Photonics Defined Radio

A New Paradigm for Future Mobile Communication of B5G/6G

Zong Baiqing

, Zhang Xiaohong

, Li Xiaotong

, Wang Jianli

and Zhang Senlin

R&D Center (Shanghai), ZTE Corporation, Zhangjiang High-Tech Park, Shanghai, China

Global Marketing and Solution, ZTE UK Ltd, London, U.K.

Keywords: Fibre Optics Links and Subsystems, Radio Frequency Photonics, Photonic Integrated Circuits, Coherent

Communications, Optical Signal Processing, Radio Access Network, Beyond 5G.

Abstract: Photonics defined radio, a new and possibly standardized paradigm, is proposed, converging integrated

coherent optics, integrated microwave photonics and photonic DSP, and expected to dominate the designs

of future communication and sensing systems. The applications of photonics defined radio are also

discussed in the next generation cloud-based radio access network (CloudRAN), sensing and

communication integrated system, as well as artificial intelligence radio.

1 INTRODUCTION

Optics and photonics have made many progresses in

the past years, especially in the areas of integrated

coherent optics, integrated microwave photonics,

optical frequency comb and photonic digital signal

processing.

In 2006, Infinera reported the first

commercially deployed and indium phosphide (InP)

based large-scale photonic integrated circuits (LS-

PICs) of coherent optics (Jacco Pleumeekers et al,

2006). This breakthrough brought optical coherent

transmission back. Nowadays, coherent optical

transmission follows the trend migrating from long

haul market into metro and access arena with main

applications in mobile fronthaul of 5G/B5G. To use

linear phase modulation (PM) and coherent

detection (CD), high linear RF photonic or coherent

radio over fibre (CRoF) links have extensively been

realized. In particular, to employ a novel attenuation

counter-propagating optical phase-locked loop

(ACP-OPLL) demodulator the ultra-high linear

CRoF links have been obtained, and to use a hybrid

integrated or a monolithically integrated ACP-

OPLL, 140dB/Hz

2/3

spurious free dynamic range

(SFDR) over 1GHz bandwidth has been expected (S.

Jin et al, 2014). As a result, CRoF shows a

promising potential to future true cloud-based

5G/B5G applications.

Integrated microwave photonics (IMWP) has

become the most active area of current research and

development in microwave photonics. Based upon

various material platforms such as indium phosphide

(InP), silicon on insulator (SOI), Si photonics and

silicon nitride (Si3N4), several particular

functionalities and sub-systems have be realized

(David Marpaung et al, 2014), including tunable

filtering, optoelectronic oscillation, true time delay,

frequency up and down conversion, etc. In the mode

of monolithic or hybrid photonic circuits, IMWP is

evolving towards the so-called application specific

photonic integrated circuits (ASPICs) where a

particular circuit and chip configuration are designed

to optimally perform a particular functionality.

Furthermore, a photonic system-on-chip (PSoC) is

being developed, such as EU HAMLET project

which is the joint development of a new kind of

photonic frontend for future 5G/B5G mobile

networks in the frequency range of 28GHz, and

using hybrid photonic integration technology to

interface seamlessly the optical fronthaul and radio

access of the remote antenna units (RAU)

(http://www.ict-hamlet.eu/).

Coherent light source with wider spectrum is

critical to IMWP, CRoF and photonic digital signal

processing (DSP). Optical frequency comb (OFC) is

a revolutionary advance in broadband coherent

source. However, the bulk OFCs based on existing

mode-locked lasers have limited applications in real-

world due to their size, weight, power and cost.

Electro-optic or parametric frequency combs such as

Kerr micro-combs have later evolved based upon

Baiqing, Z., Xiaohong, Z., Xiaotong, L., Jianli, W. and Senlin, Z.

Photonics Deﬁned Radio - A New Paradigm for Future Mobile Communication of B5G/6G.

DOI: 10.5220/0006551501550159

In Proceedings of the 6th International Conference on Photonics, Optics and Laser Technology (PHOTOPTICS 2018), pages 155-159

ISBN: 978-989-758-286-8

155

chip-compatible monolithic micro-resonators (J. E.

Bowers et al, 2016). Together with PIC, integrated

OFC provides the opportunity for applications in the

fields such as optical arbitrary waveform generation

(OAWG), microwave photonic signal processing,

optical DSP, dense wavelength division multiplexed

coherent transmission systems and future 5G/B5G

large-scale antenna systems in which an OFC-based

photonic frontend array will be an ideal option for

RF beam forming and steering.

