Shulou(Shulou.com)11/24 Report--

1. What is a wireless router? In the 5G era, the mobile phone package contains more and more traffic, and the unit price is getting cheaper and cheaper, even so, it is difficult to play without scruples.

Home broadband, which is charged by bandwidth and unlimited in traffic, can be converted into Wi-Fi signals through wireless routers, which can not only be shared by the whole family, but also connect all kinds of smart homes.

Therefore, it is not too much to call the wireless router the data hub of the home.

The name of a wireless router can be split into two keywords: wireless and routing. After understanding the technical principles behind these two words, we understand the wireless router.

Wireless is what we often call Wi-Fi. Wireless routers can convert home broadband from wired to wireless signals, and all devices can happily surf the Internet as long as they are connected to their own Wi-Fi. In addition, these devices also form a wireless local area network for high-speed local data exchange, which is not limited by the broadband bandwidth of the home.

For example, many people have smart speakers at home, which can be used to control all kinds of smart appliances. When you say Xiao X and turn on the TV, the speaker actually finds the TV and sends instructions through the local area network, and you don't need to connect to the Internet; if you let it broadcast the news, you have to get the data through the Internet.

The local area network we mentioned earlier, also known as the internal network, is represented by LAN (Local Area Network) on the router, so the Wi-Fi signal is also called WLAN (Wireless LAN), while the Internet we want to access, also known as the external network, is represented by WAN (Wide Area Network) on the router.

The wireless router interface indicates that in the internal network, the IP address of each device is different, which is called a private address, while the external network on all devices share the same public address, which is assigned by broadband operators such as Telecom.

The router is the bridge connecting the internal network and the external network. The IP address translation and packet forwarding mentioned above are the routing functions of the router.

In other words, the router is the hub of the home network, and the data of all devices must be forwarded by it before they can access each other or reach the external network, which means that as long as one person guards it, thousands of troops are difficult to occupy. Therefore, a fully functional router is also called "home gateway".

Wireless router networking 2. The key technology of Wi-Fi the wireless access function of wireless router is the wireless local area network (WLAN) mentioned earlier. At present, Wi-Fi is the only mainstream technology in WLAN, so it can be considered that the two are the same.

Wi-Fi is technologically certified and licensed by the Wi-Fi Alliance. In practical application, Wi-Fi is often written as WiFi or Wifi, but these two writing methods are not recognized by the alliance.

Wi-Fi Alliance (full name: international Wi-Fi Union Organization, English: Wi-Fi Alliance, referred to as WFA) is a business alliance that owns the trademark of Wi-Fi. . It is responsible for Wi-Fi certification and trademark authorization and is headquartered in Austin, Texas, USA. The catchy name Wi-Fi is widely regarded as an acronym for Wireless Fidelity, but it is actually misread. It is just a simple name, has no actual meaning, and certainly does not have a full name.

The technical standard behind Wi-Fi is the 802.11 series of protocols developed by the American Institute of Electrical and Electronic Engineers (IEEE).

The full name of IEEE: the development of the Institute of Electrical and Electronics Enginees2.1 Wi-Fi protocol began with the first version in 1997. The 802.11 series of protocols evolved continuously, experienced many versions such as 802.11a / b / g / n / ac, and supported increasing Internet access rates. At present, the latest version of the protocol is 802.11ax, that is, Wi-Fi 6, which has developed rapidly in recent years.

The development process of IEEE 802.11 series standards, from the first generation to the sixth generation in the first many years, although Wi-Fi has developed from generation to generation, there is no such thing as Wi-Fi in the world. Just use the protocol number of 802.11 followed by a few letters, which is very unfriendly to ordinary users.

It was not until 2018 that the Wi-Fi Alliance decided to promote the next-generation technical standard 802.11ax with the easier-to-understand Wi-Fi 6, and the previous generation of 802.11ac and 802.11n naturally became Wi-Fi5 and Wi-Fi4. As for the earlier technology, no one paid attention to it anyway, so there was no need to wear a vest.

It was only after the birth of Wi-Fi 6 that the name Wi-Fi 5 came into being. On September 16, 2019, the Wi-Fi Alliance announced the launch of the Wi-Fi 6 certification program. Since then, Wi-Fi 6 has become famous all over the world, and almost all the newly released devices support Wi-Fi 6.

Wi-Fi 6 certification mark 2.2. The Wi-Fi channel and the frequency band Wi-Fi mainly work in the 2.4GHz and 5GHz bands. These two bands are called ISM (Industrial Scientific Medical Industry, Science, Medicine) bands. As long as the transmission power meets the requirements of the national standard, they can be used directly without authorization.

The ISM band is different in different countries. As the earliest ISM band in the world, 2.4GHz has a spectrum range of 2.40GHz~2.4835GHz, with a total bandwidth of 83.5m.

Our commonly used Bluetooth, ZigBee, and wireless USB also work in the 2.4GHz band. In addition, microwave ovens and cordless phones also use 2.4GHz. Even when the internal chip of the wired USB interface is working, it will transmit useless signals of 2.4GHz, causing interference.

Thus it can be seen that there are many devices working at the same time on the 2.4GHz, the frequency band is crowded and the interference is serious. When every house is lit up and you and your neighbors upstairs and downstairs are happily surfing the Internet with Wi-Fi, the router silently chooses the channel behind it and coordinates the interference.

