How to troubleshoot the CPE in AP and Client mode when the wireless speed is slow

Updated 06-27-2022 05:39:51 AM 68409
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When two CPE devices work in AP and Client mode, the network topology is often like this in the picture as below. Some users may meet one issue that the wireless speed is slow. This article is to introduce how to troubleshoot the problem when the Client’s speed is slow.

There are some reasons (like total bandwidth, location, etc.) that may affect the speed of Client, it is inconvenient for us to confirm what the reason is. So, here we will troubleshoot the problem according to the network topology as above.

From the topology, we can know that the network topology can be divided into three parts, they are:

· Part I (between the Internet and CPE_AP);

· Part II (between CPE_Client and Client);

· Part III (between CPE_AP and CPE_Client).

Next, we will introduce these three parts separately.

Part I: Between the Internet and the CPE_AP.

· Total Bandwidth.

The most important factor that may affect the speed in this part should be the total bandwidth. For example, if the total bandwidth is 50Mbps, even you choose a 300Mbps CPE device, the speed of the Client can only get maximum 50Mbps (It is a theoretical value, in fact, the speed will be smaller than 50Mbps because of interfere, etc. ). Therefore, we should know whether the total bandwidth limits the speed of the Client.

Part II: Between the CPE_Client and Client.

· The wired speed of Client.

If the total bandwidth are not the limit of the speed, then we can check the link speed of the Client. Please refer to FAQ2265 to learn how to check the link speed on the Client.

When the real speed is lower than the link speed, there are two main factors in part B:

1) Ethernet cable.

2) Ethernet port.

So we should check the cable and port to troubleshoot the problem.

Part III: Between the CPE_AP and CPE_Client.

In this part, what we need to check is the link speed and the real wireless speed.

1. How to check the link speed?

Before checking the link speed, we need to know the maximum link speed is related to the channel width. We can see the relationship in the following table.

Take CPE510 as an example, when two CPE510 devices connect wirelessly in AP and Client mode, if we set the channel width as 10MHz, the link speed will be 72.2Mbps at most. Knowing that, we can check the link speed in the management page of CPE_AP.

In the following picture, we can see the link speed is 65Mbps in our test environment (The channel width is 10MHz.).


In the picture above, the link speed is 65Mbps, which is lower than the maximum throughput, but it may be a reasonable value because there are many factors will affect the link speed, such as long-distance, wind, etc.

2. How to check the real wireless speed?

There are some tools in CPE devices, such as Speedtest®/Ping/Survey.

Here we can use Speedtest® tool to help us test the real wireless speed. Just as the following steps:

1) Set CPE_Client as Server

2) Set CPE_AP as Client;

3) Client Start to test the wireless speed.


Because of the wireless environment, the wireless throughput can up to 1/3 or 1/2 of the real link speed.

3. How to optimize the link speed?

In the real environment, many factors that will affect the link speed, like long-distance, wind, etc. So the link speed will be lower than the maximum throughput and it is normal. But if the link speed is extremely slow, here we can check the link speed based on installation and deployment, antenna alignment, wireless settings.

· Installation and deployment

CPE devices are often installed in outdoor environment, and there are many obstacles in these places. To avoid these obstacles, we should install the CPE devices at a certain height. We can refer to FAQ907 to determine the height.


1) When building a wireless link between two remote sites, we also need to take the Earth curvature into consideration to calculate the installation height.

2) Outdoor environment is complex, the weather like rain and wind will affect the link speed.

· Antenna alignment

All CPE devices have a radiation range, only in the radiation range we can receive the signal of the CPE device. Take this into account, when installing the devices, we should align the CPE devices. In order to get a better performance, we can refer to FAQ1044 to align the CPE.

· Wireless settings.

Besides the installation and alignment, the parameters of wireless settings also have an influence on the wireless throughput. So we can also change the wireless settings to optimize the speed.

1) Transmit Power. The higher the transmit power is, the farer the signal. In order to get maximum signal, normally we set the transmit power as the maximum value.

2) Channel. The channel selection works as auto mode by default, we recommend you to use the Spectrum Analysis to analyze the channel and choose an uncongested channel.

Note: If possible, don’t select the DFS channel.

3) Channel Width. The Channel Width has an influence on the wireless speed. When there is little interfere, we recommend you to use 20/40MHz to get a better throughput.

4) Distance. Distance means the distance between the AP and station, it is mainly used to solve the communication of long distance. You can refer to FAQ2084 to set Distance.

5) MAXtream. MAXtream is a proprietary Wi-Fi protocol that is only compatible with TP-Link’s Pharos series products. MAXtream is used to solve hidden nodes, we recommend you to enable this feature to promote wireless performance. Please refer to FAQ694 to learn more information about MAXtream.

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