JeeMesh: Difference between revisions
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Latest revision as of 04:22, 4 April 2012
JeeMesh is a mesh protocol in development at HacDC to extend the JeeNode RF12 low power wireless protocol for mesh routing, packet fragmentation, and (more) reliable delivery.
RF12 has the following limitations:
- up to 30 nodes (typically 26 nodes and 4 servers/gateways)
- MTU 66 bytes
- range of about 30' to 50' at 915mhz
We intend to extend these limits somewhat:
- MTU 1023 bytes
- range up to 200' by routing through up to four nodes on a mesh
A 16 bit header is added using the first two bytes of the RF12 packet data as follows:
- 5 bits for original source node
- 5 bits for final destination node
- 2 bits for ttl
- 4 bits for fragment sequence
This allows us to reconstruct 1024 byte JeeMesh packet from 16 64-byte packet fragments. We further add another 8 bit header to the first packet fragment, reducing the MTU to 1023 bytes:
- 4 bits number of fragments
- 4 bits packet type