An efficient scheme of integer frequency offset estimate for orthogonal frequency division multiplexing （OFDM） systems is proposed based on a training symbol with several identicalparts. In this scheme, the received...An efficient scheme of integer frequency offset estimate for orthogonal frequency division multiplexing （OFDM） systems is proposed based on a training symbol with several identicalparts. In this scheme, the received training symbol is first reshaped into several sub-symbols.It shows that the reshaping process in-troduees time diversity multiplexing.After a special fast Fourier transform （FFT） algorithm is applied to the sub-symbol,the integer frequency is estimated by finding the maximum magnitude of the resulting fre-quency domain signal.To improve the estimate performance,diversity combining methods are presented to makefull use of the multiple frequency domain sub-symbols.Compared to the traditional scheme, theproposed one has an improved estimate performance demonstrated by the computation simulation, while maintaining a very low complexity.展开更多
Due to the fast changing competitive environment faced by organizations, companies are forced to find ways to quickly adapt to technological innovations, changing demands of customers, and strategic actions taken by c...Due to the fast changing competitive environment faced by organizations, companies are forced to find ways to quickly adapt to technological innovations, changing demands of customers, and strategic actions taken by competitors. The purpose of the paper is to further the relationship between top management team （TMT） strategic decision speed and firm performance, considering the team processes when making strategic decisions in the face of complex environments. Measures of TMT strategic decision speed, firm performance, team orientation, and environmental complexity were collected from 29 top management teams of Mexican companies, which represented a total of 118 questionnaires. Pearson correlations among the variables and moderated regression analyses were performed, to test the hypotheses included in the study. Results show a positive relation between environmental complexity and TMT strategic decision speed and between team orientation and speed. Furthermore, results show that there is a positive relation between TMT strategic decision speed and firm performance in the presence of team orientation. In other words, team orientation moderates the relationship between TMT strategic speed and firm performance. Among the implications for managers is that they must ensure effective team processes （e.g., building consensus, active participation, and trust among team members） when making strategic decisions in order for the firm to perform better.展开更多
This paper presents anew way to extract concept that can beused to improve text classification per-formance (precision and recall). Thecomputational measure will be dividedinto two layers. The bottom layercalled docum...This paper presents anew way to extract concept that can beused to improve text classification per-formance (precision and recall). Thecomputational measure will be dividedinto two layers. The bottom layercalled document layer is concernedwith extracting the concepts of parti-cular document and the upper layercalled category layer is with findingthe description and subject concepts ofparticular category. The relevant im-plementation algorithm that dramatic-ally decreases the search space is dis-cussed in detail. The experiment basedon real-world data collected from Info-Bank shows that the approach is supe-rior to the traditional ones.展开更多
In orthogonal frequency division multiplexing(OFDM) systems,for given total transmit power,insertion of the noninformation bearing cyclic prefix(CP) will reduce the effective energy per information bit.Generally,the e...In orthogonal frequency division multiplexing(OFDM) systems,for given total transmit power,insertion of the noninformation bearing cyclic prefix(CP) will reduce the effective energy per information bit.Generally,the energy loss is proportional to the ratio of CP length to the symbol duration.If the CP is too long,the energy loss will be considerable high.In this paper,we propose an energy efficient transmission scheme for OFDM systems in Long Term Evolution(LTE) which is developed based on reduction of the CP energy.Simulation results show that the proposed method can save up to about10%of the total energy,while keeping almost the same bit-error-rate(BER) performance in some applications.展开更多
The higher peak-to-average power ratio(PAPR) is a major shortcoming of coherent optical orthogonal frequency division multiplexing(CO-OFDM) systems. Selective mapping(SLM) technology can effectively reduce the probabi...The higher peak-to-average power ratio(PAPR) is a major shortcoming of coherent optical orthogonal frequency division multiplexing(CO-OFDM) systems. Selective mapping(SLM) technology can effectively reduce the probability of high PAPR, but it has higher computational complexity, and requires additional bandwidth to transmit the side information, which will affect the transmission efficiency of the system. In response to these shortcomings, a novel improved SLM(NI-SLM) scheme with low complexity and without side information is proposed. Simulation results show that the proposed scheme can exponentially reduce the computational complexity, and the bit error rate(BER) performance can greatly approach the original signal. What's more, it shows the better PAPR reduction performance.展开更多
文摘An efficient scheme of integer frequency offset estimate for orthogonal frequency division multiplexing （OFDM） systems is proposed based on a training symbol with several identicalparts. In this scheme, the received training symbol is first reshaped into several sub-symbols.It shows that the reshaping process in-troduees time diversity multiplexing.After a special fast Fourier transform （FFT） algorithm is applied to the sub-symbol,the integer frequency is estimated by finding the maximum magnitude of the resulting fre-quency domain signal.To improve the estimate performance,diversity combining methods are presented to makefull use of the multiple frequency domain sub-symbols.Compared to the traditional scheme, theproposed one has an improved estimate performance demonstrated by the computation simulation, while maintaining a very low complexity.
