Fog radio access network(F-RAN) is one of the key technology that brings cloud computing benefit to the future of wireless communications for handling massive access and high volume of data traffic. The high fronthaul...Fog radio access network(F-RAN) is one of the key technology that brings cloud computing benefit to the future of wireless communications for handling massive access and high volume of data traffic. The high fronthaul burden of a typical cellular system can be partially diminished by utilizing the storage and signal processing capabilities of the F-RANs, which is still not desirable as user throughput requirement is in the increasing trend with the increment of the internet of things(IoT) devices. This paper proposes an efficient scheduling scheme that minimizes the fronthaul load of F-RAN system optimally to improve user experience, and minimize latency. The scheduling scheme is modeled in a way that the scheduler which provides the lower fronthaul load while fulfilling the minimum user throughput requirement is selected for the data transmission process. Simulation results in terms of user selection fairness, outage probability, and fronthaul load for a different portion of user equipments(UEs) contents in fog access point(F-AP) are shown and compared with the most common scheduling scheme such as round robin(RR) scheme to validate the proposed method.展开更多
This paper studies the effect of phase noise and fronthaul compression on a downlink cloud radio access network(C-RAN), where several remote radio heads(RRHs) are coordinated to communicate with users by a baseband un...This paper studies the effect of phase noise and fronthaul compression on a downlink cloud radio access network(C-RAN), where several remote radio heads(RRHs) are coordinated to communicate with users by a baseband unit(BBU) on the cloud server. In the system, the baseband signals are precoded at BBU, and then compressed before being transmitted to RRHs through capacity-limited fronthaul links which results in the compressive quantization noise. We assume the regularized zero-forcing precoding is performed with an imperfect channel state information and a compression strategy is applied at BBU. The effect of phase noise arising from nonideal local oscillators both at RRHs and users is considered. We propose an approximate expression for the downlink ergodic sum-rate of considered C-RAN utilizing large dimensional random matrix theory in the large-system regime. From simulation results, the accuracy of the approximate expression is validated, and the effect of phase noise and fronthaul compression can be analyzed theoretically based on the approximate expression.展开更多
Nonlinear distortion is one of key limiting factors in radio over fiber (RoF) transmission systems. To suppress the nonlinear distortion, digital pre-distortion (DPD) has been investigated considerably. However, for m...Nonlinear distortion is one of key limiting factors in radio over fiber (RoF) transmission systems. To suppress the nonlinear distortion, digital pre-distortion (DPD) has been investigated considerably. However, for multi-band signals, DPD becomes very complex, which limits the applications. To reduce the complexity, many simplified DPDs have been proposed. In this work, a new multidimensional DPD is proposed, in which in-band and out-of-band distortion are separated and the out-of-band distortion is evaluated by sum and differences of all input signals instead of all individual input signals, thus complexity is reduced. An up to 6-band 64-QAM orthogonal frequency division multiplexing (OFDM) signal with each bandwidth of 200 MHz in simulations and a 5-band 20 MHz 64-QAM OFDM signal in experiments are used to validate the pro-posed DPD. The validation is illustrated in the means of power spectrum, AM/AM and AM/PM distortion, and error vector magnitude (EVM) of the received signal constellations. The average EVM improvement by simulation for 3-band, 4-band, 5-band and 6-band signals is 19.97 dB, 18.65 dB, 16.64 dB and 15.44 dB, respectively. The average EVM improvement by experiments for 5-band signals is 8.1 dB. Considering the ten times of bandwidth difference, experiments and simulation agree well.展开更多
It is very attractive to apply a directly modulated laser(DML)-based intensity-modulation and direct-detection(IM/DD)system in future data centers and 5G fronthaul networks due to the advantages of low cost,low system...It is very attractive to apply a directly modulated laser(DML)-based intensity-modulation and direct-detection(IM/DD)system in future data centers and 5G fronthaul networks due to the advantages of low cost,low system complexity,and high energy efficiency,which perfectly match the application scenarios of the data centers and 5G fronthaul networks,in which a large number of high-speed optical interconnections are needed.However,as the data traffic in the data centers and 5G fronthaul networks continues to grow exponentially,the future requirements for data rates beyond 100 Gbaud are challenging the existing DML-based IM/DD system,and the main bottleneck is the modulation bandwidth of the DML.In this paper,the data rate demands and technical standards of the data centers and 5G fronthaul networks are reviewed in detail.With the modulation bandwidth requirements,the technical routes and achievements of recent DMLs are reviewed and discussed.In this way,the prospects,challenges,and future development of DMLs in the applications of future data centers and 5G fronthaul networks are comprehensively explored.展开更多
基金supported by Incheon National University(International Cooperative)Research Grant in 2015
文摘Fog radio access network(F-RAN) is one of the key technology that brings cloud computing benefit to the future of wireless communications for handling massive access and high volume of data traffic. The high fronthaul burden of a typical cellular system can be partially diminished by utilizing the storage and signal processing capabilities of the F-RANs, which is still not desirable as user throughput requirement is in the increasing trend with the increment of the internet of things(IoT) devices. This paper proposes an efficient scheduling scheme that minimizes the fronthaul load of F-RAN system optimally to improve user experience, and minimize latency. The scheduling scheme is modeled in a way that the scheduler which provides the lower fronthaul load while fulfilling the minimum user throughput requirement is selected for the data transmission process. Simulation results in terms of user selection fairness, outage probability, and fronthaul load for a different portion of user equipments(UEs) contents in fog access point(F-AP) are shown and compared with the most common scheduling scheme such as round robin(RR) scheme to validate the proposed method.
