Community discussions

MikroTik App
 
Roger
just joined
Topic Author
Posts: 20
Joined: Sat Jul 03, 2004 1:58 pm

Multiple AP's and fast moving clients/cars

Tue Dec 04, 2007 12:23 am

Hi,

We're thinking about setting up a wireless network (probably at 5 GHz) with approx. 10 AP's around a race-track. We'll use/place several clients inside race-cars and we'll use the (IP) connection to broadcast MPEG4 encoded video from within the car. For the whole (wireless) network (AP's and clients) we would like to use Mikrotik.

We have done some testing with a 3 AP setup and this worked more or less, but we do have a problem with roaming. Unfortunately the client stays too long connected with an AP. So when the client is connected to AP1 and when the client is already receiving the (much) stronger signal of AP2 it still stays connected to AP1. The same happens when connected to AP2 and AP3. When the client stays too long connected at the end the bandwidth drops way too much to keep a stable signal.

So ... is there a way (I have not found it yet) to setup a sort of client threshold or is there a way to push a client of an AP at a certain level? Or has anyone else maybe a better idea .... any help would be appreciated!

Thanks!

Roger
 
User avatar
Letni
Member
Member
Posts: 375
Joined: Tue Dec 05, 2006 5:16 am
Location: South Carolina

Re: Multiple AP's and fast moving clients/cars

Tue Dec 04, 2007 2:20 am

I have not done this before but have heard of it being done.
Try adding the MAC to the Connect List. Then you should be able to specify the Min Signal Strength. That way you can force them to be dropped off at set level.

-Louis
 
uldis
MikroTik Support
MikroTik Support
Posts: 3439
Joined: Mon May 31, 2004 2:55 pm

Re: Multiple AP's and fast moving clients/cars

Tue Dec 04, 2007 10:08 am

in the car, setup the router to use WDS and enable RSTP bridging on all the router.
 
0ldman
Forum Guru
Forum Guru
Posts: 1447
Joined: Thu Jul 27, 2006 5:01 am

Re: Multiple AP's and fast moving clients/cars

Tue Dec 04, 2007 11:31 am

In roaming with Windows clients, set a static IP on the client as well. I've had seemless roaming with XP only with a static IP. I can't say for MT ROS as a client, but the DHCP request and renew causes the connection to drop in XP for a second, long enough that you notice it. I tested playing an MP3 from my file server and it didn't skip with a static, it completely freaked out without.
 
Roger
just joined
Topic Author
Posts: 20
Joined: Sat Jul 03, 2004 1:58 pm

Re: Multiple AP's and fast moving clients/cars

Tue Dec 04, 2007 1:54 pm

@Letni: thanks for the tip, we'll try this!

@Uldis: why using WDS? I forgot to mention that all the AP's will be connected to a wired (fiber) LAN, so if I'm not wrong there is no need to use WDS!?

@Oldman: all the clients will have a static IP to overcome the DHCP request time-out.

Thanks!
 
uldis
MikroTik Support
MikroTik Support
Posts: 3439
Joined: Mon May 31, 2004 2:55 pm

Re: Multiple AP's and fast moving clients/cars

Tue Dec 04, 2007 2:27 pm

What you will use on the client side, RouterOS?
WDS is for the communication between the cars wireless client and the rest of the APs - it will roam between the APs faster as it will already have connection to the other APs.
 
Roger
just joined
Topic Author
Posts: 20
Joined: Sat Jul 03, 2004 1:58 pm

Re: Multiple AP's and fast moving clients/cars

Tue Dec 04, 2007 4:01 pm

The plan is to use Mikrotik hardware with RouterOS.

Would enabling WDS also take care of my roaming problem/question?
 
pixitha
newbie
Posts: 27
Joined: Thu Jun 14, 2007 1:52 am

Re: Multiple AP's and fast moving clients/cars

Tue Dec 04, 2007 10:58 pm

I thought one the points of the WDS system (specification) was to make the client only see 1 AP, even though it is actually multiple different access points?

