Uplink Transmit Diversity Parameter Derivation
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Solution Overview
Problem
Existing uplink transmit diversity schemes in cellular radio systems face reliability issues due to unreliable downlink control signals, leading to incorrect adjustment of transmit diversity parameters, which can result in reduced performance and increased interference to neighboring cells, especially in poor radio conditions or near cell borders.
Innovation Solution
A method in user equipment (UE) that estimates the received signal quality of downlink control signals and only uses reliably received signals to derive uplink transmit diversity parameters, applying these parameters to control uplink transmit diversity operations, and includes mechanisms for reporting unreliable conditions to the network, allowing for network adjustments to improve signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If closed loop transmit diversity schemes are used with network control signaling, then uplink performance gain is improved, but reliability of parameter adjustment deteriorates due to unreliable downlink control signals in poor radio conditions
Solution Approach 1:
The UE performs preliminary actions by autonomously adjusting transmit diversity parameters before receiving network control signals. The UE monitors downlink signal quality in advance and only applies network commands when confidence thresholds are met, preventing erroneous parameter adjustments from unreliable signals while maintaining performance gains from closed-loop control
Solution Approach 2:
The system implements feedback mechanisms where the UE continuously monitors downlink control signal quality and feeds this information back to determine whether to apply network commands. This feedback loop ensures that only reliable control signals trigger parameter adjustments, resolving the contradiction between performance gain and adjustment reliability
2Adaptability or versatility
If transmit diversity parameters are frequently adjusted based on downlink control signals, then uplink adaptability is improved, but system stability deteriorates due to erroneous adjustments from unreliable signals
Solution Approach 1:
The UE performs preliminary monitoring of downlink signal quality before executing parameter adjustments. By pre-assessing signal reliability and establishing confidence thresholds, the system maintains adaptability to changing radio conditions while preventing unstable erroneous adjustments from degrading system stability
Solution Approach 2:
The system applies beforehand cushioning by requiring confidence thresholds and signal quality assessments before applying network control commands. This protective mechanism cushions against erroneous adjustments, allowing frequent adaptability updates while filtering out unstable changes from unreliable downlink signals
3Device complexity
If UE autonomously adjusts transmit diversity parameters without network control, then implementation complexity is reduced, but uplink performance gain is limited
Solution Approach 1:
The control function is segmented into two parts: autonomous UE-based parameter adjustment (simplifying implementation) and network-controlled refinement (enhancing performance). The UE handles basic adjustments independently while utilizing network commands only when reliable, achieving both low complexity and performance gains
Solution Approach 2:
The UE performs self-service by autonomously monitoring downlink signal quality and independently adjusting transmit diversity parameters without requiring continuous network control. This self-service capability reduces implementation complexity while maintaining the ability to achieve performance gains when network signals are reliable
Data Source
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AI summary
Methods and devices are provided wherein a user equipment transmits using at least two uplink transmit antennas and receives a set of control signals in the downlink direction from a cellular network. The user equipment estimates a received signal quality for each control signal in said set of control signals and determines, based on said received signal quality, which control signals that have been reliably received. The user equipment derives one or more parameters related to the uplink transmit diversity operation using a subset of control signals from the set of control signals, said subset only including control signals determined as reliably received; and transmits in the uplink direction applying the derived one or more parameters to control the uplink transmit diversity operation. The accuracy of the transmit diversity parameter values derived/set by the UE can be improved. This will enhance the performance of the uplink transmit diversity and will also reduce interference to the neighbor cells.