Hello,


we recently mounted a wireless network with a lot of APs in a very big and in-movement site. Lots of trucks and machines moving. It's a container terminal were my customer handle a massive volume of containers. You can see a panorama here:

As we installed 15 APs with 2 radios to serve 8 Futurepad I think the number of antennas is OK. We are using 2.4GHz, 14dBi pannels and 120 degree sectors, depending on the site of coverage. The APs are installed at 25 meters height and the antennas are pointing to the floor.

The futurepads has 2 or 3 diferent versions, but the one I opened has a CM9 on it. We have to use 2.4GHz freq for this. We have 2 more APs working with 5GHz for big machines that are statically working during the day.

If we are walking around ALL the container terminal, in and out of container stacks, across the streets, from right to left, with our DELL Latitude 630, we have no problems and the roaming is very good. We always can ping the server without problems and we can see that the laptop is doing roaming very good (when the ping grows and you lose a packet or two).

The problem comes with the Futurepads. I'm sure the futurepads are doing roaming diferently. This embedded windows machine is waiting to make roaming till the connection is lost or is very bad (I can see signals of -9x) and the machine stays there.. The problem is that a machine connects to the AP1 with -50 of signal and stays there till -9x signal. You can stay in from of AP2 and receiving -60 signal, but the AP1 still being the connected AP.
If you disconnect the wireless and reconnect it, then it connects to AP2, of course.

We noticed that the wireless software has 5 types of roaming to configure (very low, low, normal, agressive and extreme), but we tryed many and it works same xD

We tryed to configure signal level in the APs, but.. once you are conected there with a good signal, the AP don't drop you when you reach the limit.. then, the AP only limits the connection if you try to connect to it with a bad signal.
We tried to reduce power from the APs, but it's the same.

Why the laptop is working well and the futurepads aren't? Can we try something else to fix this issue? The problem is when the ping goes to 50-100-150-200 ms and the futurepad stay connected, the program server drops the machine and you have to reconnect to the program and people that is working with the futurepads has to make his work very fast, because are very busy...


Thanks!

You could set rules in the Connect/Access lists on the APs to force roaming if signal level goes lower than a predetermined value.

This will cause the Units to re-associate, but adversely, if signal is low, and no other AP is available, they will have no network coverage.

Do the future pads have a firmware update, or something that could help with the roaming settings not working?

Unfortunately you seemed to have bumped into two common issues faced in such environments:

1) The Futurepads use an embedded OS with bad quality drivers. The wireless hardware/software was built to simply connect to a WiFi AP. On the contrary, your laptop uses mature hardware (Intel?) and software (Windows) which are designed to roam frequently in a corporate environment. We have seen this with many embedded devices. You usually have better luck with devices designed for mobile voice/video as these are designed to roam smoothly.

2) There is no IAPP support in MikroTik. RouterOS was never designed to support mobile 802.11 clients. It works fine if you use Mesh, but that is limited to MikroTik APs and MikroTik stations. Take a look at http://features.techworld.com/mobile-wi ... he-basics/ for an overview of what roaming involves.

Finally, the rule of thumb is that roaming in WiFi is client-initiated. The 802.11 standards do not have any means to force a client to roam to another AP, it is always the client that initiates the roam. Protocols like IAPP and Cisco's CCX help, but it's still up to the client when to roam and which AP to roam to.

In other words, sorry to say, but you did not design your network with your clients in mind. You will need to work with the Futurepads manufacturer to improve their roaming algorithms.

Andrea! Nice to read you!!

These futurepads have CM9 built in. One older futurepad has Intel card.. this one is working terrible!

I dont have any issues with my laptop(XP with intel abgn card). My laptop is working well with the roaming. The movement is at 5km/h.. People walking.

I recomended my cusromer to update drivers of winxp, but they said that this embedded windows sucks, because it's hard to reconfigure the drivers.

I reinstalled all the network, because another company installed all at 60m height and nothing worked never.. Then.. "my" problem is that the futurepads was there when we started x(.

Thanks for the nice post Andrea ; )

Hi Martin,

How about a script running each 10 seconds that would get all the wireless clients connected, and those with bad signal disconnect them?

This could be a little help to solve your access-list problem.

Best regards,

Hi,

you could write a sctipt that disconnects clients with signal lower than -8XdBm. The
script should be run onec a minute. If you have clients that move fast around the WiFi area
you should set the time for the script run to less then one minute.

Regards,
Christian

Hi,

Sorry for opening this old thread, but I have a similar project and your advice would be grateful.

I have to add wifi coverage to a small container area. I am thinking of installing several 30 meter pillars to also go over some container cranes. I plan to add 2 lanes of pillars, spaced 100 meters apart, 30 meters height.

I was thinking to use 2.4 GHz radio, as coverage seems to be better, despite interference in the 2GHz band.
This seems ok, from my point of view, to install on the pillars: http://routerboard.com/RB912UAG-2HPnD-OUT
For the roaming clients, I plan to go with the http://routerboard.com/RBGrooveA-52HPn

Any advice some of you, more experienced, can give about this setup?

Thank you!

Container terminal has bucketloads of reflections. More coverage = more reflections. You don't want a lot of coverage. Use 5ghz

Mikrotik as a station uses break-before-make roaming. In other words it's the worst roamer you can have. Look for client devices designed specifically for roaming.

Hi andreacoppini, thanks for your answer!

I am aware of the reflection problem, and I will go for 5GHz like you sugested. I`ve been using Mikrotik for quite a while and I really like the hardware + software, so I would like to use this vendor for the whole solution, if possible.

About the roaming issue, all clients will be behind a CPE device, so I am also thinking to put AP`s on the terminal fence, about 6 meter high to radiate between lanes of containers. There are 5 lanes of containers 600 meters long, so I am thinking about 6 AP`s (QRT 5 ac) and GrooveA 52HPn for CPE, on the client side.

For the roaming issue, I can use a config script on CAPsMan to kick clients with low signal, thus force the CPE to search for a better AP:
/caps-man access-list
add action=accept interface=all signal-range=-80..120
add action=reject interface=all signal-range=-120..-81

I think in these kind of setups there is also a lot of trial and error and testing on site, after deploying.

Kind regards.

You're right, there will be lots of trial and error, but others have tried before you and they have error'd more than trial'd.

What application will you be running? In my experience, container terminals normally use old console-based applications which are crudely transplanted to telnet which is very intolerant of jitter, let alone the 3-4 seconds of packet loss while roaming with MT. The net effect will be an unresponsive application (operator pushes 'load' but nothing happens, because the client is roaming and the 'load' packet got dropped).

If you want to stick to MT, the best way you can make this happen is to use WDS and Mesh. This requires all your APs to be running on the same channel, but at least your clients will be connected to all APs within range. This is the closest you will get to make-before-break roaming and is the fastest roam you will get, but you will have to contend with having all your APs on one channel.

Since these are moving vehicles in a highly reflective environment, you may wish to use a 2x2 device such as an OmniTik which will give you a degree of radio diversity. A 1x1 like Groove in such an environment has a great chance of the antenna being in null spots.

Hi andreacoppini,

It is not a console based application, it`s more modern, running on Win CE, socket based. I should probably check how tolerant is to jitter and packet loss. For console-based there is narrowband hardware.
Thanks for the OmniTik suggestion, I think this is better for the client end point on the trucks.

But in any case, from the above discussion I should probably check some other vendors that implement 802.11r, or some sort of hand-off protocol.