Validating simulation model is one of the important aspects for modeling and simulation. Some methods of validating model are compared and analyzed. Several typical methods, such as TIC’s inequality coefficient, gray...Validating simulation model is one of the important aspects for modeling and simulation. Some methods of validating model are compared and analyzed. Several typical methods, such as TIC’s inequality coefficient, gray interconnected analysis, direct spectrum estimation, maximum entropy spectral estimation based on Burg or Marple, are chosen and programmed in C language. Some examples by using the program are given. The results show that the program is available and it is best to adopt multi methods for validating models.展开更多
In this paper,a space-time correlation based fast regional spectrum sensing(RSS)scheme is proposed to reduce the time and energy consumption of traditional spatial spectrum sensing. The target region is divided into s...In this paper,a space-time correlation based fast regional spectrum sensing(RSS)scheme is proposed to reduce the time and energy consumption of traditional spatial spectrum sensing. The target region is divided into small meshes,and all meshes are clustered into highly related groups using the spatial correlation among them. In each group,some representative meshes are selected as detecting meshes(DMs)using a multi-center mesh(MCM)clustering algorithm,while other meshes(EMs)are estimated according to their correlations with DMs and the Markov modeled dependence on history by MAP principle. Thus,detecting fewer meshes saves the sensing consumption. Since two independent estimation processes may provide contradictory results,minimum entropy principle is adopted to merge the results. Tested with data acquired by radio environment mapping measurement conducted in the downtown Beijing,our scheme is capable to reduce the consumption of traditional sensing method with acceptable sensing performance.展开更多
The majority of existing papers about spectrum sensing have the assumption that secondary users(SUs) are stationary. However,mobility is an essential feature of mobile communications networks. In this paper,the detect...The majority of existing papers about spectrum sensing have the assumption that secondary users(SUs) are stationary. However,mobility is an essential feature of mobile communications networks. In this paper,the detection performance of spectrum sensing by mobile SUs was analyzed. Three performance metrics,i.e.,detection probability,miss detection probability and false alarm probability,were thoroughly investigated. In our analysis,a critical variable was the real-time received primary user signal power by a mobile SU. Its probability distribution and mathematical expectation were analytically derived. Moreover,the three performance metrics in single-node spectrum sensing and multi-node collaborative spectrum sensing systems were also derived. Extensive simulations were performed. The results are consistent with the theoretical analysis. And it is concluded that SU mobility has a significant impact on the detection probability and the miss detection probability,but not on the false alarm probability.展开更多
In this paper,potential use of perfect but delayed channel estimates for variable-power discrete-rate adaptive modulation is explored.Research is concentrated on block by block adaptation.At first,a new quantity-TAUD(...In this paper,potential use of perfect but delayed channel estimates for variable-power discrete-rate adaptive modulation is explored.Research is concentrated on block by block adaptation.At first,a new quantity-TAUD(Tolerable Average Use Delay)is defined,it quantifies the performance of an adaptation scheme in tolerating the delay of channel estimates.Then,the research on TAUD shows that the delay tolerating performance declines with the increase in average power,the scheme working with more modulation modes can tolerate a longer delay,and such improvement will be more significant with the increase of average power.Finally,it shows that,as the delay tolerating performance determines the maximum block length,it has a great effect on the maximum spectral efficiency.The criterion for determining the block length appropriate for the target BER is described and a simple method of calculating the maximum block length is presented.展开更多
To improve the detection performance of sensing users for primary users in the cognitive radio, an optimal cooperative detection algorithm for many sensing users is proposed. In this paper, optimal decision thresholds...To improve the detection performance of sensing users for primary users in the cognitive radio, an optimal cooperative detection algorithm for many sensing users is proposed. In this paper, optimal decision thresholds of each sensing user are discussed. Theoretical analysis and simulation results indicate that the detection probability of optimal decision threshold rules is better than that of determined threshold rules when the false alarm of the fusion center is constant. The proposed optimal cooperative detection algorithm improves the detection performance of primary users as the attendees grow. The 2 dB gain of detection probability can be obtained when a new sensing user joins in, and there is a 17 dB improvement when the accumulation number increases from 1 to 50.展开更多
