Design of GPRS CQT Test System Based on ARM Platform

GPRS, as the bearer network of China Mobile's data services, supports a variety of data services involving different network elements. Any failure of any network element will directly affect the normal use of data services. It is very important to ensure end-to-end use by users.

GPRSDT/CQT test simulates the use of terminal users and describes the use process of data services with tools such as time charts, event lists, and layer 3 signaling, which helps engineers accurately locate and analyze problems encountered in the test. In the past, CQT testing was mainly carried out in the form of manual testing. First, a test plan was formulated and handed over to the tester to conduct the test at a designated location. The test tool was generally a special mobile phone for signal testing. The data obtained from this test was manually recorded by the tester, and then statistically sorted and analyzed. There was a lot of subjectivity and lack of authenticity and accuracy. At present, the characteristics of the construction of base stations in mobile communications are large numbers and wide distribution. It is impossible to conduct signal tests on a large number of base stations and their coverage areas, so that some places become test blind spots.

The CQT test system designed based on embedded ARM in this paper adopts remote detection mode. The test terminals are distributed at the target test site and receive test task instructions from the remote monitoring center. They automatically perform tests and then generate reports to send back to the monitoring center. Experiments show that the scheme has good practicality and reliability.

Structural design of the test system

While GPRS is being commercialized on a large scale across the country, China Mobile Group has formulated technical specifications for on-site testing of GPRS network operation quality. The main method of on-site inspection of GPRS network operation quality in major cities across the country is to conduct fixed-point dialing tests on important places in the urban area and DT road tests on urban roads to evaluate the GPRS network quality of the city from the perspective of user experience. The test content of GPRSDT/CQT (GPRSDriveTest/Call Quality Test) includes Attach test, PDP activation test, Ping test, FTP download test, WAP test, Kjava, SMS test, and MMS test. China Mobile DT and CQT test specifications and assessment specifications (hereinafter referred to as test specifications) stipulate the content and methods of each test. The experimental device designed in this paper implements most of the test content of CQT.

The structure of the CQT test experimental system is shown in Figure 1, which consists of two parts. The test terminal is installed at the test site. Its function is to receive task instructions from the monitoring host, automatically test the GPRS network according to the task, collect data, and finally send it to the database of the monitoring host. The monitoring host includes two parts: task management and database. It can remotely control the test tasks of the test terminal and accept test data reports submitted by test terminals from all over the country, so as to generate reports and realize unified scheduling and data management. The SIM card used by the test terminal can be any brand of China Mobile card with GPRS data service function. The Shenzhouxing card was used in the experiment. The monitoring host can use both wired and wireless access methods. If the test is carried out in the APN of CMNET, ordinary ADSL wired access to the Internet network can be used, or a set of GPRS Modem wireless access network can be used; if accessed in CMWAP or dedicated APN, the monitoring host must use GPRS wireless access in the same network segment.

There are two types of test tasks: offline test and online test. The former does not initiate PPP dial-up for the time being, but collects test data such as GPRSATTACH, PDPACTIVATE, and SMS according to the requirements of the test task, and the results are temporarily stored in the Flash memory of the test terminal; the latter first performs PPP dial-up to connect to the CMNET access point. After successful connection, it generates frames together with the offline test data, and sends back the monitoring test task to perform PING, FTP and other tests, and then the host performs unified data management. The dial-up test requires continuous initiation and termination of PPP dial-up connections, which is between offline and online. For the convenience of design, it is classified as an online test project in this system. [page]

Hardware structure design of test system

The hardware structure of the test terminal is shown in Figure 2. The main processor uses the S3C2410 with Samsung ARM920T core, which is very suitable for developing high-performance handheld and portable smart devices or terminals. In this GPRSCQT test terminal, the following parts are emphasized:

• Storage system: 64M NandFlash, 64M (32M × 2 pieces) SDRAM;
• Ethernet: A 100Mbit/s Ethernet port is designed for debugging and upgrading;
• Serial port: Two serial ports are designed on the board: UART0 is the console and UART1 is the communication interface with GPRS Modem.

The GPRS module uses the Q2403A module from France's WaveCom company, which supports voice, short message, data and fax functions. It is suitable for SMS center, wireless meter reading, GPRS wireless Internet access, GPS, repeater monitoring, etc. It has an ultra-thin and ultra-small design and stable performance. A standard Modem interface can be realized by adding a few peripheral circuits. It is connected to the UART1 interface in this system, and standard AT commands are used to achieve communication between the mainboard and GPRS Modem.

Test software design

In the underlying software, this solution transplants the currently widely used soft real-time embedded operating system armlinux. Embedded Linux has a complete set of commonly used network protocols (TCP/IP, UDP, FTP, etc.) and related tools, and its performance is stable and reliable. In this experiment, the linux2.4.18 kernel is transplanted. In order to realize functions such as PPP dial-up, select PPP protocol support when configuring the kernel in makemenuconfig, and select related tools pppd and chat. In order to test UART1, the tip serial port debugging tool is also transplanted.

The following focuses on the test methods of several CQT projects implemented in this experiment. All are implemented using C programming under Linux. Offline testing is mainly serial port programming, and online testing involves related network socket programming.

ATTACH attachment test first uses AT+CGATT? in the AT instruction set to query the attachment status. Returning 1 means it is attached, and returning 0 means it is not attached. If it is attached, send AT+CGATT=0 to GPRSModem to let it exit the attachment, then send AT+CGATT=1, start the timer, wait for the return, stop the timer when OK is received, and collect one ATTACH test data. The waiting time is set to 15 seconds in the experiment, and the timeout is considered a failure. According to China Mobile's DT and CQT test specifications and assessment specifications (hereinafter referred to as test specifications), 10 ATTACH data should be collected.

PDPACTIVATE test can be tested using AT+CGACT command. First, send AT+CGACT? to GPRSModem to query the PDP activation status, and return +CGACT:0 0 indicates that it is not activated, and +CGACT: 0 1 indicates activation. If it is activated, send AT+CGACT=0,0 to return the PDP to the inactive state, then send AT+CGACT=0,1 and start the timer, wait for the return +CGACT: 0 1, then stop the timer and collect a PDP ACTIVATE test data. The timeout period is also 15 seconds.

The SMS text message test is also carried out using the relevant AT commands. Perform 10 sending tests and detect the sending report. For the convenience of testing, the SMS is set to Textmode, which can be set using AT+CMGF=1, AT+CMGS=[,] followed by the message content, ending with, send the SMS, and AT+CMGR= read the SMS.

After the offline test is completed, the system temporarily stores the test data, then starts the ARMlinux system's pppd and chat programs to initiate a PPP dial-up connection to the CMNET access point, and generates a frame format, immediately sends the offline test data to the monitoring host, and then enters the following online test.

The dial-up test configures PPP related files, uses the Linux pppd/chat program to initiate dial-up, detects whether the ip-up script program is started or not to determine whether the dial-up is successful, and calculates the time consumed. A total of 10 dial-up tests were performed.

PING and FTP tests were performed according to the test specifications. The sites in the GGSN LAN were pinged with a 500-byte packet length. Each site was tested 10 times. The FTP test downloaded a 500-KB file once.