.At first,the information symbols of each antenna are divided into two half frames along the Doppler domain.Then,the guard symbols are carefully arranged to eliminate the interference between two half frames,and to ensure the equivalent channels of two half frames being identical.By considering the positions of the guard symbols,the transmission codeword is designed and a low complexity linear detection is proposed.Finally,simulation results validate that the bit error rate performance of the proposed scheme has the superiority over the existing works.展开更多
Transmit diversity has been recently proposed to reduce the effects of fading channels in various wireless applications. Orthogonal transmit diersity (OTD) is one of the standardized techniques in 3G systems. In this ...Transmit diversity has been recently proposed to reduce the effects of fading channels in various wireless applications. Orthogonal transmit diersity (OTD) is one of the standardized techniques in 3G systems. In this paper, we apply orthogonal transmit diversity technique to multicarrier CDMA systems. Andlysis and simulation results show that performance benefits can be achieved compared with conventioal MC-CDMA systems in multipath fading channels.展开更多
In this paper,a time-switched space-time(TSST) coded orthogonal frequency division multiplexing(OFDM) scheme against the time-varying channels is proposed.In the TSST-OFDM scheme,it is equipped with four transmit ante...In this paper,a time-switched space-time(TSST) coded orthogonal frequency division multiplexing(OFDM) scheme against the time-varying channels is proposed.In the TSST-OFDM scheme,it is equipped with four transmit antennas,but only double of them are used for coding in every time slot.It is shown that the signal to inter-antenna interference ratio is a function of Doppler frequency in time-varying channels for a given space-time code.The analyses and simulations results validate that the proposed scheme not only gets timeswitched diversity and lower decoding complexity,but also suffers less time-varying impairments.Hence,it exhibits better performance than quasi-orthogonal space-time coded scheme.展开更多
Plenty of work have been done on Space-Time processing in which multiple transmit / receive antennas are used in conjunction with coding to exploit both spatial diversity and time diversity. Constant Mode Algorithm (...Plenty of work have been done on Space-Time processing in which multiple transmit / receive antennas are used in conjunction with coding to exploit both spatial diversity and time diversity. Constant Mode Algorithm (CMA) is an efficient blind adaptive Multi-User Detection (MUD) algorithm for CDMA systems. In this paper, we put forward a novel receiver, which combines CMA blind adaptive Multi-user Detection with STBC technique, and compare the performances of the system using different CM algorithms including SDCMA ( Steepest-Descent CMA), Standard Linearity Confine CMA(SLCCMA) and Least Squares CMA(LSCMA). Simulations have been done with multi-path Rayleigh channel.展开更多
The performance of transmit diversity (TD) assisted amplify-and-forward (AF) relay system with partial relay selection, which experiences mixed Rayleigh and Rician fading channels, is investigated. We first invest...The performance of transmit diversity (TD) assisted amplify-and-forward (AF) relay system with partial relay selection, which experiences mixed Rayleigh and Rician fading channels, is investigated. We first investigate the closed-form expression of the cumulative distribution function for the end-to-end equivalent signal-to-noise ratio (SNR), and then the exact expressions of outage probability and average symbol error probability (SEP) are derived. The theoretical observations are verified by the Monte Carlo simulation results.展开更多
Multiple antenna wireless systems can provide larger channel capacity and enable spatial diversity to combat fading. In this paper we conduct an investigation into the design of coded space-time system obtained by ser...Multiple antenna wireless systems can provide larger channel capacity and enable spatial diversity to combat fading. In this paper we conduct an investigation into the design of coded space-time system obtained by serially concatenating channel code module and space-time code module with an interleaver in between. As an example, the system is constructed by employing low decoding complexity turbo-SPC (single parity check) code as outer module and linear complex field space-time code as inner module, which achieves full diversity and lossless equivalent channel capacity. Simulation results prove that our designed system performs well and it only loses 0.8 dB from multiple-input multiple-output (MIMO) capacity at BER = 10^-5 in the case of information bit length 6048. Compared with turbo code-based systems, it also has lower error floor.展开更多
To satisfy the request of wireless communication for new generation communication system, a new scheme consisting of a combination of adaptive technology and space-time code-OFDM is presented. The proposed method, exp...To satisfy the request of wireless communication for new generation communication system, a new scheme consisting of a combination of adaptive technology and space-time code-OFDM is presented. The proposed method, exploits adaptive bit allocation scheme over multipath fading channel. Numerical simulations have shown that the proposed scheme can greatly improve the performance of non-adaptive STBC-OFDM system.展开更多
