Optical Mobile Fronthaul Research Articles

5G NR RoF System Based on a Monolithically Integrated Multi-Wavelength Transmitter

We propose and demonstrate the use of a monolithically integrated multi-wavelength transmitter for multiband 5G new radio (NR) radio-over-fiber (RoF) systems, simultaneously operating in the standalone (SA) and non-standalone (NSA) modes. The novel integrated photonic circuit, integrating eight tunable and directly modulated distributed feedback lasers, aims to reduce the transmitter complexity and footprint, enabling compact, high-performance and low-cost 5G solutions for frequencies up to 10 GHz. We report the implementation of a 4G/5G shared optical mobile fronthaul using two 5G NR and a LTE-A signals, evaluated in two distinct scenarios, as a function of root mean square error vector magnitude (EVMRMS) and in accordance to the 3GPP Release 15 requirements. In the first phase, three optical carriers in C-band are independently modulated with three mentioned RF signals, whereas subcarrier multiplexing (SCM) is applied to the second scenario for jointly modulating an optical carrier at 1554 nm. Gbit/s throughput is demonstrated for validating the applicability of our monolithically integrated multi-wavelength transmitter either for enabling multiapplication and/or diverse RF standards, using a single wavelength or multiservice exploiting different wavelengths from an unique optical source.

A comprehensive optical mobile fronthaul network toward high-fidelity, flexible and low-latency transport

Cloud radio access network and the subsequent next-generation fronthaul interface are the key solutions for the upcoming 5G deployment. In both architectures, the baseband units (BBUs) are centralized, and remote radio units (RRUs) are separately allocated, where the BBUs and RRUs are connected through a fronthaul network with common public radio interface (CPRI) and its subsequent eCPRI. Today, a cost-effective fronthaul transport network is paramount for 5G deployment. In this paper, we proposed a comprehensive optical mobile fronthaul network (COMF) to meet the various fronthaul requirements. The COMF design has the features of low-cost high-speed transmission, bandwidth reduction, low link latency, high signal fidelity and flexible connection. To support both the CPRI and eCPRI interfaces, several low-cost high-bitrate optical transmission techniques are comparatively studied. Meanwhile, time-division multiplexing-based analog radio over fiber solution is also discussed. Furthermore, to achieve flexible fronthaul delivering, optical switching technologies based on arrayed waveguide grating router and wavelength selective switch are presented, respectively. In the end, the novel strategies for low-delay resource management are investigated.

Hierarchical Edge Cloud Enabling Network Slicing for 5G Optical Fronthaul

Network slicing has been proposed as an innovative concept to partition a physical network into different configurable slices, thereby allowing the network to meet the diverse requirements of expected services in the 5G era. Existing network-slicing schemes focus almost exclusively on the partitioning of the core network or the radio access network. However, to achieve greater flexibility and better resource utilization in service provisioning, the potential of network slicing in the 5G optical mobile fronthaul (MFH) network should be jointly exploited. To address this challenge, we propose a flexible hierarchical edge cloud architecture to enable 5G optical MFH network slicing. Additionally, a corresponding integrated network resource management scheme is proposed to support various quality-of-service (QoS) requirements and diverse resource requests of the network slices. Simulation results indicate that the proposed scheme is able to jointly allocate the bandwidth resources to network slices and realize cloud-computing offloading to meet various QoS requirements, and therefore reduce the fronthaul bandwidth burden.

Reconfigurable Optical Mobile Fronthaul Networks for Coordinated Multipoint Transmission and Reception in 5G

