The Model of the Communication Channel with Mobile Objects using
the Temporary Switch
I. Knyshev and D. Saprykin
Russian University of Transport, Moscow, Russia
Keywords: Telecommunication network, radio network, information, subscriber, activity, telecommunication network
structure, communication channels, fault endurance, technological process.
Abstract: The article is devoted to the consideration of the dynamic model of the train communication radio channel
(PRS). A block diagram of the model, a temporary switchboard (VC) taking in account the nature of the
movement of subscribers, expressions for reliability parameters are presented and described, comparative
calculations with the traditional calculation method are presented, ways to increase the reliability of the PRS
network are presented.
1 INTRODUCTION
During recent years, the argument that information
technologies have the most direct impact on the state
and the development of the economy has become
almost universally recognized. The computer world
became networked decades ago. The network
infrastructure makes it possible to quickly exchange
data and access information resources, both at the
local level and on a global scale. The problem is the
weakness of the telecommunications infrastructure.
In many cases, the use of wired or fiber-optic
communication lines is impossible or economically
impractical. In this situation, one of the most effective
solutions to the communication problem, and often
the only possible one, is the use of radio data
transmission networks.
2 MANUSCRIPT PREPARATION
The traditional variant of the wireless communication
is the conventional communication systems, which
are implemented by the radio stations that are not
integrated into any technical system that provides
resource management, signaling and other
coordinating procedures.
Today, a lot of conventional radio systems are in
operation around the world. The systems of this type
have been, and continue to be, the most popular type
of terrestrial mobile radio communication systems.
Due to the simplicity of implementation,
conventional systems are widely used to solve the
mobile communication problems, which are built on
the principle of "point-to-point" and "star" (with a
base radio station) without access to public telephone
networks.
GSM-R technology, described by the European
Telecommunications Standards Institute (ETSI TS)
in ("Russian Railways", 2011), makes it possible to
transfer train and manoeuvre radio communications
to a new powerful unified digital system platform and
is designed to replace a lot of different heterogeneous
radio communication systems.
GSM-R equipment allows for continuous
communication between the driver and the dispatcher
at a rolling stock speed of up to 350 km/h and
therefore allows you to remove one of the main
barriers to the creation of high-speed trains. GSM-R
integrates with GPRS to provide packet-based
switching services. Thanks to this, it is possible to
receive real-time telemetry information from any
locomotive, any station or stretch of road.
Information about the location and speed of the train
is transmitted via the GSM-R network to the control
centre, which will fully automate the process of
regulating train traffic. The use of such a system in
the passenger complex will greatly increase the safety
of passenger transportation.
Separately, it is worth noting cellular radio
communication solutions based on the DMR
standard. The first release of the standard was
released in 2005 (Digital Mobile Radio (DMR)
124
Knyshev, I. and Saprykin, D.
The Model of the Communication Channel with Mobile Objects using the Temporary Switch.
DOI: 10.5220/0011580100003527
In Proceedings of the 1st International Scientific and Practical Conference on Transport: Logistics, Construction, Maintenance, Management (TLC2M 2022), pages 124-128
ISBN: 978-989-758-606-4
Copyright
c
2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)
Systems, 2019) describing the radio interface (Part 1),
as well as the voice and basic functional features of
the standard (Part 2). The third part of the DMR
standard was added, describing the packet data
transmission protocol.
Now the network of JSC "Russian Railways" is
transposed and uses equipment for various purposes:
base radios, automatic telephone stations (ATS),
multi-level multiplexers, spectral compaction
equipment, packet switching equipment, servers of
various architectures, both cable and fiber-optic
communication lines. For the security purposes,
equipment from various manufacturers has been
introduced. The combination of embedded
communication devices forms a huge communication
structure.
One of the most important parameters of
communication systems is the reliability of
information exchange channels between subscribers.
The reliability parameters become important in
communication systems with mobile subscribers,
when messages, commands and data used in the
process of controlling the movement of objects are
transmitted through the channel. In this regard, the
question of determining reliability indicators when a
subscriber moves in such a large and diverse network
arises acutely.
