WiFi is increasingly becoming the preferred mode of global Internet connectivity. According to information released by the blog site Gigaom, by 2020, there will be 24 billion devices connected to the Internet. Most devices will use the wireless way to access the Internet. Although more and more people know about WiFi, how it actually works is not known to most people. Even in the IT expert circle, certain facts about WiFi networks are often misunderstood. Here are some of the top ten common misconceptions about WiFi in the industry.
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Shared media
The radio signal is programmed at each access point (AP) to operate on a single channel. Within this single channel, multiple clients can connect and communicate. All clients using it share this single channel medium.
However, the fundamental problem with radio systems is that a wireless station cannot listen while transmitting, and therefore cannot detect collisions. With this in mind, developers of the 802.11 specification have created a collision avoidance mechanism called Distributed Control Function (DCF). According to the DCF, a WiFi station only transmits when it believes that the channel is clear. As a result, the probability of collisions increases with increasing traffic or when the mobile stations cannot "hear" each other. Although there are some protocols for controlling operations, WiFi is similar to the Layer 2 HUB technology of traditional wired networks.
2.802.11b and traditional protocols "slow down" media
The result of having the old protocol run in the same environment is to "slow down" all other clients. In fact, traditional customers need to spend more session time sending the same amount of data as new 802.11n or 802.11 ac clients. The call fairness algorithm proved to be effective in solving this problem.
3.L1/L2 802.11 function
It is widely believed that WiFi uses radio frequency (RF) technology and there is no physical wired connection between the sender and the receiver. When an RF current is supplied to the antenna, an electromagnetic field is created and then propagated through space. In fact, the 802.11 protocol is an L2 technology that uses the underlying L1 of the OSI stack to perform its duties. The communication between the client and the access point is connected in the air. Over-the-air communication is handled by L2 QoS based on the 802.11e standard.
4.Downstream and Upstream
There is a significant difference between the downstream from the access point to the client and the upstream from the client to the access point. Currently, most WiFi over-the-air technologies only offer downstream enhancements.
5. Uplink rate and downlink rate
The only rate that is generally accepted by the industry is the transmission rate. However, the asymmetric rate is typical, and the transmission rate seen at our connectable clients does not necessarily represent the reception rate. This is also confirmed in terms of access points and infrastructure, which demonstrates a separate uplink rate Tx and downlink rate Rx in the WiFi world.
6. Same transmit power for all rates
Setting the radio of an access point to "maximum power" does not mean that power can be used for all rates. The default wireless transmit power is set to 20dBm. Typically, the higher the data rate in use, the more the access point will be forced to reduce the power of these frames (defined by FCC and ETSI). This concept has become more common with the 802.11ac VHT specification.
7. Always set the radio to maximum power
Setting the radio to maximum power seems like a good thing to do, but it may not be a good idea. This has been shown to cause signal distortion when the radio emits sound at maximum power. There are many reasons for this, including Cell size planning. Simply setting the radio power to maximum is not a best practice.
8. Signal strength to signal to noise ratio (SNR)
There is often confusion between the measurement of signal strength and the measurement of signal-to-noise ratio. In fact, the performance of a WiFi network depends in part on the signal strength. Between a computer and a wireless access point, the signal strength in each direction determines the available data rate for that connection. Therefore, the stronger the signal, the better the connection. The signal-to-noise ratio is preferably a large number, which means that the received strong signal has a large difference from the background noise that affects the overall quality.
9.MIMO and spatial streams
MIMO and spatial streams are probably the most confusing issues since the 802.11n protocol. Multiple Input and Multiple Output (MIMO) technology is a wireless technology that uses multiple transmitters and receivers to simultaneously transmit more data. All wireless products with 802.11n support MIMO, which is part of the technology that allows 802.11n to achieve higher speeds than those without 802.11n support. MIMO involves antennas and paths, and the number used indicates how many antennas and paths can be used to transmit and receive signals. For example, 3 x 3 means 3 antennas and path transmission and 3 antennas and path reception.
The spatial stream relates to the data actually sent. For example, a 3-way spatial stream device can send 3 unique data streams to a receiving station and be reconstructed into a data set. Finally, adding MIMO and spatial streams is equivalent to the achievable overall throughput. 3 × 3: 3 means that three antennas are used to transmit three spatial streams, and three antennas and path reception are used.
10. The respective capabilities of the access point and the client
This is a very simple question, but it is often overlooked, and the smallest common denominator is always the winner. In order to achieve the highest data rates and real-world throughput, access points and clients must have the capabilities. It's important to understand the capabilities of the client to truly understand what WLAN deployments will be implemented in the real world.
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