The fifth generation of mobile communication is characterized by ultra-dense cellular networks, where massive small cells are deployed in hot spots to increase the network capacity. As a promising technology in the small-cell scenario, coordinated multipoint (CoMP) is proposed to improve cell-edge user throughput by converting inter-cell interference into useful signals. In this paper, we study how reconfigurable fronthaul enabled by optical networks can help improve the CoMP service. According to the baseband unit (BBU) that serves the purposes of coordination, we classify the CoMP service into intra-BBU CoMP and inter-BBU CoMP. Inter-BBU CoMP will cause data exchange between the BBUs, which requires backhaul to support a large bandwidth and low latency. Our proposal is to associate coordinated RRHs with a single BBU to reduce the data exchange. To achieve this goal, we propose two heuristic algorithms: a minimum-cut graph-based lightpath reconfiguration (MCG-LR) and a BBU weightbased lightpath reconfiguration (BW-LR). The two algorithms are emulated on a time and wavelength division multiplexing passive optical network-based fronthaul under different cell conditions. The simulation results show that the reconfigurability of fronthaul can improve the CoMP service through elastic radio resource allocation. In addition, we can observe that MCG-LR achieves a lower inter-BBU CoMP ratio and lower BBU migration than BW-LR after lightpath (wavelength) reconfiguration.

Two-level modulation scheme to reduce latency for optical mobile fronthaul networks.

A system using optical two-level orthogonal-frequency-division-multiplexing (OFDM) - amplitude-shift-keying (ASK) modulation is proposed and demonstrated to reduce the processing latency for the optical mobile fronthaul networks. At the proposed remote-radio-head (RRH), the high data rate OFDM signal does not need to be processed, but is directly launched into a high speed photodiode (HSPD) and subsequently emitted by an antenna. Only a low bandwidth PD is needed to recover the low data rate ASK control signal. Hence, it is simple and provides low-latency. Furthermore, transporting the proposed system over the already deployed optical-distribution-networks (ODNs) of passive-optical-networks (PONs) is also demonstrated with 256 ODN split-ratios.

Wavelength Resource Sharing in Bidirectional Optical Mobile Fronthaul

In this paper, we propose high-capacity spectrally-efficient optical mobile fronthaul (MFH) architectures featuring wavelength resource sharing, where multiple cell sites share one dense wavelength division multiplexing (DWDM) channel instead of occupying a number of separated DWDM channels. In the downlink (DL), subcarrier multiplexing (SCM) is integrated with DWDM passive optical network. The key technical innovation lies in the reception of uplink (UL) signals being optically aggregated with ultrasmall spacing. We introduce two novel schemes for spectrally-efficient and low-complexity upstream transmissions. The first method is based on SCM in remote radio heads (RRHs) and coherent detection in baseband units (BBUs), achieving channel spacing of as small as 100 MHz. For the first time, successful coherent reception of LTE signal, whose symbol rate (15 ksps) is much smaller than the laser linewidth, is achieved by pairing a radio frequency pilot tone from each RRH. Bidirectional transmission of four 20-MHz 16-QAM-OFDM LTE-like signals with 100-MHz spacing aggregated on one wavelength is demonstrated. For the second proposed UL scheme, we report a low-complexity ultradense WDM over DWDM allocation with 1-GHz wavelength spacing and novel phase-noise-insensitive heterodyne detection using MHz-linewidth lasers and an off-the-shelf envelope detector. We experimentally demonstrate the transmission and simple detection of multichannel 100/200 Mb/s OOK or 200 Mb/s 16-QAM-OFDM signals with 1-GHz spacing over 30-km standard single mode fiber using 5-MHz-linewidth lasers. By enabling ultrahigh spectral efficiency, high receiver sensitivity, and low-complexity, the proposed approach achieves a significant breakthrough for future high-capacity mobile fronthaul systems.

SDN-controlled topology-reconfigurable optical mobile fronthaul architecture for bidirectional CoMP and low latency inter-cell D2D in the 5G mobile era.

We demonstrate the first SDN-controlled optical topology-reconfigurable mobile fronthaul (MFH) architecture for bidirectional coordinated multipoint (CoMP) and low latency inter-cell device-to-device (D2D) connectivity in the 5G mobile networking era. SDN-based OpenFlow control is used to dynamically instantiate the CoMP and inter-cell D2D features as match/action combinations in control plane flow tables of software-defined optical and electrical switching elements. Dynamic re-configurability is thereby introduced into the optical MFH topology, while maintaining back-compatibility with legacy fiber deployments. 10 Gb/s peak rates with <7 μs back-to-back transmission latency and 29.6 dB total power budget are experimentally demonstrated, confirming the attractiveness of the new approach for optical MFH of future 5G mobile systems.