Wi-Fi divides the 83.5m bandwidth in the 2.4G band into 13 channels, one for every 20m. Note that these channels are overlapping, originally can only put down 3, but now rigidly squeeze in 13, the interference between each other is inevitable, can only be reduced as far as possible, the big deal everyone is slower, the queue turns to use.

2.4G spectrum and channel (channel 14 is not allowed in China) to what extent do channels overlap? It can be seen intuitively from the following figure that in these channels, only the three groups of 1pd6 and 11 or 2pd7 and 12, or 3pd8 and 13 are not overlapped at all, which shows the degree of congestion in the 2.4GHz band. It is like a very narrow road, but there are a lot of cars passing above, and frequent traffic jams are bound to cause a decline in traffic speed.

2.4G non-overlapping channels are distributed to 802.11n, and users can use 40m channels, but the 2.4GHz band still has a total bandwidth of 83.5m, so it can only accommodate two channels. Therefore, only when the network is idle in the dead of night, is it possible for a single user to use the 40m channel, coupled with the interference from the old Wang's house next door, the high rate of 802.11n is largely difficult to achieve.

2.4G 40m bandwidth channel if the 2.4GHz band is a small path, the 5GHz band is undoubtedly a broad road.

The available range of the 5GHz band is 4.910GHz~5.875GHz, with a bandwidth of more than 900m, more than 10 times that of 2.4G! This spectrum is too wide, and different countries define the range within which Wi-Fi can be used according to their own conditions.

For example, in China, there are 13 20m channels in the 5GHz spectrum that can be used as Wi-Fi, and continuous 20m channels can also form 40m, 80m, or even 160m channels.

China's 5G channel distribution map 5GHz has a large bandwidth, less equipment running above, natural speed and less interference. Therefore, if you want the home network to achieve a good speed experience, you can consider using 5GHz to cover the whole house.

However, the ruler has its shortcomings and the inch has its strong points. Although the bandwidth of 5GHz is large and the interference is small, the signal propagation and attenuation is fast, and it is easy to be blocked, and the ability to penetrate the wall is very weak.

The penetration loss of 2.4G and 5G Wi-Fi signals therefore, 5GHz signals are usually much weaker than 2.4GHz signals. As for how many meters each they can cover, it is difficult to specify because of the antenna gain of the router, the reception sensitivity, the distribution of walls and obstacles in the home, and the Internet speed that individuals expect to achieve.

If you only consider the networking of all kinds of smart homes at home, the coverage and capacity of 2.4GHz is usually sufficient. But if you need high-speed Internet access to maximize the value of home broadband, you must rely on 5GHz to achieve.

Therefore, the Wi-Fi coverage proposal does not consider the 2.4GHz, and directly takes the 5GHz whole house coverage as the design goal. In general, it is difficult for a single router to achieve dead-corner coverage in a complex home environment, so the networking and roaming problems between multiple routers need to be considered, which will be discussed later.

2.3. The key technology of Wi-Fi Why is the speed of Wi-Fi getting faster and faster? In fact, the 802.11 series of protocols in IEEE have been learning from 3GPP's 4G and 5G, and the underlying technologies used are common.

OFDM/OFDMA

The full name of OFDM is orthogonal frequency division multiplexing. The system will divide the carrier bandwidth into multiple orthogonal subcarriers in the frequency domain, which is equivalent to dividing a road into parallel lanes, so the traffic efficiency will be greatly improved.

In Wi-Fi 5 and before (802.11a / b / g / n / ac), the subcarrier width was 312.5KHz, but in Wi-Fi 6 (802.11ax), the subcarrier width was reduced to 78.125KHz, which is equivalent to dividing a road of the same width into more lanes.

Wi-Fi 6 has more subcarriers under OFDM, each user must occupy all subcarriers under full bandwidth at the same time. If someone does not have so much data to send and is dissatisfied with the use of frequency resources, other users will not be able to use them flexibly and have no choice but to wait in line, and the use of spectrum resources is not efficient.

In order to solve this problem, Wi-Fi 6 introduced OFDMA technology, followed by the letter A, its full name is also changed to orthogonal frequency division multiplexing multiple access. Multiple access means multi-user reuse.

OFDM vs. OFDMAOFDMA can support multiple users to share all subcarriers at the same time It is equivalent to that the transportation company uniformly packages the data of multiple users, loads the car together, and makes full use of the carriage capacity, so that everyone's delivery speed is accelerated and the spectrum efficiency is improved.

MIMO / beamforming

The number of antennas on the router is increasing, from invisible antennas to one, two, three, four, six, eight. Now no matter what the price of the router, all look like a crab, open teeth and claws so as not to bluff.

Why do you use so many antennas? Is to better implement MIMO (multiple input multiple output) technology. To put it simply, when a signal is transmitted, multiple antennas are used to send multiple different data at the same time, and the speed is naturally doubled; when receiving, multiple antennas receive signals from mobile phones at the same time, just like wearing hearing aids. The reception sensitivity has also been enhanced.

Single-user MIMO (SU-MIMO) is called single-user MIMO (SU-MIMO) if all antennas serve only one user at the same time. Further, the router four-way transmission, mobile phone four-way reception, can also be more finely called 4x4 MIMO.

Sometimes, the antenna of the router is so powerful, but I look around and find that all the mobile phones are weak. The router can send 4-way signals, but the mobile phone can only receive two channels at most, and eventually the router will have to cooperate with only two channels. Isn't that a waste?

