Common displays such as CRT or LCD screens have limited capabilities in displaying most color spectra correctly. The main disadvantage of these devices is that they work with three primaries and the colors displayed a...Common displays such as CRT or LCD screens have limited capabilities in displaying most color spectra correctly. The main disadvantage of these devices is that they work with three primaries and the colors displayed are the mixture of these three colours. Consequently these devices can be confusing in testing human color identification, because the spectral distribution of the colors displayed is the combined spectrum of the three primaries. We have developed a new instrument for spectrally correct color vision measurement. This instrument uses light emitting diodes (LEDs) and is capable of producing all spectra of perceivable colors, thus with appropriate test methods this instrument can be a reliable and useful tool in test~ing human color vision and in verifying color vision correction.展开更多
The growth of the wireless and mobile communication data traffic has brought severe challenges to the present telecommu- nication systems. To meet the ever-increasing mobile traffic demand in the next 5th generation ...The growth of the wireless and mobile communication data traffic has brought severe challenges to the present telecommu- nication systems. To meet the ever-increasing mobile traffic demand in the next 5th generation （SG） communication systems, deploying 5G in the unlicensed spectrum （SG-U）, has been regarded as a promising technology. The Third Generation Partnership Project （3GPP） has specified the standardization of the Li- censed Assisted Access （LAA） and its extension enhanced LAA （eLAA）, to opportunistically transmit in the unlicensed spectrum. The LAA/eLAA systems share unlicensed spectrum resource with other networks, e.g., the Wi-Fi systems. In this article, we analyze the coexistence between the eLAA and the Wi-Fi systems in the unlicensed spectrum. We firstly establish the system model where the eLAA coexists with the Wi-Fi systems. Then, we theoretically derive and figure out the unfairness in the multi-channel occupancy rate between the eLAA and the Wi-Fi systems. After that, we propose a weight based channel selection method to improve the fairness of the coexistence. The numerical results demonstrate that by avoiding contentions and declining collisions, our method not only enhances the fairness, but also improves the overall unlicensed spectrum usage rate.展开更多
To overcome the problem of channel fading and noise uncertainty,cooperative spectrum sensing(CSS)is developed to enhance the sensing performance in cognitive radio networks(CRNs).Considering that the non-ideal reporti...To overcome the problem of channel fading and noise uncertainty,cooperative spectrum sensing(CSS)is developed to enhance the sensing performance in cognitive radio networks(CRNs).Considering that the non-ideal reporting channels of CSS can cause an adverse impact on the detection performance,the throughput maximization problem for multi-channel CSS cognitive radio under reporting channel errors is investigated.While providing all the primary users with sufficient protection,the average throughput of secondary users(SUs)is maximized by jointly optimizing the sensing duration,detection threshold and SU assignment.To address the non-convex optimization problem,the optimal energy detection threshold is derived first.Then,a sub-optimal greedy algorithm is proposed to obtain the optimal sensing duration and the optimal SU assignment.Analysis and simulation results show that the proposed algorithm can output the same performance as the exhaustive search algorithm at a much lower level of complexity.It is also shown that the impact of imperfect reporting channels should be considered especially in low signal-to-noise ratio environments and the reporting channel errors significantly reduce the performance of CSS.展开更多
In this paper, a fast algorithm to reconstruct the spectrum of non-uniformly sampled signals is proposed. Compared with the original algorithm, the fast algorithm has a higher computational efficiency, especially when...In this paper, a fast algorithm to reconstruct the spectrum of non-uniformly sampled signals is proposed. Compared with the original algorithm, the fast algorithm has a higher computational efficiency, especially when sampling sequence is long. Particularly, a transformation matrix is built, and the reconstructed spectrum is perfectly synthesized from the spectrum of every sampling channel. The fast algorithm has solved efficiency issues of spectrum reconstruction algorithm, and making it possible for the actual application of spectrum reconstruction algorithm in multi-channel Synthetic Aperture Radar (SAR).展开更多
We present an advanced schematic arrangement of the radio-wave spectrometer with a few parallel optical arms for processing the data flow. This arrangement includes two principal novelties. First of them consists in t...We present an advanced schematic arrangement of the radio-wave spectrometer with a few parallel optical arms for processing the data flow. This arrangement includes two principal novelties. First of them consists in the proposed design, where each individual optical arm exhibits its original performances providing parallel multi-band observations within a few different scales simultaneously. These optical arms have the beam shapers providing both the needed incident light polarization and apodization to increase the dynamic range. After parallel acousto-optical processing, data flows of all the optical arms are united by the joint CCD matrix on the stage of the combined electronic data processing. The second novelty is in usage of unique wide-aperture bastron-based acousto-optical cell providing one of the best performances at the middle-frequencies (about 500 MHz) in comparison with the other available crystalline materials in this range. Such multi-band capabilities have a number of applications in astrophysical scenarios at different scales: from objects in the distant universe to planetary atmospheres in the Solar system. Thus one yields the united versatile instrument, which provides comprehensive studies of astrophysical objects simultaneously with precise synchronization in various frequency ranges.展开更多
文摘Common displays such as CRT or LCD screens have limited capabilities in displaying most color spectra correctly. The main disadvantage of these devices is that they work with three primaries and the colors displayed are the mixture of these three colours. Consequently these devices can be confusing in testing human color identification, because the spectral distribution of the colors displayed is the combined spectrum of the three primaries. We have developed a new instrument for spectrally correct color vision measurement. This instrument uses light emitting diodes (LEDs) and is capable of producing all spectra of perceivable colors, thus with appropriate test methods this instrument can be a reliable and useful tool in test~ing human color vision and in verifying color vision correction.