Previously, reliability indicators were determined
by the classical method. The most important
characteristics of the communication channel are
known: failure rate, operating time for failure,
recovery rate, etc. When determining reliability, we
relied on the prerequisites specified in (Almazyan,
2011). The radio network was a closed system, the
elements of which are homogeneous in parameters.
The reliability scheme of the PRS network shown
in Fig. 1 clearly shows the fundamental elements of
the reliability of the train dispatcher–driver
communication channel (DNC-PM). The network
structure is radio conductive. The administrative
station (AS) of the train dispatcher (DNC) is
connected to the base stations (BS) of each station
attendant (DSP) via a wired communication channel
(CC). The radio stations carried on mobile units (PS)
establish the connection of the driver (PM) with the
BS via the radio channel (RC) throughout the entire
dispatching section (circle).
The classical approach in (Almazyan, 2011;
Roenkov, 2017) to determine the reliability of the
communication channel is based on a static model,
which includes all the elements forming the
communication channel, and when the subscriber
moves and changes the elements of the model or its
parameters, this is reflected as a set of model variants.
According to (Rules of technical operation of
railways of the Russian Federation, 2010), DSP-PM
radio communication should be provided on the entire
stretch adjacent to the station. This leads to a
complete overlap of communication zones on all
stages of the dispatch circle.
Figure 1: Probabilistic model of the PRS network for
calculating the value of the traditional radio network
availability coefficient.
In (Almazyan, 2011), it is proposed to define
K
as one of the reliability parameters of the
DNC-PM channel as follows:
K
=1−
(
1−К
)
−
(
N−1
)(
1−K
)
(1)
In view of such large-scale systems, it is incorrect
to determine reliability by the traditional method due
to the movement of the subscriber, and it is necessary
to introduce an amendment for the duration of the
locomotive radio station's stay in the service area of a
particular BS and the influence of only this BS on
reliability indicators. In (Knyshev, 2021), it is
proposed to use a dynamic definition of reliability
that takes in account the subscriber's schedule.
According to the study of signal levels in the work
(Almazyan, 2011; Roenkov, 2017; Knyshev, 2021a),
it is proposed to delimit the service areas and present
them in the form of cells to simplify calculations, as
shown in Fig. 2.
Figure 2: Base station service areas.
To reflect the subscriber's transition from one BS
zone to the service zone of another BS in work
(Knyshev, 2021b), it is proposed to include a virtual
switchboard (VC) in the reliability model, which
The Model of the Communication Channel with Mobile Objects using the Temporary Switch
125
switches the BS serving the subscriber in accordance
with the subscriber's traffic schedule. The block
diagram of the PRS network using VC is shown in
Fig. 3.
Figure 3: Dynamic model of the PRS network using VC to
calculate the integral value of the radio network availability
coefficient.
The principle of time switching is to move the
subscriber from the coverage area of one BS to the
coverage area of another with the implementation of
the "handover" procedure. In other words, this is a
temporary shift of the subscriber's position. At each
moment of time, the territorial information of the
identified subscriber is transmitted. If this
information is transmitted to another BS, then this
means moving the subscriber to the area of operation
of another BS. An element of the reliability model
that implements the principle of time switching is
called a virtual switch VC. The virtual switchboard is
characterized by such parameters as: the number of
base stations, respectively, the number of radio
channels connected to the VC inputs, the number of
switched portable radio stations connected to the VC
outputs, and the subscriber traffic schedule that
determines the switching order. An example of a
traffic schedule is given in (Knyshev, 2021).
Thanks to the handover, the subscriber is not tied
to a specific BS, but is given the opportunity to move
within the coverage area of the radio network without
disconnecting the connection. When moving a
subscriber in existing conventional networks, the VC
does not have a technical implementation of such a
procedure and is due solely to the movement of the
PS.
In the case of cellular systems that implement the
handover procedure, there is a corresponding piece of
software and hardware that implements the switching
of the subscriber station to another BS.
