5Ghz -- Channels 36, 40, 44, 48

[azazel1024]

Still not sure why you are seeing such a huge difference. I see none. With my airport express, I see a signal drop of around 3dB when switching to the lower 5GHz channels. This is based off my laptop. I am not using the airpor utility.

I don't normally run the airport express as an AP (I run it wired only as an airplay receiver for some speakers).

I see no actual propogation differences between upper and lower 5GHz bands, other than actual power output differences on pre-regulatory change router/APs.

At a guess, either the antennas is so badly designed to have massive loss at 5.8GHz compared to 5.2GHz or something similar. That or there is a very, very weird multipath issue where you are locating things that is resulting in the signal polarization being twsited for the 5.8GHz range, resulting in the terrible gain.

I don't have a router or AP that can produce a stronger signal Channel 36-48 compared to 149-161/165. Either the upper band is stronger (likely due to higher Tx power) or they are no more than 1dB different (which I consider margin of error).

Tx is limited to 50mw for channels 36-48 before the FCC regulatory changes this past June (July?). It is now the same 1w that channels 149-161 of UNI-II upper are (165 is actually ISM band, but is also 1w).

I certainly don't observe any dramatic differences in signal strength and zero performance differences on my iPhone 5, my wife's iPhone 6 or her iPad 2 between the upper and lower channels on my one post regulatory change router and all of the pre stuff performs slightly better on the upper channels than the lower channels.

This includes when actually using my Airport express (early 11n) as an AP.

 

[peaks]

with iPhones, if AP output doesn't vary, you should still be seeing a 3db increase for the lower bands due to antenna design, as you can see here (iPhone 5):

more details here. So if you see them all as flat, maybe it is because your AP is lowering the lower bands by 3db? Anyway, that table makes the point very clearly that if power is the same from the AP, lower bands will have a 3db minimum advantage.

Edit: That link also shows that the iPhone 5 output power is 1db higher for lower bands. Yet another reason to start there.

Frequency bands supported:

• 2.4 GHz ISM (Channels 1 – 11), Power Output ~16dBm
• 5 GHz UNII-1 (Channels 36 – 48), Power Output ~14dBm
• 5 GHz UNII-2 (Channels 52 – 64), Power Output ~13.5dBm
• 5 GHz UNII-2Ext. (Channels 100 – 140), Power Output ~12dBm
• 5 GHz UNII-3 (Channels 149 – 161), Power Output ~13dBm
• 5 GHz ISM (Channel 165), Power Output ~13dBm

 

[peaks]

One more Apple reason to go with the lower bands: Apple TV 3 added a second wifi antenna that ONLY works on 36-48. So if you want both antennas to connect on your ATV, you have to use the lower bands. This means any other bands are at best half the throughput. That's another good reason. More info here.

Generally speaking, Apple seems to optimize for 36-48.

 

[sfx2000]

One more Apple reason to go with the lower bands: Apple TV 3 added a second wifi antenna that ONLY works on 36-48. So if you want both antennas to connect on your ATV, you have to use the lower bands. This means any other bands are at best half the throughput. That's another good reason. More info here.

Generally speaking, Apple seems to optimize for 36-48.

Apple tends to optimize for all bands/channels whenever/whereever they can... the referral link you mention is for AppleTV only, and for the diversity receive antenna - the main story for the ATV v3 is that the antenna gain was improved across the board.

A little tidbit of info... Apple, a few years ago, just after the iPhone 4 AntennaGate issue, put a huge amount of emphasis on RF performance, and put one team in charge of all things RF - Macs, iPhones, iPads, AirPorts, etc... and an incredible investment in RF chambers to ensure it.

I guess Steve Jobs was pretty horked off having to give away a few million iPhone 4 cases, and resolved not to have to do it again...

One of the interesting things - as CableCo's (and similar) deploy "Wireless Set-Top boxes", many of them are running in the UNII-3 band (149-165), and this is raising the noise floor - and they're hidden SSID's so tools like Inssider and similar don't see them... which may be a reason why the UNII-1 band is looking better for many folks.

Even with the pre-FCC relaxations on Tx power, the lower noise floor is worth experimentation and use in the lower channels...

 

[azazel1024]

inSSIDer will still see it (okay, I assume it will), it'll just be an empty SSID. inSSIDer will see my Xbox One/controller using Wifi direct (5GHz channel varies and no way to control what it uses. It is "boot dependent". I assume it does SOME kind of channel scanning to determine which channel to use). It is just an unknown SSID with unknown link rate.