To overcome the timing jitter and bandwidth

limitations of electrical ADC, photonic analog-to-

digital conversion (PADC) has been the subject of

extensive research in recent years (Thomas R. et al,

2015). Nowadays, in order to efficiently connect the

optical sampling module and eliminate the electrical

device limitation, it is essential to realize the all-

optical operation in both quantization and signal

processing. Extensive optical quantization and

photonic DSP schemes have been proposed. The

proposed photonic DSP is capable of performing

reconfigurable signal processing functions including

temporal integration, temporal differentiation and

Hilbert transformation (Weilin Liu et al, 2016). The

demonstration of photonic DSP also implies that the

chip-scale fully programmable all-optical DSP has

great potential for achieving a photonics defined

system.

In spite of above mentioned advances, the

applications of integrated optics and photonics in

radio systems are still too small and fragmentary. On

one hand, these technologies belong to different

disciplines and technological areas, as a result, there

are almost as many technologies as applications and,

due to this considerable fragmentation, the market

for many of these application-specific technologies

is too small to justify further development into low-

cost industrial mass-volume manufacturing

processes (Daniel Pérez et al, 2016). On the other

hand, MWP as a complementary method for

designing radio systems was proposed early several

decades ago, and was determined that it is difficult

to become a dominate paradigm for designing radio

systems. Moreover, at the present state MWP is

addressing lower volume market, hence lower

volume PIC productions. These are the aspects that

may force PIC technology players to take a different

approach to integrated MWP (Daniel Pérez et al,

2016). However, the next generation of radar

systems and B5G even 6G mobile networks, in

which the systems will be with higher carrier

frequencies for smaller antennas and broadened

bandwidth for increased resolution, need a new

paradigm and disruptive technology.

Integrated

Coherent

Optics

Integrated

CRoF

IMWP ASPIC/PSoC

OFC

Chip Scale

OFC

PADC

All Photonic

DSP

Photonics

Defined

Radio

Figure 1: Convergence and evolution of PDR.

Photonics Defined

Radio ( B5G/6G )

Software Defined

Radio (4G Era)

Digital Radio

( 2G Era)

Figure 2: Key enabling technologies via intergenerational

evolution of mobile networks.

In addition, standardization is an important

aspect for new technology introduction into the

market and support of a healthy ecosystem. To

overcome the above problems, in this paper, we

propose a new and possibly standardized paradigm

named photonics defined radio (also called

photonics-based radio or photonic radio),

converging integrated CRoF, IMWP and photonic

DSP, and expected to dominate the designs of future

radio and sensing systems. Referred to digital radio

for 2G and software defined radio for 4G, photonics

defined radio (PDR) will be the fundamental

enabling technology of B5G/6G. Inspired by large

scale RAN market, PDR will drive and promote

mass production and development of PIC. Fig.1 and

Fig.2 show the convergence and evolution of PDR,

the key enabling technologies via intergenerational

evolution of mobile networks, respectively.

PHOTOPTICS 2018 - 6th International Conference on Photonics, Optics and Laser Technology

156

2 THE CONCEPT AND

ARCHITECTURE OF

PHOTONICS-DEFINED RADIO

The key idea of PDR is to build an open,

standardized, modular radio system by analog and

digital photonic signal processing. PDR has also the

features of ultra-broadband spanning from

microwave to light, EM immunity and flexibility.

Fig.3 shows the function model of PDR. The

photonic frontend (PFE) with optional RF frontend

(RFE) performs the transmission, reception and

conversion of light or RF signal. The photonic

engine (PE) implements the signal generation and

processing in optical domain. The functions of

spectrum computing (SC) are that, they act as

electronic arbitrary waveform generation (eAWG),

symbol generation, electronic DSP and deep

cognitive radio engine. Configurations can be

programmed to offer the main functionalities

required for PDR by software and control module.

Fig.4 is the network architecture of next generation

CloudRAN based on PDR.

OFC

PFE

Software and

Control

Figure 3: The function model of PDR.

Spectrum Computing

Cloud

Photonic Engine

Cloud

MUX/WSS

PFE

RFE

Figure 4: The network architecture of NG CloudRAN

based on PDR.

