Raylı sistemlerde kablosuz haberleşme
Wireless communication at railway systems
Yazar: SERHAT BOYNUKALIN
Danışman: DR. HASAN BÜLENT YAĞCI
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Raylı Sistemler Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 2017
Konu: Elektrik ve Elektronik Mühendisliği = Electrical and Electronics Engineering ; İletişim Bilimleri = Communication Sciences
Dizin: Elektronik haberleşme = Electronic communication ; Modem haberleşmesi = Modem communication ; Uydu haberleşme sistemleri =

Özet:
Avrupa Demiryolu Trafik Kontrol Sistemi (ERTMS) ilk tren komut-kontrol ve tren-yer haberleşmesini tanımlayan uluslararası haberleşme standardıdır. ERTMS' nin iki temel birimi vardır. Birincisi Avrupa Tren Kontrol Sistemi (ETCS)' dir. İkincisi ise GSM-R (Global System for Mabile Communication for Railway)'dır ve ERTMS' nin seviye 2 ve seviye 3' teki haberleşme arayüzüdür. Avrupa ülkeleri 1980'lerin sonlarında özellikle yüksek hızlı tren taşımacılığında ülkeler arası geçişlerde veya ülke içindeki farklı hatlardaki geçişlerde haberleşme birimleri arasında ortak çalışabilirliğin olmaması nedeniyle yaşanan problemlerin önüne geçmek için standart geliştirme ihtiyacını duymuşlardır. Bu standardın iki önemli servisi vardır.
•	Raylı sistemlerin haberleşme uygulamaları için farklı servisleri için öncelikli kanal yönetimi yapmak
•	Sesli arama özelliğinde dinamik adresleme ve grup aramaları yapmak
Zamanla artan verim ihtiyacı GSM-R' ın sağladığı temel iki serviste kapasite problemlerini birlikte getirmiştir. Bundan dolayı alternatif çözümler geliştirilme ihtiyacı doğmuştur. Tezin konusu özellikle GSM-R' ın veri bağlantısı servisine yardımcı servis veya alternatif sunabilmektir. Bunun için temel olarak makas durum verilerinin hattan alınıp araç üstündeki mantık birimine taşınması ele alınmıştır.
Yapılan prototip çalışmasında hattaki makasın durum bilgisini RS232 ile röle üzerinden okuyan ve bu okuduğu bilgiyi UHF veya internet bağlantısı üzerinden araç üstündeki mantık bloğuna aktaran terminal uygulaması geliştirilmiştir. Araç üstü için bütün sistemlerin ortak yerden haberleşmesine olanak sağlayan, gerekirse farklı yazılım dilleri arasında haberleşmeyi destekleyen ve makas durum bilgilerini alıp bir veri deposuna kayıt eden web servis yazılmıştır. Ayrıca gelen verilere göre makasın sapanda mı normalde mi olduğunu, hangi anda durumunun değiştiğini ve durum değişikliği bilgisinin ne zaman mantık birimine ulaştığını gösteren indikasyon yazılımı da geliştirilmiştir.
Tezin konusu makasın durum bilgisinin üretilmesi değil bu bilginin üretildikten sonra güvenli bir şekilde mantık birimine taşınması ve verinin taşınma şekline farklı alternatifler sunularak sonuçta sistemlerin performansları veri aktarım hızı, destekledikleri mesafe açısından incelemektir. Makasta oluşan durum bilgilerinin makas bölgesinden araç üstüne aktarılması için aşağıdaki yollar ile denenmiş ve incelenmiştir.
•	802.11p ile doğrudan radyo yayını modunda haberleşme
•	UHF radyo ile Master /Slave modunda haberleşme
•	Modem üzerinden yakın alanda WiFi (IEEE 802.11b/g/n 2.4GHz) ve Ethernet üzerinden haberleşme
•	Uzak alan LTE veri hattı ile modem üzerinden gelen veriyi yakın alanda WiFi (IEEE 802.11b/g/n 2.4GHz)  ve Ethernet ile haberleşme
•	Uzak alan fiber veri hattı ile modem üzerinden gelen veriyi yakın alanda WiFi (IEEE 802.11b/g/n 2.4GHz) ve Ethernet ile haberleşme

Abstract:
ERTMS is the first international communication standard which defined the train command- control and train-ground communication. ERTMS has two key elements. The first one is ETCS that is Automatic Train Control Protection (ATP) system and the second one is GSM-R which is a radio network for railway voice and data service provider. GSM-R is the communication interface of ERTMS at advanced levels of 2 and 3. At late 1980's European countries has suffered from the compatibility problems specially caused by the different communication interfaces when high speed trains were changing country or within same country but with route segments differ in communication standards. To eliminate this problems, the European countries had to find out a common communication standard. The standard provides two important service.
●	Channel priority management for different services of railway system communication applications 
●	Dynamic addressing and group calls with voice call feature

