Two optimal power control （PC） schemes under the power constraint for space-time coded multiple input multiple output systems over the flat Rayleigh fading channel with the imperfect channel state information （CSI...Two optimal power control （PC） schemes under the power constraint for space-time coded multiple input multiple output systems over the flat Rayleigh fading channel with the imperfect channel state information （CSI） are presented. One is based on the minimization of a bit error rate （BER）, and the other is based on the maximization of a fuzzy signal-to-noise ratio. In these schemes, different powers are allocated to individual transmit an- tennas rather than equal power in the conventional one. For the first scheme, the optimal PC procedure is developed. It is shown that the Lagrange multiplier for the constrained optimization in the power control does exist and is unique. A practical iterative algorithm based on Newton＇s method for finding the Lagrange multiplier is proposed. In the second scheme, some existing schemes are included, and a suboptimal PC procedure is developed by means of the asymptotic performance analysis. With this suboptimal scheme, a simple PC calculation formula is provided, and thus the calculation of the PC will be straightforward. Moreover, the suboptimal scheme has the BER performance close to the optimal scheme. Simulation results show that the two PC schemes can provide BER lower than the equal PC and antenna selection scheme under the imperfect CSI.展开更多
Recently, Cooperative diversity in wireless communication systems has gained much attention. A simple two-user cooperative diversity scheme called decode-and-forward cooperation scheme has been presented by Laneman (2...Recently, Cooperative diversity in wireless communication systems has gained much attention. A simple two-user cooperative diversity scheme called decode-and-forward cooperation scheme has been presented by Laneman (2004). Each user has one partner to decode its information and retransmit it by employing repeti-tion coding. This scheme can offer diversity order of two. But the bandwidth efficiency is low. In this paper, we propose a bandwidth efficient three-user cooperative diversity scheme based on relaying superposition symbols. Each user has two partners and each partner relays superposition symbols of the other two users instead of repetition. Thus, the bandwidth efficiency is improved compared to the baseline decode- and-forward cooperative diversity scheme presented by Laneman. Moreover, the proposed scheme can also offer diversity order of two. Then, in order to improve the system performance, a new constellation labeling for the superposition 8PSK modulation is designed. It is a simple way to exploit the symbol mapping diver-sity and a gain of about 2 dB can be obtained. Furthermore, the performance improvement comes at no addi-tional power or bandwidth expense.展开更多
The ability to detect the primary user＇s signal is one of the main performances for cognitive radio networks. Based on the multi-different-cyclic-frequency character- istics of the cyclostationary primary user＇s sig...The ability to detect the primary user＇s signal is one of the main performances for cognitive radio networks. Based on the multi-different-cyclic-frequency character- istics of the cyclostationary primary user＇s signal and the cooperation detection advantage of the multi-secondary-user, the paper presents the weighted cooperative spectrum detection algorithm based on cyclostationarity in detail. The core of the algorithm is to detect the primary user＇s signal by the secondary users＇ cooperation detection to the multi-different-cyclic-frequency, and to make a final decision according to the fusion data of the independent secondary users＇ detection results. Meanwhile, in order to improve the detection performance, the paper proposes a method to optimize the weight on basis of the deflection coefficient criterion. The result of simulation shows that the proposed algorithm has better performance even in low signal-to-noise ratio （SNR）.展开更多
