WIFI problem at Bridge club

[think2]

There's an interesting article here about them
review
It looks like the controller software can show percentage of dropped packets sent and dropped packets received.

Here's a link to some screenshots of the wifi db levels

wifi db levels

Channels 6 and 11 are our two access points. There's two 5 GHz channels as well which we're not using. p9.png was directly underneath channel 11 access point. p8.png is directly under channel 6.
Do these db levels look reasonable? There's a ton of extraneous 2.4 GHz signals coming into the building, including one on channel six at -59 db.

 

[mxnerd]

Signal level looks good, with few clients. You should check the signal level when the club is full of people.

Besides, do you know if bridge players brought their own smartphones/tablets and connected to the AP for internet access watching Youtube things like that bogged down the bandwidth?

Maybe you should consider whitelisting the tablets using MAC addresses and block others.

 

[think2]

Thanks. I doubt if any members have the wifi password but I will check. Lots of people have phones though so maybe we should ask them all to power off or switch to airplane mode. Someone from another club told me that disconnecting their server from the internet while a session was in progress helped them. A couple of weeks ago, we turned off auto updating on all the tablets, but they weren't actually auto updating for some reason and the problem has got worse since we did that.

I'd like to try and see how much packet loss we're getting. Do you know of any suitable software we could install on some of the tablets that would let us do some tests?

Also, is changing to use two different SSIDs the best way of forcing a tablet to use the access point that is physically nearest to it?

 

[mxnerd]

Prohibit internet access during a session definitely an option.

Generic ping tool is the only tool that I know can test dropped packets. There should be better tools, but I'm not familiar with them.

Use 2 different SSIDs of course can help forcing which AP the tablets can connect to using whitelist, but why not try the load balancing feature first?

 

[JackMDS]

Ask all of them (as a try) to switch the WIFI off in their phones setting.

 

[teejee]

Forget about seamless roaming, it is not relevant to your issues.

Do you have coverage in the whole area with one AP? In that case do like this:
1. use in total 3 AP's and make sure they are placed so each of them cover the whole area
2. Assign them to channel 1, 6 and 11 respectively , 20Mhz channel width and different SSID (wifi network names)
3. Connect 1/3 of the tablets to each AP

You can of course start by testing with two AP's instead of 3.

 

[think2]

Unbeknown to me, the club put in a third access point yesterday. The clubrooms are a "U shape" so they can't all cover the whole area - but they're all on the same SSID. I do not know how the tablets will pick a channel as all three signals are strong. For some reason, last night there were virtually no problems with getting information to the tablets, yet on two nights a few days ago, almost every tablet in the half of the room that I play in had issues. It was reported to me that the other end of the playing area had no problems on those nights. If it's interference, how could there be such big changes in behaviour. I ran ncx network express checker on one of the tablets last night, repeatedly for an hour or so and it reported zero packet loss every single time I ran it. Yesterday was a colder day than we've been having.

 

[JackMDS]

If a Real Roaming hardware/Software is Not used.

The best practice is to use different SSID names and one password for the whole Wireless systems.

By doing so the users can choose the best signal for their device.

 

[think2]

We don't want users to have to choose the best signal. I've confirmed that the tablets are automatically switching channel when needed however most of them get a strong signal (less than -50dbm) from all three access points and the access points support 200 clients. We have typically 25 to 45 tables/ tablets.

The problem manifests itself in more than one way. On some nights there's only a small number of problems but the characteristic is that if the feedback fails, no matter how many times you retry, it never succeeds until you turn the wifi off and on. This is different to what I saw two weeks ago when just about every tablet had trouble getting feedback all night long but it usually came through on the second attempt. This seems to me more like a software bug than an interference problem. How could it go from almost no interference on one night to almost saturation interference at one end of the building only on another night. The access points had new firmware put in them a couple of weeks ago. The tablets, Lenovo TB3 710F, have a range of firmware from S0000020 to S0000028.

I'm not in charge of investigating this problem. If I were, we would be monitoring the percentage of dropped packets reported by the access points.

 

[mxnerd]

Well, I have a tablet that will never reconnect to my wifi router once it lost the connection. I always have to reconnect manually or disable and re-enable the wifi on the tablet to reconnet. Sometimes I even have to re-enter the password.

In the past, wired ethernet was always the first option to get network access, nowadays wifi becomes the first option.

