Label: Wireless LAN wireless signal interference
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With the rapid development of wireless LAN technology, the application of wireless local area networks in homes, small and medium-sized offices and enterprises has developed rapidly. However, due to the limitations of the WLAN technology itself, the most common problems that home users often encounter when deploying WLANs, such as signal interference, transmission distance, coverage and penetration, and communication performance of wireless networks, It has always been a topic of concern for wireless network enthusiasts, and the devices involved in this topic are usually wireless APs and wireless routers. For the convenience of writing, this article is generally referred to as a wireless AP. Let's talk about the influencing factors in the home wireless network. The existence of such factors may make the connection speed of the wireless network decrease or not reach at all.
1. Interference from wireless signals
Since the wireless radio frequency of the wireless local area network uses the ISM (industrial, scientific, medical) wireless frequency band, the 802.11b and 802.119 standards use the 2.4G frequency band, and the 802.11a standard uses the 5.8G frequency band. Therefore, the WLAN will be affected by the radio frequency interference of some sudden wireless devices in the same frequency band in the actual operating environment. Such as microwave ovens, Bluetooth mobile phone signals are in the 2.4G frequency band.
Therefore, when working in a wireless LAN, a microwave oven is suddenly turned on in its area, or a Bluetooth mobile phone uses a Bluetooth headset, or suddenly other wireless devices operating in the same frequency band interfere with the wireless signal of the wireless local area network. Changes in the physical environment of the wireless network, such as sudden large obstacle movements between the wireless AP and the wireless client, will directly lead to a sudden and large decrease in the network performance of the wireless local area network, and directly lead to wireless signal interruption. Or the rate is reduced.
Another interference comes from the WLAN itself, which is the interference of different channels in the same frequency band. This interesting situation occurs in the home user and can only be caused by mutual interference of wireless APs on adjacent or adjacent buildings on the same floor. Different channels without interference should be used between adjacent wireless AP devices. For example, 802.11b and 802.11g can eliminate interference by using channels with five frequency bands. The typical interference-free channels are set to 1, 6, and 11, respectively.
2. Wireless signal coverage and penetration
In the home environment, the distance is short. Generally, the wireless LAN devices are said to have a transmission distance of more than 100 meters, so the signal transmission distance is not a problem. But the family environment has brought a new problem, that is, the family space is crowded, the space is not wide enough, and the walls in the room are the main obstacles. Because the wireless local area network uses the wireless microwave frequency band. The biggest characteristic of microwave is the near-straight-line propagation, and the diffraction ability is very weak, so the wireless receiving device behind the obstacle will receive a weak signal or no signal. So what about penetration?
This is a problem that many netizens are most concerned about. Everyone hopes that the wireless signal can penetrate at least the partition wall inside the house. To improve the ability of wireless signals to penetrate the partition wall, an effective way is to increase the gain of the antenna. When purchasing a wireless AP, we should choose a product with a high antenna gain, which is generally at least 2 dBi. According to experience, the 2dbi gain antenna signal can penetrate two walls. If there are too many rooms and there are many partitions, it is better to detach the equipment to configure high-gain antennas, such as changing the 5dBi omnidirectional antenna.
The obstacle of the metal object not only blocks the microwave wireless signal, but also absorbs the electromagnetic energy and generates a weak current to drain. Therefore, the obstacle of the largest metal object without the wireless signal in the home environment is the inner steel bar. The floor of the net, the signal in this direction is almost impossible to penetrate. To be able to penetrate, the signal is very weak. With such a large size obstacle, microwave diffraction is even more impossible. If the antenna of the antenna device is placed in the center of the house, the wireless signal can only be emitted from the window straight from the open path.
After we all know the above factors, we have to choose the best place to place for the wireless AP. The requirements for this placement point are as follows:
First, the position should be higher, so as to radiate downward in a higher place, reduce the blockage of obstacles, and minimize the signal blind zone;
Second, the location point selection should be to make the signal pass through the partition wall as little as possible, preferably the wireless client in the room can be seen between the wireless AP.
Therefore, the best placement point for wireless APs at home should be chosen in the living room and can be viewed visually with the computer host in the room.
3. Wireless LAN performance
With the rapid development of wireless local area networks, users have been running more and more critical applications on wireless local area networks, so many common high-bandwidth consumption applications, such as video applications, require wireless LANs to provide higher bandwidth. To achieve high quality performance! We know that wireless AP devices are a "wireless sharer" that accesses wireless client devices together and runs Ethernet CSMA/CD (Carrier Sense Multiple Access/Collision Detection) It is clear that it is a "shared" network. Like the same network working principle of the previous network hub, it just abandoned the cable of the hub and changed it to wireless.
Such a shared environment is an inherent drawback of wireless local area networks, so to use the current network applications smoothly, the general recommendation is that a wireless router or wireless AP can only access up to 30 wireless clients. If it exceeds, the transmission performance of the network will be greatly reduced. It seems that home users generally do not have so many wireless clients, so the wireless network is completely acceptable to the family. However, the wireless network should try to avoid using these P2P downloading software such as BT and eMule, because it is possible to get rid of the entire wireless network.
BT and eMule use file segmentation and multipoint transmission to improve file transfer speed. The BT software first divides a file into several parts on the uploader side and provides it to the user for download. The downloader does not download the split files in order when downloading these files. The remaining parts of the download do not have to be uploaded to the uploader's computer, but can be distributed to other users through the distributed cross-download program of BT software. Download the downloader there. In this way, the downloader also undertakes part of the uploading work at the same time of downloading, downloading and uploading synchronously, which greatly improves the download speed of the file, but the premise is that many people download the same file at the download point at the same time. When there are only one or two downloaders, the download speed will not be very fast.
BT downloads are more commonly considered heavyweight killers of bandwidth. This is the biggest reason given by many broadband operators when they announced the ban on BT. In a shared network, if BT download is used, it will cause a large degree of occupation for other other Internet applications, making the overall network slower or even larger.
Summary: As long as we can correctly understand the wireless characteristics of wireless LAN and wireless AP, deploying wireless network at home can be used very comfortably. A summary of the factors affecting the wireless network: avoiding wireless devices in the same frequency band in the wireless network area and avoiding interference from the wireless channel. The wireless AP should be placed in a higher location, and the wireless client should be as visible as possible to avoid blind spots and avoid penetrating too many partition walls to avoid being blocked by metal obstacles. Since the wireless network is a shared network, BT-type download software that uses large traffic and even causes network congestion should be avoided.
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