Re: Marriott wifi blocking

[Owen DeLong <owen () delong com>]

On Oct 6, 2014, at 11:53 AM, Clay Fiske <clay () bloomcounty org> wrote:

> On Oct 6, 2014, at 8:41 AM, Owen DeLong <owen () delong com> wrote:
>
> > Actually, in multiple situations, the FCC has stated that you are responsible
> > when deploying a new unlicensed transmitter to insure that it is deployed in
> > such a way that it will not cause harmful interference to existing operations.
>
> I recognize that you were making this statement in the context of colliding SSIDs, but to me this could be an 
> interesting point in another way.
>
> Suppose from Marriott’s perspective that your personal wifi network is interfering with the throughput of their 
> existing network. After all, if you fire up your personal AP, with a non-colliding SSID, and start downloading 
> multi-GB files, that’s bound to impact[1] anything else using that channel. While there are at least a few 
> non-overlapping channels on most wifi networks, if Marriott(’s third party network operators) had any sense they 
> likely would have situated their APs and channels to provide the most range with the least amount of frequency 
> overlap. Now here your personal AP on one of those channels consuming enough of its bandwidth to significantly 
> degrade performance for anyone else, and they may not have access to (or usable signal strength or bandwidth on) 
> another channel from their hotel room.

The FCC has specifically stated that sharing of the spectrum bandwidth in this manner is not considered “harmful 
interference” in at least a few rulings. This is the “normal and expected result of deployment of multiple networks 
onto limited spectrum”.

> During a big convention for example, the hotel network is probably at its busiest while the number of guests using 
> personal APs is likely also at its peak. This may be a stickier case, as no one user is causing the issue but one 
> could make the case that, in aggregate, they are very much interfering with existing operations.

Yes, but not in a manner the FCC fits into the definition of “harmful interference” under 15.3 and/or 15.5.

> There are probably a couple of different angles to consider, but I’m thinking in terms of the “first come, first 
> served” concept. At what point is the extra bandwidth consumed by your personal wifi network considered to be 
> harmfully interfering with an existing network?

It isn’t (unless you run afoul of 47CFR333 and are consuming bandwidth for the sole purpose of denying it to others).

> FWIW I am not defending Marriott’s actions, nor even positing that this was the reason for them. I just want to gain 
> understanding.

Yep. Understood. Hope the above helps.

> -c
>
> [1] This is of course assuming you’re getting decent throughput from your 3G/4G provider’s network. But even though 
> it’s almost certainly slower than wifi it’s probably generating enough packets in a collision-based medium to impact 
> other flows.

Actually, I usually get better 4G service on my LTE devices than I get from most hotel WiFi networks. It’s one of the 
reasons I wish Apple would let me choose the interface preference order rather than locking me to “if Wifi is on and 
can find an AP, then I won’t use LTE”.

Owen