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[[Category:FMC234 Configuration]]
[[Category:FMC234 Configuration]]
==GNSS Jamming==
[[Image:GNSS_Jammingass.PNG|{{{general|size}}}|right]]
GNSS Jamming is the transmission of radio signals that disrupts communications between tracker and satellites by decreasing the signal to noise ratio.
When a device detects GNSS signal jamming, it activates the GNSS Jamming scenario. The device then generates and sends a record to the server, depending on hardware model activates Digital Output and optionally sends SMS notification to configured GSM number. After device regains GNSS signal, Digital Output is immediately deactivated and a new record is sent to the server. This Digital Output activation can be used to trigger measures to disrupt potential thieves using GNSS signal jamming to steal your vehicle.
GNSS Jamming record is stored in AVL ID 318 parameter and has 3 possible values:
*0 - No Jamming,
*1 - Jamming warning status, which means that signal and accuracy is disrupted but device is able to hold GPS fix for at least 5 seconds.
*2 - Jamming critical status, which means that device is not able to acquire GPS fix.
Worth mentioning, that Jamming Detection can go from any state to any other in 1 second intervals. It is completely dependent on received NMEA data by GNSS receiver. Therefore, it is possible in repeated jamming scenario for the state to rapidly go from 0 to 2 and backwards.
Also, GNSS Jamming functionality is capable to separate indoor areas (e.g. underground parking) from events when jamming is actually happening. This is possible because in-band jamming will affect internal PGA (Programmable Gain Amplifier) degrade, as a result, CNR (Carrier-to-noise ratio) will degrade as well. On the other hand, if CNR degrade is degraded only because of underground or signal covered, internal PGA gain will keep almost the same.
Eventual Records parameter can be configured: when it is disabled scenario status value will appear in each AVL record, otherwise, it will be appended only to eventual records.
'''Note:''' GNSS Jamming is only available since 03.29.00.Rev.601 or newer firmware version.
'''Note:''' GNSS Jamming is not available on 3.80, 3.82 but available on 5.10, 5.1.5, 5.1.8 or newer GNSS module firmware versions. GNSS module version can be checked by SMS\GPRS command - getver
'''Note''' that this scenario will not work with [[FMC234 Sleep modes#Deep Sleep mode|Deep Sleep]], [[FMC234 Sleep modes#Ultra Deep Sleep mode|Ultra Deep Sleep]] and [[FMC234 Sleep modes#Online Deep Sleep mode|Online Deep Sleep]] modes, since they disable the device's GNSS module to save power.
