Texas Instruments CC2520, Руководство пользователя

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6.2 Packet Error Rate (PER) testing
The PER number is the ratio between number of packets being lost and the total number of
packets being sent. PER relates to the more traditional Bit Error Rate (BER) through the
formula
length packet
BER PER
_
) 1 ( 1
− − =
The sensitivity threshold of the radio is the lowest input signal strength at which the receiver
can decode the signal with a reasonable degree of correctness. Usually, a PER of 1% is used
as the limit for determining the sensitivity threshold.
It is possible to perform practical range testing with the PER test application which is
preprogrammed on the CCMSP-EM430F2618 boards. Place the transmitter at a fixed location
and place the receiver at a given distance from the transmitter. Then run the PER test to
measure packet errors and possibly the signal strength. Repeat at different distances to get
an idea of the range that can be obtained.
By adding a jammer (a third node that generates either noise on the same channel or a strong
signal on an adjacent channel) it is also possible to measure co-channel rejection and
selectivity/blocking performance.
The same PER test application can be used for simple sensitivity measurements with the
CC2520EM and/or with your own prototype hardware. In this case, connect the unit you want
to test to a known good transmitter with coaxial cables and attenuators. Add more attenuators
until the PER value is 1%. The signal strength at the receiver side is then the sensitivity limit
of the system.
For more information about sensitivity testing, please refer to “DN002 – Practical Sensitivity
Testing” (www.ti.com/lit/swra097).