Abstract— This article describes the analysis of return channel for digital terrestrial television (DTT), through the development of interactive application called ShoppingCar buying and selling. Using the middleware Ginga-NCL, Lua and MySQL, to get evidence of the return path for the interactive application and determines the capacity of server performance.

I. INTRODUCTION

On March 26, 2010, Ecuador officially adopted the Japanese-Brazilian standard (ISDB-Tb) for digital terrestrial television. The digitization of television allow improved image quality and sound, increasing the supply of TV channels, high definition and other features such as interactive program guide.

Interactivity can be of two types, local interactivity is what allows the viewer to interact with information on set-top-box, while the interactivity with return channel allows exchanges with extern agents via the Internet.

In this article, has developed an interactive return channel, which aims at the inclusion of DTT in society, focusing the T-Commerce, which is the purchase through the TV screens, to perform the analysis of the return channel using the Wireshark tool.

II. DIGITAL INTERACTIVE TELEVISION

A. Middleware

Ginga is the name of open middleware Brazilian Digital TV System. Allows the possibility of presenting content in different receptors. The Ginga-NCL was developed by the Pontifical Catholic University of Rio de Janeiro, PUC-Rio, provides an infrastructure for interactive presentation of such declarative language written in NCL (Nested Context Language), where NCL is an application of XML (Extensible Markup Language) which can facilitate aspects of interactivity, synchronicity, time-space between objects of Midia, adaptability, support for multiple devices and support the production of live interactive programs non-linear [1].

B. Lua

Lua is an extensible programming language designed for general procedural programming utilities for data description. It also offers good support for object-oriented programming,

*Resrach supported by Digital TV Group - ESPE. Ana Paredes, Nancy Tongino, Freddy Acosta and Gonzalo Olmedo,

Department of Electrical and Electronic Engineering, Army Polytechnic School, ESPE, Quito, Ecuador, E-mails: fracosta@espe.edu.ec, gfolmedo@espe.edu.ec.

functional programming and data-oriented programming. Lua is intended to be used as a powerful scripting language and light for any program that needs it [1].

III. RETURN ON TV CHANNEL DIGITAL

As mentioned earlier, one of the most important advantages in digital television, is the possibility that the user can interact with the television via the remote control, allowing you to view additional information, manipulate the programming of TV channels, purchase services or products, enter contests, voting, etc. However, this type of applications in addition to needing a platform for interactive applications, require a two-way communication, they need to add a return channel to provide for the existing downspout, so that the user is able to interact directly with the external server (Remote Interactivity) or who has access to Internet (Full Interactivity).

In the DDT can perform interactive programs with return channel, which is necessary for the user to have the Set Top Box, Internet access and that here in one of the ways you can do to upload and download programs viewer's choice.

The Set Top Box is linked to the connection point to the network, which through a broadcast will arrive to load applications from the point of our plant, which would mean that the user can navigate from your TV and be part of real-time applications. Applications include: education, it could mean that download information from a search engine or give online tests, purchases, and you can have an online store, restaurants, jewelry stores, and internet access thanks can make bank transfers preference, as well as review the statement with which we, entertainment, what could make development of online questions, games and more.

IV. DATABASE FOR INTERACTIVE APPLICATIONS

A. Creating the Database

A well-structured database can handle more information in an organized manner, and access the data properly so they can be used as needed by the application. Our database was created in MySQL, the same is free software that manages one or more databases in a relational, multi-threaded and multi, using the same as administrator of phpMyAdmin, which is a software tool free, which allows you to interact with the database very easily and from a web interface, one of the main features is to manage users and privileges [2].

B. Design Database

For this project has designed the database called ShoppingCar, it aimed to make the purchase of three products using the DDT interactive.

Performance Analysis on Return Channel for Interactive Digital TV ISDB-Tb System

Ana C. Paredes, Nancy M. Tonguino, Gonzalo F. Olmedo and Freddy R. Acosta.

ShoppingCar to design tables were created to the database, and proceeded to the phpMyAdmin outline as seen in Fig. 1, identified variable types, the relationship between primary key tables, the it is an identifier that allows the association of the parameters in tables.

Figure 1. Tables Created for ShoppingCar

(Original System with spanish legend)

C. Connecting to the database through a Web Service

To establish the connection between the application built on NCL-LUA and the MySQL database, we used protocols that focus on the internet, such as Simple Object Access Protocol (SOAP), which is a standard protocol that defines how two objects in different processes can communicate via XML data exchange, it is an extensible markup language, allowing the exchange of information in the applications through HTTP.

To create the NCL-LUA communication with the MySQL database extract the information from the Web Service, communicating through the application layer via HTTP and once the connection between the two could interact successfully with the base data. Fig. 2 shows the basically client-server type.

