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
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
随着LTE网络的大规模商用部署,全新的网络构架BBU集中部署模式应运而生。在BBU集中部署的模式下,Fronthaul网络的建设尤为重要。在移动互联网时代,运营商面临着无线接入网高昂的投资和运维成本,以及快速增长的数据流量和ARPU（Average R...随着LTE网络的大规模商用部署,全新的网络构架BBU集中部署模式应运而生。在BBU集中部署的模式下,Fronthaul网络的建设尤为重要。在移动互联网时代,运营商面临着无线接入网高昂的投资和运维成本,以及快速增长的数据流量和ARPU（Average Revenue Per User）增长放缓等挑战。展开更多
We apply a Peak Shrinking and Interpolating(PSI)scheme to improve the Peak-to-Average Power Ratio(PAPR)performance in Multiple Intermediate-Frequency-over-Fiber(M-IFoF)based mobile fronthaul.The key idea is to detect ...We apply a Peak Shrinking and Interpolating(PSI)scheme to improve the Peak-to-Average Power Ratio(PAPR)performance in Multiple Intermediate-Frequency-over-Fiber(M-IFoF)based mobile fronthaul.The key idea is to detect the high peaks of the signal and shrink them,and then the shrunk peak values are interpolated into the original signal to reduce the PAPR.We also compare the PSI technique with the previous Tone-Reservation(TR)technique and Phase Pre-Distortion(PPD)technique in terms of PAPR reduction effect and computational complexity.The simulation results indicate that the PSI scheme can reduce the PAPR by more than 4.3 dB at 0.1%CCDF,which outperforms the two previous schemes with lower computational complexity.Furthermore,we find that altering M-IFoF system parameters has little effect on the performance of the PSI technique.展开更多
The utilization of optical fiber in fronthaul transmission within radio access networks(RANs)offers significant advantages in terms of high quality,stability,and long-reach capabilities.Simultaneously,distributed acou...The utilization of optical fiber in fronthaul transmission within radio access networks(RANs)offers significant advantages in terms of high quality,stability,and long-reach capabilities.Simultaneously,distributed acoustic sensing(DAS)enables network surveillance and human activity detection through environmental monitoring.However,the implementation of large-scale strain measurement remains a challenge.In this paper,we propose a novel linear frequency modulated(LFM)pilot-aided radio OFDM fronthaul waveform specifically designed for integrated sensing and communication over fiber(ISACoF).The continuous LFM pilots facilitate the demodulation process at the communication side and serve as sensing probes to detect vibrations along the fiber using pulse compression techniques.Furthermore,by leveraging the large bandwidth of OFDM radio signals,the frequency-demodulated DAS enabled by multiple LFM pilots overcomes the limitations of traditional phase-demodulated DAS in scenarios involving large dynamic vibrations.We experimentally demonstrate the transmission of OFDM radio signals through a 10-km fiber and a 4-m free-space channel,assisted by 128 LFM pilots.By utilizing millimeter-wave(MMW)radio signals operating within a frequency range of 27.2 GHz to 29 GHz and a bandwidth of 1.8 GHz,dynamic vibration measurements of up to 6μεare achieved.Additionally,by optimizing the power ratio between OFDM payloads and LFM pilots,we achieve a sensing sensitivity of 0.81.and a demodulated signal-to-noise ratio of over 20 dB for 64-QAM-OFDM.Various modulation formats and vibration waveforms are validated via experiments,thereby confirming the feasibility of implementing the proposed ISACoF system in practical RAN design.展开更多
Beyond providing user access to the core network,the radio access network(RAN) is expected to support precise positioning and sensing for emerging applications such as virtual reality(VR) and drone fleets.To achieve t...Beyond providing user access to the core network,the radio access network(RAN) is expected to support precise positioning and sensing for emerging applications such as virtual reality(VR) and drone fleets.To achieve this,fronthaul-the link connecting the central units/distributed units(CUs/DUs) to wireless remote units(RUs) in centralized RAN-must realize both high-capacity transmission and low-timing-jitter clock synchronization between RUs.However,existing solutions fall short of supporting these functions within one simple,cost-effective network.In this work,we propose a solution that simultaneously achieves picosecond-level timing jitter clock distribution and Tb/s data transmission with simp lified DSP,using an electro-optic(EO) comb cloning technique to enable multifunctionality in fronthaul systems.Through the delivery of pilot comb lines,a 1 ps(integrated from 1 Hz to 40 MHz) low-timing-jitter 100 MHz clock is distributed by the beating of adjacent pilot comb lines and subsequent frequency dividing,realizing frequency synchronization between the CUs/DUs and RUs.Moreover,the delivery of pilot comb lines also facilitates self-homodyne structures through EO comb cloning,and supports wavelength division multiplexing(WDM) transmission with a line capacity of 2.88 Tb/s and a net capacity of 2.5 Tb/s.Thanks to the clock-synchronized and self-homodyne structure,DSP is streamlined,with digital timing recovery,carrier phase estimation,and frequency offset estimation all omitted.This work lays the technical foundation for implementing a 6G WDM fronthaul architecture that integrates ultra-wide wireless bandwidth with precise positioning and sensing.展开更多
