What should I do if WiFi roaming does not switch? The mobile phone clings to 2.4G and does not switch to 5G. First turn off the dual-band integration and then adjust these two numbers.

What to do if WiFi roaming does not switch: First turn off the dual-band integration, then adjust the weak signal threshold and 2.4G power diagram

I discovered this problem in my own home. The router uses TP-LINK XDR3030, which is placed on the TV cabinet in the living room, and the mobile phone is Redmi K70. I was watching videos smoothly in the living room. When I went to the master bedroom and lay on the bed, the videos started to spin in circles. Open the WiFi details and see that the signal is full, but the connection rate is only 86Mbps. Looking up further, it is still connected to 2.4G, and the 5G next to it is just sitting there unused. I thought the phone was broken at first, but later I figured out that the problem was not with the phone, but with the small dual-band switch on the router, plus two values that had never been touched.

Find out first: Why do mobile phones prefer 2.4G to 5G?

2.4G and 5G are not two independent things, they are two sets of WiFi sent by the router. 2.4G is strong through walls, but not fast. The theoretical speed of my unit is only 574Mbps, but in practice it often drops to around 86Mbps across a wall. ； 5G's wall penetration is a bit weaker, but its bandwidth is wider, and it's not difficult to cover hundreds of megabits at a short distance. When a mobile phone encounters WiFi when going out, the basis for choosing which one is not "which one is faster", but "which one has better signal numbers".

When dual-band is on, the two sets of WiFi have the same name, for example, they are called XDR3030. The phone only recognizes this name and will not jump to 5G just because it reaches the bedroom. Most ordinary routers do not have the 802.11k/v/r roaming agreement of enterprise APs, and will not actively kick mobile phones out of 2.4G. So I looked at my phone and saw that 2.4G was still -58dBm at the moment, which was quite stable, and then stopped moving. ； 5G actually has -74dBm, which is usable, but the phone is too lazy to mess with it.

So don't blame the phone. It operates according to conservative logic. As long as the current network is not disconnected, it is not willing to take the risk of switching. If you want it to be replaced, you can give 5G a separate name so that the phone can be chosen. ； Either set up a line in the router and kick it off when the line is as weak as dBm. These two actions are the core of what I want to talk about today.

first step: Turn off dual-band integration and split 2.4G and 5G into two names

I did this step first because I don’t need to know too many parameters and the effect is the most direct. Enter the backend of TP-LINK 192.168.0.1 After logging in, go to the wireless settings and turn off the "Dual-band-in-one" or "Smart Selection" switch. After turning it off, there will be two SSIDs below. I changed them to XDR3030-2.4G and XDR3030-5G so that they can be distinguished at a glance.

The paths for other brands are similar, but the names are changed. Xiaomi and Redmi are here 192.168.31.1 Look for Dual Band One in the WiFi settings ； The old firmware of Mercury and Tenda will be written as multi-band in one or dual-band preferred. ； ASUS is usually hidden near Wireless Network → Professional Settings. If you really can't find it, just check if there are "WiFi name" and "WiFi dual-band in one". 90% of the time it has a switch.

After deleting the name, the phone needs to do a thorough job: Delete the old WiFi you remembered and reconnect to 5G. Otherwise, many mobile phones will continue to paste the old files to 2.4G. I have actually gone through this step with my Redmi K70. I didn’t delete the old network after turning it on and off, and it still connected to 2.4G. ； After deleting the old network and re-entering the password to connect to the XDR3030-5G, the speed immediately jumped to around 780Mbps.

But there is a price to pay for stripping names. Some smart devices at home only recognize 2.4G, such as my Mijia camera and an old thermometer and humidity meter. If the mobile phone is connected to 5G during network distribution, they may not be able to detect the 2.4G signal of the router. Therefore, my habit is to temporarily connect the phone back to 2.4G during the few minutes it is paired with this type of device, and then switch back to 5G after the configuration is completed, without affecting daily use.

Step 2: Adjust these two numbers before the router is willing to let go.

Turning off dual-band integration solves the problem of "having a choice of mobile phones", but some people are lazy and still stick to 2.4G ； Or if you have Mesh or AC+AP at home, you need to automatically switch devices between several nodes. At this time it is the turn of the two values in the background.

The first number is called the weak signal elimination threshold, and different brands have different names. TP-LINK and Mercury commonly call it "weak signal elimination" or "weak signal offline", ASUS calls it "roaming assistant", and Xiaomi's new firmware has a "roaming threshold" option. What it manages is: When the signal of a certain device is weak below the set value, the router will kick it offline and force it to find a signal again. The first time I plugged in my XDR3030, it was turned off by default. I set it to -70dBm and tried it one night. When I walked from the living room to the bedroom, the 2.4G was kicked off when it dropped to around -73dBm. After two seconds, it was reconnected to 5G.

The second number is the transmit power. Many people don’t know that the power of 2.4G and 5G in the router can be adjusted separately. I lowered 2.4G from high to medium and kept 5G on high. In this way, the life-saving straw of 2.4G in the bedroom becomes weaker, 5G becomes relatively more cost-effective, and mobile phones are more willing to go to 5G. If you have a child at home, this method is gentler than simply adjusting the threshold, and there will be no repeated sideways jumps where the phone is kicked and reconnected.

