S-MAC Software: Frequently Asked Questions

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  • What mote platforms does S-MAC support?
    Current S-MAC implementation supports Mica and Mica2 motes.

  • I'm using motes with Cygwin. The motes communicate, but the snooper can't hear anything. What's wrong?
    The problem does not happen in Linux. It looks like that the baud rate of the serial port is not correctly set after initial Cygwin installation.
    Here's a workaround. Open the HyperTerminal, and use it to set the baud rate of the serial port that you're using. For Mica2, the baud rate is 57600 (b/s). After you set it, the HyperTerminal is connected to the serial port. Now turn on a mote that sends packets (e.g., PhyTestSender), the HyperTerminal should receive some garbage bytes -- indicating data has passed over the serial port. Now turn off the HyperTerminal and run snoop.c again. It should work correctly.

  • Does S-MAC measures the signal strength of received packets on motes?
    Yes. S-MAC measures the signal strength (RSSI) of each received packet. The value is given as the raw reading from the ADC. You can convert the raw ADC value into dBm by the following equation (from xbow documentation).

    RSSI(dBm) = -51.3 * Vrssi - 49.2 (for 433 and 315 MH motes)
    RSSI(dBm) = -50.0 * Vrssi - 45.5 (for 915 MHz motes)
    where Vrssi = Vbatt * ADC_value/ 1024.

  • I don't have any motes. Can I run S-MAC in simulation on PC?
    Yes, you can run S-MAC in different simulators!
    1. ns-2.
      We have implemented S-MAC in ns-2. You can find download instructions here.
    2. Avrora.
      With Avrora, all TinyOS code that runs on the mica2 mote can directly run on PC. Therefore, our S-MAC protocol should be able to directly run in Avrora without modification. For details, look at Avrora website.
  • Can I run S-MAC in TOSSIM?
    The short answer is "no". You can't directly run S-MAC in TOSSIM, because S-MAC has a different implementation of the low-level components in the communication stack than standard TinyOS stack. These components need to support TOSSIM (i.e., the pc platform) in order to run S-MAC in TOSSIM. If you are interested to add such support, you may also want to look at Power TOSSIM.

  • Why can't I see energy savings of node sleeping in ns-2?
    You are probably running an ns-2 version that is too old. There was an important update to the ns-2 energy model on June 14, 2005. Make sure you get a ns-2 snapshot after that date.

  • Does S-MAC work with any routing protocols in ns-2?
    Yes, S-MAC works with Directed Diffusion and DSR in ns-2. Please note that S-MAC may have large delays on multi-hop data forwarding due to the sleep on each node. The default parameters of most routing protocols to find a path is normally set for 802.11-type of network with high bandwidth and low latency. Therefore, when they run over S-MAC (modeled on a low-bandwidth radio), the routing protocols may time out too fast in finding paths, and won't be able to establish a path. We have modified DSR parameters (user-adjustable) so that it can successfully run over S-MAC.
    We haven't tried S-MAC with other routing protocols. If plan to try, keep the above point in mind.

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    Last modified on Sept. 27, 2005.