GNSS receivers have been developed over 40 years with increasing levels of integration and performance, and are now able to operate in much more severe signal-degraded environments than before. Despite this, the goal of ubiquitous positioning with GNSS-only receivers is still far away, and GNSS receivers generally need support by combining, loosely or tightly, with other positioning systems.

This paper describes the Enhanced GPS system (EGPS), a system that tightly couples timing measurements and timing-based positioning made using cellular network signals, with GNSS receivers in cellular telephones. The system is able to achieve a near ubiquitous positioning capability, along with improvements in time to fix.