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

[bodean]

Do many people use these channels with on 5Ghz? Wondering what the advantage is, if any, to using them, opposed to 149,153,157,161?

 

[jegesq]

Do many people use these channels with on 5Ghz? Wondering what the advantage is, if any, to using them, opposed to 149,153,157,161?

AFAIK, there are only a couple of reasons that one might prefer to use one or the other band, and it probably comes down to doing a simple InSSIDer scan of your area to learn which channels have the least overlap with neighboring networks, i.e., where you'll get the least interference. This becomes important with 802.11ac if you're trying to use 80mhz channel width, since if another network is detected on your primary channel, the router will drop down to 40mhz width.

On the other hand, I've read some people say that they prefer to use the lower band principally because of less chance for interference from competing networks. They argue this is because the lower band of channels uses only 1/20th the power of that is required to push the same signal in the upper band (i.e., the signal on channel 161 needs to be roughly 20 times stronger than on channel 48 to travel the same distance). So the thought among some is that this increased power also increases the chances for cross-interference from other networks as well. My own experience says that this isn't the case and the transmit power is relative; my experience has been that I get the best throughput and speeds using channel 161 as my primary channl at 80mhz channel width (which I prefer because there's no one within miles of me using any of the adjacent channels).

The best thing to do, and really the only way to know which channels will work best in your setting is to learn how crowded your airwaves are, and the only way to know is to do a site survey with something like InSSIDer or another wifi analyzer app (there are tons of them for Android and iPhones).

One other reason that some people prefer to use the lower channels is that older 5ghz DECT phones use the same upper band channels that are now available for wifi and they can interfere with the upper channels. Most people have by now switched over to using phones (to the extent people still use wireless phones to extend landlines) that are DECT 6.0, which uses the 1.9ghz frequencies, so they don't interfere with 5ghz. But there are still some older DECT phones out there. Personally, I've never experienced any problems from portable phones (or microwaves, or baby monitors, etc.).

On last possible concern, and I mention it because some people have had issues using the upper band of channels with consistency. There is a fairly long thread here at SNB which discusses the effects of nearby aviation, weather and military radar, and the issue is this: If you are near (within about 30 miles) of a military, weather, or civil aviation installation, there is a chance that because of channel "bleeding" at the outer edges of those channels in the upper band that abut adjacent channels where radar is used, that you might experience the effects and impacts of DFS (Dynamic Frequency Selection) and TPC (Transmit Power Control). Without getting too technical about this, if your router detects a radar burst on a channel, DFS and TPC are supposed to cause the router to cease broadcasting on that channel, to lower transmit power and to switch to another channel and not try to operate on the channel where radar was detected for a minimum of 10 minutes and as long as 30 minutes. This can obviously lead to a situation-- if it occurs-- where the channel you've selected doesn't work. Theoretically this should not be a problem because your router would just shift to another channel, but some here contend that it has caused them issues with the upper band.

One SNB user, Kenhlan, is particularly convinced, after doing a significant amount of research on this issue, that his problems with his 5ghz signal being interrupted in an aperiodic manner was caused by DFS/TPC being triggered by adjacent military and aviation radar. You can read the thread here: http://forums.smallnetbuilder.com/showthread.php?t=7742 and decide for yourself. I live in an area surrounded by several airports and have not had any issues with my use of the upper channels on 5ghz. So YMMV.

 

[enr00ted]

So, upper vs lower

What no one makes it clear is what channels offer better range aka penetrate better walls etc, if any. Also some devices might not work with higher frequencies like my Nexus 4.

 

[jegesq]

What no one makes it clear is what channels offer better range aka penetrate better walls etc, if any. Also some devices might not work with higher frequencies like my Nexus 4.

The differences in terms of range in the 5ghz band are insignificant. The lower end, the UNI-II band (channels 36, 40, 44, and 48) because they are "lower" than the UNI-IIExt band channels, will "travel" farther....but again, the differences are insiginificant in the grand scheme of things, and the better comparison is between the 2.4ghz band and the 5 ghz channels and obviously, the 2.4ghz channels, at lower frequencies, have greater range and can travel farther than the higher frequencies found in 5ghz.

