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MacBook Pro WiFi speed issues

I have just been comparing my MacBook Pro Internet speed when connected via the internal Airport WiFI and via an external USM WiFi dongle.  I am finding that when using the MacBook's internal Airport the Internet speed test result is consistently slower.  Typical results: 29 Mb/s compared with 14 Mb/s on 2.4GHz channel and 36 MB/s (similar to Ethernet) compared with 30 Mb/s on 5GHz channel. 

Notes

1 There are several other 2.4GHz WiFi sources but only one at 5GHz and that is on another channel.

2 The router is about 3 feet away from the Macbook.

One thing I noticed is that graph for the speed test show a near constant speed when the USB dongle is used but the speed fluctuates greatly when the MacBook’s Airport is used.  

The second thing I noticed is that mirroring to an Apple TV3 works perfectly when I use the external USB WiFi dongle but there is some stuttering in the audio if I use the internal Airport. I suspect this relates to the Airport connection slowing down at times.

The mirroring audio issue only started when I upgraded from Mavericks to El Capitan. I know some people had problems with WiFi when El Capitan first came out but I wondering if there is still a minor issue with the El Capitan Airport drivers.

What model and what year is your MacBook Pro?

Hold down the Option key while you click the Wi-Fi Icon on the menuBar to get a display like this:

what do you get for PHY Mode and channel?

what do you get for RSSI or signal or signal to noise?

what do you get for Transmit rate?

and how many other networks do you see?

OR- post screen shots of the SCAN graph, like this one:

(drag and drop on Preview to enlarge)

OR- post graphs from the inexpensive (and three-day free trial) or WiFi Explorer available at Mac App Store:

(drag and drop on preview to enlarge)

.

Hi Grant and Joe,

Thanks for your replies.  The parameters you asked for are:

RSSI= -49dBm

Noise=-90 dBm

Speed= 300 Mb/s

Channel 44

The USB WiFi dongle I am comparing the MacBook WiFi with is a D Link DWA 182. This supports 802.11ac.  I know the my MacBook only supports 802.11n but the router I am using also only supports 802.11n so the extra speed the 11ac dongle provides should not be influencing the comparison.  There is also a similar problem on the 2.4GHz channel.

There is only one other 5GHz network within range RSSI -72 dBm channel 100.

For my tests I deliberately put the MacBook close to the router to get the best possible link speed. 

One new test I did was to use Mirroring on the Apple TV with a WiFI extender in the link.  The mirroring worked perfectly when I used the USB dongle but when I used the internal WiFi it only worked in very short burst.  It is almost as if the Mac is detecting the Network delay and slowing down the link to account for it.

Thanks

Ian

Hi Joe_7399,

I have given a detailed response Grant's comments but I missed your suggestion about running the diagnostics.  I have tried this several times.  The main things that come up is that in 2.4GHz band there are several interfering sources.   However, in the case of the 5GHz band there are no comments.  I have just noticed that in my original post I mention a USM WiFi and I think that may have mislead you, sorry for that I am using a fairly standard D-Link USB WiFi dongle.

Thanks

Ian

I presume these are the numbers for your Wi-Fi dongle.

To get your shown 300 Mbits/sec, you are likely using two antennas, because the baseband speed available for 802.11n is maximum 150.

802.11 ac has three antennas available, which can allow it start with a faster baseband speed of either 200 or 433, and (if the Router can also use three antennas) triple that.  But it does not run in the 2.4GHz band at all. (it would drop back to n-mode and fewer antennas if 2.4GHz were the strongest signal-to-noise).

So these numbers show that the Wi-Fi itself is NOT an impediment to getting the full speed your ISP is sending you, provided that is about the 30M bits/sec you cited originally. (you have eliminated the usual suspects: not enough signal, no 5GH band when the 2.4GHz band is swamped by too many neighbors. Leaving only lack of 802.11ac in your Router as a possible culprit.

--------

If your built-in numbers are substantially lower, it could indicate a disconnected antenna or a broken antenna wire inside your computer. Depending on model, these sometimes go through the screen hinge area, and are subject to chafing. Models older than about 2011 may have only one antenna, which can also reduce speeds dramatically when channels are otherwise clear.

Hi Grant,

The results are for the MacBook's internal airport on the 5GHz channel.  The Macbook is the mid 2012 version with an i7 processor. 

That was an interesting point about 11ac.  I knew 11n used two antennas but I didn't know 11ac used 3.

I understand from the Netgear website that the actual transfer speed can be a lot lower than the link rate.  For example the actual transfer rate of a 300Mb/s link can be as low as 50Mb/s.  My concern is that in my case the transfer speed is even lower than this.

It sounds like my problem is not common so my concern is that I may have a hardware fault in the Macbook e.g. a high bit error rate on the wifi channel.

