Ten common misunderstandings of WiFi

Ten common misunderstandings of WiFi

WiFi has increasingly become the first choice for global Internet connections. According to the information posted on the blog website Gigaom, 2020 devices will be connected to the Internet by 24 billion. The vast majority of devices will use wireless access to the Internet. Although more and more people know about WiFi, they do not know how they actually work. Even in the IT expert circle, some facts about Wi-Fi networks are often misunderstood. The following lists the top ten common misunderstandings about Wi-Fi in the industry.

 

1. shared media

Radio signals are programmed at each access point (AP) to run on a single channel. In this single channel, multiple clients can connect and communicate. All clients that use it share this single channel media.

However, the fundamental problem in the radio system is that a wireless station cannot listen while sending messages, so it cannot detect collisions. In view of this, 802.11 developers have created a collision avoidance mechanism called the distributed control function (DCF. According to DCF, a Wi-Fi station sends messages only when it deems the channel clear and clear. In this way, the probability of a collision will increase as the traffic increases or when the mobile stations cannot "hear" each other. Although there are some control protocols, WiFi is similar to the L2 HUB Technology of traditional wired networks.

2.802.11b and traditional protocols "slow down" media

The result of running the old protocol in the same environment is to "slow down" all other clients. In fact, traditional customers need to spend more time sending the same data volume as 802.11n or 802.11 ac new clients. The call fairness algorithm is proved to be effective in solving this problem.

3. L1/L2 802.11 features

It is widely believed that WiFi uses Wireless RF technology and there is no physical Wired connection between the sender and receiver. When an RF current is provided to an antenna, the electromagnetic field is created and then transmitted through space. In fact, the 802.11 protocol is a L2 technology that uses the underlying L1 of the OSI stack to perform its duties. Communication between the client and the access point is connected in the air. Air communication is processed through L2 QoS Based on the 802.11e standard.

4. Downstream and Upstream

There is a significant difference between downstream from the access point to the client and upstream from the client to the access point. Currently, most Wi-Fi air technologies only provide downstream enhancement.

5. uplink and downlink speeds

The only widely accepted rate is the transmission rate. However, the asymmetric rate is typical, And the sending rate seen on our connectable client does not necessarily represent the receiving rate. This is also evidenced by access points and infrastructure, which proves that there is a separate uplink rate Tx and downlink rate Rx in the WiFi world.

6. For the same sending power at all rates

Setting the radio of an access point to the "maximum power" does not mean that the power can be used at all rates. The default wireless transmission power is set to 20dBm. Typically, the higher the data rate in use, the Access Point will be forced to reduce the power of these frames (defined by the FCC and ETSI ). This concept has become more common with the 802.11ac VHT specification.