基金supported in part by the Natural Science Foundation of China (NSFC) under Grant U1805262, 61871446, and 61671251supported by NSFC under Grant 61625106 and Grant 61531011
文摘This paper studies the effect of phase noise and fronthaul compression on a downlink cloud radio access network(C-RAN), where several remote radio heads(RRHs) are coordinated to communicate with users by a baseband unit(BBU) on the cloud server. In the system, the baseband signals are precoded at BBU, and then compressed before being transmitted to RRHs through capacity-limited fronthaul links which results in the compressive quantization noise. We assume the regularized zero-forcing precoding is performed with an imperfect channel state information and a compression strategy is applied at BBU. The effect of phase noise arising from nonideal local oscillators both at RRHs and users is considered. We propose an approximate expression for the downlink ergodic sum-rate of considered C-RAN utilizing large dimensional random matrix theory in the large-system regime. From simulation results, the accuracy of the approximate expression is validated, and the effect of phase noise and fronthaul compression can be analyzed theoretically based on the approximate expression.
文摘Nonlinear distortion is one of key limiting factors in radio over fiber (RoF) transmission systems. To suppress the nonlinear distortion, digital pre-distortion (DPD) has been investigated considerably. However, for multi-band signals, DPD becomes very complex, which limits the applications. To reduce the complexity, many simplified DPDs have been proposed. In this work, a new multidimensional DPD is proposed, in which in-band and out-of-band distortion are separated and the out-of-band distortion is evaluated by sum and differences of all input signals instead of all individual input signals, thus complexity is reduced. An up to 6-band 64-QAM orthogonal frequency division multiplexing (OFDM) signal with each bandwidth of 200 MHz in simulations and a 5-band 20 MHz 64-QAM OFDM signal in experiments are used to validate the pro-posed DPD. The validation is illustrated in the means of power spectrum, AM/AM and AM/PM distortion, and error vector magnitude (EVM) of the received signal constellations. The average EVM improvement by simulation for 3-band, 4-band, 5-band and 6-band signals is 19.97 dB, 18.65 dB, 16.64 dB and 15.44 dB, respectively. The average EVM improvement by experiments for 5-band signals is 8.1 dB. Considering the ten times of bandwidth difference, experiments and simulation agree well.
基金The International Cooperation Project of Sichuan Province,Sichuan Science and Technology Program(2020YFH0108)NWO Zwaartekracht program on Integrated Nanophotonics+2 种基金ZJUTU/e IDEAS projectand Key Research and Development Program of China(2018YFE0201000)Anhui Provincial Natural Science Foundation of China(1808085MF186).
文摘It is very attractive to apply a directly modulated laser(DML)-based intensity-modulation and direct-detection(IM/DD)system in future data centers and 5G fronthaul networks due to the advantages of low cost,low system complexity,and high energy efficiency,which perfectly match the application scenarios of the data centers and 5G fronthaul networks,in which a large number of high-speed optical interconnections are needed.However,as the data traffic in the data centers and 5G fronthaul networks continues to grow exponentially,the future requirements for data rates beyond 100 Gbaud are challenging the existing DML-based IM/DD system,and the main bottleneck is the modulation bandwidth of the DML.In this paper,the data rate demands and technical standards of the data centers and 5G fronthaul networks are reviewed in detail.With the modulation bandwidth requirements,the technical routes and achievements of recent DMLs are reviewed and discussed.In this way,the prospects,challenges,and future development of DMLs in the applications of future data centers and 5G fronthaul networks are comprehensively explored.
