Universal ranging code generator of GLONASS and GPS open navigation signals

GNSS signals are modulated by various ranging codes. The codes spread the signals' spectrums and help to measure propagation delays. There are plenty of signal types in modern systems, and, as a result, any navigation receiver must be able to generate different codes: Gold codes, maximum length sequences, Kasami codes and so on. The pluralism of codes causes the multiplicity of generators and additional receiver channel's complexity. This paper proposes a universal ranging code generator for GLONASS and GPS open service signals. The generator is an adjastable structure, which can be run-time reconfigurated for any signal type. It covers both the legacy and modernized signals and can be applied to other radio systems. The paper reviews the proposed generator, enumerates initialization parameters, shares experimental results and a programmable logic utilization analysis.

I. Introduction

Satellite navigation systems are used to determine the position and synchronization of users of these systems. Each system includes a satellite constellation in orbit, broadcasting navigation information and signals. One of the core functions performed by the navigation receiver is to measure the delay of the received signal. By estimating the travel time of signals from different satellites to receiver, the user's location can be calculate. The signal in GNSS is modulated by a pseudorandom sequence to increase the accuracy of the delay measurement. These sequences are known as the ranging (or primary) codes. Such signals are used not only for GNSS, but also for local navigation systems [1].