Hi David Yes, I ignored 802.11 interference. Thanks for your advice. That is a much better solution. On Sun, Apr 20, 2008 at 4:40 PM, David Moss <[EMAIL PROTECTED]> wrote:
> You don't need other nodes around for the hardware CCA to show the > channel is in use. WiFi and other transmitters will cause energy and noise > on the channel. > > > > An RSSI based approach is good for deciding the best channel to establish > a network, if you're trying to find a quiet channel. Traverse all channels > and average up many samples of RSSI on each channel, then pick the channel > with the quietest average RSSI. > > > > -David > > > > > > > ------------------------------ > > *From:* [EMAIL PROTECTED] [mailto: > [EMAIL PROTECTED] *On Behalf Of *renjie huang > *Sent:* Sunday, April 20, 2008 4:17 PM > *To:* tinyos-help > *Subject:* [Tinyos-help] CCA for channel detection > > > > Hi > > > > I am trying to use CCA for a node to detect all radio channels around. If > CCA is false, then there may be some nodes transmitting packets on > corresponding channel. But in my test there has some problem. When a > node uses a channel , eg 11, while no other nodes are around, it will report > channel 11 deteced. That means when the channel is not busy(no nodes are > transmitting, including itself), CCA also can be false. > > > > for(ccaCheck = 0; ccaCheck < 400; ccaCheck++) > if(!call CC2420RadioControl.getCcaStatus()) > count++; > if(count > 200) > debug(DBG_ERR, "channel =%i is detected \n", call > CC2420Control.GetPreset()); > > > This seems that CCA is not relaible. I don't know what is wrong with my > code. Any advice is appreciated. Thanks > -- > Renjie Huang > Sensorweb Research Laboratory > http://sensorweb.vancouver.wsu.edu/ > Washington State University > -- Renjie Huang Sensorweb Research Laboratory http://sensorweb.vancouver.wsu.edu/ Washington State University
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