There is also a solution to multi-user MIMO (MU-MIMO). If one mobile phone has fewer receiving antennas, won't more mobile phones add up? As a result, the router considers multiple mobile phones together as a powerful virtual mobile phone, so that it can achieve high-level MIMO again. This kind of multi-phone MIMO is called multi-user MIMO (MU- MIMO), also known as virtual MIMO.

In addition, multiple antennas can also form a narrow directional beam through beamforming technology, aiming at the accurate coverage of users. Because of the energy concentration of the narrow beam, it can be covered farther, and the effect of passing through the wall can be improved.

Beamforming from this point of view, the more antennas a router has, the better. Do you have to choose more antennas when you buy a router? This could be a trap. No matter how many antennas are, they are just piling up some externally visible hardware, which looks powerful and shiny, but it is unclear whether the internal design can support so many antennas.

More importantly, both MIMO and beamforming need to be supported by software algorithms, which is much more complex than hardware, and different manufacturers have different optimization capabilities, which may lead to great differences in performance.

Therefore, it is recommended that when buying a router, do not pay too much attention to how many antennas can be seen outside, but to see their product promotion, whether they support beamforming, 4x4MIMO, or MU-MIMO? If the manufacturers have a lot of publicity in this area, it at least shows that they are confident in these features and use them as a selling point.

Modulation and coding strategy (MCS)

Modulation coding is divided into two parts: modulation and coding, which together determine the number of bits that can be transmitted at the same time per unit time. The modulation and coding strategy generally divides the two parts of modulation and coding into multiple levels, and the higher the level, the faster the data transmission rate.

The function of modulation is to map the encoded data (a random combination of zeros and ones) to the smallest unit of the frame structure mentioned earlier: the OFDM symbol. Only after being modulated can the signal be finally transmitted.

The commonly used modulation methods of BPSK,QPSK,16QAM,64QAM and 256QAM constellation include BPSK, QPSK, 16QAM and 256QAM. The number of bits that can be transmitted at the same time is 1, 2, 4, 6 and 8. Wi-Fi 6 can support 1024QAM and can send 10 bits of data at the same time, which naturally increases the speed greatly.

However, when coding the original data, a lot of redundant bits are added in order to correct errors, but the real useful data is only part of it. When we consider the Internet rate, we are only talking about the sending and receiving rate of useful data, and the redundant bits are discarded when decoding.

It is necessary to introduce the concept of code rate, that is, the proportion of useful data in the total amount of data after coding. If the bit rate is 3max 4, it means that in the encoded data, 3max 4 is useful data, and 1max 4 is the redundant bits added later.

Different modulation methods and different bit rates constitute the modulation and coding strategy (MCS). The following table is the MCS table in Wi-Fi 6. You can see that the highest order MCS is 11, which corresponds to the bit rate of 1024QAM plus 5 hand 6.

It is through the continuous evolution of these technologies that the MCS meter of Wi-Fi 6 is moving forward from generation to generation, and the speed is getting higher and higher, making it easier for us to surf the Internet.

3. The Internet speed of Wi-Fi estimates how fast the Wi-Fi can achieve?

Router manufacturers advertise that the Wi-Fi 6 can reach 1800Mb psp3000Mbps, or even 5400Mbps speed. How on earth is it calculated?

To calculate the peak rate that can be achieved by Wi-Fi, several techniques mentioned earlier must be used: OFDM,MCS, and MIMO.

OFDM: orthogonal frequency division multiple access divides the bandwidth of the whole system into multiple orthogonal subcarriers. The finer the granularity of the division is, the more subcarriers are, the more data can be transmitted at the same time, and the higher the rate is.

In addition, OFDM technology will eventually package the data into a symbol (Symbol) to send, the shorter the time it takes for each symbol, the smaller the Guard Interval,GI between the two symbols, the higher the rate.

MCS: modulation and coding strategy, which mainly affects the rate in two aspects: modulation mode and code rate. The better the wireless environment, the higher the modulation order that can be used, the more bits can be carried per unit time, the less redundant bits used for error detection and correction can be added, and the transmission rate of useful data is naturally accelerated when the code rate is increased.

MIMO: that is, the number of data streams that can be sent simultaneously in space through multiple antennas. The more the number of spatial streams, the higher the rate. For example, the theoretical rate of 4x4MIMO is twice as fast as that of 2x2 MIMO, and the effect is immediate.

To sum up, the peak rate of a single band Wi-Fi can be calculated using the following formula. Similar to the calculation of 5G peak speed, the above formula can also be compared with the highway system.

The space flow number of Wi-Fi peak rate calculation formula is equivalent to multi-layer traffic, the number of subcarriers is equivalent to multiple lanes on each layer of highway, the modulation order is equivalent to the volume of freight cars on the road, the code rate is equivalent to adding packing boxes to goods, and the length and interval of OFDM symbols are equivalent to the traffic time of trucks on the road plus departure intervals.

Analogy between Wi-Fi speed and highway capacity: with the evolution of the protocol, more and more spatial flows can be supported by Wi-Fi, which promotes the peak speed.

As shown in the following table, the 802.11ac developed by IEEE can support up to 8 streams, but the Wi-Fi Alliance (WFA) feels that this capability is too strong and expensive to implement, so it is divided into two phases: wave 1 and wave 2.

The number of spatial streams supported by each Wi-Fi protocol version is also relatively conservative, and the design capability of IEEE has not been finally realized. Wave 1 can support 3 streams and Wave 2 can support 4 streams.

When it comes to 802.11ax, it can support up to 8 streams. The Wi-Fi Alliance packaged it as Wi-Fi 6 and no longer made a transitional version. But how many levels your router can support depends on the specific implementation of the manufacturer.

