LTE-U vs. Wi-Fi: What You Need To Know

[thiggins]

It's time to understand the impact mobile networks may have on 5 GHz Wi-Fi networks from the impending use of LTE-U / LAA.

Read on SmallNetBuilder

 

[digitalfreak]

Great, more congestion. I already see large numbers of wireless routers/APs and DirecTV and Uverse receivers in the 5Ghz band where I live. This is only going to make it worse.

 

[pete y testing]

This is only going to make it worse.

unless you move to the new architecture and employ it instead of using your own home wifi

here in oz we already have the ability to walk in from a cell tower phone connection and then move to a wifi without dropping the call so this may be the next logical step

as long as its standardized and regulated it may one day be the next big thing

 

[sfx2000]

It's time to understand the impact mobile networks may have on 5 GHz Wi-Fi networks from the impending use of LTE-U / LAA.

Nice article - I've been a participant on both sides of the argument wearing my 3GPP/3GPP2 and IEEE hats, and I've been fairly vocal on my thoughts on this topic...

This is truly being rammed down the throat of the community by a coalition of big telco providers and their suppliers under the guise of FCC Part 15 (and similar regulations in other regions).

They're being aided and abetted by a newly compliant FCC chair (Pai) that is business focused on his policy objectives and perspectives, rather than promoting policies favorable for the common good - both business and private.

IMHO - It's a blatant land-grab by incumbent license holders in other bands (Cellular/PCS/AWS) which lays fallow and not utilized fully... Rather than continue to develop and grow things out there - they'd rather move into the ISM/UNII bands, which contributes a massive amount of commercial and personal value for the WiFi people that _are_already_there_ - we can't play in those bands, and now...

(just for perspective - I'm a Ham, and we have rules about what can be done in our bands - yes, as a Part 97, I can do things in ISM/UNII, but not for commercial purposes, just like on the other bands that I'm allowed to use, and even there, I'm not allowed to interfere with other users of the spectrum)

This was not the intent of the ISM/UNII bands - commercial usage - yes, I know that we have carriers already there - with WiFi hotspots and things like Voice over WiFi - it's a thin line, but it's still WiFi, and all stations do try to cooperate there to some degree.

But this is something entirely different - once LTE gets into a UNII channel - it's going to own it - seriously - if someone is in the range of a LTE pico/femto base station operating in the same channel - you're done...

802.11 a/n/ac won't have a chance to break in to an LTE session that's already in play..

I understand the listen before talk aspects of LTE over unlicensed, but what folks are not talking about is the inverse - once LTE is there, WiFi won't transmit because the channel will be continuously busy.

Once that happens - 5GHz will be as hopeless, actually moreso, than what we have with 2.4GHz now...

 

[Fatawan]

Galaxy S8 will be the first to use LTE-U https://www.wirefly.com/blog/news/t...ces-will-be-first-use-carrier-s-lte-u-service

 

[thiggins]

But this is something entirely different - once LTE gets into a UNII channel - it's going to own it - seriously - if someone is in the range of a LTE pico/femto base station operating in the same channel - you're done...

802.11 a/n/ac won't have a chance to break in to an LTE session that's already in play..

I understand the listen before talk aspects of LTE over unlicensed, but what folks are not talking about is the inverse - once LTE is there, WiFi won't transmit because the channel will be continuously busy.

So "Nice article", Tim, but you're wrong, eh?

The Wi-Fi Coexistence test specifically checks to make sure that a Wi-Fi network can be set up when LTE-U is using the channel. It also checks that LTE-U never uses more than 50% of channel capacity.

What did I miss?

 

[sfx2000]

So "Nice article", Tim, but you're wrong, eh?

The Wi-Fi Coexistence test specifically checks to make sure that a Wi-Fi network can be set up when LTE-U is using the channel. It also checks that LTE-U never uses more than 50% of channel capacity.

What did I miss?

Perhaps I was stronger in expressing my opinion, but I'm not saying anyone is "wrong"...

There are still a lot of concerns and issues with that test plan...

 

[thiggins]

Perhaps I was stronger in expressing my opinion, but I'm not saying anyone is "wrong"...
There are still a lot of concerns and issues with that test plan...

I share your concern about the test plan. That's why I went through it and specifically cited what it does and doesn't do.

802.11 a/n/ac won't have a chance to break in to an LTE session that's already in play..

The information I presented said the test plan specifically checks for this. That's where you are saying what I wrote is incorrect.

 

[sfx2000]

The test cases omit certain use cases - and that's the problem with the test plan - and also consider that the primary objective to that test plan is that LTE-U passes, to the financial benefit of the chipset vendors and telcos - not to the end-users presently using WiFi in the UNII bands.

 

[ColinTaylor]

I understand the listen before talk aspects of LTE over unlicensed, but what folks are not talking about is the inverse - once LTE is there, WiFi won't transmit because the channel will be continuously busy.

