This presentation presents several technologies for future mobile transport networks using the seamless convergence of fiber and wireless access networks. We first present a flexible and efficient mobile fronthaul system for ultra-dense small cells using a convergence of fiber and millimeter-wave systems. We then present a simple and low cost optical system for simultaneous transmission of multiple heterogeneous wireless signals, such as multi-RATs, operators, mobile signals and fronthaul/backhaul signals, using subcarrier multiplexing intermediate frequency over fiber system and efficient data mapping and de-mapping algorithms. Finally, we present an efficient solution to provide high-speed communications to high-speed trains using a seamless convergence of wavelength-division multiplexing radio-over-fiber and linearly located linear cell systems. Author : Pham Tien Dat, NICT Japan Presented at ITU-T Focus Group IMT-2020 Workshop and Demo Day, 7 December 2016. More details on the event : http://www.itu.int/en/ITU-T/Workshops-and-Seminars/201612/Pages/Programme.aspx

1. Technologies for future mobile
transport networks
Pham Tien Dat1, Atsushi Kanno1, Naokatsu Yamamoto1, and Tetsuya Kawanishi1,2
1National Institute of Information and Communications Technology, Japan
2Wasdea university, Tokyo, Japan
FG IMT-2020 Workshop and Demo Day: Technology Enablers for 5G

2. Outline
 Flexible fiber-wireless mobile fronthaul
• Downlink system
• Bidirectional transmission
 Seamless fiber-wireless for moving cells
 Multiple radios over fiber system
 Conclusion
2

3. Flexible fiber-wireless transport systems
BBU BBU BBU
BBU pool
Core
network
MUX/
DEMUX
Control
office
MUX/
DEMUX
RRH
RRH
RRH RAU RAU RAU
3

4. Fiber-wireless convergence
Seamless optical and MMW connection: Low latency, low power
RAU
Digital
E/O O/E
DSP
FE
LO
MMW
Conventional optical-MMW link: Large latency, high power
RAU
Digital
E/O O/E FE
Opt. LO
MMW
4

5. Operating principle
λ1
λ2
f
E/O O/E Down.
Microwave
Millimeter
Microwave
λ1
λ2
O/E
converter
Optical fiber
λ
λ1 λ2
Δf
Freq.
f = |c/λ1-c/λ2|
Up.Down.E/OO/E
Microwave
LO
Millimeter
Microwave λ
5

6. VSA: Vector Signal Analyser
LNA: Low Noise Amplifier
ATT: Attenuator
OBPF: Optical Band Pass Filter
MZM: Mach-Zehnder Modulator
EDFA: Erbium-Doped Fiber Amplifier
VSG: Vector Signal Generator
PD: photo-detector
Downlink system: experimental setup
6
P. T. Dat et al., ECOC (2016)
1 m
89.2 – 92.45
GHz
CS
AWG
Two-tone
opt. gen.
MZM
20km
PCAWG
LNALNA
RRH
88.1 GHz
LTE-A
F-OFDM
÷
PDPA
RAU
ATT
1,549.4 1,550 1,550.6
-90
-70
-50
-30
-10
10
Wavelength (nm)
Power(dBm)
EDFA
EDFAOBPF OBPF

7. Downlink system: experimental results
7
Data 1 Data 2
-2 0 2 4 6 8
Tx. LTE-A Power (dBm)
8
12
16
20
24
EVM(%)
Sig. 1, data 1
Sig. 1, data 2
Sig. 2, data 1
Sig. 2, data 2
Sig. 3, data 1
Sig. 3, data2
Sig. 4, data 1
Sig. 4, data 2
0 1 2 3 4 5 6
Rx. Opt. Power (dBm)
8
12
16
20
24
EVM(%)
Sig. 1, data 1
Sig. 1, data 2
Sig. 2, data 1
Sig. 2, data 2
Sig. 3, data 1
Sig. 3, data 2
Sig. 4, data 1
Sig. 4, data 2
Performance versus received optical powers Performance versus LTE-A signal powers
P. T. Dat et al., ECOC (2016)
1 1.5 2 2.5 3 3.5 4 4.5
-70
-60
-50
-40
-30
-20
-10
Frequency (GHz)
Power(dBm)
Sig.1
Sig.2
Sig.3 Sig.4