The number of effective subcarriers: 802.11 series of protocols divide the subcarriers more and more carefully, and the channel bandwidth that can be supported is getting larger and larger, which make the number of effective subcarriers increase continuously.

As shown in the table below, 802.11n can support up to 40m channel bandwidth, while 802.11ac can support 160m bandwidth, so the number of effective subcarriers has more than quadrupled.

The carrier bandwidth and the number of effective subcarriers supported by each version of the Wi-Fi protocol are up to 802.11ax, and the maximum channel width is 160m, but the subcarrier interval is only 1 beat 4 of the previous protocol, so the maximum number of supported subcarriers is four times higher than that of 802.11ac.

Modulation order: 802.11ac supports maximum 256QAM, and the modulation order is 8, that is, each symbol can carry 8 bits of data at the same time.

The modulation order 802.11ax supported by each Wi-Fi protocol version is up to 1024QAM, and each symbol can carry 10 bits of data at the same time, which is 25% higher than that of the previous generation.

MCS and bit rate: the protocol defines a variety of modulation modes and rate combinations, that is, modulation and coding strategy (Modulation Coding Scheme, MCS).

The higher the MCS modulation order supported by each Wi-Fi protocol version, the higher the code rate, and the worse the anti-jamming ability is. Therefore, when the wireless signal strength is enough and the interference is very small, the high-order MCS can play a role.

Symbol length + symbol interval: in 802.11ac and before, the length of a single symbol is 3.2 microseconds, and the symbol interval is 0.8 microseconds, but 0.4 microseconds are also supported. We calculate the peak rate at short intervals, of course, so the symbol length + symbol interval of 802.11ac is 3.6 microseconds.

The symbol length and symbol interval supported by each Wi-Fi protocol version is up to 802.11ax, the symbol length is 12.8 microseconds, and the interval length is at least 0.8 microseconds, which adds up to 13.6 microseconds.

Although this value is much higher than the previous agreement, it seems to suffer a loss, but 802.11ax is very good in other aspects, and the speed is still crushing the older generation.

Bring the data from the above tables into the formula calculation, adopt the highest-order debugging mode and code rate that the protocol can support, use the minimum value of symbol interval, do not consider the number of spatial streams first, and the calculation results of single stream are shown in the table below.

Different Wi-Fi protocol versions support different Wi-Fi peak rates of different wireless routers, which are mainly reflected in the bandwidth that can be supported in the 2.4G and 5G bands, as well as the number of spatial streams.

2.4GHz usually supports a maximum of 40m bandwidth, while the 5GHz band can support a maximum of 160m bandwidth. according to the different version of the protocol and the number of spatial streams, adding up the peak rate that the two bands can support is the peak rate officially advertised by the router.

The peak rate supported by each type of router is shown in the picture above, which estimates the channel bandwidth and the number of streams that can be supported in the 2.4GHz and 5GHz bands according to the nominal rate of the router, and validates the rate calculation.

For example, for AC1200, AC means that it can support up to the 802.11ac protocol (Wi-Fi 5), the 2.4GHz band can only use 802.11n, support 2x2 MIMO, the rate can reach 300Mbps, the 5GHz band is also 2x2 MIMO, the rate is 867Mbps, and the sum is 1167Mbps, so it is advertised according to 1200m.

For AX5400, AX means that it can support 802.11ax protocol (Wi-Fi 6) at most, 2.4GHz band supports 2x2 MIMO, the rate can reach 573.6Mb psjol 5GHz band can support 160m channel bandwidth and 4x4 MIMO, the rate is 4804Mbps, the sum is 5377.6Mbps, so it is publicized according to 5400m.

4. Home Wi-Fi networking guidelines in ancient times, I always had a sense of anxiety when I traveled to Asia, Africa and Latin America, fearing that the hotel or dormitory I stayed in had no network or Wi-Fi, so I had to carry a plug board, a network cable and a portable router with me. In recent years, it has been found that Wi-Fi is almost everywhere, and this set of equipment has gradually been covered with thick dust.

This portable router can be directly plugged into the network cable and can be used without care. Most of the routers that have been used at home are directly plugged into the power supply and simply configured with a mobile phone. As for what kind of working mode and networking scheme is used, there is no special attention.

Recently, I took out a dusty portable router and found that it was not that simple. In order to achieve better coverage effect, routers can be flexibly networked and have a variety of working modes. After understanding these principles, we will be able to have it in mind when planning for home network coverage.

4.1. Two basic concepts SSID

The full name of SSID is Service Set Identifier, and its translation into Chinese means service set identification. This concept seems classy, but it is actually the name of the Wi-Fi signal.

No matter where you are, as long as you search with a computer or mobile phone, you are bound to see a series of Wi-Fi SSID and their signal strength. These Wi-Fi signals can be encrypted or unencrypted.

Computer found SSID list this is the core function of SSID: divide a wireless local area network (WLAN) into several sub-networks that require different authentication, each sub-network requires independent authentication to prevent unauthorized users from entering the network, the general home network will set a password.

SSID name implies that a general dual-band router can divide the two bands 2.4GHz and 5Hz into two SSID, but this may cause confusion, and it is often difficult to switch to 5GHz because of the SSID connected to the 2.4GHz band. Therefore, many routers also support dual-frequency integration, the system automatically sets the signal switching threshold, the user is not aware of it.