So it only sees 1 AP, but really there are 3 with the same SSID and same channel, therefore allowing the APs to decide the roaming and not the client.

It seems like if the racetrack wasn't too large, it would make more sense to have 1 omni antenna in the center, and do it that way anyhow?

-pix
 
Roger
just joined
Topic Author
Posts: 20
Joined: Sat Jul 03, 2004 1:58 pm

Re: Multiple AP's and fast moving clients/cars

Tue Dec 04, 2007 11:31 pm

The terrain is too large for that and there are too many obstacles (several buildings, fences, etc). The track is 4.3 Km long and is not even completely flat. If it would be possible for sure we had taken the easy approach :)

During and event there is also a lot of 'ether noise', this is also a reason why we'll use 5.x Ghz. There are already more then > 25 2.4 Ghz AP's in the neighboorhood :(
 
User avatar
jp
Long time Member
Long time Member
Posts: 603
Joined: Wed Mar 02, 2005 5:06 am
Location: Maine
Contact:

Re: Multiple AP's and fast moving clients/cars

Wed Dec 05, 2007 3:42 am

Maybe this is a job for a 900mhz system that can roam. If the spectrum is clean in that band, some products like Alvarion BA-II can be configured to hand off roaming very quickly and works at very low signal levels. Not sure it would meet the bandwidth needs though. We use it in police cars locally here for basic data needs.
 
uldis
MikroTik Support
MikroTik Support
Posts: 3439
Joined: Mon May 31, 2004 2:55 pm

Re: Multiple AP's and fast moving clients/cars

Wed Dec 05, 2007 9:59 am

I thought one the points of the WDS system (specification) was to make the client only see 1 AP, even though it is actually multiple different access points?

So it only sees 1 AP, but really there are 3 with the same SSID and same channel, therefore allowing the APs to decide the roaming and not the client.

It seems like if the racetrack wasn't too large, it would make more sense to have 1 omni antenna in the center, and do it that way anyhow?

-pix
there is a feature update for WDS, which you may call WDS MESH, where the AP (in your case racing car - client) creates a WDS link to all the backbone APs that it sees. And then when the car drives and gets worse signal for the AP where it transmits the data, the bridge will recalculate the path cost and will send the data to the AP whichs has better signal/throughput (less cost).
Question is how many cars will have such APs that transmit the data and at what speed and what protocol?
 
Roger
just joined
Topic Author
Posts: 20
Joined: Sat Jul 03, 2004 1:58 pm

Re: Multiple AP's and fast moving clients/cars

Wed Dec 05, 2007 11:46 am

Uldis this sounds interesting!

The maximum amount of clients is not determined yet, because this also depends on the available bandwidth. We probably will start testing with 4 cars and each car should have a > 3 Mbit upload. We have the following streaming options: RTP over UDP *, TCP *, Multicast (* with or without Multicast enabled).

Could we maybe order some pre-configured hardware? I think that would be the fastest and easiest way to go.
 
uldis
MikroTik Support
MikroTik Support
Posts: 3439
Joined: Mon May 31, 2004 2:55 pm

Re: Multiple AP's and fast moving clients/cars

Fri Dec 07, 2007 4:35 pm

we are not offereing preconfigured routers. But you can contact one of the MikroTik Certified Consultan, that could help you to configure that for you. Or maybe someone from here (forum), could help you.

