I'm not sure exactly your question? I'm also not sure there is a "purpose", as much as reporting what occurs. I'm also not sure if you are looking for an answer at the "waveform" level versus the "Link budget" level?
RSSI is a factor related to Modulation. More specifically with OFDM. Often in manufacturer spec sheets, it will list the minimum rssi level in order to use a specific modulation. This is not just a random number picked. Someone else will probably explain it better, and I welcome them to, but for now I'll try :-) It has something to do with how OFDM takes the signal and breaks it up into lower powered sub carriers. As modulations are higher, they get broken down into more sub carriers, hence QAM 32,64,256, etc. I believe it has something to do with how the math works with Watts versus DB, when the signal gets split and added back togeather again at a later process. There are two side effects that come... As higher modulations are used, it more work for the card and Transmit power becomes less, and receive sensitivity becomes higher (worse). I guess what I'm saying is that its possible to use a specific modulation at many different power levels/ receive levels (RSSI). It depends on the power rating of the card. However, the point I'm making is, at a given set power level or sensitivity rating of a card running a low modulation, if the modulation type is raised, it will have a calculatable/predictable effect on the signal strength received and sent. Tom DeReggi RapidDSL & Wireless, Inc IntAirNet- Fixed Wireless Broadband ----- Original Message ----- From: "Rogelio" <[EMAIL PROTECTED]> To: "WISPA General List" <[email protected]> Sent: Monday, June 16, 2008 10:06 PM Subject: [WISPA] modulation question > I've got a question, which I'm afraid might be a little stupid to some, > particularly those with RF backgrounds... > > I've always thought that modulation rate was directly tied to RSSI (for > some law of physics reason or something), but someone else told me that > it's not like that (in theory) and what I'm seeing is just certain > vendors do that for a particular purpose. > > What is this purpose? > > > -------------------------------------------------------------------------------- > WISPA Wants You! Join today! > http://signup.wispa.org/ > -------------------------------------------------------------------------------- > > WISPA Wireless List: [email protected] > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ -------------------------------------------------------------------------------- WISPA Wants You! Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: [email protected] Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
