Spread Spectrum Signal Acquisition via Fragment Correlation
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Solution Overview
Problem
Existing spread spectrum signal receivers, particularly in cellular telephones, face difficulties in acquiring signals due to received signal strength, interference, and multipath distortion, and may experience fragmentation due to performance limitations or intentional disabling during busy processor conditions.
Innovation Solution
The method involves generating a replica signal with a pseudorandom noise code and coherently correlating it with a subject signal containing two fragments of the spread spectrum signal, with options to include a discontinuity or dummy data corresponding to the elapsed time between fragment receptions, to improve signal acquisition and handle fragmentation issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the receiver processes spread spectrum signals in a cellular telephone with a busy processor, then cellular communications can be maintained, but the spread spectrum signal acquisition deteriorates due to processor unavailability
Solution Approach 1:
The spread spectrum signal reception is segmented into multiple fragments that can be processed independently. The receiver collects signal fragments during periods when the processor is available, rather than requiring continuous processing. This segmentation allows the system to maintain cellular communications (high productivity) while still acquiring spread spectrum signals (maintained reliability) by processing signals in available time slots.
Solution Approach 2:
The receiver performs preliminary actions by collecting and storing signal fragments in a buffer during periods when the processor is available for cellular communications. These fragments are then correlated later when processing resources are available. This preliminary collection approach ensures that signal acquisition is not blocked by processor busy-ness, resolving the contradiction between maintaining communications throughput and ensuring signal acquisition reliability.
2Object-affected harmful factors
If the receiver is intentionally disabled during transmitter activity, then interference is reduced, but signal acquisition is interrupted causing fragmentation
Solution Approach 1:
The signal reception is divided into fragments collected during periods when the receiver is enabled, with gaps corresponding to when the receiver is disabled during transmitter activity. The correlation process is designed to handle these fragments and the gaps between them, allowing the system to reduce interference (by disabling the receiver during transmission) while still achieving reliable signal acquisition (by correlating the fragmented signals).
Solution Approach 2:
A correlation processor acts as an intermediary that bridges the fragmented signal segments. It correlates the received fragments with replica signals, effectively joining the discontinuous reception periods into a coherent acquisition process. This intermediary processing allows the system to benefit from reduced interference during transmission while maintaining signal acquisition reliability.
3Reliability
If coherent correlation is performed over signal discontinuities, then signal acquisition improves in difficult conditions, but the complexity of handling fragmented signals increases
Solution Approach 1:
Replica signals are prepared in advance with the same discontinuities and gaps as the expected received fragments. This preliminary preparation of matched replica signals simplifies the correlation process, as the receiver can directly correlate the fragments with pre-matched replicas without needing complex real-time analysis of the gap patterns, thus improving acquisition reliability while limiting complexity growth.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables better acquisition and handling of spread spectrum signals, ensuring unfragmented signal reception even under conditions of processor busy-ness or intentional receiver disabling, enhancing the reliability of signal processing in cellular telephones.
Implementation Method 1
coherently correlating the replica signal with the subject signal over the two fragments
Data Source
AI summary
A method of acquiring a received spread spectrum signal, especially a GPS signal, is disclosed together with a spread spectrum signal receiver and a cellular telephone incorporating such a receiver. The method comprises the steps of: providing a replica signal containing a pseudorandom noise code, corresponding to that of the spread spectrum signal; providing a subject signal containing two fragments of the spread spectrum signal initially received during respective time periods between which a further time period elapses; and coherently correlating the replica signal with the subject signal over the two fragments.