introduction
4G-Ready, as an area of ​​key preparation technology for future 4G mobile communications, has important application prospects in the construction of wireless communication networks and wireless data communication systems. Among them, 4G-Ready is integrated with Wi-Fi technology, Blutooth Bluetooth technology, GPS global positioning system and ARM core-based embedded technology, and application software systems are developed in Linux-C and Java programming languages, which can constitute a variety of The embedded Wi-Fi wireless communication network terminal system with superior functions, technical performance and advanced practicality can meet the needs of wireless data communication applications in the fields of building urban intelligent traffic management, municipal environmental protection monitoring and scenic area information management.
1 Main technical analysis
The main technologies applied in embedded systems based on 4G-Ready and Wi-Fi architecture are analyzed below.
1.1 Wireless communication technology
1.1.1 Introduction to 4G-Ready
4G-Ready is a description of the currently developing 4G communication technology. At present, it is internationally believed that the data transmission rate provided by 4G is generally 10 ~ 20Mb / s, the maximum data transmission rate exceeds 100 Mbit / s, and each 4G channel will occupy The 100 MHz spectrum has wide network spectrum performance.
4G should have a variety of communication functions, including access to the Internet, voice and data communication, streaming media transmission, integration of wireless communication networks of different modes, cellular signals, broadcast TV to satellite communication, so that mobile users can roam freely among multiple standards Services etc.
1.1.2 Wi-Fi technology and networking
The technical standard of Wi-Fi is IEEE 802.11 issued by the Institute of Electrical and Electronics Engineers (IEEE, InsTItute of Electrical and Electronics Engineers), including IEEE 802.11a, IEEE 802.11b, and IEEE 802.11g, of which IEEE 802.11g is commonly used.
Wi-Fi is a short-range wireless transmission technology that can support Internet wireless access within hundreds of meters.
1.1.3 Introduction to Bluetooth technology
Bluetooth (Bluetooth) is a short-range wireless communication technology, the working frequency band is 2.4 GHz, which belongs to the industrial, scientific and medical frequency band (ISM, Industrial ScienTIfic Medical), and its data transmission rate is 1Mb / s, using a time division duplex transmission scheme, Use IEEE802.15 protocol. The embedded system described in this article is equipped with a Bluetooth 2.0 Bluetooth interface to collect real-time graphics, images and location information.
1.1.4 GPS wireless positioning technology
GPS consists of a space part, a ground control system and user equipment. The space part consists of 24 satellites evenly distributed over the earth. The ground control system consists of a monitoring station, a main control station and a ground antenna. User equipment generally refers to GPS signal receivers. The embedded system designed and analyzed here uses a separate structure GPS receiver.
1.2 Embedded (Embedded Technology) technology
The embedded system consists of a 32-bit word-length microprocessor, ROM memory, RAM memory, and information I / O interface modules and components. The embedded Linux operating system is stored in the ROM.
1.2.1 ARM technology
The ARM core embedded microprocessor is the core of the embedded system. It is designed by the British ARM company (IP, Intellectual Property core) core, designed by various semiconductor companies as chip products, and then OEM manufacturers form embedded system products. The EP9302 system used in the current project is an embedded system with an ARM9 core processor as the core technology.
1.2.2 Embedded Linux operating system
Linux is a free, free, open-source operating system software. It has complete software functions and complete network functions. It inherits the UNIX technology of multi-user, multi-task, multi-thread, and multi-CPU.
The current version used in embedded systems is embedded Linux 2.6.21, which supports kernel-mode preemptive scheduling with a scheduling period of 1 ms.
2 Build technology development platform
Figure 1 shows the schematic diagram of the embedded Linux development platform based on LAN.
Figure 1 Embedded Linux development platform based on LAN
The Linux server in Figure 1 serves as a common platform for embedded Linux kernel compilation and application compilation. The workstation (PC, Personal Computer) is one or more terminal computers in the local area network, which realizes the file transfer between Windows and Linux.
The embedded target system is connected to the workstation through a serial interface, using the "Super Terminal" function provided by Windows; it can also be connected to the local area network through the Ethernet RJ45 interface to achieve the connection to the network's FTP / NFS server.
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