A family of space-time block codes(STBCs)for systems with even transmit antennas and any number of receive antennas is proposed.The new codeword matrix is constructed by concatenating Alamouti space-time codes to form...A family of space-time block codes(STBCs)for systems with even transmit antennas and any number of receive antennas is proposed.The new codeword matrix is constructed by concatenating Alamouti space-time codes to form a block diagonal matrix,and its dimension is equal to the number of transmit antennas.All Alamouti codes in the same codeword matrix have the same information;thus,full transmit diversity can be achieved over fading channels.To improve the spectral efficiency,multi-level modulations such as multi-quadrature amplitude modulation(M-QAM)are employed.The symbol mapping diversity is then exploited between transmissions of the same information from different antennas to improve the bit error rate(BER)performance.The proposed codes outperform the diagonal algebraic space-time(DAST)codes presented by Damen[Damen et al.IEEE Transactions on Information Theory,2002,48(3):628–636]when they have the same spectral efficiency.Also,they outperform the 1/2-rate codes from complex orthogonal design.Moreover,compared to DAST codes,the proposed codes have a low decoding complexity because we only need to perform linear processing to achieve single-symbol maximum-likelihood(ML)decoding.展开更多
Cognitive radio(CR)is a promising technology.The most fundamental problem of CR is spectrum sensing.Energy detector is often considered for spectrum sensing in CR,and if the noise power is exactly known,energy detecto...Cognitive radio(CR)is a promising technology.The most fundamental problem of CR is spectrum sensing.Energy detector is often considered for spectrum sensing in CR,and if the noise power is exactly known,energy detector has admirable performance.However,in practice,noise power is always inexactly known.To solve this problem,Dandawate[Dandawate et al.IEEE Transactions on Signal Processing,1994,42(9):2355-2369]has proposed a nonparametric single-cycle detector based on cyclostationarity,which is robust to noise uncertainty.In this paper,based on Dandawate’s single-cycle detector,a joint multi-cycle detector is further proposed,which is also nonparametric and immune from noise uncertainty.Simulation results have shown the validity and superiority over single-cycle detector of the proposed detector.展开更多
A two-path amplify-and-forward(AF)relaying scheme,which uses two relays to retransmit for the source alternately,was proposed by Rankov[Rankov et al.IEEE Journal on Selected Areas in Communications,2007,25(2):379–389...A two-path amplify-and-forward(AF)relaying scheme,which uses two relays to retransmit for the source alternately,was proposed by Rankov[Rankov et al.IEEE Journal on Selected Areas in Communications,2007,25(2):379–389].This scheme can avoid half-duplex loss in spectral efficiency,but it cannot work well when the interrelay channel gain is strong.An efficient detection scheme for two-path AF relaying system is proposed in this paper.In the proposed scheme,interference cancellation is first performed at the destination so that the received signal after interference cancellation is the superposition of two symbols with noise.Then,a low complexity soft maximum a posteriori(MAP)decoder and an iterative soft decoder are employed to extract the diversity of the two relay-destination links.The proposed detection scheme can efficiently improve the system performance compared to the detection scheme presented by Rankov(2007),especially when the inter-relay channel gain is strong.展开更多
With the progress of research on cognitive radio in ultra-wideband(UWB)open frequency-band,a joint detection algorithm integrating the energy and bispectrum detection is proposed in detail for non-Gaussian signal dete...With the progress of research on cognitive radio in ultra-wideband(UWB)open frequency-band,a joint detection algorithm integrating the energy and bispectrum detection is proposed in detail for non-Gaussian signal detection from Gaussian noise.The performance of the algorithm was evaluated by simulation,the result of which indicates that the joint detection not only solves the problem of the signal detection in low signal-to-noise ratio(SNR)but also improves the operational speed and the detection probability.Thus,the joint detection algorithm has definite prospect in practice.展开更多
Orthogonal space-time block codes(OSTBCs)have attracted considerable attention due to their low complexity linear decoding and full diversity in Rayleigh fading channels.However,OSTBCs exist only for certain numbers o...Orthogonal space-time block codes(OSTBCs)have attracted considerable attention due to their low complexity linear decoding and full diversity in Rayleigh fading channels.However,OSTBCs exist only for certain numbers of transmit antennas and do not provide full code rate when more than two transmit antennas are used.In this paper,a novel rate-2 algebraic space-time code that combines coordinate-interleaving and group precoding is proposed.By properly choosing the designed parameters,the coding scheme can achieve full diversity order and high coding gain.The receiver adopts polynomial complexity sphere decoding algorithm to get maximum likelihood(ML)performance.Analysis and simulations illustrate that the new code exhibits significant performance gain over the conventional OSTBCs and diagonal algebraic space-time code.展开更多
