It is worth buying fake encyclopedias, but also talk about home routers Chapter 1: IP protocol basic knowledge of additional changes (2017-06-3010:21:39): text has several data errors have been valued friends found. For example, the total amount of ipv4 is 42 Billion is not 420 million, /23 mask corresponds to 254 is not 252. Thanks for correcting :) Preface What is worth buying? If it is not value for money, how can it be worth buying? In recent years, the rising popularity of home router configuration and prices have skyrocketed, we Why spend hundreds of thousands of oceans to buy it? It's cute ribs | Like 445 Comments 470 Favorites 2k View Details 
It is worth buying fake encyclopedias, but also talk about home routers Part II: routing table and DNSPreviouslyOn "IPBasis" ... (US drama is visual sense) The previous article said a lot of basic content of the IP network. Although you have the address you can send Express delivery, receiving express delivery, but the light knows the address, if you do not know how to go the road does not work, Beijing, Shanghai express hair is always to Jiangsu transit once? The address is more difficult to remember, can only express a single A three, Li Four? Here we talk about the IP network path and name issues cute ribs | Like 55 reviews 53 Favorites 410 View Details Previously On "Route Table & DNS"... The first two articles shared some of the router's soft knowledge to the valued friends. There was also a hard knowledge that had to be discussed. That was Wife.... No, it was WiFi! (The whole egg was your grandfather). This series The topic is home routing, and current home routing is basically equal to wireless routing, so some things of WiFi are very necessary to understand. Like the previous two, I will not speak very thin and deep, first, because 99% of value We are too lazy to look. Second, because I also understand this point.
Starting with the popularity of handheld PDAs, a wireless technology called WiFi has also become popular. Then Dopod mobile phone / Android phone / Apple mobile phone / iPad continue to promote the development of WiFi. Laptop? With the mobile phone than the role of pushing the fart .
> There are many standard versions of WiFi (802.11 standard), the version number should be a~z, run out of aa~az again, it is estimated that there will be ba~bz (very foreigners really). Only part of the version will finally go to the factory.
> An organization called WiFi Alliance is responsible for the standardization of the WiFi protocol. At present, the common WiFi authentication version is a/b/g/n/ac. This should be seen on the router's box. 
> WiFi products do not have to be a standard before they can be produced and sold. When 802.11n was still around 2007, many manufacturers could not wait to launch a non-certified version n wireless router. The nominal 300m speed compared to the mainstream 54/year. 108m to attract more people. I remember when I went to colleagues to buy a dlink, spent more than 1,000 oceans, buy back and found no speed increase, network card can not keep up ... 
> WiFi is also available in 3.xG, 4.xG, etc., but no civilian use. In the near future will see 60G... 
> WiFi also has peer-to-peer mode/direct connection mode. Common use cases include NDS/3DS face-to-face connection, mobile phone control of Android TV box, wireless display, wireless printing, etc. Soft technology mainly implemented to combat Bluetooth. Soft AP function requires WiFi Direct connection function, HostedNetWork function that Win7 starts with is soft AP. 
> It was really wrong for Tianzhuang to request all incoming mobile phones to cut off the WiFi function.
1. Calculation of WiFi upper limit speed. With the constant updating of the WiFi standard, the upper limit speed of WiFi is also increasing. WiFi upper limit speed can be roughly calculated based on speed x bandwidth multiple (based on 20MHz) x number of antennas. (Note: Basic speed refers to the upper limit speed of a single antenna. Yes, just talking about the upper limit speed, talking about other businesses is not easy to advertise.) 802.11ac generally does not use 20MHz of bandwidth. (The figure below shows the maximum speed of ac w1 20M I wrote Wrong, it should be 347M) 
2. General WiFi specifications for merchants (potential consumers must use means).
Beginning with the popularity of dual-band WiFi, merchants like to add 2.4g and 5g speed together to promote (downstream).
In contrast to the above speedometers, the following table shows the difference between the number of antennas except for the 800/1000 2.4G and 2165 5G specifications (manufacturers are willing to do so). 
3. What needs special attention is:
> The most applicable combination is 802.11n/2.4G/20MHz/dual-antenna. 1 is because 2.4G penetration is good, 2 is because 20MHz is less interfered with than 40MHz, 3 is because there are few WiFis in the current mobile phone. More than 2 antennas.
> 5G choose dual antenna 867 or four antenna 1733 on the line, and then the high not to choose, now you buy a mobile phone and then expensive, books and more expensive, with WiFi only dual antenna 867mbps (I heard Samsung s8 support non-standard 5G, Theoretical upper limit of speed up to 1080/1200mbps). Asus has produced a lot of wonderful high-priced high-priced routing, the result is that the most expensive books you sell is still not 867. This is one of my main intentions to write this series. 
> Don't see how fast the numbers are, feel good. Experts know what a penny is and what the goods are. Consumers are not businessmen but they are not IQs. After reading this article, they are still fooled.
> The WiFi signal is an electromagnetic wave. Waves of different frequencies do not interfere with each other. The WiFi channel divides WiFi available frequency into several parts and can be abstracted into roads.
