Based on the mature GSM system, GSM-R is a communication system
developed for railways application development, providing a reliable
bearer network. Apart from basic railway features like VGCS, VBS, eMLPP
and emergency call, it supports functional addressing, call matrix,
location addressing and flat shunting. Many railway services can be
implemented on the GSM-R platform.
A train control system relies on the security of wireless communication
system. As railway transport capacity grows, and trains run faster and
faster, how is the safety of railway traffic ensured, how is high speed
performance ensured, and how is seamless coverage of railway scenarios
ensured; as well as improved utilization rate of frequency resources.
These are key topics faced by the GSM-R system.
For this reason, Huawei provides the GSM-R Solution, an end-to-end (E2E)
solution covering the GSM-R base station, base station controller, core
network, terminals and dispatching stations.
Profile of the Solution
Huawei's GSM-R Solution is described as follows:
Figure 1 Huawei's GSM-R Solution
Characteristics
High Reliability
GSM-R network's reliability has a direct bearing on train safety. 1+1
backup technology and resource pool technology are used to ensure the
equipment is free from single point of failure and improve
equipment-level reliability. Network-level security technology is
applied to remote disaster recovery and backup, further enhancing the
GSM-R network's reliability. For core network equipment, Huawei provides
reliability mechanism in the network layer such as dual-homing MSC,
Mini-A-Flex and HLR backup. For access network equipment, BSC backup,
BTS ring networking, active and backup BBU and redundant coverage in
wireless networks are applied to achieve reliability mechanism in the
network layer. Even if a base station suffers transmission interruption,
users in the base station area can still communicate with one another.
High Performance
The following technologies are used to ensure the high performance:
Automatic-frequency correction (AFC): Huawei uses AFC technology to
correct the Doppler frequency offset at high speed. The demodulation
threshold of AFC can reach up to 1000 Hz. Huawei AFC adapts to Doppler
frequency offset up to a speed of 500 km/h. At the same time, Huawei
applies AFC to GPRS, to ensure the GPRS performance is not affected at
high speed.
Fast handover algorithm: In the high-speed railway environment, a train
runs quickly between areas covered by different base stations. If the
traditional handover algorithm is used, there is not enough time for
mobile terminals on the train to change stations before entering the
next area, leading to an interruption of communication.
Being tailor-made for high-speed railways, fast handover algorithm ensures a real-time and reliable handover at high speed.
1) Doppler frequency offset handover algorithm is an AFC-based algorithm
designed to expedite handover decisions, narrowing the handover zone,
and improving inter-cell handover performance.
2) With the fast Power BudGeT (PBGT) handover algorithm, a fast-moving
mobile station switches quickly to a stronger cell to obtain service and
maintain connection, improving inter-cell handover performance. At the
same time, the algorithm makes it possible for the mobile station to
switch for a second time in a limited handover zone after the first
handover fails.
Distributed Base Station Addresses Problems with Railway Coverage
Made up of base band units (BBU) and remote radio units (RRU), the
DBS3900 distributed base station is an industrial-level distributed base
station specially designed for GSM-R. With the feature of flexibility, a
distributed base station, which supplements a macro base station, can
be deployed conveniently and applied in railway scenarios like tunnels,
ditches, bridges, doubling, cross-over and large-scale passenger hubs.
Moreover, when sharing one network management system with the macro base
station, the distributed base station, the installation of which is
time-saving, labor-saving and land-saving, has strong adaptability to
the environment.
Innovative RRU co-cell technology: The same frequency group is
configured for RRUs in different locations, so that multiple RRUs send
and receive signals simultaneously through BBU control. Logically, the
RRUs at these locations belong to one cell. Co-cell technology decreases
handovers and improves network performance at the same time it
increases frequency multiplexing distance. Under the same SNR, frequency
planning becomes easy.
Value of Solution
Intelligent Traffic Control, Ensuring Smooth, Efficient and Safe Transport
Huawei GSM-R provides single calls, group calls, broadcast calls,
enhanced preemptive priority and emergency calls meeting the railway
requirements. It also provides functional addressing, call matrix and
location addressing services. It allows drivers to maintain
communication with staff on duty at the station and dispatchers with the
dispatching center all the time, so that emergencies can be promptly
handled.
Dispatching command refers to the written command issued by the
dispatcher with the dispatching center to drivers. It is an important
factor for train safety. Dispatching commands are transmitted through
GSM-R improves work efficiency.
Huawei GSM-R can provide secure and reliable transmission channels for
train control signals, and integrate communication signals, to meet the
requirements of high-speed passenger dedicated line and small tracking
interval.
Heavy-haul Transport
Huawei GSM-R can be used to implement synchronized control of multi-cab
signals, provide heavy-haul transport, and improve transport capacity.
Foundation of Railway Information
Huawei GSM-R can transmit vehicle monitoring information, shunting
signals and end-of-train information, providing reliable channels for
train-ground transmission.
Sectional Mobile Order Wire Communication
Water and electricity, track maintenance, signal, communication, power
supply and bridge watch departments can all conduct the internal
communication through GSM-R operation handset. When necessary, operators
can contact staff on duty at the station, dispatchers with departments
or automatic phone users. In emergencies, operators can establish
contact with drivers. 以下图片来源于CTCS-3级列控系统视频截图: