Teach you to find the source of a wireless network instability

1. RF Interference

RF interference can take up air this wireless transmission medium, will delay the user to send and receive the data time, and cause the conflict, then causes the data to resend. If the noise intensity is large and the retry rate is high, it is generally due to the fact that RF interference is affecting your wireless network. I suggest you use NetStumbler and other tools to measure the noise. In addition, most access point APS store information on the number of test attempts, and you can view them with the help of the management console. If network performance is down, viewing the number of retries is a good step.

If the noise intensity of your network bandwidth exceeds the -85DBM, then RF interference is likely to impair network performance. In this case, the user's retry rate will exceed 10%, and the user will feel the network speed is affected. This can happen, for example, when a wireless user is in the same room as a running microwave oven.

If you decide that the problem is caused by radio frequency interference, you have to find out where the interference comes from and try to remove the interference. If you have this symptom only when the microwave or wireless phone is running, you have to try to put AP access points into different channels.

Also, you need to see if there are any other wireless networks nearby. If you find that someone else is using the same channel as you, you have to change your network to a conflict-less channel. Remember that only three channels (1, 6, 11) are not conflicting in the 2.4GHz bandwidth. Most home and small offices set their AP access point to use 6 channels, because this is the most common default channel set by the vendor. Therefore, you may need to not allow the access point on the enterprise perimeter to use this channel.

If you still can't reduce RF interference to an acceptable level, try to increase the intensity of the RF signal in the affected area. For example, you can increase the power of the launch, you can replace the original antenna with a stronger unit, or close the access point closer. This method increases the signal-to-noise ratio (averaging the ratio of a signal to a random noise in a data unit), thereby improving performance.

　2, utilization is too high

In the case of active wireless network users, or when users are operating some bandwidth-intensive applications (such as downloading large files), the application of the network is likely to reach the maximum capacity of the access point. Under this condition, the retry rate may be relatively higher (more than 10%), even if the signal strength is high and the noise intensity is low, it can affect network performance (that is, high signal-to-noise ratio). The result is a reduction in throughput due to the additional time required to retransmit the data frame.

The solution is still available. The access point AP can be placed closer to the lower power, creating a smaller RF hive. This "micro-cellular" approach can reduce the number of users per access point, thereby enabling each user to gain more capacity.

Another way to cope with high network utilization is to move some applications to a different frequency band. For example, you might consider using a 5GHz 802.11a network for your Wi-Fi phone, which allows data applications to run in 2.4GHz 802.11b/g. Network.

　　3, covering the scope of loopholes (blind spot)

After installing the wireless network, some changes may occur in the facility that adjusts the RF signal transmission. For example, a company might have to build a wall that would greatly weaken the signal. Worse, the RF location may not be investigated until the network is installed. These conditions can lead to the presence of limited or no RF signals in certain areas of the facility, which can greatly degrade performance and disrupt the operation of wireless applications.

What are some of the areas that indicate gaps in coverage? This includes low signal strength (below -75dbm), too high retry rate (above 10%), but is not related to noise intensity. In this case, the signal strength is too low, so the receiver of the wireless card is very difficult to obtain data, which leads to retransmission, low throughput and so on. For example, when a user operates in a place where the signal strength is low, he feels that throughput is down by as much as 75%.

To cope with coverage vulnerabilities, users need to improve the signal strength of the affected area. Try to increase the power of the transmission, replace the old antenna with a stronger new antenna, or better cover the entire area with the AP. In order to minimize the coverage vulnerabilities of future wireless networks, I recommend that you frequently conduct RF field surveys and measurements, such as every few months.

　4, the access point is too bad

Sometimes, the root cause of poor network performance may be that an AP access point has failed. You can check the access point to see if the antenna has been broken, the status of the lamp is not indicating the error, the power is not enough power and so on. You can try to focus on the Kai-AP, which usually resolves the firmware deadlock problem. To keep the firmware up to date, this is done to make future deadlocks less.