Acquisition Performance of Assisted and Unassisted GNSS Receivers with New Satellite Signals

Seppo Turunen

Abstract:	Location based services (LBS) are a rapidly evolving field of wireless data services that provide location related information to the users of mobile terminals. The user’s position is determined by terrestrial radiolocation or, more and more often, by satellite positioning. The LBS information is almost invariably provided through cellular telephone networks that offer the required availability, mobility and transmission capacity. They also allow assistance information to be downloaded to the GNSS receiver to facilitate satellite acquisition in poor signal conditions. Some location based services are intended for open-air use while others are meant for use in urban and indoor areas. As satellite signals suffer heavy attenuation in penetrating structures and obstacles, stringent sensitivity requirements and test specifications have been included in mobile telephone standards to make sure that the GNSS receivers integrated in phones operate properly under weak signal conditions. While the design of consumer GNSS receivers is still mainly focused on GPS C/A reception, satellite operators are envisaging signals with new coding and modulation schemes. The original GPS and Glonass specifications dedicated the short C/A codes to acquisition and the longer P(Y) codes to tracking. No similar distinction is made in the specifications of the new GPS L1C, L2C and L5 signals or in the specifications of the Galileo E1, E5 and E6 signals. Instead, all signal components in both standards have relatively long ranging codes and many of them also have high bit rates. Consequently, their search spaces are wider and bit energies lower than those of the GPS L1 C/A signal so that their acquisition is likely to be more difficult. The interface control documents of the new GNSS signals do not discuss receiver operation or performance. Supplementary analysis is therefore needed to set realistic performance targets for future receivers. This study analyses the acquisition sensitivity that can be achieved with the new signals when they are combined with various levels of assistance. Special attention is paid to the role of search space dimension under the assumption that processing capacity limitations do not constrain receiver performance.
Published in:	Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007) September 25 - 28, 2007 Fort Worth Convention Center Fort Worth, TX
Pages:	211 - 218
Cite this article:	Turunen, Seppo, "Acquisition Performance of Assisted and Unassisted GNSS Receivers with New Satellite Signals," Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007), Fort Worth, TX, September 2007, pp. 211-218.
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