Owing to the inherent central information processing and resource management ability,the cloud radio access network(C-RAN)is a promising network structure for an intelligent and simplified sixth-generation(6G)wireless...Owing to the inherent central information processing and resource management ability,the cloud radio access network(C-RAN)is a promising network structure for an intelligent and simplified sixth-generation(6G)wireless network.Nevertheless,to further enhance the capacity and coverage,more radio remote heads(RRHs)as well as high-fidelity and low-latency fronthaul links are required,which may lead to high implementation cost.To address this issue,we propose to exploit the intelligent reflecting surface(IRS)as an alternative way to enhance the C-RAN,which is a low-cost and energy-efficient option.Specifically,we consider the uplink transmission where multi-antenna users communicate with the baseband unit(BBU)pool through multi-antenna RRHs and multiple IRSs are deployed between the users and RRHs.RRHs can conduct either point-to-point(P2P)compression or Wyner-Ziv coding to compress the received signals,which are then forwarded to the BBU pool through fronthaul links.We investigate the joint design and optimization of user transmit beamformers,IRS passive beamformers,and fronthaul compression noise covariance matrices to maximize the uplink sum rate subject to fronthaul capacity constraints under P2P compression and Wyner-Ziv coding.By exploiting the Arimoto-Blahut algorithm and semi-definite relaxation(SDR),we propose a successive convex approximation approach to solve non-convex problems,and two iterative algorithms corresponding to P2P compression and Wyner-Ziv coding are provided.Numerical results verify the performance gain brought about by deploying IRS in C-RAN and the superiority of the proposed joint design.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
本文研究了智能反射面(IRS)辅助OFDMA(Orthogonal Frequency Division Multiple Access,正交频分多址接入)云无线接入网(C-RAN)的下行链路传输系统,其中基带处理单元(BBU)池通过多个远端射频头(RRH)与多个用户进行通信.RRH到用户的接入...本文研究了智能反射面(IRS)辅助OFDMA(Orthogonal Frequency Division Multiple Access,正交频分多址接入)云无线接入网(C-RAN)的下行链路传输系统,其中基带处理单元(BBU)池通过多个远端射频头(RRH)与多个用户进行通信.RRH到用户的接入链路采用OFDMA接入技术.对于BBU池到RRH,采用无线前传链路,并且部署多个IRS以增强链路传输能力.在BBU池和每个RRH发射功率约束下,本文提出通过联合优化前传链路和接入链路资源配置使下行用户和速率最大化.由于该资源配置问题是非凸的,首先采用连续凸逼近(SCA)对目标以及约束条件进行转换.其次,将转换后的问题拆分成三个子问题来交替性求解.最后,计算机仿真结果显示了所提出的联合资源分配方法与其他基准方案相比具有显著的传输性能增益.展开更多
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.
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.
文摘随着LTE网络的大规模商用部署,全新的网络构架BBU集中部署模式应运而生。在BBU集中部署的模式下,Fronthaul网络的建设尤为重要。在移动互联网时代,运营商面临着无线接入网高昂的投资和运维成本,以及快速增长的数据流量和ARPU（Average Revenue Per User）增长放缓等挑战。
文摘We apply a Peak Shrinking and Interpolating(PSI)scheme to improve the Peak-to-Average Power Ratio(PAPR)performance in Multiple Intermediate-Frequency-over-Fiber(M-IFoF)based mobile fronthaul.The key idea is to detect the high peaks of the signal and shrink them,and then the shrunk peak values are interpolated into the original signal to reduce the PAPR.We also compare the PSI technique with the previous Tone-Reservation(TR)technique and Phase Pre-Distortion(PPD)technique in terms of PAPR reduction effect and computational complexity.The simulation results indicate that the PSI scheme can reduce the PAPR by more than 4.3 dB at 0.1%CCDF,which outperforms the two previous schemes with lower computational complexity.Furthermore,we find that altering M-IFoF system parameters has little effect on the performance of the PSI technique.
文摘The utilization of optical fiber in fronthaul transmission within radio access networks(RANs)offers significant advantages in terms of high quality,stability,and long-reach capabilities.Simultaneously,distributed acoustic sensing(DAS)enables network surveillance and human activity detection through environmental monitoring.However,the implementation of large-scale strain measurement remains a challenge.In this paper,we propose a novel linear frequency modulated(LFM)pilot-aided radio OFDM fronthaul waveform specifically designed for integrated sensing and communication over fiber(ISACoF).The continuous LFM pilots facilitate the demodulation process at the communication side and serve as sensing probes to detect vibrations along the fiber using pulse compression techniques.Furthermore,by leveraging the large bandwidth of OFDM radio signals,the frequency-demodulated DAS enabled by multiple LFM pilots overcomes the limitations of traditional phase-demodulated DAS in scenarios involving large dynamic vibrations.We experimentally demonstrate the transmission of OFDM radio signals through a 10-km fiber and a 4-m free-space channel,assisted by 128 LFM pilots.By utilizing millimeter-wave(MMW)radio signals operating within a frequency range of 27.2 GHz to 29 GHz and a bandwidth of 1.8 GHz,dynamic vibration measurements of up to 6μεare achieved.Additionally,by optimizing the power ratio between OFDM payloads and LFM pilots,we achieve a sensing sensitivity of 0.81.and a demodulated signal-to-noise ratio of over 20 dB for 64-QAM-OFDM.Various modulation formats and vibration waveforms are validated via experiments,thereby confirming the feasibility of implementing the proposed ISACoF system in practical RAN design.
