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Weekly Report

03

Jul

2015

I think I've missed two of these...

I've spent a bunch of time re-wrorking my packet scheduler this past week. I wanted to allow for link-layer retransmission of packets which ht epacket scheduler was not originally designed to do. It compiles, and messages get sent however the upper MAC layers manage their own re-transmissions and ACK messages no longer get passed up and so nothing works just yet. This is a simple case of re-working the state machine to accept the new packet states; ACK, NO ACK and NOT SENT (in the case the packet fails CSMA and never leaves the radio).

ubiquiOS (which seems to be the topic of my last report) is well integrated and working. Before the packet scheduler re-work, I had 3 nodes able to simultaneously associate with the gateway node (pan coordinator). After association, the nodes would ping the gateway and measure the response times. With a beacon period of 500ms, the response time averaged at 500ms with 1% packet loss.

Adding link layer retransmission should improve that packet loss figure.

After that, I want to start working on AES. I'll hard code the keys for now, and try to install them at a sensible time. At which point, I can celebrate because that's the infrastructure I needed to start my project! I can then remove the hard coded keys, and replace them with authentication and key exchange.

Stretch goal is to add 6LoWPAN on top - which shouldn't be too difficult, as I've essentially made a pipe that correctly sized packets can be piped into.