@sfx2000 @thiggins Please excuse my stupid question but once LTE has "camped" itself on a channel is a Wi-Fi access point even aware of its existence. Or would it simply perceive it as indeterminate background noise and transmit anyway?

 

[sfx2000]

@sfx2000 @thiggins Please excuse my stupid question but once LTE has "camped" itself on a channel is a Wi-Fi access point even be aware of its existence. Or would it simply perceive it as indeterminate background noise and transmit anyway?

Your wifi AP and clients will not know, as they cannot decode LTE...

To WiFi clients and AP's - LTE is noise - and as a result, the noise floor jumps up, and rates go down - the test plan that Tim mentions does not take this in to account here for adjacent networks...

 

[sfx2000]

@thiggins - please don't be a shill for the licensed guys...

We pay rent to use licensed spectrum - the 3G/4G/LTE owners there, and we pay them handsomely for usage of it.

We have our community commons - unlicensed spectrum

The LTE landlords want to use the common unlicensed space for their benefit, and for their customers, at the cost of everyone else...

Tragedy of the Commons

They don't need this spectrum for LTE capacity or speed...

Right or wrong - this is really my argument here.

 

[ColinTaylor]

Your wifi AP and clients will not know, as they cannot decode LTE...

To WiFi clients and AP's - LTE is noise - and as a result, the noise floor jumps up, and rates go down

OK thanks for the clarification, that was my suspicion.

Then again... Say a Wi-Fi AP decides to use a channel(s) that is currently used for LTE regardless (perhaps because the owner set the AP channel manually); wouldn't the LTE's coexistence testing force it to vacate that channel? Just thinking aloud here.

 

[sfx2000]

OK thanks for the clarification, that was my suspicion.

Then again... Say a Wi-Fi AP decides to use a channel(s) that is currently used for LTE regardless (perhaps because the owner set the AP channel manually); wouldn't the LTE's coexistence testing force it to vacate that channel? Just thinking aloud here.

Probably not...

 

[sfx2000]

Right or wrong - this is really my argument here.

@thiggins - I know I've been one of the more vocal opponents here on this issue - heck, I was one the of the first to bring things up as a concern...

I've done the models as a standards engineer for both WiMax and LTE - and as a former Telco guy, made my recommendations, and we deployed services - and there, we did find a way to extend our services over WiFi for Voice and Messaging Services....

But the services we deployed - it was WiFi - not just 5GHz, but also 2.4GHz - and we understood the risks and the uncertainties...

Putting an LTE channel into WiFi space - even with QC's WiFire approach, it's a mess at best... much like it was with the Wimax Example I posted earlier...

 

[thiggins]

OK thanks for the clarification, that was my suspicion.

Then again... Say a Wi-Fi AP decides to use a channel(s) that is currently used for LTE regardless (perhaps because the owner set the AP channel manually); wouldn't the LTE's coexistence testing force it to vacate that channel? Just thinking aloud here.

As I described in the article, Wi-Fi devices can't detect LTE-U or LAA. They operate with different protocols. The equal sharing burden is on the unlicensed LTE equipment.

The LTE-U and LAA channel selection algorithms first try to find an unused channel. If they can't, they then share a used channel, up to a limit of 50%.

 

[thiggins]

SFX: If trying to write an accurate, fact-based article is being a shill, I'm guilty as charged.

Regulations are on the side of anyone who wants to use the unlicensed bands as long as they follow the rules.

The Wi-Fi industry isn't exactly innocent when it comes to hogging bandwidth.
What's worse, a neighbor running a 160 MHz bandwidth Wi-Fi network, eating up every available 5 GHz channel (DFS excluded), or LTE-U sharing one 20 MHz channel?

 

[Razor512]

One thing I feel will happen is, at first there will be some coexistence, but one company will break away and turn it off in order to boost performance, and then the other companies will follow in order to stay competitive.

 

[thiggins]

One thing I feel will happen is, at first there will be some coexistence, but one company will break away and turn it off in order to boost performance, and then the other companies will follow in order to stay competitive.

Anything is possible. But there will plenty of Wi-Fi companies watching and testing for this.

 

[sfx2000]

What's worse, a neighbor running a 160 MHz bandwidth Wi-Fi network, eating up every available 5 GHz channel (DFS excluded), or LTE-U sharing one 20 MHz channel?

That LTE channel...

The person use that 160MHz 11ac channel(s) - 802.11ac has ways to deal with that one in the WiFi context...

That LTE channel will preclude even trying to do 160 (flat) or 80+80 as it will be a strong noise source in that candidate channel...

Also note that while 5GHz is far and wide - LTE has to play the same game as WiFi for DFS - which means that it's gonna get pretty tight.

I'll also follow up in that LTE-U - it's not a level playing field - most folks have to play Part 15 - not necessarily the case with LTE-U, there's a loophole that allows a lot more power there...

If I have said it enough - I'll go on record here...

LTE-U, Multifire, whatever - not good for WiFi, not good for customers...