A good example are those those "thumper" bass woofer units some kids put in their cars....the ones that can be heard coming at you blocks away....very low frequencies; whereas you can only hear the high frequencies from the tweeter when the car drives right by you.

But at the 5ghz band of channels, there's not enough of a difference between the lower and upper frequency channels to really make a difference in "range". The real issue of which set of channels to use comes down to how much cross-interference you're experiencing from other adjacent routers using the same channels.

Bottom line: Use InSSIDer or some other wireless net analyzer tool, do a survey of your home and surrounding areas, and figure out which channels will provide you with the best experience, the best speeds and the best throughput There is no single "right" answer. There are too many moving parts involved to give you a simple "this" or "that" answer.

 

[stevech]

the lower band in many regulatory regions has limits on radiated power that are much lower than the upper band's frequencies.

This of course constrains range.

 

[sm00thpapa]

I always go with CH 157 and get my full speed and more on my devices. I have a 150 Mbps connection and get up to 172 Mbps on all devices.

 

[stevech]

I always go with CH 157 and get my full speed and more on my devices. I have a 150 Mbps connection and get up to 172 Mbps on all devices.

what net IP layer throughput do yet get (e.g., using Speedtest.net).

Those numbers you gave are the WiFi connection speeds, right? Those usually suffer 60% or so overhead from WiFi duplexing, frame overhead, etc.

 

[thiggins]

the lower band in many regulatory regions has limits on radiated power that are much lower than the upper band's frequencies.

This of course constrains range.

Power restriction was removed as of June 2014. New AC routers generally use the higher allowed power in the lower band. But there are no upgrades for products in the field. Power change requires re-certification.

 

[remixedcat]

I got mine on 161

 

[bodean]

Thanks.

InSSider recommends 149 for me. There is only 1 other 5GHz in my condo building, and inSSider says he is using 153. Surprised it didnt recommend 161 for myself

 

[bodean]

Actually I just moved my router into my living, and inSSider says it now recommends channel 36. I find that kind of odd, as there is only 1 other 5ghz in the area, and he is on 153.... Wonder how reliable inSSider's recommendations are.

 

[azazel1024]

AFAIK, there are only a couple of reasons that one might prefer to use one or the other band, and it probably comes down to doing a simple InSSIDer scan of your area to learn which channels have the least overlap with neighboring networks, i.e., where you'll get the least interference. This becomes important with 802.11ac if you're trying to use 80mhz channel width, since if another network is detected on your primary channel, the router will drop down to 40mhz width.

On the other hand, I've read some people say that they prefer to use the lower band principally because of less chance for interference from competing networks. They argue this is because the lower band of channels uses only 1/20th the power of that is required to push the same signal in the upper band (i.e., the signal on channel 161 needs to be roughly 20 times stronger than on channel 48 to travel the same distance). So the thought among some is that this increased power also increases the chances for cross-interference from other networks as well. My own experience says that this isn't the case and the transmit power is relative; my experience has been that I get the best throughput and speeds using channel 161 as my primary channl at 80mhz channel width (which I prefer because there's no one within miles of me using any of the adjacent channels).

The best thing to do, and really the only way to know which channels will work best in your setting is to learn how crowded your airwaves are, and the only way to know is to do a site survey with something like InSSIDer or another wifi analyzer app (there are tons of them for Android and iPhones).

One other reason that some people prefer to use the lower channels is that older 5ghz DECT phones use the same upper band channels that are now available for wifi and they can interfere with the upper channels. Most people have by now switched over to using phones (to the extent people still use wireless phones to extend landlines) that are DECT 6.0, which uses the 1.9ghz frequencies, so they don't interfere with 5ghz. But there are still some older DECT phones out there. Personally, I've never experienced any problems from portable phones (or microwaves, or baby monitors, etc.).

