How to fix intermittent Wi-Fi?

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How to fix intermittent Wi-Fi?

I have a 2015 MacBook Pro running 10.11.1. For a while I have been experiencing issues with the Wi-Fi randomly dropping. Turning the Wi-Fi off and on to reconnect to the internet, or renewing the DHCP lease usually fixes it for about 20 mins and then it happens again. I have an iPhone, iPod, and iPad but this MP is the only device that has this problem. Through a process of elimination, at this point I'm 90% convinced that hooking up the machine to an external display with an HDMI is what is triggering the issue. I know it sounds weird but I want to figure out if others are having a similar issue to determine if they too think it could possibly have to do with the HDMI. Here's why I've reached that conclusion.

1) The first time I contacted apple and explained the problem, they recommended that I delete my network from Keychain and also from the wifi preferences, and then restart the computer. At first that worked, but I often hook up my laptop to my TV with an HDMI cord, and the next time I did that the problem started once again. Just to be clear, turning off and on the wifi will fix it immediately, but I have to repeat that process every 30 mins or so which is incredibly annoying and frustrating.

2) Next, I called again and was told to try out using the machine on safe mode. Once again, this fixed the problem until the next time I hooked up my computer to the HDMI. It's at this point that I started to realize the correlation between the HDMI and the problem. If I restart the computer and connect to the internet I won't have any issues, but after I hook up once to the HDMI it will continue, even after I unplug it, until I restart it.

3) Create a new user. The last person that I talked to advised me to create a new user without linking the account with my iCloud and use it for a while to figure out if that works. It didn't. My last resort now is to make an appointment and take the machine in to the apple store, however, I am still concerned because this is the type of issue that occurs so randomly and sporadically that when you try to show it to someone it always seems to be working fine. As I said before, turning wifi off and on will fix it from anywhere of 20-50mins, so it's very frustrating.

4) More recently, I've been looking on these forums to figure out if others might have a similar pattern that could help me figure out why there's a correlation with the HDMI and the issue. I found another thread (New Macbook with intermittent internet connection, wifi OK) that seemed to be raising the same issue and tried resetting the SMC and PRAM. However, I can't tell yet whether it worked since it's only been about 10 mins since I did that.

Please let me know if any of you are familiar with the problem and can recommend any solutions to it. Also, if you have the issue and haven't found a solution, can you comment to tell me if you also suspect it might be linked to the HDMI connection?

MacBook Pro with Retina display, OS X El Capitan (10.11.1)

Posted on Nov 7, 2015 3:43 PM

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Answer 1

Nov 7, 2015 4:03 PM in response to Zyve

If you think it correlates with the HDMI, try a new cable. An HDMI cable with a disconnected shield might spew all sorts of EMI-RFI trash.

There are some problems that can be caused by simple things in your setup. If you hold down Option and click on the WiFi Icon on the menuBar, you get a display like this one:

what do you get for:

PHY Mode and Channel?

Signal Strength or RSSI?

Transmit Rate?

and most important, how many other networks do you see?

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Answer 2

Zyve Author

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Nov 8, 2015 1:40 PM in response to Grant Bennet-Alder

This is what I get

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Answer 3

Nov 8, 2015 5:05 PM in response to Zyve

You have a really strong signal at -37dB. But you are on the very crowded 2.4GHz band. Using 802.11n, there are only about two clear channels there. You are directly competing with 13 others Routers.

You should have your Router channel set to "automatic" so that whenever it powers up, it will sniff for the most lightly loaded channel and take that one. (This is why step one of most debugging procedures says "reset your router".)

A dual-band Router would get you access to the wide-open 5 GHz band, and let you have a wider channels with no competition.

If you want to look harder at this, you can open Wireless Diagnostics and see what it says about your connection. After one pass, it will let you save a wad of information to send to Apple if you need to, or allow you to continue monitoring in the Background. While monitoring, you can look at several other interesting graphs. One is your Wi-Fi performance, looks like this:

another is a scan of all networks nearby, which will confirm that your 2.4GHz is way overloaded:

(click to enlarge)

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Answer 4

Feb 27, 2016 3:35 PM in response to Zyve

I just signed up for Apple Support Community to let you know you are not alone!

I am running El Capitan 10.11.3 (latest GA version as of this post), and this issue FREQUENTLY happens to me...the kicker is that I religiously stream shows to my TV through an HDMI cable just as you mentioned. I recently switched routers, and unfortunately the same issue JUST happened -- hence, my search here. All my other devices are fine, and able to access the internet via WiFi. The strange part is that my WiFi connection shows full signal, but I receive no packets (did not confirm if I was trying to send egress packets), and DNS resolution completely fails. I took it into Apple, and they just did some basic network resets (e.g. clearing network cache, restarting network service, ensuring correct permissions on network folders, etc), but the issue returned a day later.

I am using a Bluerigger HDMI, and after reading your post, I do not remember this issue ever occurring when it was not plugged into an HDMI cable. I will have to check the next time this issue re-occurs (could be any minute now) to see the signal to noise ratio at that time, and compare it with what I am seeing now (after having rebooted it).

@Zyve, while I hope this issue is fixed for you, please let me know if that's not the case, and what type of HDMI cable you are using? Also, I would be curious to know the difference of your Network metrics (when pressing option + wifi icon) when you are having the issue vs. initially after you reboot your router -- this would really help me get to the bottom of this issue that I have been trying to figure out for a LONG time!

Thanks!

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Answer 5

Feb 27, 2016 6:49 PM in response to Grant Bennet-Alder

Duane pointed out that WiFi Explorer (US$15 with three-day free trial) can show you the distribution and competition of surrounding Networks:

(click the graphic to expand)

From the diagram, you can see the spectrum overlap of two Networks on Channel 1 (Red and Green) and two other networks around channel 5 and 6 (orange and blue).

it illustrates how few clear channels may be available at 802.11b/g/n speeds many Routers try to use in the 2.4GHz band.

In the 5GHz band, a neighbor's network at channel 155 is way too low a signal to be useable by you.

Duane's Network (orange) has shoe-horned its way between the usual bands and is using channel 5, but competing vigorously with the networks on both sides.

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