Iterative Decoding with Reduced SIR for Faster TPC Convergence
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The outer loop transmit power control (TPC) in WCDMA systems converges slowly for low block error rate (BLER) targets, leading to inefficient use of system capacity due to prolonged higher signal-to-interference ratios (SIR) levels.
Innovation Solution
A method and apparatus to determine the excess SIR of a communication channel by decoding received information blocks with reduced effective SIR, allowing for adaptive adjustment of the down-step in power control algorithms, such as the Jump Algorithm, to achieve faster convergence and optimize SIR targets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer loop TPC uses conventional power control algorithms (e.g., Jump Algorithm) to achieve low BLER targets, then the block error rate is reduced, but the convergence speed becomes slow and system capacity is wasted due to prolonged use of higher SIR targets
Solution Approach 1:
The patent applies preliminary action by performing iterative decoding with intentional SNR/SIR reduction before final decoding. The receiver decodes the information block multiple times, reducing the effective SIR in subsequent iterations to determine the excess SIR. This preliminary iterative process enables the system to anticipate the exact SIR needed for successful decoding, allowing the outer loop TPC to converge faster by avoiding prolonged use of higher SIR targets than necessary.
Solution Approach 2:
The patent implements feedback by using the decoding results from iterative decoding with reduced SIR to determine the excess SIR, which then feeds back into the outer loop TPC algorithm. The excess SIR calculation provides precise feedback about the actual SIR requirement, enabling adaptive adjustment of the down-step in power control algorithms. This feedback mechanism allows the system to learn from each decoding attempt and adjust future power control decisions accordingly, significantly improving convergence speed while maintaining low BLER targets.
2Reliability
If the outer loop TPC maintains higher SIR targets for extended periods to ensure decoding reliability, then the block error rate is kept low, but system capacity is wasted and efficiency is reduced
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the effective SIR during iterative decoding. Instead of maintaining a fixed high SIR target throughout the decoding process, the system progressively reduces the effective SIR in subsequent decoding iterations. This parameter change strategy allows the system to maintain decoding reliability through the iterative process while ultimately achieving lower average SIR requirements, thereby improving system capacity utilization and reducing waste.
3Measurement precision
If the receiver decodes information blocks multiple times with reduced effective SIR to determine excess SIR, then the accuracy of SIR estimation is improved, but the processing time and computational complexity increase
Solution Approach 1:
The patent applies partial or excessive action by performing iterative decoding with intentional SNR/SIR reduction a limited number of times rather than indefinitely. The system stops the iterative process when the excess SIR determination is sufficiently accurate, avoiding excessive computational complexity. This balanced approach ensures adequate SIR estimation accuracy for effective outer loop TPC control while preventing unreasonable processing time penalties.
Data Source
AI summary
The excess signal-to-interference ratio (SIR) or the like of a communication channel is determined by repeatedly decoding received information with successively reduced effective SIR. The step size in an outer power control algorithm, for example a Jump Algorithm, such as that commonly used for transmit power control in communication systems can then be adaptively adjusted based on the excess SIR, enabling faster convergence. Decoder hardware already present in a user equipment, such as a mobile telephone or other receiver, can advantageously be used.