Dual Port CDMA Signal De-correlation for Receive Power
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Solution Overview
Problem
Dual transmission of the same wireless signal in wireless communication systems can result in power fluctuations and signal cancellation at the receiver due to phase relationships between the signals, especially in highly correlated channels, leading to reduced receiver signal strength and potential performance worse than single transmission in certain scenarios.
Innovation Solution
The implementation of an open loop or feedforward technique using different code division multiplex access (CDMA) codes for dual transmission, where a first CDMA code is applied to a baseband signal to generate a first signal transmitted via one antenna and a second CDMA code is applied to the same baseband signal to generate a second signal transmitted via another antenna, allowing the receiver to extract each signal using its respective code, thereby avoiding signal cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If dual transmission of the same wireless signal is used to increase receive power, then the transmit power is doubled, but signal cancellation occurs due to phase relationships between the signals
Solution Approach 1:
The patent divides the single transmission signal into two separate transmission paths, each applying a different CDMA code to the same baseband signal. This segmentation allows the signals to be transmitted simultaneously through different antenna ports while maintaining distinguishability through code orthogonality, preventing cancellation while achieving power diversity.
Solution Approach 2:
The patent changes the code parameter by applying different CDMA codes (first CDMA code and second CDMA code) to the same baseband signal in dual transmission. This parameter change ensures that even though the signals are transmitted simultaneously, they remain distinguishable at the receiver through code-based separation, avoiding phase-related cancellation while maintaining power benefits.
2Reliability
If dual transmission is used to improve signal strength, then more signal instances are sent, but the system complexity increases due to need for code management and separation
Solution Approach 1:
The patent employs feedback mechanisms where the receiver detects the transmitted signal, determines the phase relationship between the dual transmitted signals, and feeds back this information to the transmitter. This feedback enables the transmitter to adjust the CDMA codes or transmission parameters to maintain optimal signal separation, managing system complexity through intelligent control rather than purely structural complexity.
Solution Approach 2:
The patent introduces CDMA codes as an intermediary layer between the baseband signal and the physical transmission. These codes act as mediators that enable signal separation at the receiver without requiring complex hardware modifications. The codes provide a mathematical framework for distinguishing between simultaneously transmitted signals, simplifying the overall system architecture compared to other dual transmission methods.
3Reliability
If different CDMA codes are applied to separate the signals, then signal cancellation is avoided, but the processing complexity at the receiver increases
Solution Approach 1:
The patent replaces physical signal separation mechanisms (such as spatial or temporal separation) with code-based separation using CDMA. Instead of using complex hardware to separate signals in the physical domain, the system uses mathematical code orthogonality to achieve separation through processing. This substitution reduces hardware complexity while managing processing requirements through efficient correlation-based detection.
Data Source
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AI summary
User equipment (UE) applies a first code division multiplex access (CDMA) code to a baseband signal to generate a first signal, and a second CDMA code to the baseband signal to generate a second signal. The UE then transmits the first signal to a receiving device via a first antenna, and the second signal to the receiving device via a second antenna. The receiving device receives the first and second signals as a combined signal at an antenna, and extracts the first signal from the combined signal using the first CDMA code, and extracts the second signal from the combined signal using the second CDMA code. The CDMA codes may be real-valued or complex-valued. In some embodiments, the UE may separate the baseband signals into first and second portions, and transmit the first portion as part of the first signal and the second portion as part of the second signal.