Intro
------
Relay is a function to extend the coverage of WSN network. It adds the 
functionality to re-broadcast pkts to other nodes which in turn can
re-broadcast pkts further on etc,

It is designed to be a very simple and efficient. Virtully no con-
figuration is needed- Also another of the design goals is to do de-
bugging understandable and simple. The text below describes the function 
but in most cases no user interaction should be needed.


How relays works
-----------------
A relay enabled node checks incoming packets for the RIME address and 
the SEQNO.


 1) Incoming pkts are checked for version 1. Otherwise discard
 1) Incoming pkts are checked for TTL. TTL with. 0. Discard
 2) Incoming pkts are checked for Rime ADDR if same as us, Discard

 3) If cache does not have an entry for the ADDR/SEQNO. the exact 
    data report is sent/relayed, TTL is decreased. sent stats is 
    updated and if the RELAY debug  option is set. The yellow LED 
    is flashed.

 4) If cache already have an entry for the ADDR/SEQNO. No relay packet
    is sent and packet is silently discarded. dup stats are updated.
 
Firmware
--------
The beta-5.0.hex and later firmware for model S2 adds realy support.


What's needed (model S2)
------------------------
As the report nodes are fully asynchronous the following criteria
must set:

* radio must be on in the relays node. (Approx 20 mA). 
   USB-TTL cable or firmware command "log on" and power 
   node via DC-input.

All nodes are by default configured to relay. 
 
See relay command:

"relay on"    To enable
"relay off"   To disable relay.
"relay"       To show setting

Monitor
-------

There is also a new firmware command "relay stats" to monitor the relay
function.

relay stats
sent=37155 dup=35172 ignored=20337 ttl_zero=0

Also a new debug option RELAY that flashes Yellow LED when pkt is relayed.

Neighbor "ne" command should be useful for understanding 
radio coverage. It's extened as follows:

DUP=2 ADDR=51.54 SEQ=206 TTL=14/14 RSSI=0/5 LQI=255
DUP=0 ADDR=195.37 SEQ=45 TTL=15/15 RSSI=5/5 LQI=255
DUP=0 ADDR=56.90 SEQ=34 TTL=15/15 RSSI=12/12 LQI=255

Key to the neighbor table:
--------------------------
DUP  = Number of received pkts with same ADDR/SEQNO 
ADDR = Rime ADDR
SEQ  = pkt sequence number. 0-255
TTL  = TTL for first packet/TTL for packet with best RSSI
RSSI = RSSI for first packet/RSSI for packet with best RSSI

TTL
---
Maximum and default TTL is 15. S2 model has a command for 
setting lower TTL. "ttl"

Example topology
----------------
To be added.


Firmware Support
----------------
Model S2 >= 5.0 New header, Support relay
Model S1 >= 5.0 New header
FOSS            New header, relay will be added. (Contiki Open Source Port)


Experiences and feedback
-------------------------
Please use mailing list for experiences and issues. wsndev@herjulf.se