As the time elapse, increased sufficiency requirements has brought up lack of capacity problem at GSM-R two main services. So, there are two ways to solve the problem.
1.	Supportive action to GSM-R 
2.	Transition to new technologies like LTE-R, UHF etc. 
First way is mainly focused on supportive action on GSM-R, like carrying some of data with alternative technology instead of GSM-R. 
Second way might be considered as two parts of solution. First part is a temporary solution until LTE-R (next generation of GMS-R) fully developed. If it is necessary to switch to LTE-R, an alternate supportive technology may only have a short time to support data carrier for GSM-R. When LTE-R is ready GSM-R and the alternative supportive system should be replaced by LTE-R. Second part is UHF, GSM based fully alternative solution instead of GSM-R. If it is not so important to switch to the LTE-R, GSM-R might be replaced with the alternative solutions.
Thus, developing alternate solution was necessitated. The topic of the thesis is not to produce position data of the point machine but send the data to the logic unit in a secure way after it has been produced and to offer alternative data carriage methods and to analyze the performances of all the systems depending on their data carriage speeds, and supported distances. The undermentioned methods have been tried and examined to transfer the position data of the point machine from the point machine area to the railway vehicle.
●	Communication in direct radio broadcasting mode via 802.11p
●	UHF radio communication in Master/Slave mode
●	Local area network communication over WiFi (IEEE 802.11b/g/n 2.4GHz) and Ethernet via modem
●	 Communication via modem over LTE data link for wide area network and over WiFi (IEEE 802.11b/g/n 2.4GHz) and Ethernet for local area network
●	Communication via modem over fiber data link for wide area network and over WiFi (IEEE 802.11b/g/n 2.4GHz) and Ethernet for local area network

This thesis is mainly focused on offering a subsidiary or an alternative service to GSM-R's data connection service. In general, transfer of the situation data of point machine from the line to the logic unit on railway vehicle is discussed. Point machine is the vital element of railway on track side and in case of any error with this component is going to affect all operation on line. So, this critical situation makes its state significant and it should not be affected from any capacity or other problems. To ensure safety on radio communication, some of CENELEC's SIL specifications are used for software testing purposes. 

As development enviroment software's:
●	Visual Studio 2015 
●	MS SQL Server 2012
Applications developed:
●	Web service application which is developed with C# 
●	Terminal application which is improved with C# 
●	Indication application which is developed with C#

All applications are developed with C# programming language as native development environment for this language is Visual Studio 2015. MS SQL Server 2012 selected for fully compatibility with C# programming language and also it has SQL Dependency support which helps to create application with the ability of notification if any change happens in the database.
In the prototype study, a terminal application has been developed which gets the position data of the point machine via RS232 interface reading over a relay and sends the data to the logic unit of the railway vehicle either via internet connection or via UHF connection. A web service software has been developed, allowing all the systems to communicate from a common place for the railway vehicle, also when needed, supporting to communicate with the other software languages, and getting the position information of the point machine to record on a database. Also depending on the data obtained, an indication application has been developed which shows the position of the point machine either in normal or in reverse and the time of change of the situation and the time of the acknowledge receipt of the logic unit.

Two web services developed with object oriented structure which helps to communicate over SOAP protocol. This protocol helps with secure structured communication and it also supports XML based communication. One of the services is for UHF radio communication which has extra COM Port timing and second one is for the other communication styles.  
A terminal application is improved to support two types of communication. 
Firstly, listening the RS232 port CTS and DSR pin's state and sending data in case of state change with SOAP protocol over the internet. 
Secondly, listening one of the RS232 ports CTS and DSR pin's state and send data over UHF radio via second RS232 port in case of any state change. If the communication is handled at receiver side over UHF it should select UHF radio communication port as open.
An indication application developed for server side to help showing data immediately when arrives. SQL Server will push as notification to indication application and it will indicate on the screen if event logged at database which are occurrence time, COM Port TX time (if UHF activated), COM Port RX time (if UHF activated) and data write time to database.
At the hardware side, Since the SIL certificated hardware's are so expensive, it was not possible to use any in this thesis due to lack of the budget.
Hardware's which are used: 
●	Three RS232 to USB converter, 
●	Two pieces 24V dry contact relay, 
●	Two computers, 
●	Two modems, 
●	A point machine with two feedback 24V over relay.
●	Two Radius PDR 221 UHF radio unit
●	Two Cohda Wireless MK5 802.11p radio unit
Hardware side comes with three configuration topologies which are 802.11p, UHF and Internet based.  
First topology:
●	Three RS232 to USB converter, 
●	Two piece 24V dry contact relay, 
●	Two computers, 
●	Two Cohda Wireless MK5 802.11p radio unit
●	A point machine with two feedback 24V over relay.
Second topology:
●	Three RS232 to USB converter, 
●	Two piece 24V dry contact relay, 
●	Two computers, 
●	Two Radius PDR 221 UHF radio unit
●	A point machine with two feedback 24V over relay.
Third topology:
●	Three RS232 to USB converter, 
●	Two piece 24V dry contact relay, 
●	Two computers, 
●	Two modems (network), 
●	A point machine with two feedback 24V over relay.
First topology is for broadcast mode for direct device to device communication type. Second topology is master-slave operation logic for UHF based device to device radio communication. Third topology splits into two sub configuration at internet network side. 
Local network:
●	Wifi (IEEE 802.11b/g/n 2.4GHz) and Ethernet over modem for local area network
Public network:
-	LTE based
●	Wifi (IEEE 802.11b/g/n 2.4GHz)  and Ethernet over modem for local area network
-	Public line based (ADSL, Fiber)
●	Wifi and Ethernet over modem for local area network
Local network is the fastest network communication type. It takes approximately 1-2 ms to communicate between point machine computer and server side computer devices which finishes job after 1-2 ms after the point machine state fired. This is an extremely fast way to communicate between devices but it has low range issue.
Public network includes not only local network, but also LTE based or public line based communication types which helps out to carry information farther away. When an event fired at the point machine, it will feedback 24V which triggers 5V relay which is supplying RS232 pins.  When RS232 get stimulated by 5V it will be sensed by the computer, at this point it will convert analog information to digital information as a point machine state. Then it will trigger web call over a modem through LTE or public line network to a remote side server. Finally, remote side server computer generates an answer for this call event and send it back to point machine pc, when response reaches to point machine pc progress will end.