Octopus: Frequently Asked Questions

Why does Octopus not show any nodes in the GUI?
There is probably a problem with the way cygwin is trying to find your java files. Best way to solve this is to uninstall all versions of java and reinstall the correct version for TinyOS 2.x.

I am changing the duty cycle of the nodes in the GUI, but they still seem to have a 100% duty cycle.
This situation arises when low power listening is disabled in TinyOS 2. You should add a line of code anywhere in the header file OctopusConfig.h as follows:

#define LOW_POWER_LISTENING

Can I set the duty cycle on a per node basis?
Yes. Assigning different duty cycles to different nodes in Octopus has only a minor effect on delivery rate, based on our lab deployment experiments. To set the duty cycle for specific nodes, you should unset the broadcast check box, click on the node and then slide the duty cycle indicator to the desired value.

The packet delivery rate is low in Octopus, especially after I send requests to change the sampling period through the GUI.
A problem has been identified with Octopus version 1.2 and earlier that causes this to happen. Upon receiving a request to change sampling periods, all nodes at the same hop count from the base station essentially become synchronized as they receive this request at the same time. This causes frequent collisions among these nodes, and if the number of nodes in your network is high, then you will observe a low delivery rate. Octopus v1.3, which is now available on the Octopus Home Page and on tinyos sourceforge page, solves this problem by forcing nodes to wait for some time before readjusting to the new sampling period.

What is automatic network size detection in Octopus?
This is a recent addition to Octopus whereby the base station determines the network size and adapts scheduling policies of all the nodes based on the network size. This mechanism avoids implicit MAC-layer synchronization through application-layer back-offs to avoid high contention scenario. To optimize the operation of this feature, you should set the node IDs in your network sequentially.