STAP-MUD Receiver for CDMA Interference Cancellation
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Solution Overview
Problem
CDMA wireless systems face challenges in maximizing system capacity due to multiple access interference (MAI), especially when power control is not effective, and auxiliary receivers need to extract low-level signals in dense multi-user environments with varying power levels.
Innovation Solution
The combination of space-time adaptive processing (STAP), interference cancellation, and multi-user detection (MUD) using adaptive temporal reconstruction filters (ATRF) enables accurate channel estimation and signal cancellation, allowing for the extraction of low-level CDMA signals even when power levels vary significantly, by recreating multipath channel structures and minimizing cancellation residuals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional matched filter receiver is used in CDMA system, then system implementation is simple, but multiple access interference degrades performance and limits system capacity
Solution Approach 1:
The receiver is divided into multiple functional components: conventional matched filter for initial detection, interference estimation unit for characterizing MAI, and cancellation unit for removing estimated interference. This segmentation allows the system to maintain implementation simplicity while improving signal reception quality through iterative interference removal.
Solution Approach 2:
The receiver employs feedback mechanisms where detection results from the matched filter are used to estimate interference, which is then canceled from the received signal. The process iterates with updated detections, creating a feedback loop that continuously improves signal quality and enables operation in high interference environments.
2Reliability
If power control is implemented to manage MAI, then link quality improves, but power control speed limitations and auxiliary receiver requirements create new problems
Solution Approach 1:
The interference estimation and cancellation units act as intermediaries between the received signal and the detector. Instead of relying on fast power control to manage interference, the system uses these intermediary components to estimate and remove MAI from the signal path, enabling reliable detection without requiring rapid power control responses.
Solution Approach 2:
The receiver performs self-service by autonomously estimating and canceling its own interference without external power control intervention. The interference cancellation unit uses the received signal and detection results to generate and apply cancellation signals, making the system independent of power control speed limitations.
3Adaptability or versatility
If auxiliary receivers operate without power control, then they can monitor system health and assist geolocation, but they must contend with wide range of received power levels making signal extraction difficult
Solution Approach 1:
The receiver employs dynamic interference cancellation where the interference estimation and cancellation processes adapt to the current signal conditions. The system dynamically adjusts cancellation parameters based on detected signal levels and interference characteristics, enabling accurate extraction of weak signals across wide power ranges without requiring power control.
Solution Approach 2:
The system moves beyond traditional single-dimension power control by introducing temporal and iterative dimensions to interference management. Through multiple detection-cancellation iterations and use of temporal signal characteristics, the receiver extracts weak signals from dense multi-user environments where power levels vary by 30 dB or more.
Data Source
AI summary
Methods and systems in a wireless receiver for enabling the reception of input signals at varied power levels in the presence of co-channel interference utilizing combinations of space-time adaptive processing (STAP), interference cancellation multi-user detection (MUD), and combined STAP/MUD techniques. In MUD, code, timing, and possibly channel information of multiple users are jointly used to better detect each individual user. The novel combination of adaptive signal reconstruction techniques with interference cancellation MUD techniques provides accurate temporal cancellation of interference with minimal interference residuals. Additional methods and systems extend adaptive signal reconstruction techniques to take Doppler spread into account. STAP techniques permit a wireless receiver to exploit multiple antenna elements to form beams in the direction of the desired signal and nulls in the direction of the interfering signals. The combined STAP-MUD methods and systems increase the probability of successful user detection by taking advantage of the benefits of each reception method. An additional method and system utilizes STAP techniques in the case where no pilot signal is available. This method compares the outputs of various hypothesized STAP solutions.