Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Need to transmit video by wireless

Status
Not open for further replies.
V

vdharan

Junior Member level 3
Joined
Apr 18, 2005
Messages
28
Helped
3
Reputation
6
Reaction score
0
Trophy points
1,281
Activity points
1,613
transmit analog video signal wireless

Hello,
I have a requirement to transmit the output of a CCTV camera with out wires over a distance of 6Km. The live video has to be shown in a TV.

Please suggest me how to do this.

Best Regards,
Vdharan
 

Will you be transmitting in one direction (point-to-point) or omnidirectional?

Ragards,
IanP
 

Even if unidirectional transmission is good enough, it will require very high
power and will require license in most countries.
I am wondering how much money can be spent to do this.
 

Yes transmission is unidirectional.

My requirement is there is going to be 20 locations each with 4 cameras in a particular region spread around 13 kms.
The base station will be located in a central place in that region. In the base station one should be able to watch the video from the 80 cameras.
And video transmission should be with out wires.

How this can be implemented. Can this be done using the gsm network.

please help.

Regards,
vdharan
 

I guess you need to tell us what data rate you desire, or alternatively what level of compression you arewilling to tolerate.
 

A plain GSM network can only guarante you 9600bits/second with a data call. You can get 28K with GPRS but I believe that depends on the call having capaity it is not using for voice calls.

>The live video has to be shown in a TV.
If you can afford 80 remote cameras you should be able to afford a CCTV monitor instead of a TV.

Obviously a low speed data link would mean either low resolution pictures or a couple of frames per minute.

You can do higher speed data on a 3G phone network howeer here there are lots of places where there is normal GSM coverage but no 3G signal and
the cheapest tariff is 1.4 euros per megabyte.
 

May be it is possible to use web-camera and 2,4 GHz wireless links?
 

>May be it is possible to use web-camera and 2,4 GHz wireless links?

There is not enough bandwidth for 80 channels of analog video. Maybe only one transmitter could be switched on at once but then you need a bidirectional link for control.

2.4GHz is usually full of wifi in citys. If other people using 2.4GHz cordless phones, wifi access points, other video transmitters and leaking microwave ovens wipe out the camera signal there is not much that can be done.

A 6Km 2.4GHz link is only possible if the local geography allows it. If there is a hill in the way it won't work. You need the beam of radio wave up above obstructions, even if you have line of sight. It may need a 40foot mast on the top of a building or a 150foot mast. Relay stations could be used.

The local radio regulator may not allow license-exempt use of high enough power or high gain antennas.

This would have to be on licensed frequencys.
Doing this with radio would require a lot of carefull system planning and site surveys to see what coverage you can get from each site with the antenna's it is possible to put up.
 

I guess you need to tell us what data rate you desire, or alternatively what level of compression you arewilling to tolerate
Click to expand...

I want the quality of video similar to what we get using webcam on a 56kbps internet connection. Iam new to this field and i could not answer you in terms of data rate and compression.

The area is in a city and it has got a very good gprs network availability. And the video received at the base station is acceptable even if it lags by few minutes.

Is there any way to use the gprs network to implement the same.
 

Your requirements sound complicated. In any case, a WiFi solution could be an alternative. Ive seen a 40km wifi network, of course with line of sight and high gain antennas (dish). Amplifiers are also available.

The necessary throughput is a problem though. Maybe a well designed intranet wifi network can supply the desired specifications. It also depends on the electromagnetic environment where the system is to be deployed on. If it is in the neighborhood of a crowded city, it will be a mess.

good luck,

marcelo
 

your datarate requirement is not that much. A well designed WiFi system would be enough i think. Instead of 2.4 Ghz, you might wanna consider the 5 Ghz band (802.11a). i think it would be less crowded.

Instead of an analog system, you might wanna consider a digital design. it is possible to convert the analog output of the camera to digital, and then encode it with a good compression method (MPEG-4, DivX for example) in real time, and serve this real-time encoded data. you will need a server program on the camera side, and on the receiver side, you will need a player program that is compatible with the server.

You might wanna use some repeaters at certain locations in the environment to overcome the cons. of 6 km distance. and also as stated, you might wanna use some good antennas with high dbi values.

systems with one receiver and one tuner is actually sold in stores i guess. at least in china :). i have bought such a receiver and transmitter. it was analog, and doing great job. but when i measured the antenna power, i was totally shocked. 1 W!!! oh my god!!! considering that WiFi regulation does not allow over 60 mW, that was huge. man ...
 

You'll use a Modulator circuit like TDA8822T ( or similar) to ransmit video+sound signal over a UHF or VHF channel.But it's restricted by law and you have to obtain a license to distribute that signal over terrestrial path.

Or you may use QAM modulation to transmit this data that is more difficult.Because analog video+sound signals are generally distributed by this way either over cable or terrestrial.

There are many possibilities but some of them needs license or permission..

Video bandwith is at least 6MHz and to trnasmit this signal without data loss, you have to use a proper modulation scheme such as QAM, analog or pi/4 QPSK ( the last is much more difficult but is quite compatible digital MPEG data transmission)
 

Instead of an analog system, you might wanna consider a digital design. it is possible to convert the analog output of the camera to digital, and then encode it with a good compression method (MPEG-4, DivX for example) in real time, and serve this real-time encoded data. you will need a server program on the camera side, and on the receiver side, you will need a player program that is compatible with the server
Click to expand...

Can you please elaborate on the server program, does it mean that the client will connect to the server and fetch the data.
 

its look like there some interesting subjects here to read and hope there will be
some more info to read soon.


Regards.

 

My suggestion is to have a MPEG2 encoder for each camera, then you have to multiplex the 4 stream and trasmit the overal signal with a digital modem at microwave frequencies.


My company developes this kind of systems.


Bye
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top