基金supported by the Open Research Fund of National Mobile Communications Research Laboratory of Southeast University(N200904)the Nanjing University of Aeronautics and Astronautics (NUAA) Research Funding (NS2010113)the National Natural Science Foundation of China (61172077)
文摘Two optimal power control （PC） schemes under the power constraint for space-time coded multiple input multiple output systems over the flat Rayleigh fading channel with the imperfect channel state information （CSI） are presented. One is based on the minimization of a bit error rate （BER）, and the other is based on the maximization of a fuzzy signal-to-noise ratio. In these schemes, different powers are allocated to individual transmit an- tennas rather than equal power in the conventional one. For the first scheme, the optimal PC procedure is developed. It is shown that the Lagrange multiplier for the constrained optimization in the power control does exist and is unique. A practical iterative algorithm based on Newton＇s method for finding the Lagrange multiplier is proposed. In the second scheme, some existing schemes are included, and a suboptimal PC procedure is developed by means of the asymptotic performance analysis. With this suboptimal scheme, a simple PC calculation formula is provided, and thus the calculation of the PC will be straightforward. Moreover, the suboptimal scheme has the BER performance close to the optimal scheme. Simulation results show that the two PC schemes can provide BER lower than the equal PC and antenna selection scheme under the imperfect CSI.
文摘Recently, Cooperative diversity in wireless communication systems has gained much attention. A simple two-user cooperative diversity scheme called decode-and-forward cooperation scheme has been presented by Laneman (2004). Each user has one partner to decode its information and retransmit it by employing repeti-tion coding. This scheme can offer diversity order of two. But the bandwidth efficiency is low. In this paper, we propose a bandwidth efficient three-user cooperative diversity scheme based on relaying superposition symbols. Each user has two partners and each partner relays superposition symbols of the other two users instead of repetition. Thus, the bandwidth efficiency is improved compared to the baseline decode- and-forward cooperative diversity scheme presented by Laneman. Moreover, the proposed scheme can also offer diversity order of two. Then, in order to improve the system performance, a new constellation labeling for the superposition 8PSK modulation is designed. It is a simple way to exploit the symbol mapping diver-sity and a gain of about 2 dB can be obtained. Furthermore, the performance improvement comes at no addi-tional power or bandwidth expense.
基金This work was supported by the National Program on Key Basic Research Project （Grant No. 2007CB310603） and the National Natural Science Foundation of China （Grant No. 60972161）.
文摘The ability to detect the primary user＇s signal is one of the main performances for cognitive radio networks. Based on the multi-different-cyclic-frequency character- istics of the cyclostationary primary user＇s signal and the cooperation detection advantage of the multi-secondary-user, the paper presents the weighted cooperative spectrum detection algorithm based on cyclostationarity in detail. The core of the algorithm is to detect the primary user＇s signal by the secondary users＇ cooperation detection to the multi-different-cyclic-frequency, and to make a final decision according to the fusion data of the independent secondary users＇ detection results. Meanwhile, in order to improve the detection performance, the paper proposes a method to optimize the weight on basis of the deflection coefficient criterion. The result of simulation shows that the proposed algorithm has better performance even in low signal-to-noise ratio （SNR）.
基金This work was supported in part by the National Basic Research Program of China(Grant No.2007CB310603)the Research Fund of National Mobile Communications Research Laboratory,Southeast University(No.2008A05)+1 种基金the National High Technology Research and Development Program of China(Grant No.2007AA01Z2B1)the National Natural Science Foundation of China(Grant No.60802005).