In case of multicast and bridging you should use bridge firewall filtering that the communication is only one way - from the cars to the APs, so that multicast traffic is not sent back to the other cars.
 
rarbolay
Frequent Visitor
Frequent Visitor
Posts: 99
Joined: Mon Aug 20, 2007 6:36 pm

Re: Multiple AP's and fast moving clients/cars

Wed Dec 12, 2007 4:19 pm

Uldis, that sounds like a very interesting solution. So you would set the APs on AP mode with Dynamic WDS and the cars on station mode dynamic wds?
 
uldis
MikroTik Support
MikroTik Support
Posts: 3439
Joined: Mon May 31, 2004 2:55 pm

Re: Multiple AP's and fast moving clients/cars

Wed Dec 12, 2007 4:31 pm

I already sent direct mail to Rogers from support. Maybe he can share this info here what I sent.
Instead of dynamic-wds (mesh) I recommend to use static-wds (mesh) as you will have all configured.
And on the car the router will be also running AP mode and transmit the date throgh the lowest cot bridge port (wds interface).
 
Roger
just joined
Topic Author
Posts: 20
Joined: Sat Jul 03, 2004 1:58 pm

Re: Multiple AP's and fast moving clients/cars

Fri Dec 14, 2007 12:00 pm

This is what I received from Uldis:
-----
Please take a look at the configuration of your network. I think it should be like that. You have one gateway with ethernet network where you have all the APs attached to it. Each AP is running the same SSID on the same freqeuncy. The APs should have RouterOSv3.0 intalled and it should have wds-mode=static-mesh configured. Then you should add static wds interfaces which will contain all clients mac address. Then you should create a bridge interface on all the APs and set it to rstp protocol mode. After that modify the APs wireless configuration - set the WDS-default-bridge=bridge1 (the bridge that you just created). On the Client AP (car) you should have the same wireless configuration (SSID,frequency,WDS configuration). On the clients APs add the WDS interfaces (all the backbones APs MAC address). Then create a bridge interface with rstp enabled and specify the wireless to use it as wds-default-bridge. On the Gateway router you should specify the bridge priority lower - so it would become a root-bridge. Also note that you should add ethernet interfaces to the bridge you can connect your network device. If you will send multicast traffic then I recommend you to add bridge firewall rules that doesn't send the multicast traffic from client1 to client2, so only communication would be from client1 to gateway. This is all the info you need for the start. After that you can tune the network.
-----

I think this could be a interesting setup, the only problem I for see is the use (and interference) of using one frequency for all the AP's (alongside the track and in the car). Most of the AP's will "see/hear" the others ... Anyone having experience with the amount of AP's (> 30) and using the same frequency on a terrain of approx. 1500x1500 m?

Roger
You do not have the required permissions to view the files attached to this post.
 
uldis
MikroTik Support
MikroTik Support
Posts: 3439
Joined: Mon May 31, 2004 2:55 pm

Re: Multiple AP's and fast moving clients/cars

Fri Dec 14, 2007 12:16 pm

also another update to this setup is if you have lot of APs in that area and you have good antennas on the cars, you can use 2 or 3 frequncies - divide all the racing cars in 2 or 3 (each group will use one specific frequency). In such case you will have 2 or 3 mesh networks.
 
andreacoppini
Trainer
Trainer
Posts: 489
Joined: Wed Apr 13, 2005 11:51 pm
Location: Malta, Europe

Re: Multiple AP's and fast moving clients/cars

Fri Dec 28, 2007 2:11 pm

I think this could be a interesting setup, the only problem I for see is the use (and interference) of using one frequency for all the AP's (alongside the track and in the car). Most of the AP's will "see/hear" the others ... Anyone having experience with the amount of AP's (> 30) and using the same frequency on a terrain of approx. 1500x1500 m?

Roger
wouldn't wds-slave on the clients solve that issue by following the AP's frequency? pick 3 frequencies and put them in the scan list and set the APs on one of those 3 channels.