In this paper, we develop and analyze an energy efficient ARQ (automatic repeat request) initialized transmit diversity protocol for cooperative communications.Medium access control (MAC) layer packet retransmissi...In this paper, we develop and analyze an energy efficient ARQ (automatic repeat request) initialized transmit diversity protocol for cooperative communications.Medium access control (MAC) layer packet retransmission limit (similar to aShortRetryLimit or aLongRetryLimit [802.11-1997]) has been used as an actuator for transmit cooperative diversity initialization.We take the channel state information (CSI) as a function of retransmission tries and the number of retransmission tries is modeled as a random variable.Relays close to the source node are chosen for the transmit cooperation.Closed form expressions are obtained for symbol error rate (SER), outage capacity and outage probability for the proposed scheme in shadowed fading channels.This cooperative scheme achieves lower signal-to-noise ratio (SNR), stumpy outage probability, higher bandwidth, and transmit energy efficiencies for desired average symbol error rate (ASER) than the preceding ARQ based cooperative protocols.Finally, the results of computer simulations are included to demonstrate the efficacy of the proposed scheme and to verify the accuracy of the analytical expressions.展开更多
基金This project was supported by the National Natural Science Foundation of China(60072041).
文摘Many common multimedia signal processing, including cropping, filtering, and perceptual coding, make watermark signal fading-like modification. A scheme that applies transmit diversity technique to improve robustness of digital watermarking is presented. First, the scheme decomposes the original image using wavelet pyramid algorithm and chooses the middle-frequency band for transmission channel that the watermark will be embedded into. Then the watermark is pseudo-randomly permuted. The scheme makes use of space-time coding and differential detection technique to embed and extract watermark. The extracting process has access to neither the original image nor channel state information. Experimental results demonstrate that the scheme improves the performance of robust watermarking.
基金Project supported by the National Natural Science Foundation of China (Grant No.60472103), the Shanghai Excellent Academic Leader Project (Grant No.05XP14027), and the Shanghai Leading Academic Discipline Project (Grant No.T0102).
文摘The paper investigates closed-loop transmit diversity (CLTD) systems with antenna selection technique. The expected received signal-noise-ratio (RxSNR) of the proposed systems is analyzed and compared with CLTD systems. An algorithm is proposed for determining the number of increased transmit antennas in terms of a reduced RF chains without performance degradation. Since a feedback channel is bandwidth-limited, we present a method of quantizing transmit-weight vectors. Simulation results demonstrate advantage of the proposed systems with full and quantized feedback information. Quantized feedback has less effect on the proposed systems than CLTD systems.
基金supported in part by the Fundamental Research Funds for the Central Universities under Grants 2020JBM081 and 2020JBZD005in part by the National Key R&D Program of China under Grant 2020YFB1806903in part by the National Natural Science Foundation under Grant U1834210。
文摘This paper investigates the transmission scheme of the orthogonal time frequency space(OTFS)system with multiple antennas.Previous works have studied the multi-antenna transmitter diversity scheme with the ideal pulse shaping in OTFS systems assuming the wireless channels of two consecutive frames duration are invariant.However,the ideal pulse shaping can not be realized in practice and the channel varies rapidly in two consecutive frames in the high-speed mobility scenarios.To this end,we redesign the multi-antenna transmitter diversity scheme to ensure its practicability in the rectangular-pulsebased OTFS systems.At first,the information symbols of each antenna are divided into two half frames along the Doppler domain.Then,the guard symbols are carefully arranged to eliminate the interference between two half frames,and to ensure the equivalent channels of two half frames being identical.By considering the positions of the guard symbols,the transmission codeword is designed and a low complexity linear detection is proposed.Finally,simulation results validate that the bit error rate performance of the proposed scheme has the superiority over the existing works.
文摘Transmit diversity has been recently proposed to reduce the effects of fading channels in various wireless applications. Orthogonal transmit diersity (OTD) is one of the standardized techniques in 3G systems. In this paper, we apply orthogonal transmit diversity technique to multicarrier CDMA systems. Andlysis and simulation results show that performance benefits can be achieved compared with conventioal MC-CDMA systems in multipath fading channels.
