075582814553
The wireless access point (WAP) or access point (AP) is an access point for mobile computer users to access the wired network, mainly used in broadband homes, inside buildings, and inside campuses, with typical distance coverage of tens to hundreds of meters.
The working principle of the wireless access point is that the network signal is transmitted through a twisted-pair cable, and after the compilation of AP products, the electrical signal is converted into a radio signal and sent out to form the wireless network coverage.
Cisco Aironet wireless access point (source: Wikipedia)
In some big cities, it is not easy to lay lines for various reasons, such as the high cost of fiber optics, twisted pair long-distance signal weakness, river obstruction, city image, etc. We all prefer to facilitate the block shortcut to connect to the network, so the formation of a WAP unlimited network has a very obvious advantage.
In this article, I have organized the related knowledge of WAP into three major modules, I hope it can help you.
The maximum allowable indoor coverage distance is 35~100 meters
The maximum distance allowed outdoors is 100~400 meters
The empirical values of 2.4G electromagnetic wave penetration loss for various building materials are as follows.
A. Cement wall (15~25cm): attenuation of 10~12dB
B.Wooden board wall (5~10cm): attenuation 5~6dB
C. Glass window (3~5cm): attenuation 5~7dB
*The effect of various building materials on the wireless signal
When the AP and the terminal are separated by a concrete wall, the AP's transmittable coverage distance is about < 5m effective distance.
When the AP and the terminal are separated by a wooden board wall, the transmission distance of the AP is < 15 meters.
When the AP is separated from the terminal by a glass wall, the transmission distance of the AP is < 15 meters.
For general open spaces with an area of less than 150 square meters, such as public lounge areas, small bars, cafes, conference rooms, western restaurants, etc., where the number of users is expected to be less than 30, one AP can be placed in each place to meet the demand.
When the space is larger, multiple APs will be installed to meet the coverage demand. When the capacity demand is larger, i.e. the number of users in the coverage area of AP is too large, multiple APs need to be placed in the same space to increase the capacity.
Regarding the application of wireless access points, the most common networking mode is AP coverage, and different application scenarios will have different networking modes.
AP network coverage
The traditional wireless access point coverage is mainly used for network coverage in some small places. It is suitable for some bookstores, small restaurants or villas, etc... It uses an AC router for AP and broadband broadcast. It works very well.
What is an AC router?
AC router is a kind of router. AC routing refers to the routing that uses the AC function. The AC controller is used for wireless coverage to centrally manage all APs. It can be called the AP "housekeeper" and its role is to manage the APs.
A router is a network device used for data communication in many companies, businesses, Internet cafes, and large networks.
For large venues, such as hotels, we can use the following networking method for wireless coverage, using PoE power supply and wireless AC. AC has the function of unified control of wireless access point, which can simplify network management and maintenance.
Plan the access layer PoE switch according to the number of APs. Please note that when choosing PoE switch, you need to know the power supply standard of PoE, and then choose the corresponding Poe switch.
PoE power supply standard:
Determine the power protocol supported by the AP (APC or IPC) (e.g. 802.3af, 802.3at or non-standard PoE). The PoE power protocol supported by the switch must be the same as the powered endpoint.
The single port output power of 802.1af standard PoE switch is 15.4W, and the single port input power of 802.3at standard PoE switch is 30W. 802.3at standard PoE switch is recommended for power-consuming devices that consume more power.
In the process of implementing AP coverage, there are two points to note in order to ensure the stability, flexibility, coverage, and scalability of the solution.
In large wireless networks, AP wireless coverage is mainly because wireless access point has many advantages: flexible network expansion, wide-coverage, easy management, and other features.
When using a large wireless network, a large number of wireless access points are needed. When managing these large numbers of wireless access points in a unified manner, APs need to be set up, however, you need to be aware of the following.
Wireless access points with overlapping signals cannot use the same channel.
All wireless access points must use the same SSID.