>>I understand from the Netgear website that the actual transfer speed can be a lot lower than the link rate.  For example the actual transfer rate of a 300Mb/s link can be as low as 50Mb/s.

That may be true if you have interference, but you have phenomenal signal-to-noise and no interference from other stations on your channel  (except that using channel 35 could send part of the signal on adjacent channels up to channel 50, so if you have a neighbor on 35, then 44 is not a clear channel.)

If you are right on top of the Router, and have the shown about 40dB of signal, and no others are using this channel, then any slowdowns you are seeing are not caused by the Radio. You could go faster on that Mac if you had an 802.11ac Router rather than just 802.11n.

What is your ISP nominal data rate? is it higher than 30?

Hi Grant,

Thanks for your help with this.  I think at this stage I can live with things the way they are.  The Mac’s internal WiFi works well enough for most things and I have the USB dongle if I need a better performance.

Just as bit of a back ground on this.  They are currently upgrading the broadband network to fibre in my area and I got a new modem/router from the ISP in preparation for this.  The new modem/router still supports the current ASDL and the WiFi is 802.11ac.   I was finding with the new router that with internet speed I was getting was about 7 Mb/s on the Mac’s 5 GHz WiFi and about 9Mb/s on Ethernet. I then repeated the test using the D-Link WiFi dongle and got the same speed as the Ethernet.  My view was that for this relatively slow Internet speed the WiFi speed should not be an issue.

I wanted to see if the problem got worse with a faster network so I did a set of tests using a Netgear 4G hotspot mounted in a hub.  This gives a speed of about 40Mb/s on Ethernet but it only has 2.4GHz WiFi so to get the 5GHz WiFi I connected it to my old router (this router only has 802.11n).  With this arrangement the D-Link dongle and Ethernet gave the same Internet speed (36Mb/s) but the MacBook’s internal WiFi consistently gave a slower speed.

I think it safe to conclude that something is not quite right in the MacBook and I agree it is not the radio.

If you have more than one 802.11n Router available, you can combine them into a roaming network by running Ethernet cables between them (top diagrams. It does not appear to require special Routers. Just give them the same network-name and password, and they become one Network. Roaming by itself is not usually the goal with this setup -- but it can be used to provide acceptabe coverage over a wider area.

The last diagram (Wirelessly Extending) is included for completeness. It is a way of connecting nearby Routers without wiring. Its large disadvantage is that you use up a lot of bandwidth forwarding packets between Routers.

Thanks that is an interesting idea.  I may try it when I reconfigure the network.  The router has a WAN ethernet port which I was using to connect to my 4G hub.  I don't think I can do the WiFi connection as my unit doesn't appear to have a WAN setting in the wireless configuration. 

On the Internet speed issue.  Your mention of two or more antennas got me wondering if the Mac was simply not able to process the El Capitan MIMO algorithm fast enough.  I worked in a RF lab some years ago and the MIMO team there were doing a lot of publications on MIMO algorithms but the problem was the current computers were not fast enough to use them in real life to run the algorithms.

I used to work for a telephone modem company. Those algorithms need to be processed too fast to have the main general-purpose CPU doing it -- they do it in specialized hardware, narrower than you would expect, and definitely NOT floating point calculations.

What is vitally important at the remote stations is to get the A to D conversion gain set up right so that the main part of the signal is centered, and when digitized, you get the essence of the signal without noise or interference. But this is doable because the Router sends out polls, and the remote receiver can "train" on the polling. Going the other way, you have more Hardware (wider A to D converter) and hardware to adjust the gain available at the Router, so the variability of signal levels answering polls is not so much of an issue.

The specs for 802.11ac allow the use of up to eight antennas. Macs and Airport Routers are using at most three. Older macs used two, and before about 2011 used one. It's definitely the newer chips that are making this possible.

You don't need a spare WAN port any longer. Almost any modern Router will adjust a "regular" port based on what you connect to it. If it does not, the only difference can be accomplished with a cable called a crossover cable.

Crossover cable is most easily explained by using a very old telephony term the called  E + M signaling (which stood for "Ear and Mouth"). The wires have to connect so that one guys Ear (receiver) connects to the other guys Mouth (transmitter) so that the signals did not clash.

Thanks that's interesting.  Is all the processing likely to be on the airport card itself?

Is all the processing likely to be on the airport card itself?

Yes. all the work of decoding the entire packet is done in the chips. Checking CRC (for packet integrity) may be done externally once the packet is received, or more likely that is handled by the chips as well. In general, the chip delivers only packets for a specific address, unless set to "promiscuous mode" where it delivers all packets going by.

Except, of course, when the demodulation falls apart, and/or the packet has error. Then all the acknowledging, non-acknowledging, and error recovery and such stuff is done in software.

Once you have serial data, data rates above about 50,000 bits/second are difficult to handle without DMA (Direct [to] Memory Access). That's bits Not Megabits.

最後更新：2017-09-08 14:29:19

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