Evaluation of High Sensitivity GPS Receivers

GPS is the popular positioning technology widely used for many applications. However, many GPS receivers have difficulty tracking signals in harsh environments such as urban canyons or indoors. So-called “high sensitivity” GPS (HSGPS) receivers have been developed to address this problem, and nowadays many different models of HSGPS receivers can be found in the market. For example, the latest mobile phones typically have built-in HSGPS chipsets. In addition, many HSGPS receivers accept “assisted GPS” (A-GPS) messages to reduce the time-tofirst-fix (TTFF) and possibly increase the sensitivity even further. However, the performance of these receivers in terms of TTFF and accuracy does vary. This paper evaluates several HSGPS receivers: ublox LEA-4P, Navman Jupiter 32, ublox EVK-5H and SiRF GSCI-5000. Several mobile phones, such as the Nokia N95 and iPhone models were also tested. Several experiments were conducted. One is a static test for a standalone GPS receiver. Four A-GPS tests were also conducted using an Open Source GNSS Reference Server to provide the AGPS assistance messages. The TTFF, positioning accuracy and the sensitivity to weak signals has been investigated. A kinematic test was also carried out. Several scenarios were utilised in order to test all HSGPS devices.