8. Bidirectional system: experimental setup
LNA LNA
Remote
Radio Head
ED
DL LTE-A
inter-band 2
VSG
UL LTE-A
LO
96 GHz
Did.
DL LTE-A
inter-band 1
VSA_1
VSA_2
Sync.
MZM
EDFA
PD PA10 km 92.5 GHz
Com.
DL LTE-A
inter-band 1
Central Station
Remote Antenna Unit
DL LTE-A
inter-band 2
VSG_2
ATT
RoF
Rx.
VSA
UL LTE-A
RoF
Rx.
LNA
ED
LNA
96 GHz
VSG_1
ATT
Sync.
EDFA
Opt. MMW
Gen.
830 840 850 860 870
-120
-100
-80
-60
-40
Frequency (MHz)
Power(dBm)
2.580 2.59 2.6 2.61 2.62
-120
-100
-80
-60
-40
Frequency (GHz)
Power(dBm)
8

9. Bidirectional: experimental results
 Successful bidirectional transmission for CA LTE-A signals
 Applicable for future 5G signal transmission (256-QAM with EVM < 3.5%)
 PONs can be applied for optical transport (ITU-T req. for PONs: 15 dB)
P. T. Dat et al., OFC (2015)
DL LTE-A signal
-2 0 2 4 6
Rx. Opt. Power (dBm)
0
2
4
6
8
10
12
EVM(%)
64-QAM, interband 1
64-QAM, interband 2
-2 0 2 4 6
Rx. Opt. Power (dBm)
0
2
4
6
8
10
12
64-QAM, interband 1
64-QAM, interband 2
Only DL With UL
-15 -10 -5 0 5
Rx. Opt. Power (dBm)
2
4
6
8
10
12
64-QAM, no DL
64-QAM, with DL
UL LTE-A signal
>17 dB
9

10. Seamless fiber-wireless for moving cells
Millimeter-wave
WDM Radio over Fiber
Linearly located remote cells
Metro/Access Network Control Station
RAU #1 RAU #2 RAU #n
Multiplexer
Aisle Seat
From outside
P. T. Dat et al., IEEE
Commun. Mag. (2015)
10

11. Network control and moving cells
Switch
Metro/Access Network
Location
position
Switch
control
Uplink power
λ1, λ2 λ3, λ4
Control Office
WDM
RoF Tx.
WDM
DEMUX
λ n-1, λn
Signal
Processing
Units
Modulation
Modulation
Modulation
11

12. Proof-of-concept: experimental setup
DPMZM: Dual-parallel MZM
OBEF: Optical band pass elimination filter
OBPF: Optical band pass filter
ATT: Attenuator
P-S: Power Splitter
ISO: Isolator
PS: Phase shifter
EDFA 1 km
MZM2 EDFA
LD2
20 km
CS
ATT
(1)
LD1 MZM1
DPMZMLD
OBEF EDFA OBPF
Opt. MMW Gen. 1LO_1
(3)
(2)
RAU_1
PD PA
X
PD
LNA
RoF
Tx.
LNA
P-S
ATT. PA
ISO ISOPS
SHD
TAU
Opt. MMW Gen. 2ATT
ATT
RoF
Rx.
ATT
LO_2LO_3
VSA
PC VSG
(4)
(5)
(6)
1548 1552 1556
-80
-60
-40
-20
0
Wavelength (nm)
1547 1551 1555
-80
-60
-40
-20
0
Wavelength (nm)
1555 1556 1557
-80
-60
-40
-20
0
Wavelength (nm)
1548 1550 1552
-80
-60
-40
-20
0
Wavelength (nm)
Power(dBm)
1548 1549 1550 1551
-80
-60
-40
-20
0
Wavelength (nm)
1548 1550 1552
-80
-60
-40
-20
Wavelength (nm)
1548 1550 1552
-80
-60
-40
-20
Wavelength (nm)
(1) (2) (3) (3) (4) (5) (6)
RF cable
10 MHz
RAU_2
AP
20 GHz
40 GHz
41.9 GHz
23.125 GHz
IF
LO
P. T. Dat et al., OFC (2016)
12

