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eLTE – The Best Choice for
CBTC Radio Bearer
UNITED MECHANICALL &ELECTRICAL | 众合机电
Contents
2
2. Current Problems in CBTC Radio Bearer
1. Introduction to UNITED MECHANICAL & ELECTRICAL
3. CBTC LTE Bearer Scheme
4. CBTC LTE Bearer Prospects
UNITED MECHANICAL & ELECTRICAL –Subordinate
Enterprise of Insigma Technology Co.,Ltd CMMI 4
One of the first domestic enterprises with ISO27001:2005
certified
SJ11234/SJ11235 standard software engineering system
Management system with ISO9001, ISO14001, and
GB/T28001-2001
Class 1 qualification in computer information system integration
Class A qualification in computer information system
integration that involves state secrets
Class 1 qualification in building intellectualization project
contracting
Mmanagement qualification in oversea contracting project
Class A qualification in engineering consultation enterprise
Class A qualification in engineering design
Class A qualification in environmental pollution control facility
operation
National information security evaluation information security
service qualification
Competence
Certification system
3
Rail Transport Services--Domains
Heavy haul
railway
Communication
signal system
Smart scheduling
optimization
Running state
monitoring
Streetcar
Communication
signal system
Express
railway
Communication
signal system
City
subway
AFC/ACC
system
Overseas
market
Communication
signal system Communication
signal system
4
Provides EPC on electrical and mechanical services for rail transport systems such as
express railway, streetcar, heavy haul railway, and urban public transport.
Provides various contracting services such as EPC, BT, BOT, PMC-Project Management
Contract, and PPP-Public-Private-Partnership.
Rail Transit Services--Partners
UN
ITE
D M
EC
HA
NIC
AL
& E
LE
CT
RIC
AL
Partners UNITED MECHANICAL & ELECTRICAL
Provides communication systems in the rail
transport domain.
1. Implements the overall integration of the communication signal project.
2. Provides the signal system in the rail transport domain.
Provides the subway CBTC signal system
technology.
1. Provides general contracting on the signal system. Organizes hardware installation,
commissioning, and operation.
2. Provides main hardware and part of software.
3. Has successfully deployed six subway lines, with the advanced domestic levels.
Provides the subway CBTC signal system
technology.
1. Provides general contracting on the signal system. Organizes hardware installation,
commissioning, and operation.
2. Provides main hardware and part of software.
3. Has successfully deployed subway line 3 at Shenzhen, with the advanced international levels.
A well-known signal company from Germany
and has a long-term partnership with UNITED
MECHANICAL & ELECTRICAL
1. Imports the safety computer platform for international safety certification from BBR.
2. Has cooperated with BBR to implement a railway signal project in a Asian country.
A well-known engineering consulting
company and has a long-term partnership
with UNITED MECHANICAL & ELECTRICAL
Has cooperated with Tewet AG in a railway signal project at an Asian country.
Has successful project cooperation with Ansaldo STS and BOMBARDIER, who had participated in the
developing of the ETCS standard and are the main western equipment vendors in China express
railway construction.
Cooperated with BBR in the streetcar domain to expand the market and import key technologies from
BBR to provide secure and efficient overall signal system solutions.
The only enterprise in the industry that has passed the interconnection test with the Huawei LTE
system and can bear the system signal.
5
Shenzhen Metro Line 3 is
awarded the eleventh Zhan
Tianyou prize
2006.12 Shenyang Metro Line 1 signal system
2007.12 Shenyang Metro Line 2 signal system
2013.07 Inter-city rail line from Shenyang to
Tieling (Metro Line 2 north extension)
2009.11 Hangzhou Metro Line 1 signal system
2012.08 Hangzhou Metro Line 2 signal system 2008.03 Shenzhen Metro Line 3 and its west
extension
2008.03 Chengdu Metro Line 1 signal system
2011.03 Chengdu Metro Line 2 signal system
2013.04 Chengdu Metro Line 1 south extension
2009.03 Xi’an Metro Line 2 signal system
2011.08 Zhengzhou Metro Line 1 signal system
2013.07 Dalian Metro Line 1 signal system
2013.07 Dalian Metro Line 2 signal system
Years of Experience in Railway Signal System Integration
6
Contents
7
2. Current Problems in CBTC Radio Bearer
1. Introduction to UNITED MECHANICAL & ELECTRICAL
3. CBTC LTE Bearer Scheme
4. CBTC LTE Bearer Prospects
8
Problem 1 in CBTC Radio Bearer: Frequent Accidents Caused by Open-Band
Interference Case 1: The train is stopped or degraded due to the use of MiFi by
passengers
Case 2: The train is stopped or degraded on the overhead railway or
ground segment
Occurring
condition
Passengers in carriage 1 or 6 (the first or last carriage) use MiFi to access to
the Internet .
