FireBug Sensor network architecture

FireBug sensor network architechture consists of the followings:

Base station (mote 0)
A bunch of Motes attached with sensor board on it (Mote1- MoteN)

Function of the Mote

For each of the work unit, they will realize the following function:
Base Station (genericbase.nc)

Distribute route messages at specific time intervals.
Receive route messages from other motes and update route table.
Receive command messages from UART port, and distribute each message to the appropriate node in the route table.
Receive data message from other motes, forwarding to PC through UART port.

Mote1-MoteN (CollectData.nc)

Distribute route message at specific time interval.
Receive route message from other mode and update route table.
Samples the data from its sensor board, originates a data message and forwards it to its parent node according to routing table.
Receive data message from its child node, forward it to its parent node according to its routing table.

Function of the Messages

There are 3 sorts of message travelling in the network,

Route Message: Any node inside the network broadcast this message at specific time interval, the node receive this message will retrieve routing information from the payload of the packet, calculate the shortest path according routing algorithm, update its routing table. Routing is accomplished using the mh6 protocol.
Data Message: Each node samples sensor data, it will generate a message which contains the useful data, and forward the message to his parent node in terms of its routing table.
- Temperature data: Each sensor is capable of measuring the temperature of its surroundings.
- Location data: Each mote is equipped with a GPS sensor. On initial deployment and at intervals after initial deployment, the GPS sensor forwards the location of the mote to its parent node.
Data messages may be originated at the mote or forwarded from a child mote.
Command Message: Only used by Base station. There is a command center which runs on top of the base station, it will send command packet which generated by the user to the base station from UART port, and base station forward the command message from radio to the target mote throughout the network

Data Structure of the Message

For Data (Originated/Forward) Message and Command Message.

typedef struct TOS_Msg

     {
	/* The following fields are transmitted/received on the radio. */
      uint16_t addr;
      uint8_t type;
      uint8_t group;
      uint8_t length;
      int8_t data[TOSH_DATA_LENGTH];
      uint16_t crc;

      /* The following fields are not actually transmitted or received 
      * on the radio! They are used for internal accounting only.
      * The reason they are in this structure is that the AM interface
      * requires them to be part of the TOS_Msg that is passed to
      * send/receive operations.
      */
      uint16_t strength;
      uint8_t ack;
      uint16_t time;
      } TOS_Msg;


      typedef struct VirtualCommheader
      {
      uint8_t source;		//
      uint8_t seqnum;		//
      } VirtualCommHeader


      typedef Struct MHSenderHeader
      {
      uint8_t mhsendertype;
      uint8_t dataseqnum;
      uint8_t realsource;   //address of mote which generate the message
      } MHSenderHeader

Originated/Forward Message and Command Message have different DataFormat.

Originated/Forward Message:

Struct DataFormat_t

{
	uint8_t addr;    //the address of mote which generate the message
	uint8_t cnt;
	uint8_t sending1;
	uint8_t sending2;
}

Command Message:

Struct DataFormat_t

{
    uint8_t destaddr;	 // the mote address the base station send the cmd to.
    xxxxxxxxx		//... whatever
}

Struct RoutePacket

Struct RoutePacket
{
	uint8_t parent;
	uint8_t hop;
	cost_t cost;
	uint8_t estlength;
}

Message Processing Flow

The software application development of motes make use of all existing low level TinyOS API function, to process the originate/forward message and route message. The followings are the flow chart for each kind of messages, red dot stands for the place of beginning of message

Mote1-MonteN The each mote does only three type of message processing:

Originate and Send a Message
Receive and Forward a Message
Send and receive a route Message

Base Station(GenericBase.nc)