文摘Due to the fast changing competitive environment faced by organizations, companies are forced to find ways to quickly adapt to technological innovations, changing demands of customers, and strategic actions taken by competitors. The purpose of the paper is to further the relationship between top management team （TMT） strategic decision speed and firm performance, considering the team processes when making strategic decisions in the face of complex environments. Measures of TMT strategic decision speed, firm performance, team orientation, and environmental complexity were collected from 29 top management teams of Mexican companies, which represented a total of 118 questionnaires. Pearson correlations among the variables and moderated regression analyses were performed, to test the hypotheses included in the study. Results show a positive relation between environmental complexity and TMT strategic decision speed and between team orientation and speed. Furthermore, results show that there is a positive relation between TMT strategic decision speed and firm performance in the presence of team orientation. In other words, team orientation moderates the relationship between TMT strategic speed and firm performance. Among the implications for managers is that they must ensure effective team processes （e.g., building consensus, active participation, and trust among team members） when making strategic decisions in order for the firm to perform better.
基金Project supported by the National Natural Science Foundation of China (No. 60082003) and the National High Technology Research and Development Program of China (N0.863-306-ZD03-04-1).
文摘This paper presents anew way to extract concept that can beused to improve text classification per-formance (precision and recall). Thecomputational measure will be dividedinto two layers. The bottom layercalled document layer is concernedwith extracting the concepts of parti-cular document and the upper layercalled category layer is with findingthe description and subject concepts ofparticular category. The relevant im-plementation algorithm that dramatic-ally decreases the search space is dis-cussed in detail. The experiment basedon real-world data collected from Info-Bank shows that the approach is supe-rior to the traditional ones.
基金the Chinese 863 Program，National "Eleventh Five-year" Project of China，the National Natural Science Foundation of China
文摘In orthogonal frequency division multiplexing(OFDM) systems,for given total transmit power,insertion of the noninformation bearing cyclic prefix(CP) will reduce the effective energy per information bit.Generally,the energy loss is proportional to the ratio of CP length to the symbol duration.If the CP is too long,the energy loss will be considerable high.In this paper,we propose an energy efficient transmission scheme for OFDM systems in Long Term Evolution(LTE) which is developed based on reduction of the CP energy.Simulation results show that the proposed method can save up to about10%of the total energy,while keeping almost the same bit-error-rate(BER) performance in some applications.
基金supported by the National Natural Science Foundation of China(Nos.61472464,61671091 and 61471075)the Natural Science Foundation of Chongqing Science and Technology Commission(No.cstc2015jcyj A0554)
文摘The higher peak-to-average power ratio(PAPR) is a major shortcoming of coherent optical orthogonal frequency division multiplexing(CO-OFDM) systems. Selective mapping(SLM) technology can effectively reduce the probability of high PAPR, but it has higher computational complexity, and requires additional bandwidth to transmit the side information, which will affect the transmission efficiency of the system. In response to these shortcomings, a novel improved SLM(NI-SLM) scheme with low complexity and without side information is proposed. Simulation results show that the proposed scheme can exponentially reduce the computational complexity, and the bit error rate(BER) performance can greatly approach the original signal. What's more, it shows the better PAPR reduction performance.
