Research on Low-power wireless routers based on open-source routing technology (1)

Research on Low-power wireless routers based on open-source routing technology (1)

Wi-Fi wireless access technology is based on the protocol and is currently the most common wireless access technology in wireless communication. However, Wi-Fi wireless access technology has a critical weakness-high power consumption. Therefore, how to reduce the power consumption of Wi-Fi wireless access technology becomes an urgent problem. Mobile Terminals connect to the Internet or locate services through Wi-Fi signals provided by wireless routers. However, due to the high power consumption of Wi-Fi, the wireless routers must be connected to the power supply to maintain normal operation, this severely limits the scope of use. We hope that wireless routers can be used in areas without power access (such as ancient scenic spots and historical relics) to provide services for mobile terminals.

1. 802.11 Protocol

The IEEE protocol is a set of wireless transmission protocols developed by the American Institute of Electrical and Electronics Engineers (IEEE. These Protocols define interfaces for communication between two or more wireless sites (or access points. This protocol mainly includes the physical layer and MAC layer, which work on the lowest two layers of the ISO protocol. This paper mainly studies the MAC layer of this Protocol.

The definition frame of the 802.11 Protocol includes the following parts:

◆ MAC header. Includes frame control, duration, address, and queue control information.

◆ Frame body with a valid length. Including frame information and frame type.

◆ FCS. Contains CRC verification information.

Control Frame: it is mainly used to assist in data Frame transmission. All Control Frames use the same Frame Control field.

Management Frame: establishes initial communication between the workstation and AP, and provides authentication and connection services, including connection request/response, polling request/response, and Beacon frame.

Beacon frame: Mainly declares the existence of the network. The beacon sent regularly allows the mobile workstation to know the existence of the network and adjust the parameters necessary to join the network. In the infrastructure network, the access point is responsible for transmitting Beacon frames.

From the frame structure of the protocol in Figure 1, we can see that if only the Beacon frame function of the Protocol is retained, only a small amount of data needs to be sent, which can greatly reduce power consumption, in addition, we can use the open-source routing technology to modify the Protocol to reduce power consumption.

2. Open-Source Routing Technology

Figure 2 shows the relationship between TCP/IP and OSI reference model. It can be seen that the router is layer 3rd, that is, the network layer, that is, in the OSI model. It is also the layer 3rd of TCP/IP protocol, that is, the Internet layer. A vro uses the "logical" network address (IP address) defined by the network layer to differentiate different networks. This allows for hundreds of connections and isolation of the networks and ensures the independence of each network. Vrouters do not forward broadcast messages, but restrict broadcast messages to their respective networks. Data sent to other networks is sent to the vro and then forwarded by the vro.

Wireless routers are based on open-source Linux operating systems. However, commercial routers do not disclose the firmware source code to protect their own technologies. Therefore, they cannot be directly developed by third-party software developers. Since Linksys released the WRT54G/GS source code, open-source software enthusiasts have developed many different versions of firmware to enhance the original functionality or add functionality that was not previously available. The following is the Linux release of mainstream wireless routing:

① Open-WRT. The first people in China who initiated the firmware update operation basically refresh their devices into Open-WRT. This shows that Open-WRT has a great influence. The firmware is configured through the SSH encryption protocol, which is similar to that of Cisco devices in many commands and operations.

② DD-WRT. This firmware is one of the most popular at home and abroad. It was released based on the Open-WRT firmware, and many functions are taken from Open-WRT. Storage applications with DD-WRT support a lot of hardware platform, and the release of the new version is also very timely.

③ Hyper-WRT. The firmware is a stable third-party same-piece device, but it is less functional than the first two. From the core code point of view, it is the firmware closest to the official Linksys firmware. For many users, the emergence of new features and applications is the main motivation for them to refresh the same piece. If they only require a single stability, simply use the official default firmware.

④ Tomato. This is a gradually popular firmware with a relatively small head, which is very stable in actual use, and the SVG-based graphical traffic diagram is very distinctive. It was developed by a team member in the Hyper-wrt r & D team.

The third-party firmware used in this article is Open-WRT. The reason for choosing Open-WRT is that it is completely Open-source, which facilitates compilation and configuration and has the firmware required by the corresponding router, it is also convenient to refresh the firmware.