Since I've confirmed the Rx power of all of my APs with my laptop and tablet (which are going to have somewhat different antenna designs) and not with my iPhone, no, the Express is reducing power in 36-48 by about 4dB from what it is using in 149-161. That isn't to say that my iPhone might not have better gain in the lowest UNI-II channels, but the Express and Pre-regulatory change AP/routers are also going to have lower Tx power in those channels, making it close to a wash for my iPhone 5 then.

The only instance where it might be better (for my phone) would be my one post regulatory change router that has the same Tx power in 36-48 as it does in 149-165.

My laptop and tablet (asus T100, not an iDevice) all show the same 4dB drop in 36-48 on my Archer C8, WDR3600 and Airport Express (1st gen 11n) over channels 149-161. My iPhone 5 conveniently enough shows lower performance on channels 36-48 by a small amount, though again, I've never bothered checking signal strength on it (and I only could with the airport utility, I can't check if on my other AP/routers, because stupid Apple).

 

[sfx2000]

azazel1024 - you are aware of the WiFi scanner capability of the Airport Utility on iOS right? Go into Settings -> Airport Utility and you'll see a switch to enable it, and then launch Airport Utility...

It'll show the SSID, BSS MAC address, RSSI, Channel, and time seen... pretty handy, and it will show "hidden" SSID's as well (it won't show what that SSID is, but it does note that it is hidden)

Might come in handy for your testing in the other thread

 

[azazel1024]

I thought it only showed Airport APs, not others? That said, to me a cell phone is too unreliable an indicator of signal strength for testing purposes. Are you holding it at the same angle you were previously, is your hand clasped on it the same way, etc. With a laptop you can set it down and not move the sucker. My tablet has a dock, and that is how I test with it so that it stays angled the same way. At least with a laptop or (docked) tablet, you have one or two fewer variables from test to test.

 

[sfx2000]

I thought it only showed Airport APs, not others? That said, to me a cell phone is too unreliable an indicator of signal strength for testing purposes. Are you holding it at the same angle you were previously, is your hand clasped on it the same way, etc. With a laptop you can set it down and not move the sucker. My tablet has a dock, and that is how I test with it so that it stays angled the same way. At least with a laptop or (docked) tablet, you have one or two fewer variables from test to test.

The WiFi scanner in Airport Utility finds any AP in the supported bands of the radio (so iPhone 4 being b/g/n obviously won't see a/n/ac, but the iPad's and iPhone 5 and later can see them)...

You have a good point about handsets - in general - most share the WiFi antenna with bluetooth, and as a result (due to that use case) is that the antenna pattern on them is very different than what one sees with a tablet or laptop... in the near field space, think of them more as a sphere, not as a donut... Not only that, but space constraints on a handset will compromise how the antenna is implemented along with not interfering with the WAN 2G/3G/4G antennas and GPS... and most of the time, all those radios are active these days...

Handsets can be useful as a site-survey tool (I keep an old Samsung Galaxy S4 just for that purpose as it's b/g/n/a/ac), but I agree with you that for certain testing, there are platforms better suited...

 

[peaks]

Phones have smaller antennas and less power. As such, if a lot of your traffic is phones, it makes sense to test with them and optimize for them, because a PC/Mac will always do well if a phone does well on the net, but the reverse is certainly not true. For phones, every db counts, and as such being aware of the 3dbi antenna gain advantage and 1 dbm Tx advantage for 36-48 really matters, and using the best band is important, more so than for computers.

 

[sfx2000]

Phones have smaller antennas and less power. As such, if a lot of your traffic is phones, it makes sense to test with them and optimize for them, because a PC/Mac will always do well if a phone does well on the net, but the reverse is certainly not true. For phones, every db counts, and as such being aware of the 3dbi antenna gain advantage and 1 dbm Tx advantage for 36-48 really matters, and using the best band is important, more so than for computers.

Agreed... and consider most handsets for WiFi - unity or lower gain on the antenna when working a planning worksheet... I usually consider mobiles at -1 dB gain, and low Tx power for link budgets at 2.4Ghz, as as the chart above shows, even lower for 5Ghz.

There is an antenna, because something has to radiate/receive, but due to space constraints, it takes second seat to the WAN radios - also SAR can limit Tx power on the WiFi as it cumulative with the WAN radios (and possibly bluetooth) when the mobile is in traffic state.

Handsets are a challenge, esp. in the enterprise and hospitality space, as most of those WLAN's were built out for Laptops, not tablets or handsets...

