Outer-Loop Adjustment for Wireless Link Adaptation
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Solution Overview
Problem
Existing wireless communication systems face inaccuracies in link quality estimation, leading to overestimation of higher throughput modulations and underestimation of lower throughput modulations, resulting in suboptimal MCS selection and degraded cell throughput.
Innovation Solution
The method involves updating outer-loop adjustment values based on Transport Block feedback messages, using acknowledgement and non-acknowledgement counters to calculate an estimated Block Error Rate (BLER), and adjusting the upward and downward step sizes for each modulation using geometric, arithmetic, or greedy methods to refine channel quality measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single upward step size is used for all modulation schemes, then the outer-loop adjustment is simple to implement, but the BLER cannot be accurately controlled for different modulation schemes with different error rates
Solution Approach 1:
The patent segments the single upward step size into multiple modulation-specific upward step sizes (up_step_64qam, up_step_16qam, up_step_qpsk). Each modulation scheme has its own upward step size parameter that is independently adjusted based on its specific BLER performance, allowing precise control while maintaining implementation simplicity through modular parameter management.
Solution Approach 2:
The patent applies local quality by making the upward step size adaptation specific to each modulation scheme's local characteristics. Different modulation schemes (64QAM, 16QAM, QPSK) have different inherent error rates and channel sensitivity, so each gets tailored upward step sizes that match its local performance requirements rather than using a uniform approach.
2Measurement precision
If modulation-specific upward step sizes are used for each modulation scheme, then the BLER control accuracy for different modulations is improved, but the system complexity increases due to multiple step size parameters
Solution Approach 1:
The patent implements self-service through automatic BLER-based adaptation of upward step sizes for each modulation scheme. The system automatically monitors actual BLER performance and adjusts the appropriate upward step size (up_step_64qam, up_step_16qam, up_step_qpsk) based on whether BLER is above or below target, eliminating the need for manual configuration and reducing operational complexity despite having multiple parameters.
Solution Approach 2:
The patent uses feedback mechanisms where actual BLER measurements are continuously monitored and fed back to adjust the modulation-specific upward step sizes. The outer-loop controller receives BLER feedback and automatically tunes up_step_64qam, up_step_16qam, and up_step_qpsk to maintain target BLER performance, making the system adaptive and reducing the need for complex manual parameter management.
Data Source
AI summary
A method and base station for adjusting outer-loop adjustment values used for link adaptation in a wireless communication network is provided. A modulation of a user equipment is determined and a success or failure of a Transport Block (TB) based on a TB feedback message is determined. Based on the TB feedback, one of an acknowledgement counter and a non-acknowledgement counter is incremented corresponding to the determined modulation. An upward step size for the determined modulation is updated based on the respective acknowledgement counter and the non-acknowledgement counter to affect link adaption.