Design of intelligent public transportation indication system based on short message

introduction

The public transportation system has been recognized by countries around the world as the best strategy to solve the traffic problems of large and medium-sized cities due to its advantages such as large carrying capacity, high transportation efficiency, low energy consumption, relatively low pollution and low transportation cost. It is also one of the important infrastructures for the survival of cities. However, due to various reasons, the operating speed of public transportation vehicles has dropped from 12-14 km/h to 4-10 km/h. The newly added capacity is offset by the decline in transportation efficiency, and the transportation volume undertaken by public transportation has continued to decline, which undoubtedly aggravates the contradiction between the continuous increase in transportation demand and the relatively backward development of public transportation. To solve these problems, it is necessary to develop public transportation that can improve transportation efficiency and truly realize the movement of people rather than cars. This requires improving the overall level of public transportation services, attracting more passengers to travel by public transportation, and reducing the number of private transportation trips. Therefore, the Intelligent Transportation System (ITS) has become the core of the entire public transportation. Only by continuously optimizing this system and strengthening the scientific scheduling of the public transportation system can the service quality of public transportation be improved, so that the role of public transportation can be maximized and ultimately solve the urban transportation problem fundamentally [1, 2].

In recent years, due to the progress of science and technology and the government's increased investment in public transportation, my country's intelligent public transportation system has begun to emerge. Cities such as Hangzhou, Shanghai, Beijing, and Dalian have built bus tracking and dispatching systems on some bus routes, and installed electronic bus stops and on-board GPS positioning equipment. This has realized the real-time tracking and positioning of vehicles, two-way communication between buses and dispatch rooms, and real-time display of the location information of the next bus on the electronic bus stop. The above functions make the dispatching process based on evidence and can realize computer-aided management. This not only saves labor and reduces the labor burden, but also improves the regularity rate and service level of vehicle operation, attracting a large number of passengers.

Based on this, this paper proposes a vehicle positioning, indication and dispatching system based on the short message function of the GSM mobile communication system. The system has the advantages of simple structure, easy implementation, powerful functions and low cost.

1 System Implementation Principle

GSM (Global system mobile) is the digital mobile cellular communication system with the widest coverage, highest system reliability and the largest number of telephones in China. It not only has a large communication range and reliable system operation, but also is economical, practical, low-investment and easy to popularize. It can reduce the repeated investment and construction of base stations of various dedicated communication networks, and monitoring centers in various places can also be easily connected to the Internet. At present, China Mobile's GSM network is the largest network in China. Relying on the GSM network with powerful digital mobile cellular communication technology as the wireless transmission network of the vehicle monitoring and positioning system can ensure the reliability of the transmission channel. The short message method is a convenient data communication method of GSM. Using GSM short messages as the wireless transmission method of the intelligent public transportation system, the optional communication modules include Siemens' TC35 and so on. Its specific system structure is shown in Figure 1.

The specific operation of the system is: when the bus arrives at the platform and the voice station announcer is pressed at the same time, the system sends the information of the current arrival station through TC35. The dispatch center and the intelligent bus indication system of the next station will display it after receiving the information, so that the dispatch center and passengers can know the station where the vehicle is at this time, so that the dispatch center can track and dispatch the vehicle. At the same time, passengers can also know the approximate time when the vehicle arrives at the next station.

Obviously, the intelligent bus indication system introduced in this article utilizes the short message receiving and display functions. The reception of short messages and the extraction of content can be completed by TC35 and the single-chip microcomputer, and the two can communicate through the RS232 serial port. TC35 is a new generation of wireless communication GSM module launched by Siemens, which can quickly, safely and reliably realize data transmission, voice transmission, short message service (Short Message Service) and fax in the system solution. The display part can be completed by light-emitting diodes, and more powerful display units such as liquid crystal displays will continue to be improved in the future.

2 Implementation method based on TC35

The functional block diagram of the TC35 module is shown in Figure 2. The module mainly consists of six parts: GSM baseband processor, GSM radio module, power supply module (ASIC), flash memory, ZIF connector, and antenna interface. As the core of TC35, the baseband processor mainly processes the voice and data signals in the GSM terminal. It covers all analog and digital functions in cellular radio equipment. It also supports FR, HR, and EFR voice channel coding without the need for additional hardware circuits. [5]

The main AT commands used in this system are reading and deleting short messages, as follows [6]:

The first one is the main command for the TC35 module to read short messages. Its format is: AT+CMGR=, where index indicates the location where the short message is stored. Suppose you want to read the second short message, then index=2. Then in the PDU format, there are:

Send: AT+CMGR=2 (read the second SMS)

Answer: +CMGR1,,22

891683108504705F0040D91683165874890F400086040428160220002963F

OK

In TEXT format:

Send: AT+CMGR=2 (read the second SMS)

Answer: +CMGR: "REC READ", "+8613567884094", "06/04/24, 18:06:22+00"

OK

The whole process can be displayed on the serial port debugger, as shown in Figure 3.

The second command is to delete the short message. Its format is AT+CMGD=. Here, index also indicates the location where the short message is stored. For example:

Send: AT+CMGD=3 (delete the third short message)

Answer: OK

After testing the above instructions, you can understand the specific process of receiving text messages. The process of using a single-chip microcomputer to control TC35 to receive short messages is essentially the process of sending instructions and how to judge whether the instructions are sent successfully. Therefore, the focus of this part is programming the single-chip microcomputer. The specific process is to initialize the TC35 module first. This design only needs to receive it in TEXT text format, and does not need to receive the encoding in PDU format (this will be the focus of future consideration); then set a new short message prompt command for TC35 so that when a text message is received, it will prompt the specific location where the text message is stored. This will facilitate us to correctly receive the content of the required text message: After completing these two steps, you can use the text message receiving command to display the text message content in the SIM card. This design needs to consider such a problem: in the SIM card used. Its capacity is limited, and when the text message is full, the SIM card will not be able to receive text messages, so you should also consider using the short message to delete the command. That is, delete the text message immediately after reading the content of a text message. In addition, in the last task of this design, it is also necessary to correctly display the content of the message on the light-emitting diode, so a display program is also needed.

3 Conclusion

The intelligent public transportation indication system based on the GSM short message system introduced in this article has the characteristics of simple structure and strong practicality, which is very suitable for modern intelligent public transportation systems. Due to the limitations of time and devices in this design, the author has only completed some circuit principles used by a simple intelligent public transportation. If you want to study intelligent public transportation more deeply, you can also make improvements in the following aspects:

(1) Diversification of short message content. The short messages in this article are mainly text, but in order to adapt to the characteristics of information diversification, multimedia message transmission and even real-time video transmission systems should be developed in the future.

(2) Diversification of display units. Multifunctional display devices such as touch-sensitive LCD screens and wireless LED dynamic display modules can be used to achieve more interactive functions.

(3) Automation of the dispatching function of the dispatching center. By developing relevant dispatching software, public transportation operations can be automatically dispatched according to real-time road conditions and vehicle operation conditions, effectively improving public transportation efficiency.