The Global Positioning System: A Shared National Asset (1995)
Chapter: Appendix H Signal Structure Options
Appendix H
Signal Structure Options
Ten signal structure enhancement options were considered by the committee, as shown in Table H-1. Each involves possible changes to L1 or L2, as well as a possible signal transmission on a new frequency. The options are listed in priority order.
Table H-1 Signal Structure Options
|
Option |
L1 |
L2 |
L4 |
Advantages Relative to the Current Configuration |
Disadvantages Relative to the Current Configuration |
Earliest Possible Implementation |
|
1 |
Y C/A |
Y |
Pa-like code wide-band signal |
Ionospheric correction; improved accuracy; anti-jam; 10-dB improvement over narrow- band in interference rejection; faster cycle ambiguity; fast acquisition; easier direct Y- code acquisition; can track to lower elevation angles than codeless receivers |
Must jam two bands; satellite and receiver costs increase; satellite power requirements increase; frequency allocation considerations |
IIR |
|
2a |
Y C/A |
Y |
C/A-like code narrow -band signal |
Ionospheric correction; improved accuracy, anti-jam; 10-dB improvement over narrow- band in interference rejection; faster cycle ambiguity; fast acquisition; easier direct Y- code acquisition; can track to lower elevation angles than codeless receivers |
Must jam two bands; satellite and receiver costs increase; satellite power requirements increase; frequency allocation considerations |
IIR |
|
2b |
Y C/A |
Y with C/A-like code added to null of L2 narrow-band signal |
Ionospheric correction; improved accuracy; anti-jam; 10-dB improvement over narrow- band in interference rejection; faster cycle ambiguity; fast acquisition; easier direct Y- code acquisition; can track to lower elevation angles than codeless receivers |
Must jam two bands; satellite and receiver costs increase; satellite power requirements increase; frequency allocation considerations |
IIR |
|
|
3 |
Y C/A |
Y C/A |
C/A- or P-like code narrow or wide band signal |
Improved accuracy, improved anti-jam for civilians; ionospheric correction; cycle ambiguity |
More difficult to deny signal by jamming; more satellite power required |
IIF |
|
4 |
Y C/A |
Y C/A |
Y-like code(military only) wide-band signal |
Improved anti-jam for the military ionospheric correction for civilians; improved cycle ambiguity; improved direct acquisition of Y-code |
Military receiver costs may increase; must jam two bands; may require more satellite power; frequency allocation considerations |
IIF |
|
5 |
Y C/A |
Y |
— |
Baseline |
Baseline |
Baseline |
|
6 |
Pa C/A |
Y |
— |
Improved accuracy, improved anti-jam; some codeless receivers will have improved performance |
current military dual-frequency receivers won't work; some current civilian codeless receivers won't work; must make changes to satellite |
IIF |
|
7 |
Y C/A |
Pa |
— |
Improved accuracy, anti-jam; civil ionospheric; correction cycle ambiguity |
More difficult to deny signal by jamming, current military dualfrequency receivers won't work; must make changes to satellite |
IIF |
|
8 |
Y C/A |
C/A |
— |
Civil ionospheric correction; improved cycle ambiguity, some jam resistance |
Military receiver costs increase; must jam two bands; satellite power may increase; no dual-frequency military ionospheric correction |
(Current) II/IIA |
|
9 |
Pa C/A |
Pa |
Y-like code(military only) wide-band signal |
Precision; improved anti-jam; provides ionospheric correction for civilian users; improved cycle ambiguity |
Military receiver costs increase; must jam two bands; satellite power may increase; possible frequency allocation difficulties; no dual-frequency military-only ionospheric correction |
IIF |
|
a. "P" refers to the unencrypted code |
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