2011 International Conference on Telecommunication Technology and Applications
Proc .of CSIT vol.5 (2011) © (2011) IACSIT Press, Singapore
Optimization of Industrial ProcessData Transfer over TCP/IP
Satellite Networks
Sorin Sintea1, Nicolae Bordea 1,Valentina Pomazan2, Vasilica Bordea 1and Vasile Pipirigeanu3
1
Constanta Maritime University
Constanta Ovidius University
3
CERONAV, Romanian Maritime Training Centre
2
Abstract. This paper presents the result of an extensive study on the possibilities to deliver real time
specific engineering information for remote controlled systems. A data channel through TCP/IP networks
over ATM satellites network is analyzed as a robust solution for delivering real time information between
two points, over satellites networks. An intermediate layer for data transmission between application layer
and TCP layer is proposed as a solution for receiving all sending requests of data from the host machine and
adding data in packages, using a special multiplexing and coding algorithm. The tests revealed significant
transmission time reductions for large packages of data.
Keywords: remote control, communications, protocols, TCP/IP, satellite networks
1. Introduction
Manufacturing requirements have changed enormously in the last few decades and today the emphasis is
put on greater responsiveness, cost effectiveness, improved production quality and shorter product lifecycles. In order to increase production flexibility and decrease production times, new system concepts based
on modular, process-optimized cell systems are being developed, Control and process technology is
being shifted away from the central cell into the production cell, thus becoming an integral part of the
system module. Through the gradual increase of communication technology in the automation field,
industrial communication could be standardized considerably to deal with all the requirements of future
automation and production strategies. Real time delivery is required in many remote control situations
required for accurate manufacturing, production, measuring systems and online services. Full information
delivering is vital for application functioning, so that processes are not to be disturbed.
Depending of own characteristics, eachcommunication environment can induce certain delays in long
distance communications. For example, communication over landlines fibber optical cables can add about
few to hundreds of milliseconds time delay in package delivery, communication over satellites networks add
about hundreds of milliseconds to seconds time delay in package delivery.
Nowadays are extensively used ATM (Asynchronous Transfer Mode) networks over landlines
communication systems, or over wireless networks or over satellites networks.Satellites networks layer
introduce a long delay time in data delivery, while the ATM packages over landlines can have different data
volumes, but time delayed is little affected by the package size.
The basics of communication over satellite data networks is TDM (Time Division Multiplexing) data
channel. This channel adds a maximum delay equal with two channel time window width.
1.1. Data communications over satellite networks
Because the satellite networks represent a backbone for planetary data communication, its default design
intent was to be able to deliver a large amount of data at long distance. The satellite networks are used to
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deliver large data blocks with medium time delay or time latency in data delivery. The data transfer package
is larger in dimensions than the data package sent over landlines data communications systems and sending
smaller data package over satellite network does not represent an optimal solution, as smaller data packages
are received with larger time delay. To deliver data from one host to another host over satellite network
systems,it is recommended to package more information from source or create one larger package of data
and send it over satellite network to destination host. The package optimum value is computed as the
difference between integer multiple of TDM data frame size (the size of data send in one TDM cycle
excluded synchronize words)and TDM synchronizing characters.At the package creationone should extract
the TCP/IP header and synchronize thecharacters length. This formula offers the optimal delivery time for
data sending.
2. Data transfer using TCP/IP networks overSatellite Data Networks
Most of communication application use TCP/IP communication layer for data delivery between two or
more hosts. This solution presents few advantages:
Easy to implement point-to-point solutions or server-client solutions into data communication
environment
Easy to create applications based on standard libraries (Berkeley Sockets Library), hosts independent
environment.
The applications are source portable, if a standard portable programmable language (C, C++, Java, C#)
is used; this ensures a easy method for application delivery on different machines, which are working
on different operating systems, or different computers.
The communication application is not code depended by the communication environment (wireless,
Ethernet networks, satellite networks, optical networks). The TCPIP layers are responsible for data
packaging, adapting, interfacing and delivery from a host to another one.
Starting from these advantages we used TCPIP as standard communication layer for data delivery
between two users. The analysis regarding data deliver from one host to another host focused on following
issues:
Transfer of small packages;
Transfer of large data packages;
Transfer of optimal packages.
2.1. Transfer of small data packages
In case of small packages (from few Bytes to 40 Bytes) or signaling packages, long time latency in
receiving packages was observed. In this case, packages are sent from source with δt time interval between
packages and we received packages when satellite transmission buffer was full filled and started
transmission of data with a time interval of data channel latency. For example,for a satellite transmission
buffer of 4 Kbytes data width, and one source small packages with 42 Bytes length, and 1 second time delay
(Δτ) between each data package over TCPIP protocol through satellite data channel to another TCPIP host
machine. The received datareturned after 97.26 seconds. The explanation lays in the 97 seconds the satellite
transmission buffer needs for fulfilling.
