Multi-Protocol Router Design Based on Embedded Linux platform (1)

With the development of social informatization and the rapid development of the Internet, it becomes more urgent to provide data services in wireless environments. Traditional wireless mobile networks are usually supported by fixed infrastructure and cannot meet people's requirements for growing communication services. AdHoc networks, a new type of wireless network, have emerged. Ad Hoc networks, also known as mobile self-networking and multi-hop networks, are flexible and fast, and are not affected by wired networks, it can be widely used in military and rescue scenarios where network facilities cannot or are inconvenient to be laid in advance. In addition, Ad Hoc networks are evolving towards network interconnection, and Internet access is one of the main contents.

Ad Hoc wireless networks have their own characteristics. When constructing a wireless work network in actual use, you must fully consider the application scale and scalability of the network, as well as the reliability and timeliness requirements of applications, select an appropriate network topology. Currently, Ad Hoc wireless networks are evolving towards a large scale and gradually show a hierarchical trend, represented by two-level networks. In a two-level network, topology 1 is shown. The network is divided into two levels: backbone network and subnet. At the subnet level, each subnet can form an independent Ad Hoc network and use different routing protocols. A backbone network consists of multiple protocol router nodes and common nodes. Common nodes distribute data and control information in the backbone network; in addition to common node functions, a multi-protocol router is also responsible for subnet management, control, and data interaction. It is the core equipment of the backbone network.

1. Features of multi-protocol Routers

As a node of the backbone network, a multi-protocol router runs a certain Ad Hoc network routing protocol to realize the function of addressing the backbone network.

In a hierarchical Ad Hoc network, multi-protocol routers interact with subnet gateways to manage subnets. The communication in the subnet is similar to that in the general Ad Hoc network. The communication between subnets must be transit through the subnet gateway node and the backbone network node, there are two scenarios: Communication Between homogeneous/Heterogeneous subnets under the same vro and communication between homogeneous/Heterogeneous subnets under different vrouters. To achieve effective communication between subnets, routers need to complete the conversion between multiple protocols.

The demand for Internet Access makes it necessary for a hierarchical Ad Hoc network to have an Access Point (AP ). Considering the network environment, this function needs to be implemented by a multi-protocol router.

To sum up, a multi-protocol router implements three main functions: routing addressing of the backbone network, protocol conversion, and Internet access AP.

2 Multi-Protocol Router Design

Generally, the routers in the Ad Hoc network are vehicle-mounted or backload routers. Therefore, multi-protocol routers must have a high degree of integration and mobility. Considering the above factors, we have selected the most popular embedded system design method. The microprocessor of the hardware platform of the multi-protocol router adopts the ColdFire embedded processor MCF5272 of Motorola, select uClinux as the operating system of the platform. This not only shortens the R & D cycle, but also facilitates the design and debugging of software and hardware.

The dotted line diagram in the multi-protocol router hardware design 2 is shown. The hardware structure of a vro is divided into two parts: the Core mode (MCF5272) is composed of the microcontroller module and the memory module (including SDRAM and Flash), and the communication interface module, it consists of asynchronous Serial control and receiving module, Ethernet Control and receiving module, and Universal Serial Bus USB (Universal Serial Bus) interface module.

The microprocessor module is mainly responsible for data processing. The memory module is divided into two parts: Flash (composed of two Flash devices, a total of 4 MB), as a program memory, used to store the operating system kernel, various routing protocols and route table constants; the other part is SDRAM, which serves as the data storage and serves as the operating space of the operating system and various routing programs.

In the communication interface module, the asynchronous serial control and receiving module is used to connect to multiple backbone network nodes and multiple subnet gateways (PRU ). The Ethernet Control and transceiver module enables Internet access. The USB interface module is used to connect to the control terminal of network devices and implement the storage control of routers on USB devices (such as USB standard mobile hard disks, used to store important routing information.

The PRU (Packet Radio Unit) in Figure 2 is equivalent to the secondary processor of the router. It is used to pre-process the received wireless subnet group.