Globalstar Product Management – Technical Support

Signal Strength Indicators on GSP-1600 and GSP-1700

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The GSP-1600 and GSP-1700 handheld phones provide realtime display of the strength of the received Globalstar Signal. The Globalstar phone tracks up to three separate satellite feeds and chooses the strongest signal(s) to use for communication with the Gateway. The phone constantly optimizes the signal reception by adjusting the system clock and other parameters as the frequency and Doppler change.

The best indicator of signal strength is the RSSI indicator, which is graphically depicted at the top of the GSP-1600/1700 display as a series of vertical bars. The RSSI is described in many wireless communications documents and is the key value for predicting the likelihood of being able to make a successful call.

In addition to the RSSI indicator, the GSP-1600/1700 can also display a pilot signal strength indicator. A special diagnostic mode is used to view this information. To enter the diagnostic mode:

1) Turn the phone on
2) Enter the following keystrokes: MENU 4, 0, 0
3) Enter Service Code, 000000
4) The display will show: Debug with a series of options
5) Select #1, Toggle Dbg
6) When the Debug mode is active, you can scroll through the debug screens with the “INFO” key.

Press the INFO key to go to the second screen, a three-line, four column display.

If you do not see this screen, keep pressing the INFO key until the screen is displayed. The columns are, from left to right: Finger mode, Satellite, Beam, the energy (Ec/Io) of the pilot signal in dB. The signal strength indicator varies from 0 (max) to –31 (lowest signal).

There are a number of different Finger Modes (U, C, F, A, others) that may be indicated in the first column of the display, but the only mode that displays the signal strength for a phone call is the Active mode, “A”.

The signal strength is the rightmost column of any row which has an “A” in the left column.

Typically, it is necessary for the pilot signal strength to be greater than about –22dB to establish a phone call. Usually the pilot signal strength is much stronger than this. However, the Globalstar system is designed to deal with very weak signals, and it recognizes that a weak signal can be a transitory phenomenon. Therefore, Globalstar will start the calling process whenever the SEND button is pressed.

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Written by Joseph Crowley

June 8, 2008 at 1:41 am

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