Jack K. Holmes

A summary of the new GPS IIR-M and IIF modernization signals

This paper discusses the planned modernization of the block IIR-M and IIF GPS satellite signals, including the addition of the new military signal. In particular a brief review of the legacy signals is presented, followed by a description of the new military signal, the M code signal (with its data and data-less components). Next the new civil signal which is the replacement C/A code for L2, is discussed. Interplex combining is then presented. Interplex modulation combines three signals and provides a constant envelope to the power amplifier by producing an intermodulation term. Finally, the new L5 civilian signal is elucidated.

Frequency Band Sharing between NRZ and Split Spectrum Signals- Analysis and Simulation Results

Srini Raghavan has over 25 years of experience in design, simulation and analysis of satellite communication systems, spread spectrum systems, and signal processing. Currently, he is supporting several communication systems and Global Positioning System (GPS)-related activities at The Aerospace Corporation, where he is a Senior Engineering Specialist. He has a B.S. and M.Tech. from India, and an M.S. and Ph.D. in Electrical Engineering from the University of MissouriRolla, and is a Senior Member of IEEE and a member of ION, Eta Kappa Nu and Sigma Xi. Jack K. Holmes is a Distinguished Engineer at The Aerospace Corporation in the Communication Systems Subdivision. He has over 40 year’s of experience in analysis, simulation, and design of communication and spread spectrum systems. He is author of the book entitled “Coherent Spread Spectrum Systems” and has published approximately 45 papers in the area of communications, synchronization, and GPS-related subjects. He has been heavily involved in the military side of the GPS Modernization effort since February 1997. He is currently the GPS Code Acquisition design risk assessment subteam leader for the GPS Modernization risk assessment team. Jack received his B.S., M.S., and Ph.D. degrees at UCLA in Electrical Engineering, and is a senior member of the IEEE and a member of ION, Tau Beta Pi, and Sigma Xi.

A NEW SIGNAL PLAN FOR GPS

GPS has become a unique satellite based service for a number of reasons. Originally a military only system, GPS civilian use has far overtaken the original user base. The limitations of the current civil service have resulted in a reevaluation of the fundamental signal structure of GPS. In this paper a proposed new GPS signal scheme is described that provides for the simultaneous modulation of the carriers with the C/A-code, the P(Y)-code, and a new military code (v-code), on the existing GPS frequencies within the allocated bands. The biggest advantage of this method is that it provides sufficient spectral isolation between the civil and military signals, allowing both user groups to co-exist in the same frequency band. Another advantage of this concept is that it allows for backward compatibility with the existing military and commercial receivers while providing an additional C/A-code on the L2 carrier. This paper outlines the assumptions and criteria used to satisfy the Presidential Decision Directive for the future of GPS using this new signal plan within the currently registered frequencies. Proof of concept results obtained through laboratory tests are presented. In addition, signal generation and receiver design are discussed.

Code loop mean slip time comparison of nrz and boc signals

When selecting signals for GPS, Galileo or other navigational systems it is necessary to obtain the minimum code tracking error and the lowest C/No threshold for the code tracking loop in order to optimize the system navigational performance. In this paper the question that is addressed is “Does the Binary Offset Carrier (BOC) symbol have a threshold advantage (mean time for code loop loss of lock) over Nonreturn to zero (NRZ) type symbols, given that the discriminator gain is larger? More generally how does the mean time to slip depend on the chip duration?” One’s intuition might suggest that since the code loop discriminator slope is greater when comparing say BOC code to the NRZ P(Y) code that the threshold is also higher, however that is not necessarily true. Both analysis and simulation will be used to address this issue. The analysis is based on mean passage time theory for first order Markov processes. Simulation will be used for comparison with the theory for first order code tracking loop mean time to lose lock. White Gaussian noise is assumed and no channel filtering has been assumed. 1. 2. 3. 4. 5. 6. 7. 8. 9. TABLE OF CONTENTS INTRODUCTION ................................... 1 PROBLEMDEFINITION. ........................ 3 DESCRIPTION OF NRz AND BOC SIGNALS.2 FIRST ORDER CODE LOOP MODEL.. ........ 3 ANALYSIS OF THE MEAN SLIP TIME.. ........ 4 MEAN SLIP RESULTS FOR BOC AND =..5 CODE TRACKING LOOP SIMULATION.. .. .. 4 CONCLUSIONS AND FURTHER WORK.. ..... 5 APPENDIX.. .................................. ..A-l

The mean cycle slip time for first-, second-, and third-order PLLs

This paper presents an analytic model for the mean time to lose lock for first-, second-, and third-order phase-locked loops (PLLs). The analytic model is of the same form as that of a first-order PLL with the appropriate corrections for second- and third-order PLLs. The modeling was done on SystemVue simulation.

A Theoretical Approach to Determining the 95% Probability of TTFF for the P(Y) Code Utilizing Active Code Acquisition

This paper deals with the problem of mathematically describing the probability specification of the time to first fix (TTFF) for a navigational receiver such as GPS, as a function of the receiver search time and the initial conditions. Commonly many analyses are based on computing the mean TTFF; however, in contrast, many navigational specifications are for the 95% probability TTFF. For the GPS P(Y) code, results are provided for both the mean TTFF and the 95% probability of TTFF, and the two times are compared. The approach is approximate, but is believed to be quite accurate.

Inter-BOC Signal Interference - Tracking Loop Performance*

Abstract-The Global Positioning System (GPS) is a spread-spectrum system that employs direct-sequence spreading of the spectrum to achieve excellent ranging accuracy. Modernized GPS will also use a directsequence spread-spectrum (DSSS) system, but unlike the current GPS signal, which uses a non-return-tozero formatting of the code symbol, it employs a code-formatting scheme known as Binary Offset Carrier (BOC) that results in split-spectrum modulation. An important consideration in the design of a spreadspectrum signal is to provide a certain level of protection against intentional and also unintentional interference that may be experienced by the spread-spectrum signal. Even without the external interference, a Code Division Multiple Access (CDMA) system such as the GPS and the Galileo must contend with the CDMA noise within the system. GPS plans to add one more BOC signal in addition to the current C/A, P and M code signals. With this new signal, additional interference potential exists, along with the normal CDMA noise. In this paper such interference due to the new BOC signal to the current M code BOC signal, we call it Inter-BOC Signal Interference, is considered. Some simulation results are also presented.

Doppler removal losses using single-sideband frequency shifting for direct-sequence BPSK links

The process of removing the Doppler frequency of the input signal in the receiver on the input is performed by a Doppler removal circuit. The paper addresses the effects of quantizing the ideal sine waves for implementing the Doppler removal (a single-sideband rotation). Quantization levels of 1, 1.5, 2, 2.5, and 3 bits are considered and the quantization losses associated with those quantization levels are determined12.