CDMA Pilot Channel Tracking Sensitivity via Coherent Summing
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Solution Overview
Problem
In CDMA systems, particularly satellite positioning systems, the energy of the pilot channel is often insufficient for accurate tracking of the pseudo random noise code, leading to reduced measurement sensitivity and increased noise in navigation solutions.
Innovation Solution
The system recombines a portion of the energy from the data channel into the pilot channel, enhancing the pilot channel's energy and improving tracking sensitivity through a coherent summing process, which involves demodulating and re-encoding data signals to create a higher-energy signal for the tracking loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the total energy is divided between DATA and PILOT channels with fixed allocation, then the system maintains simple energy distribution, but the PILOT channel energy becomes insufficient for accurate tracking
Solution Approach 1:
The patent combines the pilot channel signal with a regenerated pilot signal derived from the data channel through coherent summing. This merging of energy sources increases the pilot channel energy available for tracking without requiring additional transmit power, directly resolving the energy insufficiency problem while improving tracking accuracy
Solution Approach 2:
The system uses decoded data from the data channel to regenerate a pilot signal, creating a feedback loop where the data channel information is reused to enhance the pilot channel. This feedback mechanism allows dynamic energy reallocation based on signal conditions, improving pilot energy availability when needed
2Measurement precision
If more energy is allocated to PILOT channel for better tracking, then tracking sensitivity improves, but the data channel energy decreases
Solution Approach 1:
The system uses the data channel's own decoded information to generate a regenerated pilot signal, allowing the data channel to serve the pilot channel's energy needs. This self-service approach enables energy reallocation without external intervention or additional total energy input, maintaining the balance between data and pilot energies
Solution Approach 2:
The patent dynamically adjusts the effective energy distribution by changing the signal processing parameters - specifically, by coherently summing the original pilot with a regenerated version. This parameter change in signal combination allows flexible energy reallocation based on tracking requirements without permanently reducing data channel energy
3Measurement precision
If the system uses conventional measurement approaches with fixed pilot energy, then the system operation remains simple, but measurement noise increases
Solution Approach 1:
By merging the original pilot channel signal with a regenerated pilot signal through coherent summing, the patent combines multiple signal sources to increase the effective pilot energy. This combination reduces measurement noise by improving the signal-to-noise ratio, directly addressing the harmful effect of noise while maintaining simple system operation through unified signal processing
Data Source
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AI summary
A method comprises receiving a data signal on a data channel and a pilot signal on a pilot channel, demodulating the received data signal and the received pilot signal to obtain a demodulated data signal and a demodulated pilot signal, generating a data stream by decoding the demodulated data signal, generating a feedback signal by encoding the data stream, and performing a measurement of a coherent sum signal comprising the coherent sum of (1) the demodulated pilot signal and (2) the product of the demodulated data signal and the feedback signal.