D. Connecting PHP Server Database

In PHP dynamic web applications are developed, also used in all major operating systems, including Linux, also supports most web servers today, including Apache, IIS, etc.., Allowing you to choose freely the operating system and the web server.

PHP project created in Eclipse Galileo software for the application was called appExample, this is related to the database set forth herein, where tables were created ShoppingCar generated as classes, respecting the same parameters that were established on the basis of data.

E. Connecting to the Database from Lua through a Web Service

For communication between Lua and the database is generated in appExample a document type called php wsCar coming to the Web Service to consume, the same that contains the parameters required for check-ins, which are: Customer, product and quantity.

Web Service: This is an application that can be described, published, located and invoked over a network, usually the

Internet, using a set of protocols and standards used to exchange data between applications.

Figure 2. Schematic Connection NCL-LUA and MySQL database through

the Web

F. Programming in Lua to consume a Web Service

To use the SOAP NCLua, just add the line "ncluasoap" Lua program, variables are declared lcustomer, lamount, and lproduct where lcustomer is the application user or viewer of purchase, lproduct is the registered product code ShoppingCar and lamount in the amount of products sold, which in our case is only one. These variables will be subsequently sent to the Web Service through a table in lua.

We used the call (ncluasoap.call), which generates and sends a SOAP request and get the return XML, which becomes a lua table (with Lua XML module) to facilitate access to the feedback data with a call a remote method, sending parameters, msg (Lua table), getResponse (function that prints the message xml returned by the Web Service) and soapVersion (Version of soap).

The main parameter of the function is msg(Table ncluasoap.call), it must be a Lua table containing the data to access the Web Service method.

G. Programming Environment in GINGA-NCL

To begin, a structured document in the software NCL Eclipse Helios, which will represent multimedia, synchronize time and space to create our interactive application.

Creating regions, which is where they will play the multimedia objects, descriptors, they reproduce multimedia objects, indicating which region displays the media object with that property.

With the help of links and connectors provides the synchronization between nodes, to determine when you are playing the multimedia nodes.

In the body a Port pointing to a multimedia object, indicates that its presentation will begin when the application starts.

Below are reported multimedia nodes were used, with their respective attributes.

H. Run the Application

The interactive return channel, for our particular case, purchase of three different products to be registered in a database data, focusing the T-Commerce, whicpurchase through the TV screens.

Once loaded the application appears in the bottom of the screen are two options: Purchase and out, as shown To switch between options use the buttons from left to right and select the OK button.

Figure 3. Main Menu of the application

Shopping selecting, there are three options on the left side of the screen. To make the purchase, each of the articles is associated with a different color indicatoryellow, so when you want to make a purchase you mustthe remote control color corresponding to the product that will make the purchase. In Fig. 4 shows the shopping options in the application ShoppingCar.

Once the purchase confirmation message appears on the screen at the bottom left, returns to main

When choosing the exit option, the application terminates.

Figure 4. Submenu by selecting option SHOPPING

V. CHANNEL ANALISIS OF R

To perform the analysis of the return channel, were considered two environments for analysis: the case A, is running the application on the network where the server is up, and case B is the running application from a home located in the city of Quito with DSL Internet accessanalysis in the case B, since it is in our interest to know the

interactive return channel, for our particular case, purchase of three different products to be registered in a

Commerce, which is the

Once loaded the application appears in the bottom of the screen are two options: Purchase and out, as shown in Fig 3. To switch between options use the buttons from left to right

enu of the application

Shopping selecting, there are three options on the left side of the screen. To make the purchase, each of the articles is associated with a different color indicator, red, blue and yellow, so when you want to make a purchase you must press the remote control color corresponding to the product that

shows the shopping options

Once the purchase confirmation message appears on the screen at the bottom left, returns to main menu.

When choosing the exit option, the application

Submenu by selecting option SHOPPINGCAR

HANNEL ANALISIS OF RETURN

To perform the analysis of the return channel, were considered two environments for analysis: the case A, is

pplication on the network where the server is up, and case B is the running application from a home located

with DSL Internet access. Focusing the analysis in the case B, since it is in our interest to know the

behavior of the application ShoppingCar in a realenvironment.

The networking scheme employed is shown in Fig. 5

Figure 5. Network Structure for using Channel Return

The tool was used to analyze the respective network, Wireshark, the analyzer tries to capture network packets in order to display it in detail asthrough a graphical and userDetermining the maximum bandwidth required by the application ShoppingCar, its transmission rate, packets sent and received from the server.

In Fig. 6 shows the network traffic that occurred when making three purchases ShoppingCar application, as shown in the graph, there are oscillations in the transmission the same as are produced because the application is connected to the Internet at there are protowell, apart from the application signaling packets flow based TCP ACK packets, SYN packets, etc.

It is also noted that the time it takes to make the three purchases is about 110 seconds and the maximum bandwidth occupied by the application is 80kbps. It stressed that the scale you are working in the figures are bit vs sec.