Probability 10 times per line per day in first-tier cities
1 time per line per day in second-tier cities
Cause The 2.4 G frequency band MiFi used by passengers has interference on the
WiFi used by CBTC
Typical cases Shenzhen Metro Line 2 is stopped due to the use of MiFi by passengers.
In an internal test carried out by Shenzhen Subway Transportation Office, a
train is stopped when three MiFi hotspot is enabled in the head carriage.
Occurring
condition The train is running on the overhead railway or ground segment
Probability This problem will occur in the following conditions:
Big-data downloading or video services are performed in the near AP hotspot.
A 2.4 G high-power medical instrument is turned on.
Cause AP hotspot or the high-power medical instrument occupies the WiFi channel.
Typical cases •The Longhua Line train is stopped when passing through a overhead railway due to
interference from a high-power microwave medical instrument.
• The train in Chengdu Metro Line 2 constructed by Insigma is stopped in a ground segment
interference test.
The operation period for subway is long and therefore
the routine maintenance period is short
APs are installed with an interval of 200 m along
the road because APs have short coverage range.
Too many APs are deployed and therefore there is
a high probability of device fault.
Problem 2 in CBTC Radio Bearer: Difficult Project Implementation and Hard
Maintenance due to Too Many Devices Along the Road
00:00 04:00 05:00 23:00 24:00
Maintenance period Operation period
Use the Shanghai subway as an example, the routine
maintenance period is only four hours, and device
maintenance requires application in advance and the
maintenance period is limited.
More than 300 APs are required in a 30 km road.
WiFi WiFi
WiFi WiFi
CBTC red network
CBTC blue network
0 50 100 150
BER
Rate Km/h
1 E-6
Problem 3 in CBTC Radio Bearer: Failed to Provide Satisfactory
Services in High-Mobility Scenarios
The WiFi standard is initially developed as a radio
access method in indoor scenarios, and therefore
cannot meet the requirement in high-mobility
scenarios.
The subway rate has reached 120 km/h in design
and even 140 km/h in some lines.
The BER of WiFi increases rapidly with the subway
rate and cannot meet the BER requirement in a
subway with a rate higher than 100 km/h.
Contents
11
2. Current Problems in CBTC Radio Bearer
1. Introduction to UNITED MECHANICAL & ELECTRICAL
3. CBTC LTE Bearer Scheme
4. CBTC LTE Bearer Prospects
LTE Becoming the Solution for CBTC High-Quality Radio Bearer
Item LTE WLAN
Anti-interference
capability
Uses dedicated frequency band, avoiding inter-RAT interference
Provides Inter-Cell Interference Coordination (ICIC) and
Interference Rejection Combining (IRC) solutions to solve the intra-
RAT interference.
Uses the ISM open band, and therefore is vulnerable to external
interferences
The CSMA/CA mechanism leads to uplink and downlink data
transmission inter-RAT interference in intra-frequency networking .
Maintainability
LTE devices have long coverage distance with a tunnel coverage
distance of about 1.2 km. No device need to be installed inside the
tunnel and this facilitates maintenance.
WLAN devices have short coverage distance and plenty of APs must
be installed along the road. APs are easily damaged in tunnels and
this leads to high maintenance workload.
Mobility Supports a highest moving rate of 450 km/h. Applicable to low-rate scenarios (lower than 80 to 120 km/h). The
handover success rate decreases with the moving rate.
QoS Supports nine QoS priorities in scheduling.
Has guaranteed bandwidth, ensuring QoS.
Supports only four priority queues at the air interface, and this makes
it difficult for service expansion.
Key services do not have guaranteed bandwidth.
LTE is a feasible solution for solving the current CBTC radio bearer problems.
Backbone network
4. Competition free with
OFDMA 2. High reliability with
redundancy networking
1. High anti-interference
capability with dedicated 4G
frequency band
3. Smooth handover with
intelligent power control
④ OFDMA, avoiding access competition between trains
③ Omni-directional antenna and intelligent power control ensure smooth handover
① 4G anti-interference technology
LTE EPC
Control center
ATS server AR router Line data
Combiner
CC Train
CC TAU TAU
RRU
Station
BBU
ATS device Electrical
interlock ZC
Combiner
Station
RRU
BBU
ATS device Electrical
interlock ZC
② Redundancy networking
Implementation of CBTC LTE Bearer Technology--Scheme Design
LTE Anti-Interference Technology Ensures Stable and Reliable
Communication
OFDM ICIC
Dedicated
frequency
band
4G
Tunnel multi-
path
interference
Neighboring
cell
interference
WiFi, bluetooth,
public network,
trunking, others • The use of the dedicated frequency band
enables the system to have the anti-
interference capability with other systems
such as 2.4 G WiFi, bluetooth, public
network, and trunking.