Efficient spectrum resource allocation in wireless heterogeneous networks is important for improving the system throughput and guaranteeing the user's Quality-of-Service(QoS).In this paper,we propose an enhanced a...Efficient spectrum resource allocation in wireless heterogeneous networks is important for improving the system throughput and guaranteeing the user's Quality-of-Service(QoS).In this paper,we propose an enhanced algorithm for spectrum resource allocation in heterogeneous networks.First,the bandwidth of each user is determined by the user's rate demand and the channel state.Second,graph theory is enhanced and used to improve the spectrum efficiency.Third,spectrum resource is dynamically split between macrocell and femtocells with the changes of users' conditions.Our simulation results show that the proposed algorithm improves the system throughput significantly and also guarantees the fairness for the users.展开更多
Multiple access techniques are required to meet the demand for high-speed and large-capacity commtmications in optical networks, which allow multiple users to share the fiber bandwidth. O-CDMA （optical code-division ...Multiple access techniques are required to meet the demand for high-speed and large-capacity commtmications in optical networks, which allow multiple users to share the fiber bandwidth. O-CDMA （optical code-division multiple-access） is receiving increased attention due to its potential apphcations for LAN optical networks. O-CDMA is attractive for next generation broadband access networks due to its features of allowing fully asynchronous transmission with low latency access, soft capacity on demand, protocol transparency, simplified network management as well as increased flexibility of QoS （Quality of Service） control and enhanced confidentiahty in the network. Hence, the authors experimentally investigate an ultra short pulse O-CDMA scheme based on spectral phase encoding and decoding of coherent mode-locked laser pulses, they proposed a technique using spectral phase encoding time domain system for 32 users. This technique is proved to be much effective to handle 32 users at 4 Gb/s bit rate and 60 km SMF （single mode fiber） transmission used for SPE O-CDMA system. Results indicate significant improvement in term low BER （beat error rate） and very high quality factor in the form of QoS. The authors have used PSO （pseudo orthogonal） codes and random phase code. The simulations are carried out using OptSim （RSOFT）.展开更多
We briefly review recent results on photoemission spectroscopy based on the deep and vacuum ultraviolet diode pumped solid-state lasers which we have developed.Cascaded second harmonic generation with the nonlinear cr...We briefly review recent results on photoemission spectroscopy based on the deep and vacuum ultraviolet diode pumped solid-state lasers which we have developed.Cascaded second harmonic generation with the nonlinear crystal KBe2BO3F2(KBBF)is used to generate deep ultraviolet and vacuum ultraviolet laser radiation,which complements traditional incoherent light sources such as gas discharge lamps and synchrotron radiation,and has greatly improved resolution with respect to energy,momentum,and spin of photoemission spectroscopy.Many new functions have been developed with the advantages of high photon energy,narrow linewidth,high photon flux density,and so on.These have led to the observation of various new phenomena and the amassment of new data in the fields of high temperature superconductivity,topological electronics,Fermi semi-metals,and so forth.These laser systems have revived the field of photoemission spectroscopy and provided a new platform in this frontier research field.展开更多
The analysis on the traditional asymmetric Mach-Zehnder interferometer (AMZI) optical filter based on two 3 dB directional couplers (DCs) shows that by adding an additional nonlinear phase generated by phase-generatin...The analysis on the traditional asymmetric Mach-Zehnder interferometer (AMZI) optical filter based on two 3 dB directional couplers (DCs) shows that by adding an additional nonlinear phase generated by phase-generating coupler (PGC) to the original phase difference of the AMZI, its non-periodic frequency response can be modified, and a strictly periodic spectrum can be obtained. A novel structure of the AMZI filter using two PGCs before and after the AMZI region is proposed. With the needed free spectrum range (FSR) of 20 nm, the design and optimization of the device are performed using polymer SU-8 as the core and PMMA-GMA as the buffer. Though the insertion loss (IL) gets larger than that of the traditional AMZI filter, the FSR is nearly uniform as the expected period of 20 nm.展开更多
文摘Validating simulation model is one of the important aspects for modeling and simulation. Some methods of validating model are compared and analyzed. Several typical methods, such as TIC’s inequality coefficient, gray interconnected analysis, direct spectrum estimation, maximum entropy spectral estimation based on Burg or Marple, are chosen and programmed in C language. Some examples by using the program are given. The results show that the program is available and it is best to adopt multi methods for validating models.