Figure 6. Capture Network Traffic with Network

As can be seen in Fig. 7, the transmission rate defines a number of bits transmitted per unit time, ie the speed oftransfer that exists in the application ShoppingCar, which is 9kbps.

behavior of the application ShoppingCar in a real

heme employed is shown in Fig. 5.

Network Structure for using Channel Return

The tool was used to analyze the respective network, Wireshark, the analyzer tries to capture network packets in order to display it in detail as possible [3]. Displays data through a graphical and user-friendly and understandable. Determining the maximum bandwidth required by the application ShoppingCar, its transmission rate, packets sent

shows the network traffic that occurred when making three purchases ShoppingCar application, as shown in the graph, there are oscillations in the transmission the same as are produced because the application is connected to the Internet at there are protocols that are always running, well, apart from the application signaling packets flow based TCP ACK packets, SYN packets, etc.

It is also noted that the time it takes to make the three purchases is about 110 seconds and the maximum bandwidth

the application is 80kbps. It stressed that the scale you are working in the figures are bit vs sec.

Capture Network Traffic with Network

, the transmission rate defines a number of bits transmitted per unit time, ie the speed of data transfer that exists in the application ShoppingCar, which is

Figure 7. Capture the Transmission Rate

Keep in mind that the server has to have excellent bandwidth and that it must be able to resolve all requests that customers made, the server that was used has a 40G hard drive processor, memory 1G and has a 3Mbps internet service in both uplink and donwlink.

Performance Analysis of Web Service

To perform the analysis in wsCar server, software was used Apache JMeter [4], it is an open source application designed in Java, simulating a number of requests which measure the strength of the server, to analyze the overall system performance that is, allows sending a number of concurrent users to obtain information on how the server behaves wsCar under those situations.

Tests on the Web service is made outside the network of the ESPE, since we are interested in evaluating the performance of the server from the client's home.

Every second were sent a set of requests for: 2500, 5000, 10000, 35000 and 40000 users. Following tables show results containing the 10000 and 40000 users.

In the Table. 1 shows the results obtained by sending 10,000 requests per second, where the Media is set to 1, with arithmetic type and representing the average number of requests or samples sent. In our case the elements in the sample space increases arithmetically, so the arithmetic mean and median are equal. In addition, an output of 291.1 percent in every second, like it was an error of 0 percent.

TABLE I.

RESULTS OBTAINED WITH 10000 USERS.

Label Number

of Samples

Average Median Line 90%

Performance

Web service

request

10000

1

1

2

291,1/s

Total

10000

1

1

2

291,1/s

In Table.2 we can see the results that were obtained by sending 40,000 requests per second, where the Media is set to 1, with arithmetic type and representing the average number

of requests or samples sent. In our case the elements in the sample space increases arithmetically, so the arithmetic mean and median are equal. We also observe that performance declines relative to the increase in requests per second, which was 190.2 percent in each second, ie, the server worked at full capacity, which can cause the server no longer responds appropriately to requests requested.

TABLE II.

RESULTS OBTAINED WITH 40000 USERS.

Label Number

of Samples

Average

Median

Line 90%

Performance

Web service

request

40000

1

1

2

190,2 /s

Total

40000

1

1

2

190,2 /s

VI. CONCLUSION

Through the results obtained in tests for the application ShoppingCar was obtained an immediate response time wsCar server, verifying that there efficiency in transmitting the return channel, in addition, the maximum bandwidth used by the application 100kbps is in compliance with the ranges established for working with Web Services, managing to reach the objective.

As can be seen in the graphs obtained from ShoppingCar network traffic, the transmission rate reaches 9kbps compared with the value of Throughput 9kbps approaching, we can conclude that there is a good network performance, since the Throughput value does not exceed the value of the transmission rate.

The return channel interactivity facilitates the convergence of Internet and digital television, which allows the user to consume services designed in different programming languages.

ShoppingCar The database created for the interactive, dynamic type is, ie, the stored information can be modified over time, allowing it to update, add data, and perform basic query operations, while helping to protect phpMyAdmin preventing data tampering, using the user management, the same as administrator to assign a password.

With the characteristics of infrastructure available to the application server can have up to 40,000 users per second, so it is recommended that the application out ShoppingCar production, is considered to improve the characteristics of server infrastructure.

REFERENCES [1] Brazilian Standard, ABNT NBR 15606-2, “Digital terrestrial

television – Data coding and transmission specification for digital broadcasting – Part 2: Ginga-NCL for fixed and mobile receivers – XML application language for application coding”, Version 2009.

[2] PhpMyAdmin, http://www.phpmyadmin.net, 2012. [3] Wireshark, http://www.wireshark.org, 2012. [4] Jmeter, http://jmeter.apache.org, 2012.