RANGING – Ranging service

Agents offering the Ranging service provide time synchronization and ranging functionalities between pairs of nodes. They support a set of messages and parameters that are explained below.


Requests and Responses

Request Possible Responses Description
RangeReq AGREE, FAILURE Request range measurement
BeaconReq AGREE, FAILURE Request beacon transmission
ClearSyncReq AGREE, FAILURE Clear synchronization information
SyncInfoReq SyncInfoRsp, FAILURE Get synchronization information
ParameterReq ParameterRsp Get/set/list parameters


An agent providing the ranging service typically responds to a RangeReq agreeing to make the range measurement. The actual range measurement is sent later as a RangeNtf.

Beacons are used for one-way travel-time (OWTT) ranging to transmit a timing signal that may be used by other modems to compute range from the beacon node. Only nodes that have valid synchronization to the beacon node obtain range information from beacon transmissions. Any range information recevied at a node is sent as an unsolicited RangeNtf.

For OWTT to be used, synchronization information has to be first obtained between nodes. This automatically happens when a successful ranging exchange RangeReq is made. The lifetime or validity of the synchronization information depends on the accuracy/drift of the clocks used in the modems.


Notification Topic Description
RangeNtf default Range notification from a peer node
BadRangeNtf default Invalid range notification from a peer node
ParamChangeNtf PARAMCHANGE Notification about the modified parameter


Parameter r/w Description
lifetime rw Life time or validity for synchronization information (seconds)
minRange rw Minimum possible range (meters)
maxRange rw Maximum possible range (meters)
maxBadRangeCnt rw Maximum number of consecutive bad range estimates before discarding synchronization information for the node