• The use of the LTE OFDM technology and
mature leaky cables suppress multi-path
interference on city subways.
• The ICIC technology suppresses intra-RAT
cell-edge interferences.
Using LTE to Solve the Problem of Too Many Devices and Hard Maintenance
WiFi LTE
• WiFi APs use ISM open frequency band. To avoid
interference, APs are installed with an interval of
about 200 m and therefore many APs are installed
inside the tunnel.
• It is warm and wet inside a tunnel and WiFi APs
are easy to become faulty and the maintenance
workload is high.
• The one-way coverage range is about 600 to 800 m,
reducing the number of radio devices inside a tunnel.
• No device needs to be installed inside a tunnel with
a length less than 1.2 km.
Meeting the Requirements in High-Mobility Scenarios
Automatic frequency correction Frequency-offset-based handover
Frequency offset estimation
Frequency offset compensation Data input Corrected data
Basic principle of the AFC module
High-speed movement leads to high Doppler frequency shift. Frequency shift under 2GHz:
222.2Hz@120km/h, 648.15Hz@350km/h
The LTE standard is designed to support the high speed of 350KM/H. For example, the uplink access
queue is different in high-speed and low-speed scenarios.
LTE has dedicated frequency offset estimation and correction algorithm. The enhanced algorithm has a
frequency offset tolerance of more than 1 kHz, ensuring network performance in high-speed scenarios.
More advanced frequency correction technology
Cooperated with Huawei to perform CBTC LTE bearer tests.
At 2013 May, performed an LTE-CBTC interoperability test in a lab in Insigma Technology
Co.,Ltd. All test items are passed.
During 2013 July to 2013 September, performed outside plant tests in the rail transportation
integrative laboratory in Tongji University. All 29 test items are passed.
The test results show that the LTE network features real-time, wide bandwidth, low packet
loss rate, and low packet disorder rate. In addition ,the LTE system interoperates well with
the CBTC system and can meet the CBTC bearer requirements for rail transport.
Cooperation with Huawei in CBTC LTE Bearer Technology--Test
CBTC LTE Bearer Key Test Items
The time taken for connection setup for the vehicle mounted
terminal is less than 150 ms.
Average time: 124.75 ms
Maximum time: 138 ms
Minimum time: 99 ms
The service connection setup success rate is greater than 94%. The service connection setup success rate
reaches 100%.
The end-to-end data transmission delay from the vehicle
mounted terminal to the equipment room: 80 bytes, 300
bytes; <100ms
80bytes:
Average value: 28 ms
300 bytes:
Average value: 23 ms
The packet loss rate is smaller than 0.8%.
The packet loss rate is calculated by dividing the number of lost
or error by the total number of sent packets. 0.01%
Conclusion on the CBTC LTE Bearer Technology
• Uses dedicated LTE frequency band, avoiding inter-RAT interference
• Uses technologies such as ICIC to avoid intra-RAT interference
Anti-interference capability
• Applies flattened networking to simplifies the network
architecture and reduces the NE quantity
• Has a long single-cell coverage range, requires almost no
device in tunnels, facilitating maintenance
Maintainability
• Applies automatic frequency correction technology and frequency-offset-based handover to ensure stable signal for high-speed trains
High-mobility support
The LTE technology can meet the requirements of CBTC LTE
bearers in terms of functions or performance
Contents
20
2. Current Problems in CBTC Radio Bearer
1. Introduction to UNITED MECHANICAL & ELECTRICAL
3. CBTC LTE Bearer Scheme
4. CBTC LTE Bearer Prospects
Suggestion on the use of the LTE network as CBTC bearer
Organize experts to evaluation the CBTC LTE bearer solution and its
application.
Participate in the application of the CBTC LTE bearer solution, and inform the
industry of the progress in time.
Participate in the standard making for the application of LTE in the rail
transport domain.
We believe that LTE is the best choice for the future CBTC
bearer, and we hope to promote the application of LTE in the rail
transport domain. We suggest that all parties should:
Thank you！
UNITED MECHANICALL &ELECTRICAL | 众合机电