基金supported in part by National Natural Science Foundation of China under Grants(61525101,61227801 and 61601055)in part by the National Key Technology R&D Program of China under Grant 2015ZX03002008
文摘In this paper,a space-time correlation based fast regional spectrum sensing(RSS)scheme is proposed to reduce the time and energy consumption of traditional spatial spectrum sensing. The target region is divided into small meshes,and all meshes are clustered into highly related groups using the spatial correlation among them. In each group,some representative meshes are selected as detecting meshes(DMs)using a multi-center mesh(MCM)clustering algorithm,while other meshes(EMs)are estimated according to their correlations with DMs and the Markov modeled dependence on history by MAP principle. Thus,detecting fewer meshes saves the sensing consumption. Since two independent estimation processes may provide contradictory results,minimum entropy principle is adopted to merge the results. Tested with data acquired by radio environment mapping measurement conducted in the downtown Beijing,our scheme is capable to reduce the consumption of traditional sensing method with acceptable sensing performance.
基金supported by National Natural Science Foundation of China under Grand No.61671183
文摘The majority of existing papers about spectrum sensing have the assumption that secondary users(SUs) are stationary. However,mobility is an essential feature of mobile communications networks. In this paper,the detection performance of spectrum sensing by mobile SUs was analyzed. Three performance metrics,i.e.,detection probability,miss detection probability and false alarm probability,were thoroughly investigated. In our analysis,a critical variable was the real-time received primary user signal power by a mobile SU. Its probability distribution and mathematical expectation were analytically derived. Moreover,the three performance metrics in single-node spectrum sensing and multi-node collaborative spectrum sensing systems were also derived. Extensive simulations were performed. The results are consistent with the theoretical analysis. And it is concluded that SU mobility has a significant impact on the detection probability and the miss detection probability,but not on the false alarm probability.
基金supported by National Natural Science Foundation of China(No.61071087)Chun Lei 2009BWZ037 from SDUST,China
文摘In this paper,potential use of perfect but delayed channel estimates for variable-power discrete-rate adaptive modulation is explored.Research is concentrated on block by block adaptation.At first,a new quantity-TAUD(Tolerable Average Use Delay)is defined,it quantifies the performance of an adaptation scheme in tolerating the delay of channel estimates.Then,the research on TAUD shows that the delay tolerating performance declines with the increase in average power,the scheme working with more modulation modes can tolerate a longer delay,and such improvement will be more significant with the increase of average power.Finally,it shows that,as the delay tolerating performance determines the maximum block length,it has a great effect on the maximum spectral efficiency.The criterion for determining the block length appropriate for the target BER is described and a simple method of calculating the maximum block length is presented.
基金Sponsored by the National Basic Research Program of China(973 Program)(Grant No.2007CB310601)
文摘To improve the detection performance of sensing users for primary users in the cognitive radio, an optimal cooperative detection algorithm for many sensing users is proposed. In this paper, optimal decision thresholds of each sensing user are discussed. Theoretical analysis and simulation results indicate that the detection probability of optimal decision threshold rules is better than that of determined threshold rules when the false alarm of the fusion center is constant. The proposed optimal cooperative detection algorithm improves the detection performance of primary users as the attendees grow. The 2 dB gain of detection probability can be obtained when a new sensing user joins in, and there is a 17 dB improvement when the accumulation number increases from 1 to 50.
