gnss today

POPULAR LOCATION-DEPENDENT SERVICES HAVE SERIOUS PERFORMANCE DEFICIENCIES

Today’s mobile GNSS technology has significant reliability and accuracy limitations because it depends on L1 signaling developed in the 1970s. L1 signals are susceptible to interference, struggle with building and tree blockage, have no error correction, and have low transmission power, which limits position availability and makes legacy L1-dependent receivers less reliable. In urban areas, positioning can have 40-100 meters of error, placing users on the wrong side of the street or even on the wrong block. Large position errors significantly degrade popular location-dependent services such as rideshare, pedestrian navigation, and 911 emergency calls.

L5 – THE FIRST MAJOR NAVIGATION SATELLITE UPGRADE IN DECADES

All navigation satellite constellations now broadcast a modernized signal called L5, which has higher transmission power, wider bandwidth and error correction, and is in the protected aviation band, making L5 much more reliable than legacy L1. L5 is a dual sideband signal transmitting much more information, opening the door for receivers that can make high-precision measurements and also compensate for multipath.

HYBRID L1/L5 SOLUTIONS – DOUBLE THE RF RECEIVE CHAIN AND LIMITED BY L1 PERFORMANCE

SoC providers have adopted dual-frequency (L1/L5) architectures to use L5, but these hybrid receivers first acquire L1 before they can take advantage of L5’s accuracy—they won’t work if L1 isn’t acquired. Furthermore, hybrid L1/L5 receivers double the RF front end, increasing antenna subsystem complexity, and increasing silicon size, power, and cost for the OEM.

“While GPS works well under clear skies, its location estimates can be wildly inaccurate (with a margin of error of 50 meters or more) when we need it the most: in densely populated and highly built-up urban areas…”

Uber Engineering Blog