13.  Good performance for both backhaul and over in-train networks
 High-spectral efficiency, low fiber-dispersion, cost effective system
-6 -4 -2 0 2 4
4
6
8
10
IF Tx. Power (dBm)
EVM(%)
-4 -2 0 2 4 6
4
6
8
10
IF Tx. Power (dBm)
32-QAM, CH1
64-QAM, CH1
32-QAM, CH2
64-QAM, CH2
32-QAM, CH1
64-QAM, CH1
32-QAM, CH2
64-QAM, CH2
P. T. Dat et al., OFC (2016)
Proof-of-concept: experimental results
30-MHz OFDM signal 50-MHz OFDM signal
13

14. Multiple radios over fiber
14
Signal-1 Subcarrier
mapping
IFFT-1 CP-1
Subband-1
filter
Signal-K
Subcarrier
mapping IFFT-K CP-K
Subband-K
filter
+
Multi-RATs over seamless fiber-wireless system
Data mapping using F-OFDM
4G or control
signals DAC
+ E/O
Optical LO
BBU pool-1
BBU pool-N
DSP-based
mapping DAC
MFHRAT-1
4G LTE
O/E
 CPRI for fronthauling: bit rate >>
100 Gb/s/cell.
 RoF: high-speed components,
massive systems
Cooperation of optical and
radio access networks

15. Multiple radios over fiber: experimental setup
20 km
MZM
EDFA
LD
CS
DPMZMLD
EDFA OBPF
Frequency
Doubler
VSG VSG
LTE-A
IF
Com.
AWG
12 GHz
ATT
RRH
PD
PDATT
25-GHz
RAT
LPF
IF
signal
LO signal
OBPF
OBPF
VSA
21 GHz
User
RAU
PDATT
Div.
LTE-A
X4
OBPF
ATT PDOBPF
2.5 m
96-GHz
MFH
95 GHz
OSC
RRH
HPF
MZM: Mach-Zehnder Modulator
EDFA: Erbium-Doped Fiber Amplifier
VSG: Vector Signal Generator
Com.: RF combiner
PD: photo-detector
Did. RF Divider
VSA: Vector Signal Analyser
LNA: Low Noise Amplifier
ATT: Attenuator
(O)BPF: (Optical) Band Pass Filter
PC
15
1555.6 1556
Wavelength (nm)
-90
-70
-50
-30
-10
10
Power(dBm)

16. Multiple radios over fiber: experimental results
-8.5 -7.5 -6.5 -5.5 -4.5
Rx. Opt. Power (dBm)
10
12
14
16
18
20
EVM(%)
Signal 1
Signal 2
Signal 3
Signal 4
6 8 10 12 14 16
Tx. LTE-A Power (dBm)
10
12
14
16
EVM(%)
Signal 1
Signal 2
Signal 3
Signal 4
0.5 1 1.5 2 2.5 3
Frequency (GHz)
-110
-90
-70
-50
-30
Power(dBm)
OFDM LTE-A
Sig. 1 Sig. 2 Sig. 4Sig. 3
OFDM NOMA (16 x 16) SCMA
3.96 4 4.04
Frequency (GHz)
-90
-50
-10
Power(dBm)
OFDM
FBMC
-10 -8 -6 -4
Rx. Opt. Power (dBm)
2
4
6
8
OFDM
OFDM NOMA
OFDM SCMA
FBMC
-18 -14 -10 -6
Rx. Opt. Power (dBm)
1
2
3
4
CC1 (20 MHz)
CC2 (20 MHz)
CC3 (20 MHz)
EVM(%)
F-OFDM Signal
LTE-A Signal New RAT signal (OFDM/FBMC) 16

17. Summary
 Seamless convergence of fiber-MMW would be a
potential solution for future mobile fronthauling when
fiber cable is not available.
 Convergence of WDM IFoF and linearly located
distributed antenna systems is very promising for high-
speed communication to high-speed trains.
 Co-design and cooperative fiber-radio access networks
would be the key for future MMW and massive MIMO
mobile signal, and multi-RAT transmission.
17

18. Thank you
ptdat@nict.go.jp
This work was conducted as a part of the “Research and development
for expansion of radio wave resources,” supported by the Ministry of
Internal Affairs and Communications (MIC), Japan.