RoF-Based Mobile Fronthaul Networks Implemented by Using DML and EML for 5G Wireless Communication Systems

Next Generation Fiber-Wireless Fronthaul for 5G mmWave Networks

“…Transforming the IF into the final wireless mmWave carrier signal can easily be performed at the aRRH by employing respective IF-to-RF and RF-to-IF upand down-conversion circuitry. Also, by drawing from the recent development of high-capacity EML-based Fiber-Wireless mmWave/IF a-RoF links [9], [10] and integrated Optical Beamforming Networks (OBFNs) [11], our proposed solution employs OBFNs to maintain the phase of mmWave beams through IF-subcarrier modulation, to replace some costly RF-processing with efficient photonic alternatives, and alleviating the need for complex DSP at the RRH. The OBFNs are followed by an opto-electronic conversion to an electrical IF signal and up-conversion to mmWave RF purely for wireless transmission, simplifying greatly the cell site equipment and simultaneously reducing its power consumption since ADC/DACs are no longer required [7].…”

“…The OBFNs are followed by an opto-electronic conversion to an electrical IF signal and up-conversion to mmWave RF purely for wireless transmission, simplifying greatly the cell site equipment and simultaneously reducing its power consumption since ADC/DACs are no longer required [7]. Instead, this architecture requires centralized DSP processing, capable of sampling, temporarily storing and digitizing the aggregate incoming a-RoF traffic with sampling frequencies of a few tens of GS/s [7]- [9].…”

“…Considering the large available spectrum of NR systems, a-RoF techniques allow spectrally efficient fronthauling of a mmWave channel, by loading it on a low optical IF with simple Intensity Modulation/Direct Detection schemes without occupying excess spectrum [7], while multiple IFs can be synthesized on a single aggregate electrical signal of a few GHz bandwidth. However, the linearity of the a-RoF link will play a pivotal role in the overall system performance and thus a-RoF transmitters have mainly relied on costly Mach-Zehnder Modulators (MZMs), owing to their high linearity and chirpfree operation to alleviate the impact of the fiber chromatic dispersion [9]. Towards circumventing the associated costs when considering network densification deploying conventional chirp-free modulators with external laser source, EMLs exploiting a Distributed Feedback Laser and an Electro-absorption Modulator (EAM) as shown in Fig.…”

“…Towards circumventing the associated costs when considering network densification deploying conventional chirp-free modulators with external laser source, EMLs exploiting a Distributed Feedback Laser and an Electro-absorption Modulator (EAM) as shown in Fig. 3 form more cost-effective solution [9] but have been primarily used in digital communications and advanced modulation format transmissions with DSP techniques recovering the non-perfect linearity. However, joint optimizations of the Fiber-Wireless links have been scarce and constrained to the use of MZMs, few-channels or low bandwidths, and only very recently EMLs were shown to support multiple IF channels with user-rates >1Gb/s and aggregate capacities beyond 10Gb/s [10], satisfying the respective KPIs for multi-user 5G network environments.…”

A New Scheme to Generate Multi-Frequency Mm-Wave Signals Based on Cascaded Phase Modulator and I/Q Modulator

“…In the mobile fronthaul networks (MFH), RoF (Radio over fiber) communication system combines both the large capacity of fiber transmission and the flexible access of wireless delivery. Therefore, it has aroused a wide interest and discussion for large available bandwidth [1], [2].…”