3 THE APPLICATIONS OF

PHOTONICS-DEFINED RADIO

3.1 All Photonic, All Coherent and Full

Spectrum CloudRAN

Fig.5 is the building blocks of PE of PDR. In PE, the

interface between PE and PFE is transparent

coherent optical interface, and its Tbit-capacity is

high enough to support a true cloud-based RAN. On

the other hand, the signal processing in SC is

electrical coherent processing, so PDR is a

hierarchical coherent system in RF and optical

domains. Fig.6 shows an all photonic RAU or PFE

with multi-antennas. At the downlink, the optical

signals are forwarded to the integrated coherent

receivers (ICR), where they are detected and

processed. Due to high-power output of the uni-

traveling carrier photodetector (UTC-PD) (Zhanyu

Yang et al, 2015), arrays of UTC-PD convert the

optical signals to electrical signals that are directly

used to drive the array antenna elements. At the

uplink, the array antenna elements feed RF signals to

an array of graphne-based electro-absorption

modulators (GP-EAMs), in which RF signals are up-

converted to optical signals by optical IQ

modulation (IQM). At last, the optical signals are

multiplexed and sent to the optical network. Thus,

all photonic PFE and PE build an all photonic

CloudRAN. In addition, arrays of ICR and GP-EAM

can slice the RF and optical spectra in a very large

bandwidth, resulting in a full spectrum CloudRAN.

OFC

Wavelength Bank

OFC

ADC/DAC

OFC

PM/IQM

ICR/PADC

ADC/DAC Farm

PM/IQM Array

ICR/PADC Array

Figure 5: The building blocks of PE of PDR.

Photonics Deﬁned Radio - A New Paradigm for Future Mobile Communication of B5G/6G

157

OPLL

To PE

From PE

Circulator

DEMUX

MUX

IQM

Antenna

ICR+UTC-PD

OFC

Figure 6: All photonic PFE or RAU with multi-antennas.

3.2 Radar, LiDAR and Communication

Integrated System

In Fig.6, if the antenna array is arranged as a hybrid

antenna array of RF and optical antennas, PFE can

be used as RF and optical wireless systems,

simultaneously. For RF wireless systems, Radar and

RF wireless communication are typical applications.

For optical wireless systems, LiDAR and coherent

free-space optical (FSO) communication are

practical applications. Spanning from RF to optical,

PDR can achieve a hyper-spectral integrated system

for sensing and communication applications.

3.3 Artificial Intelligence Radio -

RadioAI

A significant challenge for future cognitive radio

systems is to instantaneously analyze RF signals

over a extreme broadband to 100GHz or more, in

real time without any scanning in frequency, and

without any prior knowledge of the signals, carrier

frequency as well as modulation format (K. D.

Merkel et al, 2014). Due to the limited bandwidth

and less agile hardware platform, conventional

cognitive radio faces a big gap between flexible,

effectively building block and the deployment in

mobile networks. PDR provides extreme broadband

and even full spectrum capacity, so it will be an

ideal platform of future cognitive radio for B5G/6G.

In addition, recent advances in machine learning

(ML) have made possible significantly different

approaches in RF signal processing, spectrum

mining and RF mapping. Unfortunately radio signal

processing has been notably absent from much of

this recent work, but the potential for applications of

recent advances in machine learning to the radio

domain is enormous (Tim O’Shea and Nathan West,

2016). Combining PDR with machine learning, a

novel framework of future cognitive radio named

artificial intelligence radio - RadioAI (or

RadioML/RadioDL) will be a key paradigm and

enabler of B5G/6G. Extreme wideband of PDR

generates a great amount of data from spectrum

sensing, providing big and well curetted datasets to

allow ML to effectively train and learn with large

parameter spaces. Fig.7 shows the framework of

RadioAI based on PDR. A PDR is used as an

extreme broadband radio platform implemented with

open interface that can be programmed to transmit

and receive a variety of waveforms. A RadioAI

engine in spectrum computing cloud is composed of

a datasets, inference engine, and a learning engine.

A well-defined API dictates communication between

the RadioAI engine and the PE/PFE.

Inference

Learning

PFE/PE

RadioAI Engine

Datasets

PDR Hardware

Platform

Spectrum Computing Cloud

Figure 7: RadioAI framework based on PDR.

4 CONCLUSIONS

In summary, the applications of integrated optics

and photonics in radio systems are still too small and

fragmentary due to the fragmentation of disciplines

and technologies. And the next generation of radar

systems and B5G/6G mobile networks need a new

paradigm and disruptive technology. Therefore, we

propose the concept of photonics defined radio, a

new and possibly standardized paradigm,

converging integrated coherent optics, integrated

microwave photonics and photonic DSP, and

expected to dominate the designs of future

communication and sensing systems. The potential

applications of photonics defined radio are also

PHOTOPTICS 2018 - 6th International Conference on Photonics, Optics and Laser Technology

158

discussed, including next generation CloudRAN,

sensing and communication integrated system, as

well as artificial intelligence radio – RadioAI.

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