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# Clear Channel Assessment (CCA) - RF Cafe Forums

 The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Below are all of the old forum threads, including all the responses to the original posts. -- Amateur Radio -- Antennas-- Circuits & Components-- Systems-- Test & Measurement

 Post subject: Clear Channel Assessment (CCA)- Posted: Thu Mar 24, 2005 9:50 pm
 Captain

Joined: Tue Mar 22, 2005 5:29 pm
Posts: 5
I found this in IEEE 802.11A Spec -
The start of a valid OFDM transmission at a receive level equal to or greater than the minimum 6 Mbit/s sensitivity (-82 dBm) shall cause CCA to indicate busy with a probability >90% within 4 µs. If the preamble portion was missed, the receiver shall hold the carrier sense (CS) signal busy for any signal 20 dB above the minimum 6 Mbit/s sensitivity (-62 dBm).

How do i intepreated "6 Mbit/s sensitivity (-82 dBm)". Does 6 Mbit/s means the data-rate? and what is this -82dBm.

How do i intepreted "any signal 20 dB above the minimum 6 Mbit/s sensitivity (-62 dBm)"?

 Post subject: Re: Clear Channel Assessment (CCA)- Posted: Mon Oct 24, 2005 11:29 am
 6 Mbit/s means the phy layer transmission data rate... and -82 dBm means the recieved power level in dBm...so the receiver will be busy for a valid OFDM transmission at a receive level equal to or greater than -82 dBm.If the preamble part of the packet has not been received due to some reason , say collision, in that case the sensitivity level is increased to -62 dBm...so the receiver will be busy for a valid OFDM transmission at a receive level equal to or greater than -62 dBm.-- MohaMMad MuTTakin SiDDique, MSc. EngrCommunication Networks University of Bremen, FB1Otto-Hahn-Allee NW1 28359 Bremen, GermanyEMail: mms@comnets.uni-bremen.de Tel : +49 421 218 3339Fax : +49 421 218 3601 www.comnets.uni-bremen.de/~mms~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ jkhoo2989 wrote: I found this in IEEE 802.11A Spec -The start of a valid OFDM transmission at a receive level equal to or greater than the minimum 6 Mbit/s sensitivity (-82 dBm) shall cause CCA to indicate busy with a probability >90% within 4 µs. If the preamble portion was missed, the receiver shall hold the carrier sense (CS) signal busy for any signal 20 dB above the minimum 6 Mbit/s sensitivity (-62 dBm).How do i intepreated "6 Mbit/s sensitivity (-82 dBm)". Does 6 Mbit/s means the data-rate? and what is this -82dBm. How do i intepreted "any signal 20 dB above the minimum 6 Mbit/s sensitivity (-62 dBm)"?

Posted  11/12/2012