基金Natural Science Foundation of Beijing Municipality(JQ24027).
文摘Beyond providing user access to the core network,the radio access network(RAN) is expected to support precise positioning and sensing for emerging applications such as virtual reality(VR) and drone fleets.To achieve this,fronthaul-the link connecting the central units/distributed units(CUs/DUs) to wireless remote units(RUs) in centralized RAN-must realize both high-capacity transmission and low-timing-jitter clock synchronization between RUs.However,existing solutions fall short of supporting these functions within one simple,cost-effective network.In this work,we propose a solution that simultaneously achieves picosecond-level timing jitter clock distribution and Tb/s data transmission with simp lified DSP,using an electro-optic(EO) comb cloning technique to enable multifunctionality in fronthaul systems.Through the delivery of pilot comb lines,a 1 ps(integrated from 1 Hz to 40 MHz) low-timing-jitter 100 MHz clock is distributed by the beating of adjacent pilot comb lines and subsequent frequency dividing,realizing frequency synchronization between the CUs/DUs and RUs.Moreover,the delivery of pilot comb lines also facilitates self-homodyne structures through EO comb cloning,and supports wavelength division multiplexing(WDM) transmission with a line capacity of 2.88 Tb/s and a net capacity of 2.5 Tb/s.Thanks to the clock-synchronized and self-homodyne structure,DSP is streamlined,with digital timing recovery,carrier phase estimation,and frequency offset estimation all omitted.This work lays the technical foundation for implementing a 6G WDM fronthaul architecture that integrates ultra-wide wireless bandwidth with precise positioning and sensing.
基金Project supported by the Zhejiang Provincial Natural Science Foundation of China(Nos.LY21F010008 and LD21F010001)the National Natural Science Foundation of China(No.62171412)the Open Research Fund of National Mobile Communications Research Laboratory,Southeast University,China(No.2020D10)。
文摘Owing to the inherent central information processing and resource management ability,the cloud radio access network(C-RAN)is a promising network structure for an intelligent and simplified sixth-generation(6G)wireless network.Nevertheless,to further enhance the capacity and coverage,more radio remote heads(RRHs)as well as high-fidelity and low-latency fronthaul links are required,which may lead to high implementation cost.To address this issue,we propose to exploit the intelligent reflecting surface(IRS)as an alternative way to enhance the C-RAN,which is a low-cost and energy-efficient option.Specifically,we consider the uplink transmission where multi-antenna users communicate with the baseband unit(BBU)pool through multi-antenna RRHs and multiple IRSs are deployed between the users and RRHs.RRHs can conduct either point-to-point(P2P)compression or Wyner-Ziv coding to compress the received signals,which are then forwarded to the BBU pool through fronthaul links.We investigate the joint design and optimization of user transmit beamformers,IRS passive beamformers,and fronthaul compression noise covariance matrices to maximize the uplink sum rate subject to fronthaul capacity constraints under P2P compression and Wyner-Ziv coding.By exploiting the Arimoto-Blahut algorithm and semi-definite relaxation(SDR),we propose a successive convex approximation approach to solve non-convex problems,and two iterative algorithms corresponding to P2P compression and Wyner-Ziv coding are provided.Numerical results verify the performance gain brought about by deploying IRS in C-RAN and the superiority of the proposed joint design.
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.
文摘本文研究了智能反射面(IRS)辅助OFDMA(Orthogonal Frequency Division Multiple Access,正交频分多址接入)云无线接入网(C-RAN)的下行链路传输系统,其中基带处理单元(BBU)池通过多个远端射频头(RRH)与多个用户进行通信.RRH到用户的接入链路采用OFDMA接入技术.对于BBU池到RRH,采用无线前传链路,并且部署多个IRS以增强链路传输能力.在BBU池和每个RRH发射功率约束下,本文提出通过联合优化前传链路和接入链路资源配置使下行用户和速率最大化.由于该资源配置问题是非凸的,首先采用连续凸逼近(SCA)对目标以及约束条件进行转换.其次,将转换后的问题拆分成三个子问题来交替性求解.最后,计算机仿真结果显示了所提出的联合资源分配方法与其他基准方案相比具有显著的传输性能增益.
