Ten misunderstandings about Wi-Fi

Wi-Fi is increasingly becoming the preferred Internet connection model in the world, which is no longer a secret. 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 access the Internet in a wireless way.

Recently, wireless technology has been widely spread. Regardless of your business, wireless technology is revolutionizing. According to Gartner's latest research, mobile device diversity and management and mobile applications and applications represent two strategic technological trends in 2014. Specifically, if you are engaged in a retail business, you can determine that your customers can wirelessly compare products and prices when they shop in the store. If you are engaged in a hotel business, you know that Wi-Fi is the most important facility for your guests. Therefore, according to the Infonetics survey, most enterprises plan to increase their Wi-Fi capability by at least 2014 in 20%.

Although everyone is familiar with Wi-Fi, it is difficult to explain how it actually works. Even in the IT expert circle, some facts about the network are often misunderstood, resulting in confusion and incorrect assumptions. The following are top 10 misunderstandings about Wi-Fi.

1) shared media

Each radio is 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, and therefore 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 collision will increase with the increase of traffic or when the mobile stations cannot hear each other.

Although there are some control operation protocols, Wi-Fi is similar to the L2 HUB Technology of traditional wired networks. Our wireless devices share space.

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 consume more session time to send the same data volume as the new client of 11n or 11 ac. Some solutions provide call fairness algorithms which prove to be effective in solving this problem.

3) L1/L2 802.11 features

It is widely believed that Wi-Fi uses radio frequency (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.

802.11 protocol is an 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

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

5) Tx rate to Rx Rate

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 in access point/infrastructure because it proves that there is a separate Tx rate and Rx rate in the Wi-Fi world.

6) Same sending power for all rates

Setting 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 20 dBm. 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 rate.

7) always set the radio to the maximum power.

It is probably not a good idea to set the radio to the maximum power. This has been confirmed that when the radio emits sound at the maximum power, the signal will be distorted. This may occur due to many reasons, including Cell size planning. Setting radio power to the maximum is not a best practice.

8) signal strength to signal noise ratio (SNR)

There is often confusion between signal strength measurement and signal-to-noise ratio measurement. In fact, the performance of a Wi-Fi network depends partly on the signal strength. Between a computer and a wireless access point, the signal strength in each direction determines the available data rate of that connection. Therefore, the stronger the signal, the better the connection. The signal noise ratio is preferably a large number. This means that there is a big difference between the strong signal you receive and the background noise that will affect the overall quality.

9) MIMO and spatial stream

MIMO and spatial streams may be the most confusing aspect of Wi-Fi since the 11n protocol.

Multi-input and multi-output (MIMO) technology is a wireless technology that uses multiple transmitters and receivers to transmit more data at the same time. All wireless products with 802.11n support MIMO, which is part of the technology that allows 802.11n to achieve a higher speed than those without 802.11n support. MIMO involves antennas and paths. The number of antennas/paths used indicates how many antennas/paths can be used to send and receive signals. For example, 3 × 3 means 3 antennas/paths are sent and 3 antennas/paths are received.

A spatial stream involves data actually sent. For example, a 3-to-space stream device can send three unique data streams to the receiving station and be rebuilt into a dataset. Finally, you can add MIMO and a space stream equivalent to the overall throughput that can be achieved. 3 × 3: 3 means sending 3 spatial streams using 3 antennas/paths and 3 antennas/paths.

10) Access Point and client capabilities

This is very simple, but often overlooked. The smallest denominator is always the winner. To achieve the highest data rate and the real-world throughput, access points and clients must have the corresponding capabilities. It is important to understand the client's capabilities to truly understand what kind of WLAN deployment can be achieved in the real world.