There may be several reasons for the need to
implement a handover:
− moving the subscriber to the service areas of
different BS,
− when the current BS cell is overloaded,
subscribers are transferred in the overlap zone
to the neighboring BS, freeing up the capacity
of the current BS cell for subscribers with
whom it is possible to maintain communication
only within the boundaries of this BS,
− when the communication channel of the BS
used is noisy,
− when the subscriber's movement speed changes
(the subscriber's speed is directly proportional
to the cell of the larger area).
Depending on the reason, it is customary to
distinguish several types of handover:
− Within one BS.
− In case of failure or overload of one of the
transceivers within one sector.
− Between sectors that screw up one BS.
− Between several BS.
− If one of the BS controllers or the BS itself fails
inside one automatic telephone exchange
(ATS).
− If the ATS malfunctions, the load is transferred
to the nearest ATS with the ability to service
the necessary zones.
− With BS of various cellular communication
standards.
Depending on the reason, the type of handover
and the network standard, various analyses are
already being put forward to the reliability indicators
of load switching (subscribers). The handover
procedure can be accompanied by failures, failures
and can be characterized by a certain probability of
success or failure, which also provides for a
temporary VC switch of the model presented in Fig.
3.
The value of the readiness coefficient of the
communication channel on the entire trajectory from
point A to point B can be determined by the weighted
sum of КrBSi for all values of i:
К
= К
γ
. (2)
The weighting coefficients γ
are defined as the
fraction of the time Δt
i
of staying in the service area
BS
i
of the total time T of moving from point A to
point B:
γ
=
∆t
T
, (3)
where Δt
i
– time spent in the BS
i
service area;
T – full driving time from p. A in p. B.
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According to the traffic schedule, the total travel time
T is determined, and it is also possible to calculate the
time spent in the BS
i
service area.
As a rule, the subscriber is given a certain speed
of movement on each stage, which he must observe.
It is possible to determine the total time of movement
of the rolling stock T . The dependence v
(
r
)
is
expressed analytically.
T=
r
v
(
t
)
dr
+t
, (4)
where r – the whole way of the subscriber from p. A
in p. B;
v(r) – the dependence of the subscriber's movement
speed on its trajectory;
t
– total time of stops in the BS
i
zone.
In this case, the weighting coefficients γ
will take
the following form:
γ
=
1
T
r
v(r)
dr +
t
, (5)
where r
и r
– define the BS
i
service area.
As an explanation, it makes sense to consider an
example of the simplest dependence v
(
r
)
with
significantly different speeds of several subscribers.
On railway transport, it can be a passenger train and
an express train. We will use a hypothetical section
for the movement of trains with outdated equipment
of communication systems and equipment that is
planned to be installed on this section in the future.
For clarity, we will determine the reliability
indicators by both the traditional method and the one
proposed taking in account the subscriber's
movement.
Section A-G is equipped with RS-46MC base
stations. It is planned to modernize the section of the
RVS-1-46 radio station. Let's make calculations for
two variants of the site:
− option 1 – only RS-46MC type BS are installed
on the site, each of which has a failure time of
Т
=7000 hours;
− option 2 – partial modernization and more
modern BS of the RVS-1-46 type have already
been installed at some stations (B, C, D),
having an operating time for failure Т
=
45000 hours.
As portable radio stations for both options, we
will use radio stations of the RV-1M type with a
failure time of Т
= 8000 hours. The readiness
coefficients of radio stations are shown in table 1
when the recovery time t
= 5 hours.
Table 1: The availability coefficients of the specified radio
stations.
t
,hours
5
К
0.999286
К
0.999889
К
0.999375
Table 2 shows the schedules of a passenger train
with all stops and a fast train (express), respectively.
For convenience, the train schedule is presented in the
form of a table.
Table 2: The train schedule.
