User's Manual

P330 Data Sheet / User Guide 11
DRAFT
 Allow the user to easily enter and transmit data.
 Allow the user to receive and display data.
 Log all messages exchanged between the Host and connected P330.
 Display range measurements taken between other units in the area for which the connected
P330 is not a direct participant.
The ability to log data also allows the user to plot performance as a function of range. This is an
excellent tool for evaluating signal propagation in a given area. For example, the information shown
in Figure 2-1 was collected as the distance between two units was increased. Basically, data was
logged with one unit held stationary while the second unit was driven away. Figure 2-1 is a plot of
the received signal strength (First Path Power) as a function of separation distance. In this figure one
can observe several items of note:
 There is a major Fresnel cancellation at 60and 130 meters as well as minor ones between 20
and 40meters.
 The minimum sensitivity of this unit is -105db.
Fig. 2-1: Received signal strength (First Path Power) as function of separation distance.
2.4.2 Networking and Localization with RangeNet
Operating a system that consists of only two units is very simple. Operating with more than two units
starts to introduce significant complexity which is increased even further when the need to determine
location is added. For example:
 There needs to be a way to prevent units from interfering with each other.
 The number of radios in the system may vary with time. Units that enter the system need to
be discovered. Units that exit the system need to be removed from the network.
 Not all units need to behave the same way. Some units might initiate and respond to range
measurement requests. Some might only initiate requests. Some might only respond. Some
units might only communicate with a subset of the system.
 Before you can convert range into location it is necessary to define a coordinate system and
measure the position of anchor (fixed reference) units relative to that system.
 The X,Y,Z location of the references needs to be communicated with all of the anchors.
 Since ranges are taken while a unit is moving, simple trilateration may not produce valid
locations. It is therefore necessary to include in the location solving engine a Kalman Filter
to both filter out noise and better compute locations.