A Flexible Subcarrier Multiplexing System With Analog Transport and Digital Processing for 5G (and Beyond) Fronthaul

Abstract

A flexible subcarrier multiplexing system combining analog transport with digital domain processing is presented. By making use of bandpass sampling and applying a systematic mapping of signals into available Nyquist zones, the multiplexing system is able to present multiple signals at the same intermediate frequency at the remote site. This simplifies the processing required for multiple antenna systems. We further propose the use of trackand-hold amplifiers at the remote site. These elements are used to extend the mapping to a mapping hierarchy, offering flexibility in frequency placement of signals and relaxation of analog-to-digital converter bandwidth and sampling rate constraints. The system allows the transport of different numerologies in a number of next generation radio access network scenarios. Experimental results for large signal multiplexes with both generic and 5th-generation mobile numerologies show error-vector magnitude performance well within specifications, validating the proposed system. Simulation results from a system model matched to these experimental results provide performance predictions for larger signal multiplexes and larger bandwidths. Index Terms-Digital signal processing, massive-MIMO (mMIMO), millimeter wave (mmW), mobile fronthaul, radioover-fiber, subcarrier multiplexing (SCM). I. INTRODUCTIONT HE establishment of heterogeneous networking and multiantenna techniques as norms for next generation radio access networks (RANs) means that new network architectures will need to be employed that can seamlessly accommodate such features. These architectures will have to meet differing requirements in terms of data rate, latency constraints, system complexity and cost.Analog transport within the fronthaul, as an alternative to digital transport based either on centralized processing with the Common Public Radio Interface (CPRI) [1], or on alternative functional decompositions [2], [3], can provide high spectral

Integrating Radio-Over-Fiber Communication System and BOTDR Sensor System

“…For further study, the proposed system configuration can be investigated for narrow wavelength spacing between data and sensor system laser wavelengths. The proposed system can be further exploited into DWDM and CWDM based communication system to improve the system performance in terms of larger bandwidth/higher data rate [15]. Furthermore, the BOTDR sensor system can be integrated with other emerging techniques, such as Raman amplification, pump pulse coding and wavelength diversity techniques [19] for further improvement in sensor system performance.…”

Comparison of digital signal processing approaches for subcarrier multiplexed 5G and beyond analog fronthaul

“…Compared to digital transport, analog transport, although susceptible to impairments of distortion and additive noise from RF and optical components, achieves higher spectral efficiencies and alleviates the latency constraints [9], [11][12][13][14][15][16][17][18][19][20][21][22][23]. Analog transport is also capable natively of supporting multiple RAN technologies from different vendors, and for different mobile operators, without interoperability issues, sharing antennas and a single fiber infrastructure (as used in Distributed Antenna Systems) [11], [12].…”

“…Analog transport is also capable natively of supporting multiple RAN technologies from different vendors, and for different mobile operators, without interoperability issues, sharing antennas and a single fiber infrastructure (as used in Distributed Antenna Systems) [11], [12]. Thus, analog transport has gained renewed interest for the fronthaul of the 5G (and beyond) RAN [9], [16][17][18][19][20][21][22][23][24]. Analog Radio-over-Fiber (RoF) can transport multiplexes of the radio signals' bandwidths, using their different carrier frequencies, or through translation to different intermediate frequencies (necessary for MIMO, when the radio signals are at the same frequency), by Subcarrier Multiplexing (SCM).…”

“…Such flexibility/adaptability is possible in an analog fronthaul that employs key Digital Signal Processing (DSP) techniques for the multiplexing/aggregation and de-multiplexing/de-aggregation of channels [19][20][21][22][23][24]. A DSP-assisted analog fronthaul that is inherently flexible, able to scale to different bandwidths, numerologies and modulation formats, was described in [22]. Furthermore, it was shown how such a system could be used with arbitrarily low sampling rates and analog bandwidth at the receiving end (i.e.…”

“…at the RU) by the introduction of limited analog processing. Thus, the focus in [22] was on the receiver side processing and on the proposed mapping technique allowing a simplification of receiver side processing.…”