基金supported in part by National Natural Science Foundation(61231008)Natural Science Foundation of Shannxi Province(2015JQ6248)+1 种基金National S&T Major Project(2012ZX03003005-005)the 111 Project (B08038)
文摘Efficient spectrum resource allocation in wireless heterogeneous networks is important for improving the system throughput and guaranteeing the user's Quality-of-Service(QoS).In this paper,we propose an enhanced algorithm for spectrum resource allocation in heterogeneous networks.First,the bandwidth of each user is determined by the user's rate demand and the channel state.Second,graph theory is enhanced and used to improve the spectrum efficiency.Third,spectrum resource is dynamically split between macrocell and femtocells with the changes of users' conditions.Our simulation results show that the proposed algorithm improves the system throughput significantly and also guarantees the fairness for the users.
文摘Multiple access techniques are required to meet the demand for high-speed and large-capacity commtmications in optical networks, which allow multiple users to share the fiber bandwidth. O-CDMA （optical code-division multiple-access） is receiving increased attention due to its potential apphcations for LAN optical networks. O-CDMA is attractive for next generation broadband access networks due to its features of allowing fully asynchronous transmission with low latency access, soft capacity on demand, protocol transparency, simplified network management as well as increased flexibility of QoS （Quality of Service） control and enhanced confidentiahty in the network. Hence, the authors experimentally investigate an ultra short pulse O-CDMA scheme based on spectral phase encoding and decoding of coherent mode-locked laser pulses, they proposed a technique using spectral phase encoding time domain system for 32 users. This technique is proved to be much effective to handle 32 users at 4 Gb/s bit rate and 60 km SMF （single mode fiber） transmission used for SPE O-CDMA system. Results indicate significant improvement in term low BER （beat error rate） and very high quality factor in the form of QoS. The authors have used PSO （pseudo orthogonal） codes and random phase code. The simulations are carried out using OptSim （RSOFT）.
基金Project supported by the National Development Project for Major Scientific Research Facility(No.ZDYZ2012-2)the National Instrumentation Program(No.2012YQ120048)
文摘We briefly review recent results on photoemission spectroscopy based on the deep and vacuum ultraviolet diode pumped solid-state lasers which we have developed.Cascaded second harmonic generation with the nonlinear crystal KBe2BO3F2(KBBF)is used to generate deep ultraviolet and vacuum ultraviolet laser radiation,which complements traditional incoherent light sources such as gas discharge lamps and synchrotron radiation,and has greatly improved resolution with respect to energy,momentum,and spin of photoemission spectroscopy.Many new functions have been developed with the advantages of high photon energy,narrow linewidth,high photon flux density,and so on.These have led to the observation of various new phenomena and the amassment of new data in the fields of high temperature superconductivity,topological electronics,Fermi semi-metals,and so forth.These laser systems have revived the field of photoemission spectroscopy and provided a new platform in this frontier research field.
基金supported by the National Natural Science Foundation of China (Nos.61107021, 61177027, 61077041 and 60807029)the Ministry of Education of China (Nos.20110061120052 and 20090061110041)+1 种基金the China Postdoctoral Science Foundation Funded Project (No.20110491299)the Special Funds of Basic Science and Technology of Jilin University (Nos.201103076 and 200905005)
文摘The analysis on the traditional asymmetric Mach-Zehnder interferometer (AMZI) optical filter based on two 3 dB directional couplers (DCs) shows that by adding an additional nonlinear phase generated by phase-generating coupler (PGC) to the original phase difference of the AMZI, its non-periodic frequency response can be modified, and a strictly periodic spectrum can be obtained. A novel structure of the AMZI filter using two PGCs before and after the AMZI region is proposed. With the needed free spectrum range (FSR) of 20 nm, the design and optimization of the device are performed using polymer SU-8 as the core and PMMA-GMA as the buffer. Though the insertion loss (IL) gets larger than that of the traditional AMZI filter, the FSR is nearly uniform as the expected period of 20 nm.
