Closed Loop Transmit Diversity Initial Access Uplink Optimization
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Solution Overview
Problem
The uplink transmission in UMTS WCDMA systems lags behind downlink transmission in terms of data rate and requires enhancement to balance peak data rates between link directions, while maintaining better service for wireless transmit/receive units at the cell edge, particularly through the introduction of MIMO technologies and transmit diversity techniques.
Innovation Solution
Implementing closed-loop transmit diversity (CLTD) methods in various radio resource control states, including Cell_FACH, Idle mode, and synchronization procedures, to optimize uplink transmission by using multiple antennas for improved coverage and resource access, especially during initial states and resource access operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transmit diversity techniques are introduced to balance peak data rates between uplink and downlink, then uplink data rate is improved, but device complexity increases due to multiple antennas and control channels
Solution Approach 1:
The patent applies preliminary action by establishing uplink synchronization and determining transmit diversity mode before actual data transmission begins. The WTRU performs synchronization procedures and determines whether to apply transmit diversity in advance, which simplifies the overall system complexity by pre-resolving configuration decisions rather than making them dynamically during transmission.
Solution Approach 2:
The patent implements dynamics by making the transmit diversity mode configurable and state-dependent. The WTRU can dynamically determine whether to apply transmit diversity based on its current RRC state and network configuration, allowing the system to adapt between single-antenna and multi-antenna modes rather than being fixed, thus managing complexity through conditional operation.
2Area of stationary object
If multiple antennas are used for transmit diversity to improve coverage, then coverage is improved, but device complexity increases due to additional antennas and control mechanisms
Solution Approach 1:
The patent applies local quality by making transmit diversity application location-specific and state-specific. Different RRC states (CELL_FACH, CELL_DCH, idle mode) have different transmit diversity configurations, allowing the system to enable enhanced coverage only where and when needed rather than uniformly across all operations, thus managing complexity through selective application.
Solution Approach 2:
The patent uses preliminary action by determining the transmit diversity mode during synchronization procedures before actual data transmission. This advance determination allows the system to prepare the appropriate antenna configuration in advance, ensuring coverage is optimized when needed while avoiding unnecessary complexity during states where single-antenna operation suffices.
3Reliability
If transmit diversity is applied in all RRC states to maintain consistent performance, then service quality is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent implements dynamics by making transmit diversity application state-dependent rather than constant. The WTRU dynamically determines whether to apply transmit diversity based on its current RRC state (CELL_FACH, CELL_DCH, idle mode, etc.), allowing the system to maintain service quality where needed while reducing complexity in states where it is not required, thus achieving adaptive performance management.
Solution Approach 2:
The patent applies parameter changes by varying the transmit diversity configuration according to different RRC states. The system changes operational parameters (whether to apply transmit diversity) based on the current state, allowing optimization of service quality relative to complexity and power consumption for each specific operational context rather than using a fixed configuration.
Data Source
AI summary
Uplink precoding in closed loop transmit diversity (CLTD). The methods and apparatus relate to precoder operations during an initial stage using default precoder tap weights, and a second stage wherein precoder weights obtained from a precoder control indicator channel information are used, provided the signal quality of the precoder control indicator channel is sufficiently reliable. The methods and apparatus also relate to procedures for responding to detection of an unreliable pre-coding control information (PCI) carried in a downlink feedback signal.