 

[peaks]

Apple tends to optimize for all bands/channels whenever/whereever they can... the referral link you mention is for AppleTV only, and for the diversity receive antenna - the main story for the ATV v3 is that the antenna gain was improved across the board..

well, i posted 2 links about detailed Apple antenna info, which isn't that easy to find. iPhone 5 and ATV3, both clearly designed for best performance in 36-48. Do you feel a diversity antenna is no big deal? We are talking a doubling of received signal, with better stability. Better dbi gain on other channels simply doesn't compare--2 antennas is a HUGE network advantage, and the Apple RF designers ONLY applied that to 36-48. I would say that from an engineering perspective, those decisions reveal a design goal to target 36-48, ultimately at the expense of the other 5GHz bands, but in these tiny devices tradeoffs must be made. My point is, Apple appears to optimize for 36-48 and these are 2 recent examples. How did you reach your conclusion about Apple "optimizing" for all bands? Of course that's ideal (flat frequency response as it were), but when tradeoffs are required it becomes impossible. Nevertheless, you didn't provide any evidence, maybe you have some links?

 

[sfx2000]

i posted 2 links about detailed Apple antenna info, which isn't that easy to find. iPhone 5 and ATV3, both clearly designed for best performance in 36-48.

<snip>

Do you feel a diversity antenna is no big deal? We are talking a doubling of received signal, with better stability.

I didn't say it was a big deal or not - and in WiFi, it definitely helps.

I can call down the hall at the office and get those numbers - again, that being said, I wouldn't be able to share them due to NDA's...

FWIW - UNII-1 band, since pre-FCC changes, was a challenging environment (and will be for older devices) as antenna gain is the only way to close the Tx/Rx gap in that band compared to UNII-2/2ext and UNII-3, so it does make some sense to optimize there - but it's a "borrow from Peter to pay Paul" effort - antenna design is still an art form, although one steeply based in physics and science..

Rx diversity is always good - I was part of the RF engineering effort to implement this for 2G/3G CDMA, and we easily saw a 3dB gain improvement on the Rx side...

sfx

 

[peaks]

Just wanted to report back, I did some same-room testing with my 2009 TC and my folks' 2009 Airport Extreme and yes indeed, the older units have 3db lower signal in the lower bands. That could explain Apple's efforts to boost the lower bands in client antenna design, but now that APs do not have to limit power to lower bands, the client boost becomes a lower band advantage if you are designing a new network.

Also explains why the old Airports tend to choose higher bands when set to auto--3dbm more power is obviously worth favoring.

peaks

 

[sfx2000]

Tag: Country Information: Country Code US, Environment Any
Tag Number: Country Information (7)
Tag length: 70
Code: US
Environment: Any (0x20)
Country Info: First Channel Number: 36, Number of Channels: 1, Maximum Transmit Power Level: 17 dBm
First Channel Number: 36
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 17
Country Info: First Channel Number: 40, Number of Channels: 1, Maximum Transmit Power Level: 17 dBm
First Channel Number: 40
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 17
Country Info: First Channel Number: 44, Number of Channels: 1, Maximum Transmit Power Level: 17 dBm
First Channel Number: 44
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 17
Country Info: First Channel Number: 48, Number of Channels: 1, Maximum Transmit Power Level: 17 dBm
First Channel Number: 48
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 17
Country Info: First Channel Number: 52, Number of Channels: 1, Maximum Transmit Power Level: 24 dBm
First Channel Number: 52
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 24
Country Info: First Channel Number: 56, Number of Channels: 1, Maximum Transmit Power Level: 24 dBm
First Channel Number: 56
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 24
Country Info: First Channel Number: 60, Number of Channels: 1, Maximum Transmit Power Level: 24 dBm
First Channel Number: 60
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 24
Country Info: First Channel Number: 64, Number of Channels: 1, Maximum Transmit Power Level: 24 dBm
First Channel Number: 64
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 24
Country Info: First Channel Number: 100, Number of Channels: 1, Maximum Transmit Power Level: 24 dBm
First Channel Number: 100
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 24
Country Info: First Channel Number: 104, Number of Channels: 1, Maximum Transmit Power Level: 24 dBm
First Channel Number: 104
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 24
Country Info: First Channel Number: 108, Number of Channels: 1, Maximum Transmit Power Level: 24 dBm
First Channel Number: 108
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 24
Country Info: First Channel Number: 112, Number of Channels: 1, Maximum Transmit Power Level: 24 dBm
First Channel Number: 112
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 24
Country Info: First Channel Number: 116, Number of Channels: 1, Maximum Transmit Power Level: 24 dBm
First Channel Number: 116
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 24
Country Info: First Channel Number: 132, Number of Channels: 1, Maximum Transmit Power Level: 24 dBm
First Channel Number: 132
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 24
Country Info: First Channel Number: 136, Number of Channels: 1, Maximum Transmit Power Level: 24 dBm
First Channel Number: 136
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 24
Country Info: First Channel Number: 140, Number of Channels: 1, Maximum Transmit Power Level: 24 dBm
First Channel Number: 140
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 24
Country Info: First Channel Number: 144, Number of Channels: 1, Maximum Transmit Power Level: 24 dBm
First Channel Number: 144
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 24
Country Info: First Channel Number: 149, Number of Channels: 1, Maximum Transmit Power Level: 30 dBm
First Channel Number: 149
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 30
Country Info: First Channel Number: 153, Number of Channels: 1, Maximum Transmit Power Level: 30 dBm
First Channel Number: 153
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 30
Country Info: First Channel Number: 157, Number of Channels: 1, Maximum Transmit Power Level: 30 dBm
First Channel Number: 157
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 30
Country Info: First Channel Number: 161, Number of Channels: 1, Maximum Transmit Power Level: 30 dBm
First Channel Number: 161
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 30
Country Info: First Channel Number: 165, Number of Channels: 1, Maximum Transmit Power Level: 30 dBm
First Channel Number: 165
Number of Channels: 1
Maximum Transmit Power Level (in dBm): 30

