Intersystem and Intrasystem Interference Analysis Methodology

The Global Navigation Satellite System (GNSS) community is quickly growing with the addition of more signals at higher power levels in the same frequency bands. Determining the effects of interference from different signals transmitted by the same system (intrasystem interference) and interference from signals transmitted by other systems (intersystem interference) warrants increasingly careful consideration. These interference effects may be determined through field testing, computer simulations, or analytical techniques. Analytical techniques do not provide the fidelity of field testing, but may give a reasonable estimate of interference effects to GNSS receivers. These analysis techniques are based on established theory and first-order estimates. The fundamental performance parameter to be analyzed is the receiver's effective carrier to noise density ratio, (C/N0)eff. Calculation of this parameter is dependent on several factors including the constellation size, signal modulations, signal power levels, and receiver filtering. While the degradation to effective C/N0 from each system is interesting to note, the receiver performance after taking into account all sources of interference is of primary interest. Different signals, systems, receiver architectures, and sources of interference can be addressed using the same, consistent, methodology merely by changing the parameter values.