Network segment

Every mobile phone or computer in the LAN has an IP (Internet Protocol, Network layer Protocol) address for communicating with each other. Our common format (IPv4) consists of 32 bits of 0 or 1.

The 32-bit binary IP address is roughly in the following format: 110000001010100000000000000000000001, but this doesn't look intuitive at all.

So we divided it into four paragraphs: 11000000.10101000.00000000.00000001, which is still not intuitive enough. So we converted it to decimal: 192.168.0.1, which finally looks much more pleasing to the eye.

For ease of management, we divide the IP address into two parts, the network prefix and the host address. The network prefix identifies a network, also known as a network segment, and the host address is used to identify each device within the network.

The IP address is shown in the figure above, with "192.168.0" in the first three segments of the address as the network prefix and "123" in the last segment as the host address. The range of 8-bit binary digits in the final host address is 0 numbers 255 and 255 for special purposes, and the actual range available is 1 bits 254.

The subnet mask uses a series of 1s to indicate which bits in the IP address are network prefixes. In the example above, the 24 bits of the first three segments of the IP address are all network prefixes, and the mask is marked 11111111111111111100000000 (no number, 24 1s), which is also divided into 4 segments and converted to 10, which is 255.255.255.0. It can also be appended to the back of the IP address, writing 192.168.0.123 and24.

The setting of IP address and subnet mask indicates that devices within the same network segment can communicate with each other, and different devices in the network segment need to be forwarded through the routing function of the router in order to communicate with each other. There are not many devices in the home network, so it is recommended to keep all the devices in the same network segment as far as possible to facilitate mutual access.

The communication between network segments is illustrated by using only a PC computer connected by a network cable as an example. In fact, each network segment can be accessed through wired or wireless means, and devices are not limited to computers, mobile phones, speakers, cameras, doorbells and other devices that can be connected to the Internet.

4.2. There are many working modes of routers and networking wireless routers, which can be divided into routing mode and AP mode. AP mode can be subdivided into AP mode (nesting doll), relay mode, bridge mode and client mode.

Based on these basic working modes, AP+AC and Mesh can be formed between multiple routers to achieve the effect of seamless coverage and automatic roaming.

The working mode and networking of routers 4.2.1 the vast majority of wireless routers work in this mode and use the wireless access function and routing function of the router at the same time.

The most common use is that the router WAN port is connected to the home optical cat, and set up PPPoE dial-up Internet access and provide a variety of routing and security functions. For the future of the bear child, it can also configure a variety of Internet access control strategies, such as IP address, URL, application access restrictions and so on.

Accordingly, the wireless access function of the router is responsible for transmitting Wi-Fi signals to form a wireless local area network (WLAN) for house-wide wireless signal coverage. Multiple devices connected to WLAN and wired LAN ports are located in the same local area network, have the same network segment, and can communicate directly in the internal network.

Route pattern indicates that in addition, you can also connect the router with the WAN port and the LAN port of the superior router to form a second-level route, and you can configure the intranet of two network segments and two different Wi-Fi names (the same is also possible).

This kind of networking can not achieve seamless roaming between two routers, one Wi-Fi signal weakens and switches to another process with the change of IP address, the network interruption is obvious.

4.2.2 AP mode AP refers to the access point (Access Point). As the name implies, the router working in this mode only has access function, and does not use routing function, so it does not mention routing, which is directly called access point.

Just because the access point does not have the routing function does not mean that the routing function does not exist, but is borne by another router. In other words, the router in AP mode can not complete the important task of surfing the Internet independently, so it needs to cooperate with another router, mostly for the expansion of coverage.

AP mode has three submodes: AP mode (nesting doll), relay mode and bridge mode.

AP mode

The router with AP mode is connected to the superior router through the network cable, only the access function is extended as wireless coverage (it can also be used as the main coverage), and the routing and DHCP functions are completed by the superior router. Therefore, the mobile phone or computer connected to the AP is in the same network segment as the superior router and can directly communicate with each other.

The wireless network name (SSID) and password of the AP can be set independently, either the same or different from the superior router. If the setting of the Wi-Fi name is different, there must be no seamless roaming between the two devices, only if one signal is too weak and then connected to the other, or manually.

Even if these AP are set to the same SSID, it seems that there is only one Wi-Fi signal at home, but in fact, there is no interaction between AP and the wireless signal of the main route, so it is difficult to configure and manage, and it is impossible to roam seamlessly.

AP mode indicates that the AP under this network has perfect functions, and each node has to be configured separately and work independently of each other, so it is called "fat AP (Fat AP)".

Fat AP are in the dragon plate, there is no unified management, their respective coverage can not roam, can make do with a small number at home, in shopping malls, airports, these super-large space, the need for a huge number of AP, we can only hire someone else.

AP+AC networking

Since fat AP is difficult to manage, we can split it again, retain only the most basic access function, separate the configuration management function, and form a brand-new device: access controller (Access Controller,AC), commonly referred to as AC.

AP+AC networking indicates that AC is responsible for managing all AP. As long as it is configured uniformly on AC, it can be automatically synchronized to all AP nodes, and the working status of all AP can be monitored in real time on AC, which is also very convenient to maintain. AP in this state only needs to do a good job, nothing else, of course, there is no fancy intestines, so it is called "thin AP (Fit AP)".

More importantly, by letting AP support the 802.11k / v / r protocol, seamless roaming between AP can be achieved.

802.11k: wireless resource measurement protocol that helps terminals quickly search for nearby AP that can be used as roaming targets.