On last possible concern, and I mention it because some people have had issues using the upper band of channels with consistency. There is a fairly long thread here at SNB which discusses the effects of nearby aviation, weather and military radar, and the issue is this: If you are near (within about 30 miles) of a military, weather, or civil aviation installation, there is a chance that because of channel "bleeding" at the outer edges of those channels in the upper band that abut adjacent channels where radar is used, that you might experience the effects and impacts of DFS (Dynamic Frequency Selection) and TPC (Transmit Power Control). Without getting too technical about this, if your router detects a radar burst on a channel, DFS and TPC are supposed to cause the router to cease broadcasting on that channel, to lower transmit power and to switch to another channel and not try to operate on the channel where radar was detected for a minimum of 10 minutes and as long as 30 minutes. This can obviously lead to a situation-- if it occurs-- where the channel you've selected doesn't work. Theoretically this should not be a problem because your router would just shift to another channel, but some here contend that it has caused them issues with the upper band.

One SNB user, Kenhlan, is particularly convinced, after doing a significant amount of research on this issue, that his problems with his 5ghz signal being interrupted in an aperiodic manner was caused by DFS/TPC being triggered by adjacent military and aviation radar. You can read the thread here: http://forums.smallnetbuilder.com/showthread.php?t=7742 and decide for yourself. I live in an area surrounded by several airports and have not had any issues with my use of the upper channels on 5ghz. So YMMV.

I believe you may be a little confused. The power LIMITS for channels 141-161 are 20 times higher (1 watt) compared to 36-48 (50mW), it is not the case that you need 1/20th the power for the signal to travel as far. The difference in signal propagation and attenuation between the 5.2GHz band (36-48) and the 5.9GHz band (141-161) is minimal.

Looking at actual radiated power levels on consumer routers pre-FCC reclassification of the 5.2GHz UNI-I band, typical radiated powers are about 3-4dB higher than the upper 5.9GHz UNI-III band (channels 141-161). This DOES typically correspond with slightly greater range and through put on the TRANSMIT side of things. There is little difference on the RECEIVE side of things as pretty univerally Wifi CLIENTS range from 18-32mW of transmit power no matter the channel/band selection. I've tested this with several clients and channel selections. At best on the Rx side of things, you'd be looking at less than 1dB of difference between 36-48 and 141-161, but Tx can be a fairly pronounced difference.

The largest I've seen was in testing with my Archer C8. In 36-48 compared to 141-157 (It won't do 161) I see roughly a 5% increase in Tx throughput at close distance, about nothing at medium distance (1-2% better, margin of error as far as I am concerned) and 10% increase at long/extreme range.

On my WDR3600 with regular 11n, I see no difference between upper and lower channels except at long and extreme range, where I see about a 5% bump in performance with the upper channels.

 

[sfx2000]

Do many people use these channels with on 5Ghz? Wondering what the advantage is, if any, to using them, opposed to 149,153,157,161?

Yes - in my area, the CableCO/Telco's are deploying into 5GHz for company supplied router/AP's, and with WiFi remotes for TV - most of them are auto-selecting to the UNII-3 band (channels 149-165) in 5Ghz, so I'm moving down into the UNII-1 band where I'm actually getting better performance for 802.11 a/n/ac clients...

It's about 3db down from the upper channels for most clients/AP's, but for now, lower power is lower interference...

 

[Deleted member 22229]

Do many people use these channels with on 5Ghz? Wondering what the advantage is, if any, to using them, opposed to 149,153,157,161?

Are you in the US cant speak for other regions? If so try John's fork firmware for your N66U i use channel 44 for 5 ghz and it positively hammers any of the newer firmwares in signal and range. Give it a try and you shall see.

 

[peaks]

I have been messing around with my APs and I have all Apple clients, Airport Extreme AC, Engenius and Netgear APs.

UNI-II antenna circuitry in the iPhone and iPad--and maybe the Macs too--gives a receive boost (+1.8db or something) to 36-48 that is NOT matched in the other bands (look up the FCC filing). As a result, the best bands for Apple client Rx will be UNI-II, barring interference issues. I don't know if this is true for Android clients etc, but designing for your clients always makes sense, so look it up.