 

[sfx2000]

The previous was from an 802.11ac Airport Extreme...

Below is from a 802.11n Airport Extreme...

Tag: Country Information: Country Code US, Environment Any
Tag Number: Country Information (7)
Tag length: 10
Code: US
Environment: Any (0x20)
Country Info: First Channel Number: 36, Number of Channels: 4, Maximum Transmit Power Level: 30 dBm
First Channel Number: 36
Number of Channels: 4
Maximum Transmit Power Level (in dBm): 30
Country Info: First Channel Number: 149, Number of Channels: 5, Maximum Transmit Power Level: 30 dBm
First Channel Number: 149
Number of Channels: 5
Maximum Transmit Power Level (in dBm): 30
Padding: 00

 

[peaks]

are you sure they aren't switched? makes it look like 11n version has no limits on lower bands but newer 11ac added the limit. that seems backwards given the latest changes in regulation. please confirm, thanks, very useful info.

 

[sfx2000]

are you sure they aren't switched? makes it look like 11n version has no limits on lower bands but newer 11ac added the limit. that seems backwards given the latest changes in regulation. please confirm, thanks, very useful info.

I double checked - note that the Attribute/Value pair says Max Tx, doesn't say what Tx actually is...

In real world, the Apple 11n and 11ac devices are very similar in output... the 11n being a 4th Gen TC...

 

[sfx2000]

I double checked - note that the Attribute/Value pair says Max Tx, doesn't say what Tx actually is...

In real world, the Apple 11n and 11ac devices are very similar in output... the 11n being a 4th Gen TC...

Pulled some older 802.11n Apple gear off the shelf - they're all 30 dBm for max Tx on the wirecaps - so obviously this is a bit optimistic... the 11ac is probably the most honest...

sfx

 

[peaks]

hmm. then it would seem testing results are still more valuable than specs. as usual! that's why we come here...

 

[peaks]

ok i did some more testing and now i can fine tune recommendations on channel usage for iphones and apple routers.

I checked with my new Airport Extreme AC (just installed last week), and found the following (all devices were fixed and not moved at all during testing):

location channel device RSSI
same room 36 mac -41
same room 36 iPhone -63
same room 161 mac -34
same room 161 iphone -41
2 walls away 36 mac -62
“ 36 iphone -79
“ 161 mac -52
“ 161 iphone -51

So CLEARLY with all the Apple APs i own, through the latest AEAC, the power output is much greater for higher bands (7-22db!). Even though the antenna design of the iPhone is favoring 36-48 by 3db, Apple lowers power so much in 36-48 that when you are using Apple gear with Apple routers, higher bands are still apparently much better. I stand fully corrected on this front!

If you have a new AP with the same power output for all bands (which you will need to confirm with testing), then lower bands will actually get a boost from the antennas and should be favored. But Apple routers should favor higher bands. I had hoped maybe the latest firmware removed the limits in lower bands as per new regs but that doesn't seem to be the case.

As for which one goes through walls better, in this little test the walls resulted in a 21db drop @36 for mac and 16db drop for phone, and @161 mac dropped 18db and the phone dropped 10db. So 36 definitely got a larger signal hit from the walls, but since it was starting at a much lower power level, faster dropoff would be expected. Hard to say with all the variables, but it certainly doesn’t support the argument that lower bands are better at penetrating walls at all.

Hopefully my process of discovery is helpful for others. I definitely keep learning about networking, every day, even after doing it for 20 years. I now have all my Apple APs on 149-161. And my Engenius on 48 is performing much better than it did on the upper bands--best outdoor wifi experience I've had with it on 48, instant response, at max speed from the very first test, go figure (161 always needed to "warm up", i chalked it up to beam forming). Test test test.