Distillation Distance,
km
Driving
time, min
Parking,
min
Passenger train
A-B 7 11 3
B-C 8 11 2
C-D 11 14 2
D-E 13 17 3
E-F 9 11 1
F-G 10 12 1
Express
A-C 15 15 3
C-E 24 22 1
E-G 19 17 1
Additionally, for example, let's take a freight train
moving non-stop from the station A to the station G
with an average technical speed of 40 km/h (travel
time 1 hour 27 minutes)
The time spent in each service area is determined
as the sum of the ratio of the distance traveled in this
zone to the speed of movement along this section and
parking time. The calculation is performed in a
written program in the high-level programming
language Python. The results of the calculations of
∆𝑡
and 𝛾
are summarized in table 3 for each of the
variants, respectively, additionally К
is given for
each BS.
According to the weighted formula, the results of
the coefficients of readiness К
on the section from
st. A to st. G for passenger trains, express trains and
freight trains are summarized in table 4.
Since the radio stations carried on each train are
the same, the static reliability coefficient of the A – G
section, calculated by the method (Almazyan, 2011),
will be the same for any type of train.
For all basic radio stations of the RS-46MC type
(the first option) static К
= 0,999372 , in the
mixed case (the second option) К
= 0,999375.
The obtained values coincide with the results of
determining reliability by static (classical) methods,
The Model of the Communication Channel with Mobile Objects using the Temporary Switch
127
which is to be expected in a network with identical
parameters of all elements.
Table 3: The results of the calculations of ∆𝑡
and 𝛾
for
integral parameters
№
BS
S
t
∆𝑡
,ч 𝛾
К
o
p
tion 1
К
o
p
tion 2
Passenger train
1 A 0,09167 0,0625 0,999286 0,999286
2 B 0,23333 0,15909 0,999286 0,999889
3 C 0,24167 0,16477 0,999286 0,999889
4 D 0,29167 0,19886 0,999286 0,999889
5 E 0,28333 0,19318 0,999286 0,999286
6 F 0,20833 0,14205 0,999286 0,999286
7 G 0,11667 0,07955 0,999286 0,999286
Express
1 A 0,05444 0,05632 0,999286 0,999286
2 B 0,11667 0,12069 0,999286 0,999889
3 C 0,19625 0,20302 0,999286 0,999889
4 D 0,18333 0,18966 0,999286 0,999889
5 E 0,18308 0,18939 0,999286 0,999286
6 F 0,14167 0,14655 0,999286 0,999286
7 G 0,09123 0,09437 0,999286 0,999286
Table 4: The availability coefficients of the specified radio
stations.
№ option Passenger
train
Express Freight
train
1 0,999286 0,999286 0,999286
2 0,999601 0,999596 0,999588
3 CONCLUSIONS
The integral values of the operating time for the
failure of Т
and К
ri
, and, especially, the influence
of the subscriber's movement, will largely depend on
the ratio of the failure rates of the model elements in
Fig. 3. So, if the RV-1M radio station with Т
=
8000 hours is used as a locomotive, and the RVS-1 or
RLSM-10 with Т
= 45000 hours is used as a BS,
as well as with digital, highly reliable CP and CC
equipment, then the reliability of the train dispatcher's
communication channel will be almost completely
will be determined by the parameters of the PS radio
station. The situation seems more realistic when a
subscriber of the Russian Federation has a highly
reliable radio station, BS are implemented on
different types of radio stations (partly on RS-46MC
with Т
= 7000 hours, partly on RVS-1 or RLSM-
10). In this case, the influence of the subscriber's
movement will affect significantly.
An example of calculating the dynamic
coefficient of readiness for a different site is
presented in (Knyshev, 2021c). The qualitatively
obtained results are identical: integral reliability
parameters more accurately reflect the reliability of
communication systems.
Theoretically, by changing the subscriber's
schedule and increasing the speed of movement in
areas with low reliability of equipment (BS), it is
possible to increase the integral reliability parameters
of the system.
REFERENCES
Technical requirements for the digital system of
technological radio communication of the GSM-R
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Almazyan, K., Verigo, A., Knyshev, I., 2011. Reliability of
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Roenkov, D., Shmatchenko, V., Yaronova, N., 2017.
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