I should also note that I have an Engenius 5GHz AP outside my garage for the yard, and an Airport Time Capsule 802.11n inside the garage/office. With the outdoor AP on 44 and indoor on 161, my inside mac kept re-associating with the outdoor AP, which i didn't want (it's only 100baseT, and the indoor AP is gigE). Looking at dbm inside, the two APs were competing at the same level--outdoor was making it well through the wall and indoor just wasn't that strong. Swapping the bands between the two resulted in the outdoor dropping almost 10db compared to indoor! This is because the UNI-II bands do go through walls better, and this is most obvious if you just do some testing at a distance through walls to compare the extremes of 36 and 161. Of course it's also partly because the client receive circuitry is optimized for UNI-II.

Interference might matter more though, so if your site survey shows 36-48 are active, you will probably do better with the higher bands.

 

[azazel1024]

That is very odd behavior. My only guess is it was more related to what power levels the Apple Time Capsule was using. Channel 36-48 is going to be limited to 50mw of power at most by older FCC regulations, which the Airport will be following. At a guess, the Engenius was NOT following FCC regulations on channel 44 (at least the old ones).

There difference in penetration between 5.2GHz and 5.8GHz is marginal at best. Unless there is some specific metal grid pattern in the wall that just happens to be small enough to interfere with 5.8GHz, but not really with 2.4GHz, there should have been no difference.

I've done a lot of testing on the UNI-II band. The lower part around 5.2GHz has no pratical different in penetration compared to the upper UNI-II/ISM 5.8GHz range (channels 149-165). Both open air and penetration through walls. I made sure I was using an access point that was certified under the newer FCC regulations, so it was using the same broadcast power in both upper and lower channels.

There was an average of 0dB difference open air and through walls between the upper and lower channel ranges.

The only difference you could have possibly been seeing is either positioning of the client or that the Apple Time capsule switched to higher broadcast power when it was switched to the higher channels (because the old one is DIFFINITELY using the old FCC regulations. That Engenius outdoor AP might not be conforming to the old regulations. I'd say it should be, but I wouldn't put it past them to not be conforming, not that it likely matters too much now).

Though an exterior wall on 5GHz, vinyl sidding over 11/32" plywood, 2x4" fiberglass insulation and 1/2" drywall I see roughly 18dB of attenuation on 5GHz. So for an outdoor access point to be at the same signal strength as an indoor one, you'd have to be at least a room or two over and physically much closer to the outdoor AP.

 

[peaks]

hmm yes it is very likely that the 2009 TC was conforming to prior regulations and that explains the difference the TC was contributing to the signal delta. That said, the Engenius ENS500EXT doesn't appear to control output based on frequency, as i had both 44 and 161 manually set to 26dbm (400mw), and even out in the open air in the backyard (line of sight) i saw at least a 6db delta between 44 and 161 (made no throughput difference though, strong signal both ways). But that might be due to the aforementioned boost that iPhone gives UNI-II, plus vagaries of signal propagation in my yard. The 500EXT is strapped to a metal downspout on the garage, so that is definitely adding some reflection and absorption to the mix, but it helps with MIMO outside and probably blocks some of the signal going into the garage.

In my recent experience, again and again, UNI-II has better signal for iDevices. Penetration differences might not be that significant on a specific wavelength physics basis (but it is happening by definition--lower freqs penetrate better, even if small delta 36 v 161), but when the whole system is considered--channels, antenna design, amplifiers, interference from neighbors, Apple clients--there is a clear difference in my testing with AExtremeAC, AExpress, TC and 500EXT. All this was done at one site, so YMMV of course--i would always optimize based on site specifics and testing, regardless of theory. But since iPhones are probably 70% of my family traffic--or more--doing what was right for the iPhone made sense to me and the results have been fast and low latency 5GHz coverage almost everywhere on my property (2.4 still plays a role at the periphery alas).

All that said, i am always looking to tweak for performance so azazel if you say it doesn't make sense, I'll probably be messing with it some more and I will report back if i find any changes!