One issue you need to consider is the doppler effect. How fast will the cars be driving at?
- No strings attached -

<< Please give good Karma if this post helped you. Press the + button above the Location entry
 
Roger
just joined
Topic Author
Posts: 20
Joined: Sat Jul 03, 2004 1:58 pm

Re: Multiple AP's and fast moving clients/cars

Tue Mar 04, 2008 12:08 am

Speed is approx between 100 - 200 kmh

Can be seen here: http://www.youtube.com/watch?v=-Mvdy7IYpbE :)
 
andreacoppini
Trainer
Trainer
Posts: 489
Joined: Wed Apr 13, 2005 11:51 pm
Location: Malta, Europe

Re: Multiple AP's and fast moving clients/cars

Tue Mar 04, 2008 2:17 am

Speed is approx between 100 - 200 kmh

Can be seen here: http://www.youtube.com/watch?v=-Mvdy7IYpbE :)
Hey Roger, looks like a finely tuned setup you've got there, didn't miss a frame!
Well done... care to share your setup?
- No strings attached -

<< Please give good Karma if this post helped you. Press the + button above the Location entry
 
Roger
just joined
Topic Author
Posts: 20
Joined: Sat Jul 03, 2004 1:58 pm

Re: Multiple AP's and fast moving clients/cars

Tue Mar 04, 2008 12:14 pm

I wish that this (already) was true :) ... I think this clip has been made with a onboard recording camera.
Tomorrow well will start some testing, but I'm still not sure which setup would be the best to use :?

So any help/suggestions is appreciated much!!

Thanks,

Roger
 
netrat
Member
Member
Posts: 403
Joined: Thu Jun 07, 2007 1:16 pm
Location: Virginia

Re: Multiple AP's and fast moving clients/cars

Wed Mar 05, 2008 6:50 am

Roger,

This is a very interesting project and I might be doing something similar at my local race track. Would you mind sharing what camera you are using and the telemetry software? I'm looking for some telemetry software to use over the wireless network.
 
Roger
just joined
Topic Author
Posts: 20
Joined: Sat Jul 03, 2004 1:58 pm

Re: Multiple AP's and fast moving clients/cars

Wed Mar 05, 2008 11:15 pm

@netrat: At this moment we test with Acti MPEG4 video encoders/decoders. Telemetry is not yet used, but will be the next (logical) step.

We tried today a small setup with two AP's (both with same SSID and different freq.). We tried the suggested AP-bridge / wds-slave setup (added just two freq. in the client scan-list), but this failed more or less because the client stays way too long connected to the first AP (until -90 or so), before it disconnects and then connects to the already much stronger second AP.

We also tried the "Signal Strength Range", even set it to: -60..120, but this did not disconnected the client from the AP at that level, but maybe this feature should be used differently?!

Next thing will be testing the suggested mesh setup, but I'm still not sure that’s the way to go because of the total amount of AP's we'll use.

(No) other suggestions?

Roger
 
uldis
MikroTik Support
MikroTik Support
Posts: 3439
Joined: Mon May 31, 2004 2:55 pm

Re: Multiple AP's and fast moving clients/cars

Thu Mar 06, 2008 5:21 pm

WDS-slave or station-wds mode on the RouterOS will not help you as the roaming to the new AP will not be so fast as you need.
Try using Mesh mode using WDS.
 
jusvir
just joined
Posts: 3
Joined: Fri Feb 24, 2012 12:27 pm

Re: Multiple AP's and fast moving clients/cars

Fri Feb 24, 2012 12:39 pm

Hi there!

Anything new concerning fast moving objects and mikrotik AP's?

I'm going to build about samekind of setup and I'm thinking to use mesh with that. For example three AP's that are bridged together with two 5GHz antennas each (mesh) and then three 2.4 GHz antennas pointing to track. Idea is that anykind of wifi -camera would be possible to put in a car and get videostream straght from it to the pit (yeah, sounds too easy and simple :). is it possible to make one virtual SSID with same channel and same MAC so that client (cam) don't have to change anything. It just streams...?

Since last post in this topic was about 4 years ago, there has been lots of new features and hopefully someone has tried and managed to do something useful. So I don't have to bang my head to wall and try everything by myself :lol:

Thanks!

Who is online

Users browsing this forum: Bing [Bot], tataram and 41 guests