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Author Topic: Wireless 5GHz - v- 2.4GHz  (Read 7864 times)

guest

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #15 on: June 23, 2014, 05:00:52 PM »

http://www.cisco.com/c/en/us/products/collateral/wireless/aironet-3600-series/white_paper_c11-713103.html

Table 2 for those wondering about the effect of number of antennae (spatial streams) & bandwidth then this shows you what's what.
« Last Edit: June 23, 2014, 05:08:10 PM by rizla »
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JGO

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #16 on: June 23, 2014, 05:02:23 PM »

[/i]

2) With router sat on desk adjacent to the MAC:

5GHz averaged 36.32 Mbps - that's slower than it is at 15 feet away!
2.4Ghz averaged 53Mbps, similar to 15 feet away.



This suggests to me that your aerials have nulls at the side near the router.   Try averaging over 360 degrees at say 30 degree intervals ( if you have nothing better to do !)

Seriously there is no such thing as a fully omnidirectional aerial. (If there was it would be infinitely small and have zero radiation efficiency !  )

 

   

 
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guest

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #17 on: June 23, 2014, 05:12:23 PM »

[/i]

2) With router sat on desk adjacent to the MAC:

5GHz averaged 36.32 Mbps - that's slower than it is at 15 feet away!
2.4Ghz averaged 53Mbps, similar to 15 feet away.



This suggests to me that your aerials have nulls at the side near the router.   Try averaging over 360 degrees at say 30 degree intervals ( if you have nothing better to do !)

Seriously there is no such thing as a fully omnidirectional aerial. (If there was it would be infinitely small and have zero radiation efficiency !  )

 

   

Given the nature of MIMO its inevitable this happens at very short ranges - unless you have really deep pockets & want to go for "steerable" antenna arrays :

http://www.ruckuswireless.com/products/zoneflex-indoor/zoneflex-7363

Even then ....
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sevenlayermuddle

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #18 on: June 23, 2014, 05:17:52 PM »

My own experiments have, I'm afraid, also rekindled my long standing scepticism about WiFi.  It serves an indispensable purpose in providing web-browsing access for mobile devices.  It is also capable, when conditions are right, of impressive data rates.   But for any 'serious' home networking it can't be relied upon and falls short of reasonable performance. That is with my devices and in my home at least, which is a modern home with only stud & plasterboard walls and I promise is not that big.   :(

You're wrong but that's because :

a) the manufacturers have always published PHY rates and you will only get 60-70% MAC efficiency so its been too much smoke'n'mirrors in the consumer market;

b) as mentioned above most 802.11n adaptors default to 20MHz b/w operation only

c) you're not spending enough money - I'm not kidding.

I have one of these :

http://linitx.com/product/ubiquiti-unifi-uap-ac-1300mbps-80211ac-24ghz5ghz-access-point/13806

and prior to that I thought as you did.

I don't now - I can max out the USB2 interface to a 802.11ac adaptor when the AP is in the same room. That's 280Mbps or so DATA TRANSFER. I put that in capitals because I simply couldn't believe it. I'm pretty sure that with an internal adaptor I could get 400Mbps burst speeds.

I can get (data, not PHY) speeds of over 120Mbps @ 5GHz through wooden floorboards/associated plasterboard but if you have any sort of blockwork/metal (pipes in my case) in the beampath (on any antenna) then it drops fast.

I bought the thing on the recommendation of RevK, and apart from it running surprisingly hot (vents may have helped here IMHO :P ) its been so trouble-free I am giving serious consideration to getting one of their external units. The AP software isn't that user-friendly but is comprehensive - eg you can have a rate-limited guest VLAN at the click of a button. The AP runs Linux & most of the advanced stuff assumes people would rather run a script than load up a "web interface".

tl;dr wireless works if you pay for proper RF engineering, which is the business-end of this sort of kit

The 7800DXL is configurable for 20/40 bandwidth, I had 40 enabled for my testing.   I also confirmed (with OS/X utioities) 802.11n was actually in use, which it was and also noticed a '+1' alongside the channel number.

It may of course be my Mac Mini that's the bottleneck, it's getting on a bit.  But that actually raises another point... you can invest big bucks in the access point, and possible get a much better AP.   But the connected devices also have their own RF front ends and, say, a tablet or laptop, or a TV with built in WiFi, you're stuck with whatever RF components the manufacturer provided.   Which is probably cheap and basic, and I argue that may deny you much of the gains from the super-duper AP.

