Early GPS receivers were painfully slow, requiring up to 20 minutes to achieve a first positional fix. Though tolerable in tight-loop tracking applications, such as jet airplanes, that delay was impractical for consumer and mobile applications.

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The evolution of dedicated search engines partially or fully implemented in hardware, coupled with network-based Ephemeris Assistance, improved fix time to 20 seconds under ideal operating conditions. Over time, these search engines have become larger and more capable. As a result, dedicated tracking engines were removed from most GPS receiver designs since redesigned search engines could perform both tracking and navigation functions.

Search and Tracking Basics

Search is fundamental to every GPS system. However, the search-engine-only architecture comes with significant design tradeoffs—higher power consumption and lower efficiency—than  a system that utilizes dedicated tracking engines.

Bill McInerney, product manager for Atheros FYX GPS solutions and FYX Location Core navigation software, holds a master’s degree in international business from the University of Texas at Dallas, and a BSME from the University of Massachusetts at Lowell.

Today’s GPS search engines perform many tasks, but consume lots of power in the process. While they can locate and track many satellite signals across the spectrum, such capacity is overkill once the satellites are located. At that point, the system needs only to track the satellites. In addition, a dedicated tracking engine is better suited to lock onto satellites than a search engine. Rather than continuously searching for a signal across the spectrum, tracking engines operate more efficiently by intelligently tracking satellite signals as they move.

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