A reminder here: Don’t set the threshold to -60dBm as soon as it is raised. dBm is a negative number. The smaller the number, the worse the signal. -60dBm is quite strong for 5G, but below -80dBm it is basically difficult to use. For home use, I recommend starting from -70dBm. If the kick is too frequent, then adjust it to -75. ； If your home is often separated by two walls and the 5G signal is only around -80dBm for a long time, don’t rush to adjust the threshold first. First, check whether the mobile phone is lagging behind in the third step.

There are three small switches on the phone. Turn off two of them first.

After the router is done, the mobile phone is not completely innocent. I tried it alternately on my Redmi K70 and my wife’s iPhone 13. There are at least three places on the side of the phone that affect WiFi switching.

The first is the mobile phone’s WLAN assistant or smart network selection. Many Android machines will have "WLAN Assistant" turned on by default. Redmi is hidden in WLAN → Advanced Settings. It will automatically use data traffic to make up for it when the WiFi is weak, and sometimes it will help you connect back to 2.4G. I suggest turning it off and letting WiFi and traffic do their own thing. The iPhone's Wi-Fi Assistant is at the bottom of the cellular network settings, and my wife's one is also turned off.

The second one is power saving mode. As soon as the phone is turned on to save power, WiFi scanning will become lazy and switching will be even less active. This is not metaphysics. I tried it with a Redmi K70. I could hold 2.4G in the bedroom for more than ten minutes without changing the power saving mode, but it took two or three minutes to switch off the power saving mode. If you are not traveling far away, do not turn on the power saving function to test WiFi.

The third one is not a switch, it is a way to see the real signal. The signal pattern of the mobile phone is too thick. For Android, you can go to Settings → About Phone → Status Information to check the WiFi signal strength, or directly open the developer options. ； Windows computers are the easiest, run from the command line netsh wlan show interfaces , look at the Signal and Receive rate lines. When I adjust the threshold, I put the computer and mobile phone in the same position and look at the dBm of the computer as a benchmark. It’s a little more troublesome to see the specific numbers on the iPhone. If you don’t have a Mac at home, don’t bother, just follow the previous two steps first.

When is a light-adjustable router useless? The accounts for single routing and mesh for small apartments are different.

At first, I thought that just by adjusting the threshold and power, everything would be fine. Later, I tested it on a friend's house and found that not every house has this set. His home is 120 square meters, the router is in the corner of the study room, and the master bedroom is far away. When 5G reaches the bedside, it is only -84dBm. At this time, even if you adjust the 2.4G power to the lowest, the mobile phone can only turn to 2.4G, because there are not many 5G signals at all, and the connection is useless.

So my judgment order is: First use your mobile phone to walk around frequently used locations to see if the 5G signal is sufficient. -Around 70dBm, it is useful to adjust the threshold and power ； -78dBm to -82dBm, barely saveable, but don’t hold out too much hope ； -Below 85dBm, there is basically no need to adjust, just consider adding nodes. How to judge WiFi dead zone, I have done this before How to self-check the WiFi signal dead zone at home It is written very carefully, and it will be clear to you if you follow it and walk around.

There are two ways to add nodes. The house is big and there are no embedded network cables at home. Mesh is the easiest one. Buy two units for wireless backhaul. The location of the nodes is very important. Don’t just shove it into the corner. I’m here. Which room has the best signal when placing the Mesh sub-router? I have tested 8 points, and the worst position can cut the speed in half. If network cables have been pre-buried during decoration, AC+AP will be more stable, each AP will be wired, and roaming will be simpler, provided that the original wires are in place.

After all, the roaming threshold in the router can only allow the device to choose among the "existing signals" and cannot change the signal out of thin air. The 5G cable has been broken, and it will be useless to try again. Coverage first, then switching, don’t reverse this order.

How to verify after adjustment: Don’t just focus on the signal grid, watch the rate and dBm change together

There are three acceptance actions I have set for myself. First, park your phone in the living room, bedroom, and bathroom for a minute each to see if it will switch from 2.4G to 5G. Second, when looking at the connection speed in the bedroom, the Redmi K70 has increased from 86Mbps to over 500Mbps, which means it is truly connected to 5G. It doesn’t matter just because the name has changed. Third, run a speed test. My home has 300M broadband and 5G in the bedroom is stable at more than 250Mbps. 2.4G used to be only 60Mbps. This gap shows that the exchange is worth it. How to measure speed so that you don’t lie to yourself? How to measure broadband speed accurately The same things as above also apply, don’t turn on your phone to save power, and don’t put it too close to the router when measuring speed.

If you are still stuck on 2.4G after adjusting, first delete the old WiFi file on your phone and reconnect. ； If that doesn't work, raise the threshold a little from -70dBm to -65dBm, but don't be too harsh. Stop and observe for a few minutes after each adjustment. You can usually see the frequency band that each device is currently connected to in the background of the router. It is most intuitive to use it as a mirror.

Finally, back to the topic. Mobile phones cling to 2.4G and don't switch to 5G. Most of the time it's not because the mobile phone is broken, but because the router bundles the two frequency bands into one name and doesn't set up weak signal rejection. First turn off the dual-band integration, then set the threshold to about -70dBm, don't max out the 2.4G power, delete the old network on your phone and reconnect, 80% of the time it can be solved. The remaining 20% is because 5G coverage is not covered in the first place, so it is not a matter of adjusting the number. You need to add a Mesh or AP. Don’t rush to change your phone, let alone your router.