[Smart Home] WiFi network structure (Part 1)

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I believe everyone knows what WiFi is. I will not describe it here. What we need to do is to gain an in-depth understanding of its working principles, including hardware and software, and network structures. First, it should be noted that WiFi complies with the 802.11 protocol, and is the first wireless LAN protocol recognized by international standards organizations. It should have been in and has been around for 15 years now. At that time, my brother was still in elementary school and never even touched the computer! Too backward... Subsequently, many standard 802.11 protocols with English letters suffix will be displayed, such as A, B, G, N, and AC.

This section does not explain the 802.11 Protocol and will be analyzed later.

Back to the topic of this article, let's start with the Wi-Fi network structure. There are too many components in the Wi-Fi network in the 802.11 protocol, so we will not explain them one by one. We will mainly introduce the components involved in the smart home wireless network. They are:

(1)Site sta (Station)The so-called site refers to devices that have wifi communication functions and are connected to wireless networks, such as mobile phones, tablets, and laptops.

(2)Access Point AP (Access Point), Also known as a base station. It is what we usually call WiFi hotspots. More commonly, it is our home wireless router. So what is its role? When we need to obtain data from the Internet and display it on our mobile phone, the access point is equivalent to a forwarder who forwards data from other servers on the Internet to our mobile phone, of course, this is just a rough description. The access point is also a type of site.

(3)Basic Service Set (BSS)A. consists of one access point and several sites. B. consists of several sites, at least two. Why? It depends on the network type of 802.11. An access point is called the basic structure basic service set (Infrastructure BSS). An access point is called the independent basic service set (independent BSS, IBSS for short, it is called an ad hoc network.

(4)Service Set Identifier (SSID)When we go to a new place, the first sentence is: "What is the Wi-Fi account and password ?", The Wi-Fi account here is the SSID. The SSID is broadcast through the access point. You can also modify the SSID name when setting a wireless router.

(5)Distributed System DS (Distribution System), Also known as the transmission system. It connects multiple basic service sets through base stations. DS is a logical component of 802.11. When a frame is transmitted to a distributed system, it is immediately sent to the correct base station and then forwarded to the destination site Sta. The distributed system must track the actual location of the site STA and transfer frames. To transmit frames to a mobile site STA, the distributed system must transmit the frames to the base stations that serve the mobile site Sta. A Distributed System is a backbone network for frame transfer between base stations. It is usually called a backbone network ).

(6)Extended Service Set (ESS)A Distributed System concatenates one or more basic service sets to form an ESS. With ess, we can extend the coverage of wireless networks.

(7)Portal), The new term 802.11 defines is equivalent to a bridge. It is used to associate a wireless LAN with a wired LAN or other networks. All data from non-802.11 LAN must pass through the door bridge to access the IEEE 802.11 Network Structure. The portal bridge enables logical synthesis of the two types of networks.

The following figure shows the relationship between components of the Wi-Fi network.

Figure 1 WiFi network architecture

Now let's talk about the network type. The network type is mainly classified in BSS. For example, the independent basic service set (independent BSS) and basic service set (Infrastructure BSS) mentioned above ).

1. Independent Basic Service Set

Independent basic service set (IBSS), 2 left. In IBSS, each site can establish communication with any other site in the same IBSS without the Access Point AP. The distance between the two must be within the range of direct communication. Generally, IBSS is a temporary network composed of a few workstations for specific purposes. The minimum IBSS is composed of two sites. IBSS is sometimes called an ad hoc network ).

2. Basic structured Service Set

Basic Service Set (infrastructurebss), 2 right. To determine whether a basic network is deployed, check whether base stations are involved. The base station is responsible for all transmission of the basic structure network, including communications between all mobile nodes in the same service area. A mobile site located in the basic service set of the basic structure. If it is necessary to communicate with other mobile sites, two steps must be taken. First, the site that starts the conversation transmits the frame to the base station. Second, the base station transfers this frame to the target site. Since all communications must pass through the base station, the basic service area corresponding to the basic structure network is equivalent to the transmission range of the base station. Although this method consumes more resources than direct transfer, it has two main advantages:

(1) the basic service set of the basic structure is defined as the transmission range of the base station. All mobile sites must be within the transmission range of the base station, but the distance between mobile sites is unlimited. Although direct communication between mobile sites can save some bandwidth, the cost is to increase the complexity of the physical layer, because each site must maintain the adjacent relationship with other sites in the service area.

(2) The role of the Base Station in the basic structure network is to help the site save power. The base station can remember which sites are in the power-saving status and save frames for them. Battery-powered workstations can disable wireless transceiver, this feature is enabled only when temporary frames are transmitted or received from the base station.

Figure 2 WiFi network type

In view of the length of the blog post, we need to divide the Wi-Fi network structure into the first and second articles. Next, read the subsequent blog "WiFi network structure (below)". Thank you!

Reprint please indicate the source: http://blog.csdn.net/Righthek thank you!

[Smart Home] WiFi network structure (Part 1)