Wireless LAN-classic Q &

The development of wireless networks has reached a mature point, but we are not limited to the use of LAN, and its faults are constantly emerging. How should we solve them?

Nowadays, the term "wireless" is often seen in the reporting media. Wireless LAN is coming closer to us with the release of the Intel "chindepro" chip. But many people do not have access to wireless LAN, so what is it? What can we do? I hope you can answer the following questions.

What is WLAN and what is the most popular wireless networking technology?

WLAN is short for Wireless LAN, that is, Wireless LAN. Wireless LAN uses wireless technology to achieve fast Ethernet access. Looking at the current market, IEEE 802.11b technology has surpassed Bluetooth, HomeRF and other technologies in terms of performance and price, and has gradually become the most widely used standard for Wireless Access to Ethernet. Due to the continuous maturity of IEEE 802.11b technology, wireless LAN applications are emerging globally.

What are the advantages of a wireless network over a wired network?

Compared with wired networks, the main advantage of WLAN is that it does not require wiring and is not restricted by wiring conditions. Therefore, it is very suitable for mobile office users and has broad market prospects. At present, it has expanded from traditional special industries such as health care, inventory control and management services to more industries, and even started to enter the fields of families and educational institutions.

Does wireless networks have adverse effects on human health?

The emission power stipulated by IEEE 802.11 cannot exceed 100 MW, and the actual emission power is about 60 ~ 70 mW. What kind of concept is this? The transmit power of the mobile phone is about 200 to 1 W, and the handheld walkie talkie is up to 5 W. In addition, wireless networks are not directly accessible to the human body like mobile phones, so they should be safe.

What are common wireless network protocols and their characteristics?

The most common examples are IEEE 802.11, IEEE 802.11a, IEEE 802.11b, and IEEE 802.11g. IEEE 802.11 is an initial Wireless LAN standard developed by the IEEE Institute of Electrical and Electronics Engineers.

IEEE 802.11b, also known as Wi-Fi, uses an open 2-4 GHz direct sequence spread spectrum with a maximum data transmission rate of 11 Mbps, you can also adjust the transmission rate to 5.5 Mbps, 2 Mbps, and 1 Mbps Based on the signal strength. No linear transmission is required. The maximum outdoor transmission range is 300 meters, and the maximum indoor transmission range is 100 meters if obstacles exist. This is the most widely used transmission protocol.

How wide can WLAN cover?

Generally, the scope of WLAN coverage depends on whether the environment is open or not. If an external antenna is not added, it is about 250 m in the field of view. If it is a semi-open space with an interval, it is about 35 ~ About 50 meters. Of course, if an external antenna is added, the distance can be further reached, which is related to the increase value of the antenna, So it depends on the user's needs.

What are the basic configurations required for building a WLAN?

Generally, a wireless network is equipped with a wireless network card and an AP, so that network resources can be shared in a wireless mode in combination with the existing wired architecture. If only a few computers are connected to the peer network, do not use AP. You only need a wireless network card for each computer.

AP is short for Access Point, which is generally translated as "Wireless Access Node" or "bridge ". It serves as a bridge between a wireless workstation and a wired local area network in the MAC of the media access control layer. With an AP, it is like a Hub in a wired network. A wireless workstation can be quickly and easily connected to the network.

What is a Roaming function?

Just as a mobile phone can roam between different base stations, a WLAN workstation can also roam between different APs. As long as the ESSID of an AP group is defined, it can roam across areas that can be covered by radio waves. This technology is mainly used in public places such as airports, exhibition centers, coffee houses, etc.

What is WI-FI certification?

Because IEEE is not responsible for testing the compatibility of IEEE 802.11b wireless products, this work is undertaken by the Wi-Fi alliance, the wireless Ethernet Association WECA, which is composed of vendors. All products that pass the test of their compatibility are granted the "Wi-Fi CERTIFIED" mark. When purchasing IEEE 802.11b wireless products, we 'd better choose products with Wi-Fi tags to ensure compatibility between products.

What are the working modes of the wireless lan?

The working modes of a wireless LAN are generally divided into two types: Infrastructure and Ad-hoc. Infrastructure refers to the working mode of AP connection, that is, the AP can be regarded as the Hub in the traditional LAN ). Ad-hoc is a special mode of work. It sets the ESSID of a set of wireless network cards that need to communicate with each other to the same value, so that you do not need to use AP, A special wireless network application mode. You can connect to each other and share resources by installing wireless NICs on several computers.

Why do some products compatible with IEEE 802.11b claim a transfer rate of 22 Mbps?

Although IEEE802.11b sets a transmission rate of up to 11 Mbps, many IEEE 802.11b-compliant products claim that their products support up to 22 Mbps. In IEEE 802.11, the standard of 22 Mbps is not mentioned in any protocol. What is this? It turns out that this is the so-called enhanced IEEE 802.11b standard launched by TI American Dezhou instrument. The theoretical speed is twice the original speed, up to 22 Mbps. This standard has been adopted by many famous brands. Because this is your own standard, you must support both the AP and the network card. If not supported by one party, the speed will automatically decrease to 11 Mbps.

Why is the actual connection rate between the AP and wireless network card I purchased only 5.5Mbps?

All devices that comply with IEEE 802.11b specifications have the ability to automatically adjust the rate based on signal strength. Although the highest data transmission rate is 11 Mbps, the transmission rate can be adjusted to 5.5 Mbps, 2 Mbps, and 1 Mbps according to the signal strength. To reach the maximum rate, you can consider adjusting the AP installation position and antenna direction. If necessary, you can add an external antenna.

How to set up home wireless broadband?

Connect to an AP and install a wireless network card on your computer. Generally, an AP is enough in a home, or even the user's neighbors. If the user is authorized, no port is required, or the user can access the Internet in a shared manner.