Focus access: Wireless Network Fault instance analysis

Faults are also emerging during the use or maintenance of wireless networks. Here we will introduce you to several detailed fault instances. The following articles will explain in detail.

The operating frequency of a wireless LAN (WLAN) is generally 2.4 GHz and belongs to the category of microwave communication. The transmission feature is linear and visible, that is, visual communication and contact methods. This shows that rain, fog, walls and other obstacles can affect the transmission quality of microwave. Therefore, we should also consider these features when using wireless technology to build a network in an appropriate environment.

The distance of wireless communication is related to the radiation power, the direction of the antenna, and the gain of the antenna. The radiation output power of a common wireless device is less than mW, and that of a wireless network adapter is generally only dozens of mW. Currently, wireless devices generally come with an omnidirectional antenna. The Omnidirectional Antenna uses the antenna as the axis and emits outward radiation in a "bagels" shape. The oriented antenna has a strong direction, there is no signal at all outside the radiation range of a small angle. A device with a detachable antenna can use an external gain antenna to increase the communication distance without increasing the radiation power of the antenna.

The cable has high transmission requirements. The loss of signals on cables and interfaces exceeds people's imagination. Ordinary cables are not suitable for transmitting antenna signals.

Common wireless network faults

In most cases, wireless device connection failure is caused by improper use. Failures are usually manifested in connection difficulties, slow communication speeds, and disconnection. There are generally three fault causes:

Environmental factors: the distance between the AP and the network card is too long; there are obstacles between the AP and the network card, such as indoor complex environment, wall, furniture.

Human Factors: Microwave Equipment Working in the GHz band, such as microwave oven, network cable, antenna cable contact failure, and oriented antenna characteristics.

Device factors: for example, the device is overheated or the cache is too small.

Examples of common wireless network faults and Solutions

Wireless Network Fault Example 1

AP + PCI desktop wireless network card combination, 300 m² office environment, AP is located in an independent single room, the farthest network card communication distance is about 30 meters, within the AP coverage. When the network adapter is connected normally at the longest distance (the connection speed is stable between 5.5Mbps and ~ 11 Mbps) fixed AP location. Multiple connection blind spots exist after the construction is completed.

Analysis and Solution: In the blind spot device area, the network card is placed on the desktop. The operator, PC device, office cabinet, and equipment are blocked between the network card and the AP, leading to communication failure. Considering that there is no ceiling in the room and the AP does not have an external antenna interface, it is not suitable to use an external antenna. Without increasing costs or damaging the appearance of the room, you can mount the AP outside the wall of the data room and maximize the installation height, after the terminal location is adjusted, the blind spots can be solved.

Wireless Network Fault Example 2

AP + AP Bridge Communication combination, the communication distance is about 150 meters, the two APs are both indoors, no architectural barriers, the communication rate is up to 2 Mbps, frequent connection failure.

Analysis and Solution: Setting up an external gain antenna is the best solution, which is close to the longest distance of AP bridging. Considering the cost, another solution can be used: Two APs are installed on the outdoor wall, and two walls are used as reflection to enhance the radiation wave in front. Using an aluminum-plastic plate between the AP and the wall as a basin-like container protection not only beautiful but also solves the waterproof and sunscreen problems, but also plays a very good reflection effect. The connection speed after processing reaches 11 Mbps, And the disconnection will not occur again.

Wireless Network Fault Example 3

AP + laptop wireless network card combination, straight line communication distance of 20 meters, terminal is in the basement location, AP is located in the third floor at a right angle with the basement building, fault phenomenon is the connection is good or bad, the connection speed fluctuates between a maximum of 11 Mbps and no signal.

Analysis and Solution: the communication distance is not long, but the isolation between the wall and the ground affects the communication quality. The changes of Environmental moving objects (vehicles) lead to complicated refraction/reflection, and the signal strength changes greatly. We can adopt the following scheme to stabilize the signal: Increase the external antenna of the NIC; adjust the angle of the AP antenna so that the antenna radiation angle is perpendicular to the NIC of the laptop in the basement; and add the reflective aluminum-plastic board at the backend of the AP antenna. In this way, the connection speed should be stable.

Wireless Network Fault Example 4

AP + laptop wireless network card + PCI desktop wireless network card home combination, this is a typical household Wireless LAN application. The user reported that, even if the network card and the AP are in the same room, the two-host ADSL dialing (with routing function) is frequently dropped.

Analysis and Solution: try to connect the vro to the PC using a USB or LAN. If the dial-up connection is stable and does not go offline for a long time, it can be determined that the fault may come from a wireless device. If no significant effect is found in attempts to improve the AP Power Quality and heat dissipation, the reason is that the AP cache is too small. The solution is to change the AP or limit the transmission rate. Consider the cost and use the speed limit solution. After the maximum connection rate of the AP is set to 2 Mbps, the failure is significantly reduced, which basically meets the needs for simultaneous Internet access between the two servers.

Wireless Network Fault instance 5

After a wireless network uses an outdoor flat gain antenna, the network terminal has no signal.

Analysis and Solution: Normally, after an external gain antenna is used, the network will increase the connection distance, and the network terminal will not have a signal, which may be a fault in the direction of the oriented antenna. After the orientation and vertical angle are adjusted, the fault will disappear. Knowledge: Generally, long-distance wireless networks usually use eight-wood antennas, raster antennas, fl antennas, and backshot antennas with high gain and strong direction. Some flat antennas, after special design, have strong directionality and gain orientation. The directionality of these antennas is easy to be ignored.

Wireless Network Fault instance 6

After the external antenna is used for a period of time, there is no signal to connect.

Analysis and Solution: A connection failure occurs after the antenna is used for a period of time. The common cause is poor interface contact. Check whether the interface is waterproof. In case of corrosion, use glass glue for external waterproof coating. In addition, it may be a special case of lightning strikes. In this case, it is generally difficult to repair, and the equipment should be changed instantly.