GPS signal structure and performance characteristics

The detailed signal structure used in the Global Positioning System satellite navigation system is described after a study of the performance requirements and concepts for high-accuracy, real-time navigation by satellites. The various perturbation effects on the navigation signal and overall system are considered. These include relativistic effects, multiple access interference between satellites, tropospheric and ionospheric propagation delays, multipath, and other interference effects. The GPS signal has two components at center frequencies of 1575.42 MHz and 1227.6 MHz. The use of L-band results in smaller ionospheric delay effects. Relativistic effects are partially compensated for by offsetting the 10.23 MHz clock rate. Both P-code and C/A-code are used to modulate the signals.