PN Array Despreading for Random-Phase CDMA Collision Resolution
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Solution Overview
Problem
Existing mesh pattern networking systems face limitations in capabilities and functionalities due to collisions and the need for orthogonal codes in multiple access communication systems, which restrict efficient data transmission and demodulation.
Innovation Solution
A random phase multiple access communication interface system that uses spread spectrum modulation without orthogonal codes, employing a pseudo-noise (PN) code with randomly selected chip offsets for non-coordinated data transmission, allowing for retransmissions to resolve collisions and enabling secure communication through unique PN codes for each tag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If orthogonal codes (Walsh codes) are used for CDMA multiple access, then different communication channels can be correlated, but the system complexity increases and requires precise code synchronization
Solution Approach 1:
The patent extracts and removes the orthogonal code requirement from the CDMA system, using only pseudo-random noise (PN) codes without Walsh codes. This simplifies the system by eliminating the need for precise orthogonal code synchronization while maintaining multiple access capability through random phase offsets.
Solution Approach 2:
The patent changes the parameter of code synchronization from precise orthogonal code alignment to random phase offset selection. By using random phase offsets instead of synchronized orthogonal codes, the system achieves multiple access with reduced synchronization requirements and lower complexity.
2Reliability
If random phase offsets are used for non-coordinated transmission, then collision resolution improves, but the timing synchronization complexity increases
Solution Approach 1:
The patent introduces dynamic random phase offsets that change for each transmission frame. This dynamic parameter allows the system to resolve collisions by ensuring that retransmissions use different phase offsets, improving reliability while the randomness inherently simplifies timing synchronization requirements.
Solution Approach 2:
The random phase offset mechanism serves itself by automatically resolving collisions without requiring complex external synchronization. When collisions occur, the random phase offsets naturally differentiate the signals, and retransmissions use new random offsets to avoid repeated collisions, eliminating the need for sophisticated timing coordination.
3Productivity
If multiple tags transmit simultaneously using the same PN code, then bandwidth efficiency improves, but signal demodulation becomes difficult due to collisions
Solution Approach 1:
The patent adds a temporal dimension to the spreading code by using the same PN code across multiple tags but offsetting them in time by random phase amounts. This transforms the problem from spatial code separation (orthogonal codes) to temporal phase separation, maintaining bandwidth efficiency while enabling demodulation through the PN array despreader that accounts for these phase differences.
Data Source
AI summary
A method for de-spreading spread data includes receiving a data stream by multiple access communication where the received data stream is spread using a pseudo-noise (PN) code; multiplying a first portion of the received data stream including data from a first user by a first portion of a PN signal to obtain a first product; providing the first product to a first counter; multiplying a second portion of the received data stream including data from a second user by the first portion of the PN signal to obtain a second product; providing the second product to a second counter; and determining whether the first portion of the PN signal and the second portion of the PN signal produce valid sequences based at least in part on the first product and the second product.