User's Manual

8 Ultra Wideband Perimeter Surveillance Pole / User’s Manual
Each network cell is implemented as a fixed TDMA scheme that supports a 4 Hz update rate.
This fixed TDMA cycle and timing information is available to each P400 and ensures only a
single P400 (within each cell) is radiating at any given time. The TDMA network for each
networking cell is 264ms in length and contains 8 time slots. The 264ms time period is
called a superframe. For a single pole, only one time slot of a superframe is used to transmit
for 24ms. Therefore per pole, the duty cycle for packet level transmissions is 9%
(24ms/264ms). Additionally, the P400 radar technology is based on short pulse UWB
technology. During this 24ms transmit time, the on-air duty cycle (pulses being sent) is
<1%. Therefore the overall on-air time (pulse level) for a pole is <0.1%.
While there are three P400s per pole, only the P400 located in the middle of a pole radiates
both the bottom and top P400s listen only. Moreover, all P400s in all networking cells
always receive, even those that are transmitting act as monostatic radars. Each receiving
P400 produces a waveform or a scan of the signal it received, which is sent via Ethernet to
the signal processing application resident on the main computer. It’s worth noting that the
USS was designed to be efficient as it relates to transmit airtime (and power). For example,
on average 18 different radars are designated to receive energy from one transmitter, thus
making the most of each transmission for the purposes of detection, localization, tracking,
and classification.
1.2.3 Processing
The processing flow consists primarily of signal processing, detection, localization, tracking,
and classification/identification. The primary inputs to the processing are the radar scans
generated by the P400s. The primary outputs of the processing are the tracks and
classification. Secondary inputs are configuration and controls. Secondary outputs are
configuration and status, and radar slot control.
The signal processing function operates on raw scans from the radar to filter and align scans
to pass to the detection function. The detection function attempts to remove the background
including clutter to report motion. The detections are then input to the localization function.
Up to this point all processing has been performed on scans from a single radar (monostatic)
or a pair of separate radars (bistatic) independently. A transmit radar/receive radar pair
(which for monostatic operation is the same device) is called a link. The localization function
combines detections from all available links along with known coordinates of the radars to
determine locations of potential targets.
The tracking function implements a tracker using the localization coordinates of potential
targets. The goal of the tracker is to identify localizations that have spatial and temporal
consistency and estimate their position over time. The outputs of this function are called
tracks. Although the tracking function may initiate and maintain a number of tracks, only
those with high confidence are provided as output to the classification function, visualization,
or external output. The classification function determines whether the track is the result of a
person or an animal.