1. INDIAN INSTITUTE OF TECHNOLOGY ROORKEE
Signal Enhancement for
Session EL4.1 : PaperID_177
Department of Electronics and Communication Engineering
Indian Institute of Technology Roorkee
Anurag Vijay Agrawal, Dr. Meenakshi Rawat
Green HSR Reliable Communication
with LTE-R using MIMO-DPD
09.11.2019
anuraga@ieee.org
3. 3
Introduction
• RAILWAY, a vital service to human society worldwide, is the transport
backbone of a sustainable economy and is a perfect fast, safe, economic
and green solution to various global problems
• Further, the demand for long distance rail journeys paves the way for
High Speed Railways (HSR) for its low cost and high convenience
benefits.
• Intelligent transportation systems (ITS), not only improve the quality of
services and safety measures provided during train journeys but make
the best utilization of railway network infrastructure.
• Different wireless communications standards, like Global System for
Mobile communications for Railways (GSM-R) and Long Term Evolution
for Railways (LTE-R), affect these ITS services differently.
• In addition, the complimentary relationship between multiple-input-
multiple-output (MIMO) and OFDM schemes makes a MIMO-OFDM
system most suitable to be used within LTE-R standard for HSR
communications.
eNB
4. 4
Introduction
• Modern complex modulation schemes are spectrally efficient, but high
peak-to-average power ratio (PAPR) puts a challenge for base stations to
have efficient radio transmission capabilities in terms of energy efficiency
as power consumption for each base station (BS) has been increasing.
• In downlink transmission, the Radio Frequency Power Amplifier (RFPA)
provides high power to connect BS to the user equipment (UE).
• The RFPA is also one of the most expensive and power-seeking devices
in the BS.
• As HSR users worldwide need additional base stations along newer rail
tracks to avail various high speed and reliable ITS services, more RFPAs
will be needed. Additionally, multiple antenna configuration-based
transceivers are the viable solutions to the requirements of enhanced
system capacity and superior throughput rates in modern practical
wireless communication structures. However, each transmit path has its
own RFPA, therefore, efficient usage of RFPA becomes a crucial aspect
in MIMO communication systems.
5. 5
GSM-R, LTE AND LTE-R SPECIFICATIONS
Parameter GSM-R LTE-R LTE
Frequency bands GSM 450 / 480 /
850/900,DCS 1800,
PCS 1900
LTE 700 / 800 / 900 / 1500 /
1700 / 1800 / 2100 / 2600
LTE 800 / 1800 /
2600
Data rate < 200 kbps > 2 Mbps ≤ 25 Mbps (for
uplink),
≤ 75 Mbps (for
downlink)
Bandwidth 0.2 MHz ≥ 10 MHz 1.4 MHz – 20 MHz
Modulation Scheme Gaussian MSK QPSK, 16QAM, 64QAM QAM (16/64/128)
Multiplexing
Scheme
TDMA OFDMA, SCFDMA OFDM
Signal transmission Circuit- Switched Packet- Switched (UDP-
based)
Packet-Switched
Data Packet
retransmission
No Yes
(UDP- based)
Yes
(IP-based)
Antenna Configuration SISO MIMO MIMO, Massive
MIMO
All IP (native) No Yes Yes
Market support Until 2025 Yes, Building standards Yes, Matured
8. 8
SYSTEM MODEL PARAMETERS
Parameter Value(s)
Transmission System LTE-R, Downlink
Channel Type Outdoor LoS, Indoor LoS
Traffic Type Full Buffer Model
Sampling Frequency 15.36 MHz
Channel Bandwidth 10 MHz
Carrier Frequency 2 GHz
Diversity Mode Full, Transmit
Antenna Configuration SISO, MIMO
Frame Mode FDD
FFT Size 1024
Radio Frames 200 (in numbers)
Subframes 2000 (in numbers)
Radio Frame Duration 10 ms
Coding Scheme FEC Turbo Coding,
Rate = 1/6
Mapping Type 64-QAM
Resource Block 12 tones over 1 ms
Subcarrier Spacing 15 kHz
Channel Estimation Scheme Minimum Mean Square Error
MIMO Detection Scheme Maximum Likelihood Detection
RFPA Type Doherty
Parameter
Value(s)
inside-
station
infrastructure-
to-train
Speeds of interest 0-3 kmph 0-200 kmph
Inter-site Distance 60 m 1732 m
BS Antenna Height 6 m 35 m
BS Antenna Gain 0 dBi 17 dBi
Minimum Distance
between UE and
the serving cell
3 m 35 m
9. 9
BLER without DPD at various train speeds for SISO and MIMO configurations
17. 17
Conclusion
• The RFPA nonlinearity compensation using DPD for green
HSR communications is analyzed.
