Acquisition and Fine Acquisition of Weak GPS L2C and L5 Signals under High Dynamic Conditions for Limited-Resource Applications

BIOGRAPHY Nesreen Ziedan received a B.S. (with honors) in Electri- cal Engineering from Zagazig University, Egypt, in 1997; an Information Technology Diploma in Computer Networks from the Information Technology Institute, Egypt, in 1998; an M.S. in Control and Computer Engineering from Man- soura University, Egypt, in 2000; and a Ph.D. in Electrical Engineering from Purdue University, USA, in 2004. She was a lecturer in the Computer and Systems Engineering Department at Zagazig University from 1997 to 1999. She also worked as a consultant in 2004-2005, and as a research associate at Miami University in 2005. ABSTRACT Acquisition and fine acquisition algorithms are developed to work with weak L2C and L5 GPS signals. The algo- rithms utilize the structures and properties of the new sig- nals to achieve high performance with reduced processing and memory requirements. This is to allow the use of the new signals with applications that have limited resources. Long coherent and incoherent integrations are used, with- out requiring any assisting information. Correlation is per- formed using new versions of the modified Double Block Zero Padding (MDBZP) that was introduced for weak L1 C/A signals. The acquisition of the L2C signal consists of three stages: Acquisition of the CM signal; fine acquisition of the phase, Doppler shift and Doppler rate; and acquisition of the CL signal. The acquisition of the I5 and Q5 channels is per- formed separately. The Q5 channel is used for the fine ac- quisition of the carrier. The coherent integration used with the acquisition of the L2C/CM code and the L5/I5 channel is a multiple of one data bit interval. The most likely data bit combination is es- timated over each PIT and used to remove the data bits prior to including each coherent integration result into a longer in- coherent accumulation. The coherent integration used with the data-less L2C/CL and Q5 channel can take any length. In addition, a method is introduced to deal with the acquisi- tion of high dynamic signals The performance of the developed algorithms are (lemon- strated using simulated GPS signals with carrier to noise ra- tio down to 10 dB-Hz, and TCXO clocks. The results have shown the ability of the algorithms to work reliably with such weak signals.