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Re: [Discuss-gnuradio] USRP1 and WBX, communication distance

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] USRP1 and WBX, communication distance
Date: Tue, 19 Apr 2011 18:03:02 -0400
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On 04/19/2011 05:44 PM, Gunther Ferdinand wrote:
   I would like to ask you a question regarding the USRP1 and WBX. Have anybody made some tests with these and other ISM band transceivers to see the communication distance indoor and outdoor? For example if I have a tranceiver on 433MHz and it has a transmission power of 17dBm, which should be the minimum distance in open air to be able to receive data packets sent from the USRP1+WBX+LP0410, (what about indoor - it depends from nr. of walls and thickness but anyway I would like to know your opinion, and your experience with this)? Right now I'm trying to make the packet (<PREAMBLE><SYNC><HEADER><DATA LENGTH><DATA><CRC>) with the help of functions from Gnuradio, and it's quite difficult, and then to make FSK modulation and send it to my transceiver. In documentation for the USRP1 the transmission power is between 50mW - 100 mW (17-20dBm)? For my transceiver that has 17dBm transmission power says that it can transmitt data as far as 800m outdoors, would it apply to USRP1, too? Indoors the transceivers works quite well, I can send data from one module to other in my whole house, the distance is around 15m, through walls (max. 3 walls between transceivers). Anybody tried to do such kind of things, and has arived to any results?
I would appriciate any comment on this.
Thank you very much,

Answering that question requires a lot of "it depends".

Maximum transmission distance is proportional to a number of parameters:

    o transmit power (or more precisely effective radiated power towards the receiver)
    o receiver sensitivity--which depends both on noise figure of the receiver, and directivity of the receive antenna
    o any impairments to the signal due to physical obstructions, causing absorption and multi-path reflections
    o bandwidth of the signal
    o modulation scheme
    o processing gain due to coding techniques, etc

So, you see, a complete model is quite complicated, so answering the question without "fleshing out the model" is not really possible.

Can you communicate beyond the edge of your desk?  Yes, almost certainly.   Beyond the edge of your living room?  Probably?  Beyond the
  edge of your city block?  Not sure.

Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

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