• The analysis is done for the infrastructure-to-train and inside-
station scenarios with and without DPD arrangement.
• The BLER and data throughput performance metrics are
evaluated for the emerging 10 MHz LTE-R communications
system with SISO and MIMO modes in terms of SNR for
64QAM downlink mapping at various train speeds upto 200
kmph and at various pedestrian speeds upto 3 kmph.
• It is investigated that the recommended LTE-R
specifications with MIMO-DPD result in a higher block error
rate due to the fast fading channel effect, and the radio link
establishment procedures need more time for radio access
with increasing speeds.
18. 18
Conclusion
• While analyzing the behavior of a modern practical
communications system, RFPA should never be assumed
linear.
• The paper establishes that RFPA nonlinearity deteriorates
the BLER and throughput performances, and that, without
DPD, more than 50 % blocks are received with errors to the
total data blocks transmitted over the RF channel.
• The BLER and throughput performances degrade further
with increasing train speeds. It implies that more
transmission power is needed to send signals at high
mobility. The additional signal power is to be given if
nonlinearity is not compensated earlier. It is also revealed
that LTE-R achieves successful data transmission with DPD
for even low strength signals.
19. 19
Conclusion
• The power requirement to drive RFPAs for reliable
broadband HSR communications at higher speeds is more,
even with DPD.
• The paper further establishes that the DPD technique, when
combined with MIMO schemes, gives optimal results and is
the ultimate approach to achieve reliable Green HSR
communications.
21. 21
Airborne Communications
• Airborne Communication utilizes two basic building blocks:
• HAP-based communication networks
• LAP-based communication networks
Communication
System
eNB
22. 22
Introduction
• The authors investigate a three-dimensional (3-D) multiple-input-multiple-
output (MIMO) Air-to-Ground (A-to-G) multipath Rician fading channel in
the simulation environment of MATLAB/SIMULINK.
• The analysis took place for the fading channel second-order statistics with
the key performance indicators, Level Crossing Rate (LCR) and Average
Fade Duration (AFD).
• The paper presents multiple measurements to carry out the effects of
transmitter speed, receiver speed, and the Rician factor on the LCR and
the AFD parameters.
• The authors analyze the low altitude platform (LAP) Airborne
Communications, and the results are useful for the modeling of LAP 3-D
MIMO propagation channels and the performance analysis of Airborne
communication systems.
Communication
System
eNB
23. 23
Practical MIMO Communication System
Parameters
Parameter Value(s)
Transmission System Downlink
Channel Type LOS Indoor Hotspot
Traffic Model Full Buffer
Channel Bandwidth 10 MHz
Diversity Mode SFBC MIMO Diversity
Antenna Configuration SISO 1×1, MIMO 2×1, MIMO 4×1
Frame Mode FDD
Number of Radio Frames (RFs) 200
Number of subframes per RF 10
RF Duration 10 ms
FEC Coding Scheme Turbo Coding
Carrier Frequency 2 GHz
Sampling Frequency 15.36 MHz
Mapping Type 64-QAM
Resource Block 12 tones over 1 ms
Tone Spacing 15 kHz
FFT Size 1024
Channel Estimation MMSE
MIMO Detection MLD
Table 1
System
Parameters
33. 33
Discussion
Table 2
BLER, EVM and Throughput values for different MIMO and RFPA configurations
MIMO Type -------> SISO 1×1 MIMO 2×1 MIMO 4×1
Study Parameters RFPA DPD +
RFPA
RFPA DPD +
RFPA
RFPA DPD +
RFPA
BLER 0.95 0.525 0.8 0.3 0.675 0.1
Throughput Fraction 5% 47.5% 20% 70% 32.5% 90%
EVM -4dB -12dB -5.5dB -12.5dB -7dB -13.75dB
34. 34
Conclusion
The analysis is done for RFPA nonlinearity effect on reliable downlink data transmission to
high data traffic loads suitable for propagation in urban cities.
It is found that after compensating RFPA nonlinearity, MIMO 4×1 has better performance
than both MIMO 2×1 and SISO 1×1.
The BLER performance for MIMO 4×1 improves by 3 times and 5 times, the throughput by
28.57 % and 89.47 %, and the EVM improves by 10% and 15% from MIMO 2×1 and SISO
1×1 respectively.
The BLER, throughput and EVM performances with MIMO 4×1 (DPD+RFPA) configuration
also improves by 6 times, 2.77 times and about 2 times respectively when compared with
the MIMO 4×1 (without DPD) values.
35. 35
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