基金Sponsored by the Science and Technology Project of Dalian,China (Grant No. 2011J21DW009)
文摘In this paper,a time-switched space-time(TSST) coded orthogonal frequency division multiplexing(OFDM) scheme against the time-varying channels is proposed.In the TSST-OFDM scheme,it is equipped with four transmit antennas,but only double of them are used for coding in every time slot.It is shown that the signal to inter-antenna interference ratio is a function of Doppler frequency in time-varying channels for a given space-time code.The analyses and simulations results validate that the proposed scheme not only gets timeswitched diversity and lower decoding complexity,but also suffers less time-varying impairments.Hence,it exhibits better performance than quasi-orthogonal space-time coded scheme.
基金This workis supported by Project of Science Committee,Jiangsu Province,and 863 Project (2002AA123046) .
文摘Plenty of work have been done on Space-Time processing in which multiple transmit / receive antennas are used in conjunction with coding to exploit both spatial diversity and time diversity. Constant Mode Algorithm (CMA) is an efficient blind adaptive Multi-User Detection (MUD) algorithm for CDMA systems. In this paper, we put forward a novel receiver, which combines CMA blind adaptive Multi-user Detection with STBC technique, and compare the performances of the system using different CM algorithms including SDCMA ( Steepest-Descent CMA), Standard Linearity Confine CMA(SLCCMA) and Least Squares CMA(LSCMA). Simulations have been done with multi-path Rayleigh channel.
基金supported by China Important National Science and Technology Specific Projects (2009ZX03007-003-01)Sino-Finland International Cooperation Program of MOST (2010DFB10410)
文摘The performance of transmit diversity (TD) assisted amplify-and-forward (AF) relay system with partial relay selection, which experiences mixed Rayleigh and Rician fading channels, is investigated. We first investigate the closed-form expression of the cumulative distribution function for the end-to-end equivalent signal-to-noise ratio (SNR), and then the exact expressions of outage probability and average symbol error probability (SEP) are derived. The theoretical observations are verified by the Monte Carlo simulation results.
基金supported by the National Natural Science Foundation of China (Grant Nos.60332030, 60572157), and the National High-TechnologY Research and Development of China (Grant No.863-2003AA123310)
文摘Multiple antenna wireless systems can provide larger channel capacity and enable spatial diversity to combat fading. In this paper we conduct an investigation into the design of coded space-time system obtained by serially concatenating channel code module and space-time code module with an interleaver in between. As an example, the system is constructed by employing low decoding complexity turbo-SPC (single parity check) code as outer module and linear complex field space-time code as inner module, which achieves full diversity and lossless equivalent channel capacity. Simulation results prove that our designed system performs well and it only loses 0.8 dB from multiple-input multiple-output (MIMO) capacity at BER = 10^-5 in the case of information bit length 6048. Compared with turbo code-based systems, it also has lower error floor.
文摘To satisfy the request of wireless communication for new generation communication system, a new scheme consisting of a combination of adaptive technology and space-time code-OFDM is presented. The proposed method, exploits adaptive bit allocation scheme over multipath fading channel. Numerical simulations have shown that the proposed scheme can greatly improve the performance of non-adaptive STBC-OFDM system.
基金Supported by the National Natral Science Foundation of China (Grant No 60602058)the National High Technology Research and Development Program of China (Grant No 2006AA01Z257)
文摘In this paper, we develop and analyze an energy efficient ARQ (automatic repeat request) initialized transmit diversity protocol for cooperative communications.Medium access control (MAC) layer packet retransmission limit (similar to aShortRetryLimit or aLongRetryLimit [802.11-1997]) has been used as an actuator for transmit cooperative diversity initialization.We take the channel state information (CSI) as a function of retransmission tries and the number of retransmission tries is modeled as a random variable.Relays close to the source node are chosen for the transmit cooperation.Closed form expressions are obtained for symbol error rate (SER), outage capacity and outage probability for the proposed scheme in shadowed fading channels.This cooperative scheme achieves lower signal-to-noise ratio (SNR), stumpy outage probability, higher bandwidth, and transmit energy efficiencies for desired average symbol error rate (ASER) than the preceding ARQ based cooperative protocols.Finally, the results of computer simulations are included to demonstrate the efficacy of the proposed scheme and to verify the accuracy of the analytical expressions.