> 2.4G WiFi frequency range is defined as 2.412 ~ 2.472G (ie 2412 ~ 2472M, and 2484M has not been used), a channel for each 5M, a total of 13 channels can be separated. WiFi minimum bandwidth is 20M ( Actually it will occupy 2M more. The minimum occupancy is 5 channels in a row. The channels that do not interfere with each other in 13 channels are 1/6/11. (The following figure is from Encyclopedia) 
> People in the city only use 2.4G with a bandwidth of 20M. Most people use WiFi under this combination for the most part. Because penetration is the best, the relative interference is the least (), and the most stable. The picture shows the status of WiFi channels in the city! 
> The 2.4M bandwidth of the 40M bandwidth is used by the rural talents. It's not because... The WiFi device density is much smaller, the signal interference is much less, the speed can be faster! The 40M in the city is tantamount to the 2.4G in the picture above. Open a solid bar on the road!
> 5G channel is very empty! There are two reasons for this. First, WiFi is only 2.4G in public areas. Second, 5G signal-intensive residential buildings are blocked by their own walls. They do not interfere with other home 5G signals. Commonly used 5G channels are 36, 40, 44, 48, 149, 153, 157, 161, 165. Of course there are other channels, but different countries have different regulations, which are a bit confusing. Even if your router/AP allows you to set up other channels, your mobile phone may not be able to support it. (An Android phone equipped with a Wifi analyzer or laptop equipped with an Acrylic Wi-Fi can look at the WiFi channel near you, and is generally similar to the above diagram)
> Because the 5G channel is relatively empty, basically no router will use 20M bandwidth. Even many manufacturers directly hide the 20M option and only provide 40/80M. Some new high-end (qian) routers also provide 160M bandwidth options. The speed is also soaring! However, it is still a joy. 99% of notebooks/mobile phones support over 40M x 2 WiFi speeds, which is at most 867mbps. The actual network speed can reach 400mbps and is almost exploding.
> Although the transmission of WiFi is electromagnetic (analog signal), the purpose is to exchange data (digital signal). Unlike telephone, radio, TV (former antenna), etc. Big. But for WiFi it is a noticeable drop in speed.
> If every room (especially the bathroom) can be equipped with a 5G AP, it will be very nice. The students who haven’t renovated yet remember that every room has been wired with a Category 5 or 6 network cable. In order to install a WiFi panel in the future!
> Although the 5G 3-8 antenna 80-160M ​​bandwidth is rarely used by the mobile phone or the instinct, it is still able to reflect the speed advantage of the wireless relay. However, it is not really easy to use in realizing the use of the antenna. At this price, only the user can understand it.
I did not intend to write this section (I mainly do not understand), but everyone generally think that the antenna is large/coarse/high-powered and the signal is strong and it is fooled by the business. In the spirit of being worth buying, I have to write. Go on!
1. The number of antennas is not related to the signal strength, but also the transmission speed does not matter!
> Starting from 802.11n, the wireless router starts to take multiple antenna routes and supports 2-4 antennas. Each antenna is responsible for 1 channel signal transmission/reception (1T1R). Because 2.4G and 5G channels are separated, they generally use 1 antenna. , This 2 antenna can be responsible for 2.4/5G dual-band dual transceiver.
Many routers hide their antennas in their bodies. But merchants later found that the antennas were pulled out to attract consumers, and that the more roots they pulled out, the stronger the signals. When Cisco sold several classic home wireless routers, the landlord had Also scouring foreign junk, interested value friends can look for the corresponding specifications of tplink routing what looks like...
> The same AC5300 router, which is a pit father, uses the same uncertified new standard as the current Dlink dir-615. However, ASUS can confuse consumers with comparable nets. The AC5300 is a four-antenna specification and each antenna can handle one 2.4G. And 2 ways 5G (the road width is 屌). In front of these two products put value friends, do you think it is obviously octopus paralyzed? Actually, Asus should not be made into 12 antennas? Not more fried?
2. Antenna placement knowledge> The parent router/AP is an omnidirectional antenna. The signal radiates mainly to the antenna in the vertical direction. The high-power and high-gain antenna can enhance the signal in the vertical direction, but the signal coverage is smaller. , the other direction signal will be less.
> In addition, regarding the use of cans to enhance signal reflection, I personally feel that the effect is certain. Actually I can't really put much effort into my heart.
At present, WiFi products and technologies are numerous and miscellaneous. Most users, including me, are likes to understand and understand. Although 99% of the real world use is 54~300M 2.4G, but it is not really true that there is no way to convince most of the banknotes in the pockets. The value of the friends dancing. The purpose of this article is to sue (wu) v. (dao) how we judge what is worth buying!
In addition, you may have questions about WiFi roaming. Personally think that WiFi roaming is far less than home investment, even if a large shopping mall/hotel/hospital/airport train station spends a huge sum of money to build a WiFi service. It is always unsatisfactory. Therefore, if you have two or more AP devices in your home, it is recommended that you set the same SSID and password, and the channels should not be the same. The device should be placed in a targeted manner so that the signal coverage does not overlap. It's home, not use.
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