Short Acquisition Signal for Fast Long PN Code Sync
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Solution Overview
Problem
In secure spread spectrum communication systems, the acquisition of signals is time and energy consuming due to the need for complex and long spreading codes, which conflicts with the requirement for fast acquisition and low probability of intercept, especially in environments with Doppler effects and asynchronous node discovery.
Innovation Solution
The use of an acquisition signal spread with a relatively short spreading code that contains information for acquiring a target signal spread with a longer code, transmitted in a separate channel, allowing for quick acquisition without compromising security, using self-jamming techniques to enhance security and reduce hardware complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If long spreading codes are used for secure communication, then security is improved, but acquisition time increases
Solution Approach 1:
The patent divides the long spreading code into multiple segments and transmits them across different channels. The acquisition signal uses a short code to quickly establish initial contact, while the full long code is transmitted in segments across multiple channels, allowing the receiver to reconstruct the complete code without searching through all possible phases, thus maintaining security while reducing acquisition time
Solution Approach 2:
The system performs preliminary acquisition using a short spreading code before transmitting the full long spreading code. The acquisition signal carries essential information that enables the receiver to quickly synchronize and then efficiently acquire the complete long code, avoiding the need for exhaustive search procedures
2Reliability
If long spreading codes are used for secure communication, then security is improved, but energy consumption increases
Solution Approach 1:
The long spreading code is segmented and transmitted across multiple channels, allowing the receiver to process smaller code segments in parallel rather than searching through the entire long code sequentially, reducing computational energy requirements while maintaining the security benefits of the full code
Solution Approach 2:
The acquisition signal acts as an intermediary that carries essential information about the target signal's spreading code. This intermediary enables the receiver to quickly identify and acquire the long code without performing energy-intensive exhaustive searches, thus reducing overall energy consumption while preserving security
3Reliability
If acquisition search examines many different codes and offsets, then reliability of signal detection is improved, but acquisition complexity increases
Solution Approach 1:
The acquisition process is segmented into two stages: first, quick acquisition of the short code to establish initial synchronization and identify the channel; second, efficient acquisition of the long code segments using information from the first stage. This segmentation reduces the complexity of examining all possible codes and offsets by breaking the problem into manageable parts
Solution Approach 2:
The system performs preliminary acquisition of essential synchronization information using the short code before proceeding to acquire the full long code. This preliminary action provides the receiver with key information that simplifies the subsequent acquisition process, reducing the need for exhaustive searches while maintaining detection reliability
Data Source
AI summary
The present invention concerns methods and apparatus for use in a spread spectrum communications system. In particular, in a method of the present invention information useful for acquiring a target signal is selected; the information is incorporated in an acquisition signal; the acquisition signal is transmitted; the target signal is spread with a spreading code; and the target signal is transmitted. At a receiving node, the acquisition information useful for acquiring the target signal is recovered from the acquisition signal and used to acquire the target signal. Apparatus in accordance with the present invention implement methods of the present invention. The methods and apparatus of the present invention can be used in node- and network-discovery situations.