Asynchronous low power listening similar to the behavior of B-MAC has been introduced for the CC2420 radio in TinyOS 2.x. This LPL CC2420 stack is not B-MAC or X-MAC, by the way. The 'experimental' version is still located in tos/chips/cc2420_lpl, but a more reliable and robust version can be found in tinyos-2.x-contrib/rincon/tos/chips/cc2420_lpl. That version is going to get a few more features before getting put back into the baseline.
The CC2420 LPL strategy is to use clear channel assessments to determine if a transmitter is nearby and modulating the channel. If modulation is detected with valid 802.15.4 data, the radio is left on for a brief moment to attempt to capture a packet. If a packet is received successfully, the radio is left on as long as communications are taking place. After a few moments of inactivity, the radio will continue to duty cycle. There isn't much literature on the design of the CC2420 radio stack. Maybe I'll put something together sometime. Basically it's a standard radio stack though: A bunch of layers down the send branch, a bunch of layers up the receive branch, and a bunch of layers to control power. Some layers can be added and removed from the stack as needed. The main reason LPL was not implemented for a long time was because it was impossible to implement B-MAC on the 2420 radio - specifically, the radio could not extend its preamble for a long duration of time. A new strategy had to be developed, and there were many people involved with evolving the CCA receive check strategy. Moteiv's Boomerang features time sychronized CC2420 radio duty cycling, which is much more efficient than the current asynchronous CC2420 duty cycling. -David -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Antonis Lambrou Sent: Monday, February 12, 2007 10:27 AM To: [email protected] Subject: [Tinyos-help] CC2420 radio stack I am currently conducting research for MAC protocols designed for Wireless Sensor Networks and I would appreciate some guidance from tinyos-help. In your FAQ you have the following answer for the MAC design: "Support for the CC2420 radio was introduced in TinyOS 1.1.7. The CC2420 uses B-MAC. However, the CC2420 radio does not have the Low Power Listening functionality; it does have the MacControl and MacBackoff interfaces but, again, the underlying functionality is not implemented." If Low Power Listening is not implemented does that mean that the radio is listening constantly for incoming packets? What are the reasons for not implementing LPL on the CC2420 radio stack? Where can I find more documentation on the design for the CC2420 radio stack on TinyOS? I have read so far the paper "Versatile Low Power Media Access for Wireless Sensor Networks", which describes the B-MAC protocol, but as I understand the protocol is slightly changed on the CC2420 radio stack. Thank you, [EMAIL PROTECTED] _______________________________________________ Tinyos-help mailing list [email protected] https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help _______________________________________________ Tinyos-help mailing list [email protected] https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
