Closed-Loop Uplink Phase Adjustment for Coarse Diversity Feedback
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Solution Overview
Problem
In mobile wireless communications, existing transmit diversity systems face challenges in providing sufficient sensitivity for optimum diversity gain due to coarse phase feedback resolution, often limited to two bits, which restricts the ability to optimize uplink transmission quality.
Innovation Solution
A method for mobile devices to adjust phase differences based on closed-loop transmit diversity feedback by calculating a modified phase parameter value between the current and previously transmitted phase values, allowing for finer phase adjustments and reducing the risk of overcorrection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a two-bit codebook size limitation is used for phase feedback, then downlink bandwidth is saved, but phase feedback resolution becomes coarse and sensitivity for diversity gain is insufficient
Solution Approach 1:
The mobile device dynamically adjusts the phase parameter by calculating a modified value between the indicated phase and previously transmitted phase, rather than directly applying the coarse feedback value. This dynamic adjustment enables finer phase control within the limited feedback framework.
Solution Approach 2:
The system changes the phase parameter incrementally by introducing a modified phase value that lies between the coarse feedback indication and the previous phase value. This parameter interpolation technique effectively increases resolution without expanding feedback bit width.
2Quantity of substance
If phase feedback options are limited to four values (0, +90, 180, or −90 degrees), then feedback signal size is reduced, but the ability to provide sufficient sensitivity for optimum diversity gain is compromised
Solution Approach 1:
Instead of directly applying the full phase adjustment indicated by the coarse feedback, the mobile device applies a partial adjustment by selecting a modified phase value between the indicated value and the previous phase value. This partial action provides finer control and prevents overcorrection, improving diversity gain optimization.
Solution Approach 2:
The system uses closed-loop feedback where the mobile device receives phase feedback from the base station, calculates a modified phase value, applies it, and continues receiving feedback. This iterative feedback process enables progressive refinement of phase alignment, achieving better diversity gain with limited feedback resolution.
Data Source
AI summary
A mobile communications method, device, and system for adjusting a phase parameter in a diversity signal, based at least in part on phase feedback from a base station. While in uplink communication with a base station, a mobile device may receive a phase feedback signal from the base station. The mobile device may calculate a modified value of a phase parameter based on the phase feedback signal in order to transmit diversity signals with a gradual change in phase difference. The modified value may be between a phase parameter value indicated by the base station's phase feedback signal and a phase parameter value initially transmitted by the mobile device.