Uplink Precoding Vector Selection Using Downlink Antenna Measurements
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Solution Overview
Problem
Current uplink transmit diversity techniques face challenges in making informed decisions about pre-coding vector changes, leading to unnecessary antenna weight changes and potential performance degradation, especially when relying on outdated channel estimates and lacking information about alternative antenna links.
Innovation Solution
A method and apparatus that measure downlink characteristics to determine pre-coding vectors for uplink transmission, allowing for informed decisions on when to change antenna weights or precoding vectors, incorporating existing feedback information and long-term downlink measurements to avoid unnecessary changes and improve robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If antenna weights are changed frequently to exploit channel variations, then user and network performance can be maximized, but channel estimates become outdated and packet errors increase
Solution Approach 1:
The system performs preliminary measurements of downlink characteristics on multiple antennas before making antenna weight changes. By measuring downlink channel conditions in advance and using these measurements to predict uplink channel quality, the system can make informed decisions about when to switch antennas, avoiding unnecessary changes that would invalidate channel estimates and cause packet errors.
2Device complexity
If switched antenna transmit diversity is used with single power amplifier, then device complexity is reduced, but the ability to perform beamforming is limited
Solution Approach 1:
The system dynamically switches between different transmit antennas based on real-time downlink channel measurements and TPC command analysis. By implementing dynamic antenna selection with switched antenna transmit diversity, the system achieves adaptability similar to beamforming without requiring multiple power amplifiers, thus maintaining low device complexity while improving performance through intelligent antenna switching.
3Reliability
If downlink measurements are performed to determine pre-coding vectors, then informed decisions on antenna weight changes are enabled, but measurement and processing requirements increase
Solution Approach 1:
The system utilizes existing feedback mechanisms, specifically TPC commands transmitted on the F-DPCH, to infer uplink channel quality without requiring new measurement procedures. By analyzing the sequence of TPC commands received from the network, the UE can determine when to switch antennas or change pre-coding vectors, leveraging already-available feedback information to reduce measurement and processing overhead.
Data Source
AI summary
The present invention relates to a method and a user equipment for use in a wireless communication system that allow for improved uplink transmit diversity performance by using downlink measurements for making informed decisions on whether or not to change precoding vector for uplink transmission. The user equipment measures (32) downlink characteristics, such as received power, on a plurality of antennas of the user equipment. Based on the measured downlink characteristics a precoding vector for unlink transmission is determined (38). The determined precoding vector is then used to perform uplink transmission (31).