All I can say is wifi is really unreliable in its nature, there is no way to get around it.

It's the same reason people get cable TV instead broadcast TV.

 

[jk20]

Hi, we have exactly the same problem at out club. We have lots of tablets and two Ubiquiti access points, but I don't think it's the Wifi, or interference. (Have investigated *extensively*) When the failed to receive feedback happens it happens for a long time. If it were interference you would expect the 2nd or 3rd retry to work, but it doesn't. And here's the thing, if at that time you just switch to a web browser instead you can surf the net fine! So the network must be working. HOWEVER, if you turn the WiFi off and on again (or switch to airplane mode and back again) then the receive feedback immediately works!

Maybe there's a fault in the bridgetab software (some table getting full or something) and resetting the wifi connection causes the bridgetab software to loop back to a point where it rebuilds its tables and recovers???

JK

 

[think2]

Hi
Whereabouts are you? I'm in Christchurch New Zealand?
What kind of tablets do you have?

 

[jk20]

Uh, same club.

 

[think2]

There's a club in Auckland with the exact same problem - same access points and same tablets. However they're not surrounded by townhouses like we are but there's lots of sources for Wifi interference. It's possible that web browsing works because it uses TCP. I'm guessing the BridgeTab software uses UDP (Unreliable Data Protocol), however for 802.11, the MAC layer does retransmissions and I don't think the MAC layer will have any clue whether it's TCP or UDP.

I think the club should do the following
1. Get better data by having a small notebook at each table for players to write down at the end of the session, how many feedback problems or lead inconsistent with deal problems they saw, plus tablet number and date.
2. Monitor the dropped packet counter info and logs in the access points - it shows both receive and transmit failures.
3. Pay the small support fee and get the software maker to help.
4. Run wireshark / tcpdump/ windump to capture the transactions occurring when the feedback fails. Even though we won't be able to decode the content, we could compare with a successful transaction. There should be very little traffic going to/ from the tablets.

I think there's more than one failure mode though, because very occasionally, almost every tablet has a problem for the whole night and turning wifi off and on doesn't help. This looked like genuine interference.

 

[mxnerd]

Application layer software usually don't care how data is transmitted using TCP or UDP. Mostly likely it will be TCP.

I suspect whether the problem is caused by tablet's power saving feature being turned on while data is being transmitted back?

Definitely will help if you can get support from software developer.

 

[think2]

It seems that the problem is caused by the software in the tablet that is timing out too quickly (2 seconds). For some reason the software on the scoring / server machine is slow to respond so the tablet reports "no response - click retry". If you hit retry, the tablet opens another TCP connection and sends the data again. There's a chance that this could result in overlapping TCP connections with the same IP / port pairs causing the tablet software to be unable to open another TCP connection until the wifi is turned off and on or the socket times out.

 

[mxnerd]

You might want to join the forum below and ask question there.

https://www.ebu.co.uk/forum/discussion/265/bridgetabs

by user rosss

Bridgetabs are more difficult to handle than Bridgemates or Bridgepads because it has more facilities and importantly relies on a connection via a router rather than a wireless connection. Setting up the link between the tablet and the router can be difficult especially when you are in an environment where there are many routers.
The method we have used is to have a private network with the link to the internet being cut off during an event.

 

[think2]

Thanks. Didn't know about that forum.

 

[Hayseed2]

Hi, we have exactly the same problem at out club. We have lots of tablets and two Ubiquiti access points, but I don't think it's the Wifi, or interference. (Have investigated *extensively*) When the failed to receive feedback happens it happens for a long time. If it were interference you would expect the 2nd or 3rd retry to work, but it doesn't. And here's the thing, if at that time you just switch to a web browser instead you can surf the net fine! So the network must be working. HOWEVER, if you turn the WiFi off and on again (or switch to airplane mode and back again) then the receive feedback immediately works!

Maybe there's a fault in the bridgetab software (some table getting full or something) and resetting the wifi connection causes the bridgetab software to loop back to a point where it rebuilds its tables and recovers???

JK

Hi. Did you get a solution? I am from the the Motueka Bridge Club with recently installed BridgeTabs.

 

[think2]

Hi. Did you get a solution? I am from the the Motueka Bridge Club with recently installed BridgeTabs.

yes we did, contact the chch club or bridgenz

https://www.chchbridge.co.nz/contact