802.11v: wireless network management protocol, used to solve the load balance between AP, and terminal power saving and other functions.

802.11r: fast roaming protocol, which is used to speed up the authentication process of mobile phones or computers when roaming.

The above roaming protocol requires both the router and the mobile phone to support it in order to work properly.

In the actual AP products of various manufacturers, most of them support 802.11k / v protocol, which is enough for home networks.

This plan is perfect. Is there any room for improvement?

We consider that a large number of AP should be connected to the AC, in addition to laying a large number of network cables in advance, but also prepare the corresponding power supply to power the AP, this workload will be heavy. Is the network cable itself also a wire? the power consumption of AP is generally not high. Can the network cable not only transmit data but also do the work of power supply?

That's pretty good. This kind of power supply mode has a special protocol, called PoE (Power over Ethernet, Power over Ethernet), which requires the support of both the connecting devices such as switches and the AP in order to supply power normally.

AP+AC+PoE power supply network indicates that in this way, we connect a PoE switch to the back of the AC, and then replace all the AP models that can support PoE, so that we can realize PoE power supply, saving the trouble of pulling power lines in many places, and immediately feel that the network is much more refreshed.

However, some people may want to say, my home only 2 rooms plus a living room, a total of 3 AP is enough, the result not only to connect to the main router, AC, and then a PoE switch, not only the cost is high, even the weak box has no room to put!

Indeed, the AC+AP scheme is mainly used for large commercial premises, and then it is also the case of multi-storey villas and many rooms, so it is really not appropriate for ordinary houses to use cow knives to kill chickens.

Routing / AC / PoE all-in-one computer + AP networking signal, but businesses have also developed a simplified scheme, combining routers, AC and PoE switches into one, called "routing / AC / PoE all-in-one machine", which is similar to the size of ordinary home switches, and the cost is also greatly reduced.

At the same time, the above scheme also integrates AP into the traditional 86 network cable socket panel, which is completely hidden in the invisible, but achieves the best state of seamless Wi-Fi coverage and strong signal.

Panel AP networking schematic diagram AC+AP has significant advantages, but it also has disadvantages. That is, all AP need to use network cable and AC connection, which requires consideration of Wi-Fi network and network cable when decorating. If there is no network cable available, other options must be considered.

4.2.3 the relay mode is different from the AP mode, in which there is no network connection between the router in the relay mode and the superior router, but simply receives the wireless signal from the superior router, amplifies it and then transmits it without any processing.

Relay mode networking indicates that the Wi-Fi name and password of the AP signal in relay mode are the same as the superior route, and all devices are located in the same network segment. For users, the effect of access relay AP and primary route is exactly the same, relay AP is only equivalent to a pipeline for extended coverage, and all processing is carried out by the primary route.

4.2.4 bridging mode is similar to trunking mode, which connects two routers wirelessly without a network cable. The difference between the two is that the relay mode works at the physical layer and cannot be set up, while the bridging mode works at the data link layer and can be configured with an independent SSID.

Bridging mode networking indicates that although the SSID can be different (or the same), the network segments of the router and the main router in bridging mode are the same, and devices can access each other after they are connected.

Routers in relay or bridge mode must be within the coverage of the main route in order to amplify the signal to access the Internet. If in the location where the signal of the main route is very poor, although the Wi-Fi signal seen by the mobile phone is full after amplification, the network speed is still very slow and may even be unstable.

Moreover, the main route does not know the existence of subordinate relay or bridging nodes, and there is no management and interaction between them, so it is impossible to roam, and the mobile phone can only wait for the signal to be disconnected and then reconnect to another node.

Is there any way to integrate wired networking like AC+AP and wireless networking such as relay or bridging, and intelligently manage the network to achieve the effect of simplified configuration and seamless roaming?

This is going to use Mesh networking technology.

4.3 Mesh networking Mesh, also known as multi-hop network, consists of multiple nodes with the same status connected to each other by wired or wireless means to form multiple paths, and finally connected to the gateway connected to the Internet. In such a network, there is a control node to manage all nodes and send configuration data.

The following figure is a case of actual networking, in which the primary route is used as the gateway and control node, and the rest of the nodes are connected to the primary route through wired or wireless, or to each other wirelessly. In this way, the network can be flexibly expanded on demand in areas with weak coverage, with or without network cables.

Mesh networking indicates that the wired connection between routers is called "wired backhaul", and the corresponding wireless connection is called "wireless backhaul".

Mesh networking is very suitable for family Wi-Fi coverage. Imagine a scenario like this:

The first step: Xiaoming bought a house, at first only the young couple lived, so he bought a router to put in the living room, and the nearby master bedroom was well covered, which the couple thought was enough.

Step 2: after the baby is born, the mother and mother-in-law will also help take care of it, but the Wi-Fi signal in other rooms is not good, so buy a router directly and Mesh the network through wired way, so the effect of seamless roaming is good.

Step 3: everyone unanimously reflects that it is difficult for the bathroom to surf the Internet, so buy a router and hang it on the wall and network with the first two Mesh wirelessly. Everyone is very satisfied, that is, the time to go to the toilet has become longer.

Although these routers have different models, they can be used together as long as they support Mesh networking, unlike AC+AP, which requires AC and PoE switches, as well as network cable restrictions. Most importantly, ordinary home routers have generally supported the latest Wi-Fi protocol, and the price is still low.

At present, different manufacturers have different implementation of Mesh networking, and their names are naturally different. In general, there is no Mesh group between routers from different manufacturers, which may limit the purchase options of routers.

