I think IEEE802.15.4 already sends beacons to its neighboring nodes to form their Routing tables, I am digging into the internals to do that... Also I think software Acks are already implemented when packets are delivered from the originating node to the next hop...
Your example makes perfect sense because the other way I was thinking of implementing it was using Collection in my application where I can send a packet (with just uint8_t data) every few minutes. Then if the ROOT does not see a packet from a particular node for a particular time, say continuously for 30 minutes, then it can inform the User/Manager about the node being Dead..... but I want a more instant reaction if the node is being turned off. This kind of application level implementation adds unnecessary memory usage so I was wondering if it can be done from the already existing code structure of MAC layer?? My testbed of 40 nodes is already sending 2 kinds of sensor data to the Root node continuously but it is event/status driven so I can't use those data packets as a "status check" because sometimes status doesn't change in particular nodes for days... the problem is that we can't really send a "power off" status from the node that has turned off so it has to be done by a neighboring node and I am pretty sure by working out from the Routing tables.... Cheers, Varun Jain From: Mohammed Billoo [mailto:[email protected]] Sent: Wednesday, 23 September 2009 10:15 AM To: Varun Jain Cc: [email protected] Subject: Re: [Tinyos-help] Using CTP to detect Node Status?? Here's a suggestion, I don't know if it meets your requirements. What if you not use CTP and just make your own app to check if nodes are alive or not. Create two types of packets (three if you want to send actual data). One packet should have a data field that has certain bytes (lets say decimal 3). This packet is used to send acknowledgement requests and this packet at a certain time interval. So, if a node wants to know which other nodes in its neighborhood are alive, it sends this acknowledgment request. A node receiving this packet checks this request using some sort of simple if statement, and sends an acknowledgment, which tells the node that sent the initial acknowledgment request that it is still alive. Then, you could do some sort of averaging to figure out that if an acknowledgment was not received after a certain number of intervals, then the node is probably dead. Let me know if that makes sense. Cheers, On Tue, Sep 22, 2009 at 7:35 PM, Varun Jain <[email protected]> wrote: I need to tell the ROOT/BaseStation node in the network about a particular node being turned off. As the neighboring nodes have information about a particular node and they receive constant beacons from each other, I am wondering that if I can work out that a beacon has not been received then one of the neighboring nodes should be able to send a message to the Root node telling that a node in its routing table is not there anymore. But then due to changes in ETX values Nodes might be changing their Routing tables, so a change in the Routing table entry in one of the neighboring nodes is not a sure shot way to find out the status of nodes. If my reasoning is correct, then how can we achieve this??? Cheers, Varun Jain From: [email protected] [mailto:[email protected]] On Behalf Of Mohammed Billoo Sent: Wednesday, 23 September 2009 6:21 AM To: [email protected] Subject: [Tinyos-help] Using CTP to detect Node Status?? Hi, Do you want to tell the same node that it has been turned off or do you want to tell another node in the network that a particular node has been turned off ? I read the TEP on CTP and didn't see any form of Acks being used so that you could determine whether a node is turned on or off based on these Acks. Maybe you could integrate an Ack method with CTP to figure out if a node is on or off. Regards, -- Mohammed Billoo Hi, If I want to know that a node has been turned off in the network, is there a way that the neighbor nodes can inform it?? I know there is an application called "Antitheft" which uses sensors to do that but I do not want to use sensors, I want to use the routing information available with the neighboring nodes to inform this. I was thinking if it can be done from within the CtpRoutingEngine???? To understand better about the CTP protocol, could someone explain what can be possible effects of the "etx" bug fixed recently (Sep 21,2009) in CtpRoutingEngine and CtpRoutingPacket if we do not commit the fix in our code. I just want to understand the misbehavior that the bug can cause (if not fixed) in the network?? Thanks, Varun Jain -- Mohammed Billoo
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