Nice to find people to discuss this with as I have been doing it obsessively in isolation so far haha

 

[L&LD]

As I have written here before, the best throughput and consistency for my customers and my personal networks work best with channel 48 (up or down one) in the 5GHz band. YMMV of course, but this is consistent here and the higher channels are simply too variable in throughput for me.

 

[azazel1024]

There is a clear difference with pre-FCC regulatory change devices. Example, my router, which is sadly just pre-FCC regulatory changes, Channel 36-48 drops the signal by 4dB (coincidentally the same 4dB delta you see on your Engenius between 36 and 161). My post FCC regulatory change router in AP mode there is zero difference between 36-48 and 149-165. Same goes on "through wall" penetration and multipathing results.

I am sure there COULD be a difference, but it isn't within the margin of error for the results I can get out of InSSIDer or out of actual throughput testing (<5% difference in actual Tx/Rx file transfer difference between lower UNI-II and upper UNI-II/ISM bands). I haven't put hundreds of hours of testing in to it, but I have probably put half a dozen hours in to testing of the post FCC regulatory change router and probably a a few dozen hours in to testing various routers within my home (both the routers themselves as well as siting them, antenna positioning, channel selection, etc.)

The pre-FCC regulatory change Archer C8 that I have, channel 149-161 does result in a boost of around 6% averaged out in download powerformance, but again, the lower channels are roughly 4dB lower transmit power (which I assume means that the lower channels are at the 50mw cap and the upper channels are transmitting at roughly 120-130mw). It is also why I have my Archer C8 setup to run channels 149-161 and the post FCC regulatory change router running 36-48.

My outdoor router I actually found that my aluminum siding was causing slight issues with receive and transmit. Its a TP-Link WDR3600 in my garage with the antennas on the end of 1m pigtails run through my garage wall. I had them right under the eves of my garage sofit with some rope caulk holding them in position. The antennas were probably 1" from the siding. When I swapped the 5dBi for 7dBi recently I mounted them to a piece of 1x3 which both slightly improved the angle (they were canted so that signal was going in to the ground by about 2-3 degrees, minor, but still not perfectly perpendicular to the ground) as well as pushed them to be about 2 inches from the aluminum siding instead of 1 inch and also moved them down so that they start about 3 inches below the sofit instead of the antenna bases being effectively up against the siding. With the 5dBi and the new positioning it resulted in a boost about 10% on 5GHz down and about 18% up. About 5% and 8% respectively on 2.4GHz. Its close to the same gain I got out of then swapping the 5dBi for 7dBi omnis. That lead to pretty darned close to a 10% gain on 5GHz and 2.4GHz up and down. All of these are at distances >15ft for 5Ghz and 25ft for 2.4GHz, as closer than that and I had "maxed out" the router's wireless performance (IE 25MB/sec down and 23MB/sec up both bands).

So now at 80ft from the router I can get about 30Mbps down and 12Mbps up on my iPhone 5 on 5GHz, where I was getting about 23Mbps down and 7Mbps up before mounting adjustments and the larger antennas. On my laptop at 40ft (I haven't tested with the laptop further) it went from 92Mbps down and 80Mbps up to 111Mbps down and 104Mbps up. I don't remember the exact 2.4GHz numbers for either now.

 

[peaks]

ok i just did a great test one more time. i put my iPhone in one spot on the table in my gazebo, line of sight to the AP, 25ft away. Ran speed tests until things stabilized, then checked RSSI using Airport Utility Wifi Scan for a few mins. I did it first with my Engenius 500EXT on 161, got an average signal of -61dbm. Switched to channel 40, got an average of -50dbm. 11 db difference. That is huge; on par with using a massive antenna or amp. With that type of advantage, the lower band should always be the focus until you have to use upper bands.

Azazel, your point seems to be earlier regulations would limit 36-48 power output, so signal would be WORSE. I am saying it is MUCH BETTER to use those bands, and this test shows that clearly to me. This is also true with my 2009 TC--the higher bands make for lower signals at the client end. So then, if it is true that the TC is limited to 50wm in 36-48, it should make it even clearer how much better propagation is for the lower bands--even in a power-limited situation it seems to outperform full power 149-161.