Audio streaming wirlessly on ISM band in India

[ankitthakkar]

Hello

I am developing an application of wireless audio broadcasting.
The condition is I need to operate in ISM band and the line of sight range required is 1.5 km between transmitter and receiver.
The codec for streaming can be wav or mp3 depending upon the speed available by wireless medium.
Anybody having any idea on that which frequency band and modulation scheme needs to be used?

regards,
ankit

 

[biff44]

I do not know the Indian ISM requirements, but assuming it has a 2.45 Ghz ism band, you could start there with 2-FSK modulation. If you want to get fancy, you could do some spread spectrum approach too.

 

[ankitthakkar]

Yes. 2.45 is ISM band in India as well. The max output power is 1 Watt. Surely 2-FSK can achieve higher data rate but i wonder if 2-fsk would interfere with the wifi frequencies. I guess in spread spectrum the data rate would be very slow.

 

[pranam77]

Yes. 2.45 is ISM band in India as well. The max output power is 1 Watt. Surely 2-FSK can achieve higher data rate but i wonder if 2-fsk would interfere with the wifi frequencies. I guess in spread spectrum the data rate would be very slow.

Could you let me know which rules and regulatiions in India says you can transmit 1 watt on 2.45Ghz? In India you are governed by the Rules and regulations of Wireless planning and co-ordination 1978, which says you can use 0.5 watt only for educational purpose without a valid license. For more power, you may get a commercial license form the Wireless planning and co-ordination Wing, Dep of telecommunication,s Ashoka Bhavan New Delhi 1. Also you need to confirm that frequency used by your transmission is not interfering with any other valid transmissions like the Army, Police, and other Licensed and commercial setups.
Cheers

 

[ankitthakkar]

I checked that.. Its 0.5W in 2.4 ghz band. Sorry for that... but how to check the interference with WIFI network..

 

[biff44]

It is purely up to what level of complexity you want to have. Wireless lan networks operate on preset channels. If you have one in you home, and you do not want this audio system to interfer with it, you would setup your wlan at one channel frequency, and set up the FSK audio link on another frequency channel. All would then be well. This is probably the best way for a hobbyist to set up such a system cheaply.

If, on the other hand, you are concerned about interfrerence with other wlan networks that you do not have control over, then the best way is to use some sort of spread spectrum system for the audio. It could still be fsk, but frequency hopped, and you would need to send the audio in packets. It could be some sort of 802.11 type modulation, using a standard chipset. There are some chipsets that can do a collision avoidance search of the rf spectrum, and pick a frequency channel that is not used too much.

 

[pranam77]

I checked that.. Its 0.5W in 2.4 ghz band. Sorry for that... but how to check the interference with WIFI network..

Your transmission should not interfere with any other valid transmissions. Thaz why the power is limited to the said level. Despite if you are aware about any of such interferences, you are expected to withdraw your transmissions immediately. Anyways, if you are applying for a valid commercial license, you'll be alloted a separate frequency to work on with a license. ...Cheers