Hwn Gateway Design

Release date: 2003-12-3 15:57:08

Abstract This article proposes to use Bluetooth technology to build a home network, namely, Personal Area Network (PAN), which is the core device of home wireless networking ). An external information transmission network is composed of G mobile communication network GPRS technology, so as to design a mobile, personalized, convenient to use, advanced technology wireless home gateway.
Key words wireless gateway home network Bluetooth GPRS

The home network is a new technology that can be expanded to connect PCs, household appliances, security systems, lighting systems, and wide area networks to neighbors and residential communities within the family. The Home Gateway is an important device for information exchange between the home and the home. High-quality life must respect the personalized style. Home gateways must get rid of the limitations of the line and use wireless networks to present a mobile, convenient, and decorative function.
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Bsp; therefore, the author designs a completely wireless home gateway. Two important wireless communication technologies, Bluetooth and GPRS, constitute an internal and external wireless network topology, which can realize high-speed information transmission and can be randomly placed in locations, adapt to personalized family layout. Figure 1 shows the function of the wireless home gateway.
According to the network topology shown in figure 1, the internal network of the home is an intranet composed of the ericesson bluetooth module. The RF is 2.4 GHz and the external network is composed of the cms91 dual-band 900/1800 GSM/GPRS 10-level module produced by Philips.
1 Bluetooth Intranet
A family is a place with distinctive personalized characteristics. It is necessary to build a personal area network in the family to achieve intelligent interconnection of personal information terminals in the family and build a personal information network, the technical implementation methods are wired and wireless. Currently, the emerging short-range wireless network technology occupies the mainstream of home networks, including Bluetooth, IRDA, home RF and Ultra-Wideband Radio.
Bluetooth is an open, point-to-point, point-to-point voice and data service communication that supports flexible, secure, low-cost, and low-power networking among various digital devices. At present, the core bluetooth technology can be easily embedded into a single CMOS chip, which can greatly reduce the cost of Ambassador, so it is particularly suitable for the formation of small family networks.
1.1 bluetooth technology and network topology
Figure 2 shows the topology of the Bluetooth Network. Bluetooth devices are equal in any valid communication range. Based on the TDMA principle and the equality of Bluetooth devices, a wireless Ad Hoc network structure can be constructed. Any bluetooth device in the Master/Slave Network (piconet) and scatternet can be used as both the master device and slave Server Load balancer, and can be both the master device and slave Server Load balancer) it is also from the slaver device. Addressing eight devices in one piconet (in fact, there is no limit on the number of interconnected devices, but only eight devices can be activated at the same time, one of which is the primary device and the other is the slave device ).
Bluetooth operates in the 2.4 GHz ISM band with a 1600 Hop/second Hop Frequency, that is, GHz as the center frequency, 79 1 MHz bandwidth channels can be obtained. When the transmitter frequency is 1 MHz, the valid bluetooth data rate is 721kb/s. Because the launch is "time division multiplexing (TDMA)", its main advantage is its low cost and good security and Error Correction performance. Bluetooth can be expanded to a small network suitable for home use without any changes.
1.2 master and slave units in the Bluetooth Intranet
With the application of Bluetooth technology in various fields, a number of world-leading telecom equipment manufacturers and PC manufacturers have formed a special interest group for Bluetooth Sig, which has accelerated the market-oriented application of Bluetooth technology. This short-distance, low-cost Spread Spectrum Technology can easily connect various portable devices, such as laptops, Information appliances, mobile phones, and digital consumer products to form a Bluetooth internal network.
In Figure 1, the master and slave are the master and slave devices in the Bluetooth Network. Bluetooth devices generally consist of four parts: antenna unit, Link Control (firmware) Unit, Link Management (software) Unit, and Bluetooth Software (protocol stack) unit. The network topology shown in Figure 2 can be constructed. In this structure, the main device is responsible for providing clock synchronization signals and Frequency Modulation Sequences in the micro-network, assigning address codes for each slave device, and only the master and slave devices can communicate with each other.
The Bluetooth specification consists of the protocol and application specification (profile. The Protocol defines the working methods of each functional element (such as the serial port simulation protocol, Logical Link Control, and Adaptation Protocol), and the application specification describes how to implement a specific application model, collaboration between protocols at different layers. The Bluetooth communication protocol adopts a layered structure, which gives the device the maximum versatility and flexibility. According to the communication protocol, various Bluetooth devices can discover other Bluetooth devices by means of manual or automatic queries, which constitute piconet or scatternet and implement various functions provided by the system, if any of the Bluetooth devices is used, a unique 48bit bd_addr can be obtained according to the IEEE802 standard. It is a public address code that can be queried manually or automatically. Based on bd_addr, various confidentiality and security codes can be obtained using some good algorithms, thus ensuring the uniqueness of device IDs globally, and device authentication and communication security during communication.