All wireless access points must use the same IP address of the same network segment and be in the same VLAN.
Wireless access point coverage
Since the coverage areas of multiple AP signals overlap each other, the channels occupied by the AP coverage areas must conform to certain specifications, and adjacent channels cannot overlap each other.
In other words, a wireless access point in the mutual coverage area cannot be used, otherwise, the same channels will cause mutual interference among APs during signal transmission, thus reducing the efficiency of APs.
Among the 11 available channels, only 3 are covered, which are channel 1, channel 6, and channel 11, and it is appropriate to use these channels for multi-cell coverage.
In addition, the wireless access points used to implement the wireless roaming network must use the same network name (SSID) and use the same network segment IP address. Otherwise, the wireless client will not be able to achieve roaming.
Wireless in the roaming network, the client's configuration is the same as the configuration in the access point network. During the movement, the user does not feel the switch between wireless access points.
wireless roaming network
When building a wireless roaming network, the following points need to be noted.
1) The wireless access point and the wireless client must be located in the same VLAN and the same IP address segment.
2) AP signal coverage areas should overlap each other. Otherwise, it will lead to a wireless network dead zone. That is, the distance between wireless access points should be less than the limited transmission distance of wireless access points.
3) The wireless access points must be set to the same SSID. Different SSIDs mean different wireless networks, and wireless roaming is not possible.
4) The same WEP or WPA encryption must be used. All wireless access points and clients must use the same WEP or WPA encryption, otherwise, they will not be able to establish a connection with each other. WEP and WPA are also case sensitive.
5) Wireless access points covering each other must use different or even non-adjacent channels, otherwise, it will cause serious interference and reduce the efficiency of AP communication.
Channel is the frequency band, IEEE 802.11b/g work in 2400 ~ 2 483MHz, the U.S. standard channel can be divided into 11, the European standard can be divided into 13, the Japanese standard can be divided into 14, each channel has a difference of 11MHz.
For example, channel1 is 2,412MHz, channel2 is 2,423MHz, and so on. In practice, there is no interference between channels 1,6, and 11.
If you install one AP in a single room, try to place the AP in the center of the hall, preferably on the ceiling of the hall, and if you install two APs, you can place them on two opposite corners of the hall.
In theory, the isolation degree of adjacent frequency points >= 35 db. According to the empirical value, when adjacent APs set the same frequency points, the interval is more than 25 meters; when adjacent APs set adjacent frequency points, the interval is more than 16 meters; when APs set adjacent frequency points, the interval is more than 12 meters.
To maintain a good quality WLAN, it is necessary to consider the number of users within the coverage area, and the number of online terminal users of a single AP should not exceed 30.
(1) Coverage principle: Prefer to ensure that the signal coverage can meet user requirements
(2) Easy installation principle: the planning site should meet the construction requirements
The load-bearing wall of the reinforced concrete structure has a strong obstructing effect on the wireless signal. Therefore, for "duplex" structure homes and villa-like home environments, the best signal coverage solution is to configure wireless routers for each layer.
In practice, indoor AP coverage may only be up to 30 meters at most.
The actual use rate of 802.11b is only about 40% of the nominal value, which translates into a data transmission rate of about 600KB/s. If set to 64/128-bit WEP encryption, the transmission rate will be further reduced.
For large homes or small and medium-sized businesses, wireless signals can be lost and lost due to the walls between rooms, and wireless accessors are an effective supplement to improve the signal coverage of wireless routers and their stability.
Therefore, it is necessary to deploy a strong and powerful wireless access point. The wireless access point is a bridge between the wired network and wireless network, its expandability will extend the user's wireless experience to a wider area.
Wireless access point brand is also quite a lot, Cisco, Huawei, tp-link, tenda, aruba, etc...
Catalogue
FPGA / CPLD
Memory
MOS 
MCU 
DSP
OCEP
Secondary 
Other 