The total amount of data (D)is computed multiplying the number of packages (Np) with their length (P):
98×42 Bytes = 4116 Bytes.
(1)
This number is larger than 4096 Bytes, transmission buffer size. In this case, after 98 packages, the
satellite transmission will start and one single buffer will be sent with contents of all 97 packages. The last
package will be sent in the next data satellite buffer.
The time (Δt) required for fillingthe satellite transmission buffer is
∆
1
∆
(98-1)×1 s = 97 s.
(2)
Theremaining260 milliseconds time delay (δt) is introduced by TDM of satellite channel and data receiving
mechanism.
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2.2. Transferring large data packages
In case of larger packages (larger than few hundreds of Bytes), we observed short time latency in receiving
packages. In this case, packages larger than satellite data sending buffer are sent from one source. One
source that sent one data package, with 8000 Bytes length, with size larger than satellite data sending buffer
(4 Kbytes). The package was delivered in 520 milliseconds. This happened because the data package
fulfilledat once the transmission buffer and the data started to be delivered through satellite data channel
immediately. The remaining of the package was to be delivered into the next buffer delivery. In this case,
data were delivered in period of time (T) that equals the time delay(δt)proportionally multiplied with the
report between package size (P) and transmission buffer size (B):
/
0.5
260
8000
/ 4096
0.5
260
2
520
(3)
2.3. Transferring optimal data packages
From the former observations one can conclude that is more efficient to send larger packages over
satellites data network than sending smaller packages. The reality is, we can send small packages of data in
real time, but we must complete the sending buffer with null bytes, so that the satellite transmission buffer is
fulfilled from first package. Another important observation refers to the case of sending smaller packages:
we can add them to one larger package and send both as one data package, so thatand the delivery time will
be shortened.
3. Solution for optimization of TCPIP data transfer over satellite data network
Having as goal to optimize the data packages size, we implemented the idea to create an intermediate
layer for data transmission between application layer and TCP layer. This layer will receive all sending
request of data from the host machine (Fig. 1) and will add data in packages with a size multiple of satellite
transmission buffer size, using a special multiplexing and coding algorithm.
Fig. 1: Source Structure
Also, the new layer can compress data to reduce the size of the packagethat will be delivered to the
destination. The algorithm is presented in Figure 2:
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Fig. 2: Source Data Transfer Algorithm
At the receival, the data will be receipted by the pair of layers, as shown in Figure 3.This service will be
responsible with data decompression, extracting, decoding and delivery of the packages to the corresponding
services.
Fig. 3: Destination Structure.
The Destination Data Transfer algorithm is presented in the Figure 4.
Fig. 4: Destination Data Transfer Algorithm
To be easy to implement of this mechanism we proposed the redirection of all TCPIP services to this
special new layer. This layer is created into one service named sat-tcpip and this service is used for data
delivery through TCPIP data services over satellite data networks.
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4. Conclusions
After implementation of this mechanism on two hosts, connected on the two sides of the TCPIP satellite
data network, the results were the following:
In case of sending of small packages, on 42 Bytes sent at 1 seconds time delay between packages, the
time delay obtained was about 260 milliseconds for each package. This valuewas obtained because at each
data sending request, the data package was completed with the null Bytes requests, so that the data be send in
first available TDM cycle.
In case of sending of large packages, for 8000 Bytes sent, the delivery time was520 milliseconds for the
package. But, for adata rate compression of 2:3, with6000 Bytes length packages instead of 8000 Bytes, we
obtained a data transmission in one TDM data frame, of 4 Kbytes. That means one package of 6000 Bytes
can be delivered in 260 milliseconds instead of 520 milliseconds.
The advantage of new introduced layer is important in many areas of activity for data
delivery:technological processes control, modular production systems, telemedicine andlong distance online
services.
5. Acknowledgements
We are grateful to Software Integration Technology Ltd. for the technical support ensuredduring this
research.
6. References
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SUA, International Technology Research Institute, 1998
[2] ***, Satellite Navigation and Location Systems, Third United Nations Conference On The Exploration And
Peaceful Uses of Outer Space, May 27, 1998
[3] Bruce R., Elbert, Satellite Communication. Applications Handbook, 2nd Edition, London, Artech House Inc.,
Boston, 2004
[4] Sorin-R. Sintea, Contribution to the Realization of the Ship Long Range Identification and Tracking Equipments,
Doctorat Thesis, University Transilvania of Brașov, 2007
[5] ***, Manual for use by the Maritime Mobile and Maritime Mobile-Satellite Services, International
Telecommunication Union, Radio Communication Bureau, pp. 81-96, pp 267-271, pp. 385-427, pp. 567-569, pp
571-574, 2005
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