In order to solve the problem of interconnection and interworking of routers from different manufacturers, Wi-Fi Alliance has introduced EasyMesh technology, which enables routers of different manufacturers to support Mesh networking.

Wi-Fi Alliance EasyMesh network but manufacturers have their own abacus, the original use of incompatible Mesh technology can encircle users, support this EasyMesh allows users to choose other products, which is obviously disadvantageous to themselves. So EasyMesh's current approval rating is not high.

In order to better support Mesh networking and let users get higher network speed, manufacturers specially use a 5GHz band to do wireless backhaul between routers, so routers need to support one 2.4GHz band and two 5GHz bands at the same time, so it is called "tri-band router".

The triple-band Mesh router indicates that there is often a question about which solution is better for home networking, Mesh or AC+AP. Here are some of your views.

First of all, whether it is Mesh networking or AC+AP, can achieve the effect of full house coverage and wireless roaming. When all wired backhaul is used in Mesh networking, it is basically equivalent to AC+AP.

Mesh networking is more flexible, with wireless backhaul, wired backhaul and mixed use, while AC+AP can only use wired connections and need to plan cabling in advance.

In addition, the AC in the AC+AP scheme can be placed in the weak box, the AP uses the panel type and does not take up space, and all the equipment does not have any network cable and power cable exposed, which is very refreshing and beautiful. On the other hand, the Mesh scheme needs to drag the grid cable and power cord, which is much worse in terms of aesthetics.

Finally, AC+AP needs to purchase at least one routing / AC / PoE integrated machine and two AP to make sense. If you want to support gigabit ports and Wi-Fi6, these devices are not cheap, while Mesh networking is more people-friendly, and the price of the two routes is much lower than that of AC+AP.

When choosing the networking scheme, it can be considered comprehensively according to the characteristics of the above two schemes.

5. Brief introduction of other functions of wireless router for wireless router, in addition to the wireless access function mentioned in the previous issues, the routing function is also very critical, which solves the problem of how to surf the Internet.

In general, when you apply for home broadband, the operator will assign you an account, which is represented by a user name and password, which is your pass to access the Internet.

The WAN port on the router is used to connect the light cat, and then you can choose the Internet access method in the WAN port configuration. In most cases, you need to choose PPPoE to dial, and after entering your user name and password, the operator will assign you an IP address and the router will successfully connect to the Internet.

Schematic diagram of Wi-Fi dial-up access the networking modes of WAN ports are dynamic IP and static IP, but domestic operators basically do not use them. If you have more than two routers at home to form a multi-level route, you need to set up the above two ways.

NAT (Network address Translation) operator assignment will only assign you a public network IP address, theoretically allowing only one device to access the Internet. But now that every family has multiple mobile phones, multiple computers, and all kinds of Internet of things devices need to be connected to the Internet, what can we do?

We know that the router's LAN port and WLAN (Wi-Fi) form a local area network, and the router will also assign a different IP address to each device accessed. These IP addresses usually start with 192.168.x.x. They are private addresses and can only be used within the local area network.

Network address translation schematic diagram for these devices to access the Internet, they must convert private IP into external public IP, which requires the use of the NAT protocol. NAT can convert multiple private addresses into public addresses, so that multiple devices can share the same public IP to access the Internet.

Safety management

As a home gateway, the function of the firewall is generally necessary and can resist network attacks.

The most common function of firewalls is DoS (Denial of Service) attack protection. DoS attack, commonly known as denial of service attack, by sending a large number of useless request packets, thus exhausting the router's CPU, memory and other resources, resulting in the failure of normal service.

In addition to the firewall, security management has many practical functions.

Many people want to restrict their children's access to certain websites, restrict the use of certain APP, or limit the amount of time they spend on the Internet, which can be achieved through the firewall function.

IP address filtering: restrict access to certain IP addresses by users who access the router, or restrict an IP address in the local area network from accessing the external network.

MAC address filtering: restrict the networking of a device in a local area network based on the MAC address. MAC address is generally fixed, combined with the configuration of the time period, this function can achieve fine device management.

URL / domain name filtering: restrict access to certain URLs or domain names by networking devices. If you have a child at home, you can effectively manage your child's visit to some websites.

Application filtering: restrict the networking of some applications, and enable time periods can be finely set. For example, you can set rules such as no games during the week and limited time on weekends as needed.

Other functions QoS (Quality of Service, quality of service): speed limit control for a device, and priority control for data packets, such as game priority, web page priority, video priority and other intelligent control.

DDNS (Dynamic DNS, dynamic domain name service): it can be used to set up WEB\ MAIL\ FTP and other servers in your own or home. With the help of router DDNS binding domain name, you can use our computer as a server function for external users to access.

Remote download: you can set the download address, and automatically download files from the specified server address to the storage space of the router (through the USB interface to external mobile hard disk), and achieve resource sharing.

In addition to dial-up Internet access and NAT, we don't usually use many of the functions of routers, but we have a general idea of them, and we may need them one day. What do you say?

6. A brief introduction to the hardware of a wireless router to the hardware of a router, many people may say, I just want to buy a router, not to build a router, what can I do if I know so many details?

This kind of thinking, in fact. That's right.

In fact, the router is similar to our commonly used computers or mobile phones, and it also contains the corresponding configurations of CPU, memory, hard disk and so on. The stronger these hardware capabilities, the stronger the performance of the router must be.