Don't get me wrong, I couldn't live without WiFi.  I'm using it right now, sending this reply from an iPad.    And I'd spend whatever was needed to make it work.   But for myself,  all I need from WiFi is web browsing.  I'll stick with gigabit ethernet and (cheap) Cat 5 for anything that's bandwidth hungry, such as my MythTV based media, which needs to be able to reliably sustain Full HD data rates between server & frontend :)
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guest

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #19 on: June 23, 2014, 05:33:50 PM »

Don't get me wrong, I prefer wired :)

It was just one of the few times I've been genuinely gobsmacked with a new bit of kit - a sort of "oh THAT'S how it should work" moment  :o

In the overall scheme of things I'd say its cheap for what it delivers - can push out 3-4 concurrent HD streams (mixed 2.4/5GHz 802.11n/ac) here with no stuttering in normal use.

You're quite right about clients but if the AP is the bottleneck then all the new shiny stuff seems slow anyway. The shiny stuff usually costs more than the Ubiquiti AP I linked anyway :D
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JGO

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #20 on: June 24, 2014, 07:55:18 AM »

WiFi always strikes me as similar to "Cordless" - a nice sounding effort saving idea, till you meet the need to charge batteries, replace them  or problems of possible explosion and  toxic waste.

Yes they both work but not with zero  effort !

Just had a look at the "Help with WiFi" instructions for my Router. In effect "If you have speed problems try Ethernet "

Pragmatic advice for most people;  I might have added " or read Hertz's 1888 Thesis !"
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guest

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #21 on: June 24, 2014, 03:25:30 PM »

Semi-on-topic....

I've been playing with some (mainly Samsung) Android devices lately & unless you mess about editing hex in a config file then they are very reluctant to use the 5GHz band.

From what I can tell if the SSID is the same for both 2.4GHz & 5GHz radios then the Android device will only use the 5GHz band if the signal strength is a few dB greater than the 2.4GHz signal. This is pretty nonsensical given the same signal strength would usually result in a less congested RF environment at 5GHz - and that in turn would result in faster speeds. Edit - and of course the signal strength of both is much the same in a single room so where there's a perfect signal it still uses the 2.4GHz band  ???

So the only way to do this on a consumer-grade access point is to have 2 SSIDs - one for 2.4GHz and one for 5GHz but that's not great really. It works but just seems like a bodge.

The AP I have can recognise clients & force them to join a "group" and as part of that group you can specify which radio they should be using & when to switch - which seems to work so far.

Seems rather dumb to me that Android (not just Samsung) devices seem to default to this behaviour. Edit2 - this is on both KitKat & Jelly Bean builds.
« Last Edit: June 24, 2014, 03:35:20 PM by rizla »
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sevenlayermuddle

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #22 on: June 24, 2014, 06:46:35 PM »

Seems rather dumb to me that Android (not just Samsung) devices seem to default to this behaviour. Edit2 - this is on both KitKat & Jelly Bean builds.

Sorry I should already know how, but if you tell me how to tell which signal the phone has connected to, I'd be glad to try that here and see if I get same results.

Even more off-topic, I have already concluded that Samsung's Android offerings are data-flawed,  in relation to 2g/3g (I did say Off Topic).   Mine works brilliantly on 3g but that's not always available, and Samsung seem to overlooked  the fact that we sometimes visit the countryside and so 2g data needs to work too.   In GPRS-only locations where many other phones, from a ten year old Motorola flip to a modern iPhone all work perfectly, the Samsung just sits there, flashing its activity indicators for an eternity, but hardly ever actually completes the task.
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guest

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #23 on: June 25, 2014, 06:15:35 PM »

I have no idea how you tell. If there is anything which does indicate what radio you're connected to then I'm buggered if I can find it :)

The only way I can tell is from the access point which tells me which clients are connected to each radio.

