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mushmx
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point - multipoint link WDS trouble

Fri Aug 01, 2008 1:09 am

Hi

My case is that I have a point to multipoint link with WDS for 6 IP Camara and I have the next equipment:

Control Center
1 MKT 532 like AP Bridge with 2 sectors 5.8ghz (sector1 with 90° and 14dbis) and (sector2 with 90° and 14dbis)

Remote Point Client "Camara IP Street"
a)1 mkt 522 (13km distance) and connect to sector1
b)1 mkt 522 (7km distance) and connect to sector1
c)1 mkt 522 (3km distance) and connect to sector1
d)1 mkt 522 (1.6km distance) and connect to sector1
e)1 mkt 522 (1.4km distance) and connect to sector1
f)1 mkt 522 (3.2km distance) and connect to sector2

All mkt 522 have a IP Camera PTZ to monitoring the traffic, so when I had only the points (a,b and e) the link and camera worked fine without problem but when I did the rest of the links :? the trouble appear and the point A and E sometime the link down and the others camera are with delay video transmission.

A friend told me that the WDS reduce 50% the bandwith and only I can do a 4 link with WDS, is true this?. The point A to E are on the side of sector1 and only the point F is on the side of sector2.

How can I resolve this situation?
Is possible do the multipoint link witouth WDS?

This is very important to me because I want use MKT solution for the Link but other people want motorola.

Best regard.
Last edited by mushmx on Sat Aug 02, 2008 12:37 am, edited 1 time in total.
 
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JJCinAZ
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Re: point - multipoint link WDS trouble

Fri Aug 01, 2008 10:09 pm

WDS on a single radio does reduce bandwidth by 50% on each hop. This is due to the fact that the radios are half-duplex: it has to listen to receive a packet, then turn around and listen to see if it's clear on the channel, then it can finally send the packet on to the next node. You can use a dual radio design 5g/2.4g to help relieve this situation, but remember that the 5g radios are half-duplex as well, so you still have to take this problem into account.

There is no limit of 4 hops on a WDS setup. There are practical limits, but no artificial ones.
 
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mushmx
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Re: point - multipoint link WDS trouble

Sat Aug 02, 2008 1:14 am

Thank's for the reply

I can't use a dual radio because the budget is limited, but I think divide the link connection of the sector1 with only 3 mkt522 and the sector2 add a splitter 5.8ghz and add a sector3 90° with direction to point A and B.

sector1
c)1 mkt 522 (3km distance) and connect to sector1
d)1 mkt 522 (1.6km distance) and connect to sector1
e)1 mkt 522 (1.4km distance) and connect to sector1

sector2 and sector3 with splitter
a)1 mkt 522 (13km distance) and connect to sector3
b)1 mkt 522 (7km distance) and connect to sector3
f)1 mkt 522 (3.2km distance) and connect to sector2

Attach the diagram of the actual link.

Do you think this change help me?
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Re: point - multipoint link WDS trouble

Sun Aug 03, 2008 2:29 am

Well, that does eliminate all the double hops and you can employ NStream to help with latency. However, here are some other points to consider:

1) I don't know your terrain, background noise levels [has anyone done a real RF study?], path calcs, freznel zone interference, or antenna types, so I can't comment on the quality of the links. I would bet the 13km link from a panel to a 90-sector is probably not going to work; at least not at the performance level you might be expecting and/or with the overhead needed to stay up 99.9% of the time.

3) You have not specified the data rates you will need on the links, but if this is a video application, you will need a lot of bandwidth to keep them all streaming at once. It looks like you are streaming 6 cameras off of a single AP radio with a splitter on it. Assuming your video streams need 1Mbps each, you have to maintain a 6Mbps throughput and that's difficult in that setup. Each of your links is probably going to run at different modulation rates and you have some bidirectional traffic to consider. You should setup a lab test with the 6 cameras to see what near-perfect RF conditions can give you. If the cameras will not all be streaming at once, maybe just one or two, then your odds for success go up.

4) Splitters on sector antenna -- I wouldn't use them with any 802.11 based technology. I'd rather purchase another 532 and radio card.

5) You will need physical separation between the AP antennas. Try to get 3 meters if you can, else your setup will look like it works with one or two 522's transmitting, but performance will suffer greatly when all the cameras are trying to stream. This is due to the fact that you cannot synchronize transmits between co-located AP's with Mikrotik.

6) You said other people want to use Motorola, but you didn't specify what Motorola product Mikrotik was going up against. I have a lot of both in the air with all sorts of applications and requirements. They do different things well but you would have to be much more detailed in specifications and requirements to be able to get better feedback from the community.

7) You are using 5.8Ghz, which is fine, but remember that in the time it took me to write this message, how many people in your area might have just plugged in some 5.8Ghz device, increasing your background noise level? Any other organizations in the area with 5.8Ghz in use? You need to factor in something extra in your link budget to account for increasing background noise and such.
 
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mushmx
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Re: point - multipoint link WDS trouble

Sun Aug 03, 2008 7:37 am

Thanks again :D

The terrain in cancun over level sea and no exist mountain only jungle and sea but the link not cross the sea. The control center has a tower of 85mts high and the mkt 532 is mounted at 80mts high and the mkt 522 are mounted over light pole about 8 or 11mts high. We used the option snopper to scan the RF and fortunately isn't saturated.

My principal problem is the link of 13km because is inestable. The point B to E are stable and the video stream is good with a few delay but the point F the video stream is amazing. The camera are PTZ so each one need about 6mb to transmit the video and they can move the camera. Unfortunately I can't do a test of this because all happened one day to the next.The others people want use proxim devices (Tsunami MP.11 5054-R with 36mb 5.8ghz), sorry for say motorola :p

Ups :p I don't have the data right now but the link B to E the TX/RX are between 62/73 with 36/48mb each one aproximatly and are stable, the point A (13km link) the TX/RX is 79/84 and sometimes this data change to 81/86 with 12/18mb and is very inestable all those point are connected to sector1. In the sector2 only the point F is connected with TX/RX with 62/65 and 36/48mb and stable. I don't remember the CCQ and noise data but the next monday I'll check this values.

so I think if I use a splitter in the WLAN2 and add the splitter the connectorA I can put a Antenna Parabolic Dish with 25dbis to connect the point A and in the connectorB of the splitter I can put the sector2 90° 14dbis to connect the point F, and leave only the sector1 with the point B to E

Point A (13km)

mkt 522(22dbis) to antenna dish (25dbis) point to point

The trade mark of the antenna is Smarteq and Svenska Antennspecialisten

Best regard.
 
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Re: point - multipoint link WDS trouble

Sun Aug 03, 2008 6:47 pm

You may need a seperate PTP setup for the 13km link to get it stable and reliable. As for the Tsnuami MP.11 5054-R stuff -- good luck there. I have a crate of those we've pulled out of service from other networks we've acquired. I would sell them to you cheap if you want to try that, but it's in no way better than Mikrotik with Nstream. I used to love the firmware upgrades on the MP.11's because it almost always meant that something was going to get bricked and you would be driving around to all your customers trying to get them back online.
 
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Re: point - multipoint link WDS trouble

Fri Aug 08, 2008 6:49 pm

Thanks for the reply

The solution with splitter is working!!! so now I hope the project is approved.

Best regard

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