User manual

Chapter 4 Capturing and Analyzing Data
The following sections describe the various ComProbe software functions that capture and display data packets.
4.1 Capture Data
4.1.1 Air Sniffing: Positioning Devices
When capturing over the air packets, proper positioning of the Frontline hardware and the Devices Under Test
(DUTs) will result in the best possible captures and will mitigate sources of path loss and interference. The
following procedures will help optimize the capture process especially if you are have problems obtaining reliable
…captures.
Problems with indoor radio propagation
Even in free space, it is well understood that radio frequencies attenuate over distance. The free-space rule-of-
thumb dictates that radio energy decreases in strength by 20 dB by each 10-to-1 increase in range. In the real-
world, the effects of objects in an outdoor environment cause reflection, diffraction, and scattering resulting in
greater signal losses. Indoors the situation can be worse. Reflections occur from walls and other large flat surfaces.
Diffraction occurs from objects with sharp edges. Scattering is produced from objects with rough surfaces and
from small objects. Also any object directly in the path of the radiation can present a hard or soft partition
depending on the partition's material properties. Path losses from partitions are difficult to estimate.
Estimating indoor propagation loss
One estimate of indoor path loss, based on path loss data from a typical building, provides a power rule.
At 2.4 GHz, the following relationship provides an approximate estimate of indoor path loss:
This approximation is expected to have a variance of 13 dB.
Mitigating path loss and interference
Bluetooth device design contributes to mitigating environmental effects on propagation through spread spectrum
radio design, for example. However, careful planning of the testing environment can also contribute to reliable
data capture process.
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