Uplink Transmit Diversity Weight Smoothing
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Solution Overview
Problem
Current uplink transmit diversity techniques in wireless communications systems face challenges in selecting appropriate pre-coding weights, leading to inferior uplink and downlink performance, especially in situations like soft handover, where abrupt changes in antenna weights can cause power discontinuities and increased interference.
Innovation Solution
The method involves detecting predetermined situations and applying restrictions on the selection and update of pre-coding weights to limit changes, ensuring that UEs and network nodes avoid using weights that could result in poor performance, by either restricting abrupt changes or only considering feedback from the serving base station during weight selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If uplink transmit diversity is implemented with dynamic pre-coding weight selection, then user and network performance can be maximized, but abrupt changes in antenna weights can cause power discontinuities and inferior performance
Solution Approach 1:
The patent implements dynamic pre-coding weight selection that adapts to channel conditions while incorporating smoothing mechanisms. The system dynamically adjusts antenna weights based on feedback from the base station but applies constraints to limit abrupt changes, thus maintaining both adaptability and stability in performance.
Solution Approach 2:
The patent modifies the pre-coding weight parameters by introducing smoothing constraints that limit the rate of change between consecutive weight selections. This parameter modification ensures that while the system can adapt to channel variations, it does so in a controlled manner that prevents power discontinuities and maintains performance stability.
2Device complexity
If switched antenna diversity is used, then implementation is simpler with single power amplifier, but channel estimates become outdated leading to worse effective signal-to-interference ratio
Solution Approach 1:
The patent applies preliminary smoothing actions to pre-coding weight transitions in switched antenna diversity. Before switching between antennas, the system prepares gradual weight transitions rather than abrupt switches, ensuring that channel estimates remain valid and effective signal-to-interference ratio is maintained while keeping the single power amplifier configuration.
3Productivity
If beam forming is implemented, then antenna beam can be shaped towards target receiver, but one power amplifier is required for each transmit antenna
Solution Approach 1:
The patent makes the single power amplifier universal by implementing smooth pre-coding weight transitions that enable beam forming-like functionality. The smoothing mechanism allows the single PA to effectively steer beams towards target receivers through controlled weight adjustments, providing multi-functionality without requiring multiple power amplifiers.
4Device complexity
If UE autonomously selects antenna weights based on TPC commands, then no new feedback signaling is required, but selection accuracy may be insufficient
Solution Approach 1:
The patent utilizes existing TPC feedback commands for autonomous antenna weight selection without requiring new feedback signaling channels. The smoothing mechanism enhances the accuracy of this autonomous selection by ensuring that weight changes are based on reliable feedback information and transition smoothly, improving selection precision while maintaining simplicity.
Data Source
AI summary
Methods and devices are described for use in a wireless communications system supporting uplink transmit diversity. If it is detected that a user equipment is currently in one of a predetermined set of situations, a set of restrictions associated with the detected situation is applied when the user equipment changes pre-coding weights. The set of restrictions limits how much the pre-coding weights can be changed. A user equipment in soft handover may also be restricted to only consider feedback information from a serving base station when selecting pre-coding weights. Thus it is possible to ensure that pre-coding weights are carefully selected in situations where there is a high risk for detrimental interference and/or inferior uplink/downlink performance. A network node may be configured to detect such a situation and notify the user equipment of any restrictions to be applied on the pre-coding weight selection.