Edit - oh & I have an ancient INQ phone which isn't remotely "smart" but does keep working for several days without charge so can't help with the Samsung phone issue. Daughter has one but try taking "her precious" away to play with :D
« Last Edit: June 25, 2014, 06:18:36 PM by rizla »
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sevenlayermuddle

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #24 on: June 25, 2014, 06:28:07 PM »

I already thought of another way.   The Billion supports multiple virtual lans, each of which has its own subnet and DHCP pool.  If I put the two WiFi bands on different vlans, but with same SSID, I can then tell which one it has conneted from the assigned DHCP address :graduate:

Or I could do it your way, which sounds less bother :D

But it's going to have to wait probably  tomorrow, will report back.   I'll be trying my iDevices too as it's an interesting excercise.
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guest

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #25 on: June 26, 2014, 11:39:32 AM »

The problem for me is that I can't really use multiple SSIDs as I want to use zero handoff* which requires a single SSID (and channel) across multiple APs. That way you don't end up with time-critical stuff like audio/video stuttering (or failing) when you roam around - I'm thinking basically inside/outside scenario where you will lose 5GHz connectivity fast unless there's an outside AP. The future seems to be more wireless devices whether I like it or not ;)

Fortunately I can force clients to use a specific radio from the APs but I'm not 100% convinced that won't bugger up zero handoff in certain scenarios on the 5GHz band. I suspect I'm going to end up editing some of the files in /system/etc/wifi on the Android kit eventually, which isn't exactly an elegant solution.

* http://community.ubnt.com/t5/UniFi-Frequently-Asked-Questions/UniFi-What-is-Zero-Handoff/ta-p/412719 & a "frendlier version" http://www.lansor-it-services.com/wi-fi/ubiquiti-zero-handoff-seamless-roaming/ Somewhat amazingly (to me anyway) it actually works :)
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sevenlayermuddle

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #26 on: June 26, 2014, 12:04:30 PM »

Well mine was a useless endeavour, my Samsung (Fame) doesn't even see the 5GHz network, it doesn't seem to be supported! :blush:

Same for 4th generation iPod touch, 5Gz apparently not implemented.

iPad 2 and latest iPad mini, both work on 2.4GHz as well as 5GHz,  and generally seem to have a predilection for 2.4, given the choice.  It is vague though, at least once the iPad 2 chose 5GHz when 2.4 was available too, not sure what was different.  I wonder if recent history of connections may play a part in choice of networks?

The Mac Mini actually seems to prefer 5GHz when it has a free choice, but doesn't seem to cope too well when I disable the connected signal, one on occasion it went into a strop that lasted several minutes, timing out on every attempt to register.  Then it suddenly worked again, after fiddling with various things that shouldn't have had any effect.
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guest

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #27 on: June 26, 2014, 12:46:19 PM »

What are you blushing for? My mobile doesn't have wireless at all :D
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Chrysalis

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #28 on: June 28, 2014, 03:00:18 AM »

I am not that surprised by kitz results.

Few thigns to consider.

First how good the wireless devices are.  e.g. if a 2.4ghz device can only do max 72mbps anyway due to the hardware, and 2.4ghz is running well, then 5ghz may well be slower.

My galaxy s3 can currently comfortably run faster on 5ghz than 2.4ghz I say 'currently' because on a different firmware it ran like rubbish due to some kind of bug in the android 4.1.x on that phone.  Since 5ghz is less popular that is more prone to bugs/software issues.  The s3 has a 80mhz band capable reciever. It forces itself to 40mhz only mode on 2.4ghz even if the router is configured to allow 80.

My AC dongle which I got from BT when I was trialling for them, is a no brainer, as it will clearly be way faster on 5ghz than 2.4.

I no longer have 5ghz to myself now as well, a VM customer is using it now.  But at least isnt super crowded yet like the 2.4 round here.  However I fear with isps offering dual band routers by default now this situation wont last its only a matter of time and 5ghz has less useable channels than 2.4.  Since alot arent selectable.

Somethign else i discovered.

after I invested in a AC router.  It became apparent so many mainstream devices lag behind on tech.  XBOX360 2.4ghz only, wii-u 2.4ghz only, ps4 2.4ghz only and thats a late 2013 kit, set top boxes, 2.4ghz only.  Also most of these devices listed are 40mhz wide max so 72mbps max on N.

Apart from cutting edge android phones and wifi dongles what has AC?
« Last Edit: June 28, 2014, 03:06:00 AM by Chrysalis »
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Mardler

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Re: Wireless 5GHz - v- 2.4GHz
« Reply #29 on: April 24, 2017, 07:30:50 PM »

Just found this a bit late whilst looking for something else.

I, too, have a 7800DXL and just found an annoying fault: 2.4 band wifi only uses channels 5 to 13 (the manual, equally daftly, says 1-7 only).

Have I missed something or is this an utterly silly problem?
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