But when you open the introduction of a router on a shopping website, you will find that all kinds of shiny publicity from most manufacturers are all about it, but they just don't want to tell you what's inside it. In any case, most people do not ask for much about it.

If you want to know in detail how many goods there are in the belly of a router and whether the workmanship is solid or not, you can only watch the disassembly video. At this point, it is necessary to understand the hardware composition and function of the router in advance.

Okay, let's get started.

CPU is called CPU, but it is actually called SoC (system on Chip) more accurately, because general processing chips integrate CPU and many other important functions to form a system on chip.

Whether it is a mid-end or high-end router, CPU is the core of computing, and all data is forwarded through CPU. Therefore, CPU determines the load capacity of the router, how much data throughput it can bear, and its performance, power consumption, heat dissipation measures and so on are very important.

In the low-end home router, CPU is responsible for routing table query and packet forwarding. In the middle and high-end home routers, CPU is mainly responsible for the operation of the operating system and other additional functions, while packet forwarding and routing table query are mainly completed by ASIC chips.

At present, there are mainly several common home wireless router CPU manufacturers: Broadcom, Qualcomm, MTK, Realtek. For users with strong hands-on ability and want to refresh the third-party firmware, they need to consider the brand and model of CPU. We usually think that Broadcom > Qualcomm > others.

In addition, the SoC chip integrated with CPU also determines the number of external network interfaces, the type of USB interface and so on. Of course, some routers use an extension of the external interface instead of an SoC integrated configuration.

Memory (RAM) the RAM here has the same meaning as what we usually call computer memory, which is also called storage on mobile phones.

The memory in the wireless router is mainly used to store operating system instructions, dynamic data, buffer messages and other data. In general, the larger the router memory, the better. If the software algorithm of the router manufacturer is optimized well, it can save a lot of memory and make the hardware more efficient.

Compared with the 6G to 8G memory of smart phones, the function of the router is less, and the demand for memory is less. Generally speaking, 128m memory is enough for gigabit routers, and 256m is already high-equipped large memory.

Flash memory (Flash) is the equivalent of a router's hard disk, which is used to store the router's firmware, that is, the operating system. Generally speaking, the capacity of 16m or 32m is enough, and the router with more additional functions or magic modifications may take 128m or even 256m, so you don't need to pay special attention to it if you don't want to brush the solid parts.

Wireless management chip

As the name implies, the wireless management chip is used to support the wireless function of the router. In other words, whether the router supports Wi-Fi 5 or Wi-Fi 6, several transmit antennas and how MIMO functions are determined by the wireless management chip. The chip can be deployed independently or integrated in the SoC chip.

The power amplifier chip is the RF front-end module (FEM), which is composed of power amplifier (PA), filter, Duplexer, RF switch, low noise amplifier (LNA), receiver and transmitter, which are also packaged in the RF chip.

RF front-end is the closest step of wireless signal processing to the antenna, and its performance is directly related to the quality and stability of Wi-Fi signals.

Wireless management chips are generally integrated with a built-in RF front-end, but manufacturers can also abandon it and use a more powerful external independent RF front-end. It is generally believed that only when each antenna has an independent RF front-end can the router achieve the best wireless performance, so many routers use this as a selling point.

The network port network port is necessary on the router, which is divided into the WAN port connected to the optical cat or the superior router and the LAN port with internal switching function.

Most home wireless routers have one WAN port and four LAN ports, so networking is generally sufficient. Considering that wireless networking has become the absolute mainstream, many routers have reduced the LAN port to one or two, and even no longer distinguish WAN port from LAN port in hardware, but rely on software to adaptively identify them.

In the era when Wi-Fi6 and more than 100m broadband have become popular, the network port rate needs to be at least gigabit. Be careful not to be deceived by gigabit routers equipped with 100-megabit ports, which are generally very low in price and need to be paid attention to when buying.

With the development of optical fiber into the home (FTTR) technology, home all-optical networking scheme has also been listed. Optical fiber as a medium can provide almost unlimited transmission capacity, which can be considered by students who have ultra-high bandwidth requirements or consider future bandwidth upgrades.

Router architecture and physical disassembly mayday has found a TP-Link router architecture diagram, we can take a brief look at this product (non-advertising, this thing is not sold in China) in the end.

First of all, the middle of the TP-Link router is Qualcomm's SoC chip, which integrates CPU with the main frequency of 700MHz and wireless management module in the 2.4GHz band, which can support 802.11g (Wi-Fi 3) and is connected to three external RF front-end modules, that is to say, 2.4GHz supports three antennas.

The router architecture diagram extends from the PCIe bus of SoC, you can see another wireless management chip that supports 5GHz band, which can support 802.11ac (Wi-Fi 5), and is also connected to three external RF front-end modules, that is, 5GHz also supports three antennas.

From this, it can be concluded that this is a dual-band router that supports Wi-Fi 5, and there are six antennas in the two frequency bands, which can support 3x3MIMO respectively.

However, there are only three antennas standing on the outside of the router. Where did the remaining three go? In fact, it is integrated inside the router, and people are so low-key.

Router physical disassembly can be seen, rely on the number of external antennas to speculate the ability of the router is very unreliable, do not superstition octopus seemingly powerful appearance, the specific performance depends on the parameters, dismantling the hardware.

All right, that's all for the introduction of wireless router and Wi-Fi. I hope it will be helpful to you.

This article comes from the official account of Wechat: wireless Deep Sea (ID:wuxian_shenhai), author: mayfly acquisition

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