文摘A family of space-time block codes(STBCs)for systems with even transmit antennas and any number of receive antennas is proposed.The new codeword matrix is constructed by concatenating Alamouti space-time codes to form a block diagonal matrix,and its dimension is equal to the number of transmit antennas.All Alamouti codes in the same codeword matrix have the same information;thus,full transmit diversity can be achieved over fading channels.To improve the spectral efficiency,multi-level modulations such as multi-quadrature amplitude modulation(M-QAM)are employed.The symbol mapping diversity is then exploited between transmissions of the same information from different antennas to improve the bit error rate(BER)performance.The proposed codes outperform the diagonal algebraic space-time(DAST)codes presented by Damen[Damen et al.IEEE Transactions on Information Theory,2002,48(3):628–636]when they have the same spectral efficiency.Also,they outperform the 1/2-rate codes from complex orthogonal design.Moreover,compared to DAST codes,the proposed codes have a low decoding complexity because we only need to perform linear processing to achieve single-symbol maximum-likelihood(ML)decoding.
基金supported in part by the National Basic Research Program of China(Grant No.2007CB310603)in part by the Research Fund of National Mobile Communications Research Laboratory,Southeast University(No.2010A05).
文摘Cognitive radio(CR)is a promising technology.The most fundamental problem of CR is spectrum sensing.Energy detector is often considered for spectrum sensing in CR,and if the noise power is exactly known,energy detector has admirable performance.However,in practice,noise power is always inexactly known.To solve this problem,Dandawate[Dandawate et al.IEEE Transactions on Signal Processing,1994,42(9):2355-2369]has proposed a nonparametric single-cycle detector based on cyclostationarity,which is robust to noise uncertainty.In this paper,based on Dandawate’s single-cycle detector,a joint multi-cycle detector is further proposed,which is also nonparametric and immune from noise uncertainty.Simulation results have shown the validity and superiority over single-cycle detector of the proposed detector.
基金supported in part by the National Basic Research Program of China (No.2007CB310603)the Research Fund of National Mobile Communications Research Laboratory,Southeast University (No.2008A05)+1 种基金the National High Technology Research and Development Program of China (No.2007AA01Z2B1)the National Natural Science Foundation of China (Grant No.60802005).
文摘A two-path amplify-and-forward(AF)relaying scheme,which uses two relays to retransmit for the source alternately,was proposed by Rankov[Rankov et al.IEEE Journal on Selected Areas in Communications,2007,25(2):379–389].This scheme can avoid half-duplex loss in spectral efficiency,but it cannot work well when the interrelay channel gain is strong.An efficient detection scheme for two-path AF relaying system is proposed in this paper.In the proposed scheme,interference cancellation is first performed at the destination so that the received signal after interference cancellation is the superposition of two symbols with noise.Then,a low complexity soft maximum a posteriori(MAP)decoder and an iterative soft decoder are employed to extract the diversity of the two relay-destination links.The proposed detection scheme can efficiently improve the system performance compared to the detection scheme presented by Rankov(2007),especially when the inter-relay channel gain is strong.
文摘With the progress of research on cognitive radio in ultra-wideband(UWB)open frequency-band,a joint detection algorithm integrating the energy and bispectrum detection is proposed in detail for non-Gaussian signal detection from Gaussian noise.The performance of the algorithm was evaluated by simulation,the result of which indicates that the joint detection not only solves the problem of the signal detection in low signal-to-noise ratio(SNR)but also improves the operational speed and the detection probability.Thus,the joint detection algorithm has definite prospect in practice.
基金supported in part by the National Basic Research Program of China (No.2007CB310603).
文摘Orthogonal space-time block codes(OSTBCs)have attracted considerable attention due to their low complexity linear decoding and full diversity in Rayleigh fading channels.However,OSTBCs exist only for certain numbers of transmit antennas and do not provide full code rate when more than two transmit antennas are used.In this paper,a novel rate-2 algebraic space-time code that combines coordinate-interleaving and group precoding is proposed.By properly choosing the designed parameters,the coding scheme can achieve full diversity order and high coding gain.The receiver adopts polynomial complexity sphere decoding algorithm to get maximum likelihood(ML)performance.Analysis and simulations illustrate that the new code exhibits significant performance gain over the conventional OSTBCs and diagonal algebraic space-time code.
