In cognitive radio （CR）,power allocation plays an important role in protecting primary user from disturbance of secondary user. Some existing studies about power allocation in CR utilize ＇interference temperature＇...In cognitive radio （CR）,power allocation plays an important role in protecting primary user from disturbance of secondary user. Some existing studies about power allocation in CR utilize ＇interference temperature＇ to achieve this protection,which might not be suitable for the OFDM-based CR. Thus in this paper,power allocation problem in multi-user orthogonal frequency division multiplexing （OFDM） and distributed antenna cognitive radio with radio over fiber （RoF） is firstly modeled as an optimization problem,where the limitation on secondary user is not ＇interference temperature＇,but that total throughput of primary user in all the resource units （RUs） must be beyond the given threshold. Moreover,based on the theorem about maximizing the total throughput of secondary user,equal power allocation algorithm is introduced. Furthermore,as the optimization problem for power allocation is not convex,it is transformed to be a convex one with geometric programming,where the solution can be obtained using duality and Karush-Kuhn-Tucker （KKT） conditions to form the optimal power allocation algorithm. Finally,extensive simulation results illustrate the significant performance improvement of the optimal algorithm compared to the existing algorithm and equal power allocation algorithm.展开更多
阐述了色散的基本原理,通过对ROF(radio over fiber)系统的研究指出,随着传输速率的升高,光纤色散会限制系统的传输性能,严重的还会造成信号的失真.在幅度调制方式(DSB调制与SSB调制)、波长数调制(单波长调制与双波长调制)及传输中对信...阐述了色散的基本原理,通过对ROF(radio over fiber)系统的研究指出,随着传输速率的升高,光纤色散会限制系统的传输性能,严重的还会造成信号的失真.在幅度调制方式(DSB调制与SSB调制)、波长数调制(单波长调制与双波长调制)及传输中对信号所造成的啁啾现象的3个不同方面,综合分析了色散对ROF系统影响,得出了SSB调制要优于DSB调制的结论,为改善ROF系统的性能提供了一定的理论基础.展开更多
为提高光载无线(radio over fiber,RoF)传输系统中的光波信号的利用率,本文提出了一种基于两个平行马赫-增德尔调制器(Mach-Zehnder modulator,MZM)的RoF传输系统。两个平行MZM经射频(radio frequency,RF)信号调制后,产生5个光边带信号...为提高光载无线(radio over fiber,RoF)传输系统中的光波信号的利用率,本文提出了一种基于两个平行马赫-增德尔调制器(Mach-Zehnder modulator,MZM)的RoF传输系统。两个平行MZM经射频(radio frequency,RF)信号调制后,产生5个光边带信号,分别是正负一阶光边带、正负二阶光边带和光载波。其中正负二阶光边带使用基带数据进行调制,经光电检测器(photodiode,PD)拍频后产生已调数据的毫米波信号,再由天线发射出去。正二阶边带和光载波经PD拍频后产生未调制数据的毫米波,该毫米波用于接收端解调的本振信号(local oscillator,LO)。负二阶边带信号用于上行链路的光载波。在本系统中,5个光边带信号都被充分利用,提高了光信号的利用效率。此外,还分析了该系统通过色散介质的传输特性,为RoF通信系统提供了一种实用化的解决方案。展开更多
In this paper, a 10 GHz radio over fiber system is analyzed. The Brillouin fiber-optic ring laser is used in the center station （CS） to suppress the optical carrier for the modulation depth enhancement. Simultaneous...In this paper, a 10 GHz radio over fiber system is analyzed. The Brillouin fiber-optic ring laser is used in the center station （CS） to suppress the optical carrier for the modulation depth enhancement. Simultaneously, the Stockes wave induced by the Brillouin amplification injects and locks the Fabry-Perot （FP） laser to output a signal-mode optical source, which works as the uplink optical carrier.展开更多
The combination of Radio Frequency and Optical Fiber has resulted high capacity transmission at lower costs components and makes Radio over Fiber as a current trend of large broadband communication. In Fiber optics fi...The combination of Radio Frequency and Optical Fiber has resulted high capacity transmission at lower costs components and makes Radio over Fiber as a current trend of large broadband communication. In Fiber optics field, the use of Fiber Bragg Grating (FBG) was been proposed in recent research with different purpose of uses. However, the compensation of dispersion method of Fiber Bragg Grating (FBG) can boost significantly the system performance. This paper investigates the performance capacity improvement of adaptive Radio over Fiber system. The system design was performed using OptiSystem 7.0 software, which 10 Gb/s Non Return to Zero (NRZ) signal was launched into 50 Km Universal Mode Fiber and Fiber Bragg Grating was used as a compensator of dispersion before frequency up conversion. Therefore, the system performances were investigated by comparing the Bit Error Rate (BER) and Q-factors of Positive Intrinsic Negative (PIN) and Ultrafast Avalanche Photodiode (APD) as optical receivers. The Eye diagram analyzer showed acceptable improvement due to use of Fiber Bragg Grating as a compensator of dispersion.展开更多