2 GPRS Construction of Information egress external network
2.1 GPRS technology
GPRS is short for general packet radio service. It is a 2G wireless mobile communication technology that adds ggsn (Gateway GPRS Supporting Node) to the existing GSM network, the Gateway GPRS Support Node) and sgsn (serving GSN, service GPRS Support Node) are combined into another network, which retains all the characteristics of the GSM network. The newly added GSN node is the most important network node in the GPRS network. It has the mobile route management function. It can connect to various types of data networks and connect to GPRS registers.
Compared with the original GSM dial-up circuit exchange data transmission mode, the GPRS group exchange technology, it has the advantages of "real-time online", "pay-as-you-go", "Quick Logon", "high-speed transmission", and "easy switch. The maximum theoretical value of the data transmission rate can reach 171.2 kbps, and users can keep in touch with the network at any time. However, the network fee is charged based on the number of packets actually received or sent by the user, at the same time, the network data transmission and voice transmission services can be simultaneously performed and can be freely switched. The advantages of GPRS technology allow wireless transmission technology in many application fields to improve the information level. Therefore, using GPRS mobile network to transmit user data in the home network is both convenient and economical. It can be seen that it is used as the information of the home wireless network and exported to the external network, is very broad prospects.
2.2 Development of GPRS data service functions
As a carrier of mobile data services, GPRS can provide users with various forms of applications. In the GPRS network, you can send and receive data in the end-to-end group transfer mode without using network resources in the circuit switching mode. This provides an efficient and low-cost wireless grouping data service. It is particularly suitable for intermittent, burstable, and frequent, small amount of data transmission, and occasional transmission of large data volumes. It has two important features: transparent data transmission and virtual private network (VPN.
Figure 3 shows the conversion process of the GPRS data service sending and receiving protocols. The data to be sent is converted through the UDP, IP, and PPP protocols, and a wireless link is established to send the data. Otherwise, the received data packet is restored to user data after the PPP, IP, and UDP processes. This is the data service process of the GPRS network.
2.3 GPRS network configuration
Figure 4 shows the configuration and information transmission process of the GPRS network. The terminal device is connected to the GPRS Modem in serial mode, and the GPRS Modem communicates with the GSM base station. In the figure, BTS is the receiving and sending system of the base station, BSc is the base station controller. Unlike circuit switching or data calling, the GPRS data group sends data from the base station to the sgsn node instead of connecting to the voice network through the mobile switching center MSC. The sgsn can communicate with the gateway node ggsn. The ggsn processes the grouped data and sends the data to the destination network, such as the Internet or X.25 network. It comes from the Internet and identifies an IP packet with a mobile IP address, received by ggsn, then forwarded to sgsn, and then transmitted to mobile platform.
3. Embedded Control System
The home gateway uses the embedded processor Atmel at91r40807 and the operating system μCOS ⅱ to meet the intelligent needs of the product. Among them, at91r40807 is a ARM7TDMI high-performance 32-bit CPU. It has powerful thumb extension commands, rich interfaces, and complete network functions. Embest IDE development system, JTAG simulator, C language can easily write program source code, and embedded operating system μCOS ⅱ can be easily transplanted to the application system.
1 shows that the home gateway can combine various devices in the home automation system into a home LAN and connect to the Internet or other data networks through the GPRS internet, allows users to remotely access network devices in the home through the Internet or mobile devices.
The home gateway, which is easy to use and breaks through the space location restrictions, has the following functions:
(1) enable the electronic devices in the home to form piconet, and communicate seamlessly with the Internet or personal mobile data terminals;
(2) You can remotely access all devices on the home network through IE or other browsers;
(3) low cost, replacing PC or industrial computer gateway;
(4) run the embedded software platform with the source code of μCOS ⅱ;
4 Conclusion
In this paper, the design scheme of the wireless home gateway is proposed, which completely breaks through the limitations of cables, gives full play to the advantages of wireless, and puts forward a new design idea of the home gateway. The Bluetooth technology that enables different manufacturers and devices to form the Network to form the home Intranet, and an external network composed of G mobile communication technology GPRS. The core system is configured with a powerful arm core processor, the entire system has high-performance information processing and network functions, and is the core of the home network system. &
References
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