基金partly supported by the National Science and Technology Major Project(grant no.16510711600)the National Natural Science Foundation of China(grant no.61631013)partly supported by the National Natural Science Foundation of China(grant no.61401440)
文摘The growth of the wireless and mobile communication data traffic has brought severe challenges to the present telecommu- nication systems. To meet the ever-increasing mobile traffic demand in the next 5th generation （SG） communication systems, deploying 5G in the unlicensed spectrum （SG-U）, has been regarded as a promising technology. The Third Generation Partnership Project （3GPP） has specified the standardization of the Li- censed Assisted Access （LAA） and its extension enhanced LAA （eLAA）, to opportunistically transmit in the unlicensed spectrum. The LAA/eLAA systems share unlicensed spectrum resource with other networks, e.g., the Wi-Fi systems. In this article, we analyze the coexistence between the eLAA and the Wi-Fi systems in the unlicensed spectrum. We firstly establish the system model where the eLAA coexists with the Wi-Fi systems. Then, we theoretically derive and figure out the unfairness in the multi-channel occupancy rate between the eLAA and the Wi-Fi systems. After that, we propose a weight based channel selection method to improve the fairness of the coexistence. The numerical results demonstrate that by avoiding contentions and declining collisions, our method not only enhances the fairness, but also improves the overall unlicensed spectrum usage rate.
基金The National Natural Science Foundation of China(No.61771126)the Key Research and Development Plan of Jiangsu Province(No.BE2018108)。
文摘To overcome the problem of channel fading and noise uncertainty,cooperative spectrum sensing(CSS)is developed to enhance the sensing performance in cognitive radio networks(CRNs).Considering that the non-ideal reporting channels of CSS can cause an adverse impact on the detection performance,the throughput maximization problem for multi-channel CSS cognitive radio under reporting channel errors is investigated.While providing all the primary users with sufficient protection,the average throughput of secondary users(SUs)is maximized by jointly optimizing the sensing duration,detection threshold and SU assignment.To address the non-convex optimization problem,the optimal energy detection threshold is derived first.Then,a sub-optimal greedy algorithm is proposed to obtain the optimal sensing duration and the optimal SU assignment.Analysis and simulation results show that the proposed algorithm can output the same performance as the exhaustive search algorithm at a much lower level of complexity.It is also shown that the impact of imperfect reporting channels should be considered especially in low signal-to-noise ratio environments and the reporting channel errors significantly reduce the performance of CSS.
文摘In this paper, a fast algorithm to reconstruct the spectrum of non-uniformly sampled signals is proposed. Compared with the original algorithm, the fast algorithm has a higher computational efficiency, especially when sampling sequence is long. Particularly, a transformation matrix is built, and the reconstructed spectrum is perfectly synthesized from the spectrum of every sampling channel. The fast algorithm has solved efficiency issues of spectrum reconstruction algorithm, and making it possible for the actual application of spectrum reconstruction algorithm in multi-channel Synthetic Aperture Radar (SAR).
文摘We present an advanced schematic arrangement of the radio-wave spectrometer with a few parallel optical arms for processing the data flow. This arrangement includes two principal novelties. First of them consists in the proposed design, where each individual optical arm exhibits its original performances providing parallel multi-band observations within a few different scales simultaneously. These optical arms have the beam shapers providing both the needed incident light polarization and apodization to increase the dynamic range. After parallel acousto-optical processing, data flows of all the optical arms are united by the joint CCD matrix on the stage of the combined electronic data processing. The second novelty is in usage of unique wide-aperture bastron-based acousto-optical cell providing one of the best performances at the middle-frequencies (about 500 MHz) in comparison with the other available crystalline materials in this range. Such multi-band capabilities have a number of applications in astrophysical scenarios at different scales: from objects in the distant universe to planetary atmospheres in the Solar system. Thus one yields the united versatile instrument, which provides comprehensive studies of astrophysical objects simultaneously with precise synchronization in various frequency ranges.