5G is emerging, but the current fronthaul transmission technologies used for 3G and 4G may not be efficient and appropriate for 5G. It has been found that frequency division multiple access （FDMA） and time- division...5G is emerging, but the current fronthaul transmission technologies used for 3G and 4G may not be efficient and appropriate for 5G. It has been found that frequency division multiple access （FDMA） and time- division multiple access （TDMA） based radio over fiber （RoF） may be considered the most appropriate for 5G fronthaul transmission technology. Due to analog RoF transmission, broadband linearization is required. In this work, both electrical and optical broadband linearization techniques are reviewed.展开更多
文摘In cognitive radio （CR）,power allocation plays an important role in protecting primary user from disturbance of secondary user. Some existing studies about power allocation in CR utilize ＇interference temperature＇ to achieve this protection,which might not be suitable for the OFDM-based CR. Thus in this paper,power allocation problem in multi-user orthogonal frequency division multiplexing （OFDM） and distributed antenna cognitive radio with radio over fiber （RoF） is firstly modeled as an optimization problem,where the limitation on secondary user is not ＇interference temperature＇,but that total throughput of primary user in all the resource units （RUs） must be beyond the given threshold. Moreover,based on the theorem about maximizing the total throughput of secondary user,equal power allocation algorithm is introduced. Furthermore,as the optimization problem for power allocation is not convex,it is transformed to be a convex one with geometric programming,where the solution can be obtained using duality and Karush-Kuhn-Tucker （KKT） conditions to form the optimal power allocation algorithm. Finally,extensive simulation results illustrate the significant performance improvement of the optimal algorithm compared to the existing algorithm and equal power allocation algorithm.
文摘阐述了色散的基本原理,通过对ROF(radio over fiber)系统的研究指出,随着传输速率的升高,光纤色散会限制系统的传输性能,严重的还会造成信号的失真.在幅度调制方式(DSB调制与SSB调制)、波长数调制(单波长调制与双波长调制)及传输中对信号所造成的啁啾现象的3个不同方面,综合分析了色散对ROF系统影响,得出了SSB调制要优于DSB调制的结论,为改善ROF系统的性能提供了一定的理论基础.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.60377024, 60877053)the Science Foundation of Science and Technology Commission of Shanghai Municipality (Grant No.08DZ1500115)
文摘In this paper, a 10 GHz radio over fiber system is analyzed. The Brillouin fiber-optic ring laser is used in the center station （CS） to suppress the optical carrier for the modulation depth enhancement. Simultaneously, the Stockes wave induced by the Brillouin amplification injects and locks the Fabry-Perot （FP） laser to output a signal-mode optical source, which works as the uplink optical carrier.
文摘The combination of Radio Frequency and Optical Fiber has resulted high capacity transmission at lower costs components and makes Radio over Fiber as a current trend of large broadband communication. In Fiber optics field, the use of Fiber Bragg Grating (FBG) was been proposed in recent research with different purpose of uses. However, the compensation of dispersion method of Fiber Bragg Grating (FBG) can boost significantly the system performance. This paper investigates the performance capacity improvement of adaptive Radio over Fiber system. The system design was performed using OptiSystem 7.0 software, which 10 Gb/s Non Return to Zero (NRZ) signal was launched into 50 Km Universal Mode Fiber and Fiber Bragg Grating was used as a compensator of dispersion before frequency up conversion. Therefore, the system performances were investigated by comparing the Bit Error Rate (BER) and Q-factors of Positive Intrinsic Negative (PIN) and Ultrafast Avalanche Photodiode (APD) as optical receivers. The Eye diagram analyzer showed acceptable improvement due to use of Fiber Bragg Grating as a compensator of dispersion.
文摘5G is emerging, but the current fronthaul transmission technologies used for 3G and 4G may not be efficient and appropriate for 5G. It has been found that frequency division multiple access （FDMA） and time- division multiple access （TDMA） based radio over fiber （RoF） may be considered the most appropriate for 5G fronthaul transmission technology. Due to analog RoF transmission, broadband linearization is required. In this work, both electrical and optical broadband linearization techniques are reviewed.
