JeeMesh

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