Precoding Weight Feedback Segmentation for Interference Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing SDMA wireless communication systems face inefficiencies in user scheduling due to insufficient feedback information, leading to increased interference and reduced uplink data rates, particularly when multiple users share the same resource.
Innovation Solution
The method involves isolating and transmitting precoding weights representing long-term channel information at a reduced rate, with optional short-term channel changes, to provide reliable feedback while minimizing resource usage, and using a two-codebook structure to differentiate between 'best companion' and 'worst companion' precoding weights for interference management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full precoding weight feedback is transmitted at high rate, then scheduling precision and interference control are improved, but feedback overhead and uplink resource consumption increase
Solution Approach 1:
The precoding weight feedback is segmented into two codebooks: Codebook 1 for long-term channel statistics (spatial correlation) and Codebook 2 for short-term channel variations. This segmentation allows differential feedback rates where only Codebook 2 is reported frequently while Codebook 1 is reported less frequently, reducing overall feedback overhead while maintaining scheduling precision.
Solution Approach 2:
The feedback transmission is made periodic with different rates for different codebooks. Codebook 1 (long-term statistics) is reported at a lower periodic rate, while Codebook 2 (short-term variations) is reported at a higher periodic rate. This periodic action with differentiated rates reduces feedback overhead compared to transmitting full precoding weights at high rate continuously.
2Productivity
If multiple users are scheduled on the same resource in SDMA, then system throughput is improved, but inter-user interference increases
Solution Approach 1:
The system uses feedback from users about their preferred precoding weights and interference conditions to enable the base station to make informed scheduling decisions. Users report PMI (Precoding Matrix Indicator) and CQI (Channel Quality Indicator) which help the base station select user combinations that minimize inter-user interference while maximizing throughput.
Solution Approach 2:
The base station changes precoding weight parameters dynamically based on channel conditions and user combinations. By adjusting precoding weights according to reported feedback parameters (PMI, CQI, and best companion information), the system optimizes beamforming to direct energy toward intended users and minimize interference to other users scheduled on the same resource.
3Reliability
If best companion precoding weights are reported, then interference management is improved, but feedback complexity and processing overhead increase
Solution Approach 1:
The invention extracts only the essential interference management information from the full precoding weight feedback. Instead of reporting complete precoding weights or all possible companion information, the system extracts and reports only the 'best companion' precoding weight indicator and associated interference metric (delta CQI). This extraction reduces feedback complexity while maintaining reliable interference control.
Solution Approach 2:
The feedback mechanism focuses on local quality information relevant to interference management rather than global channel characteristics. The best companion reporting provides localized interference information specific to potential user pairings, allowing the base station to make targeted interference management decisions without processing extensive global channel state information.
Data Source
Figure 1~3
Figure 4~6
AI summary
The present invention relates to a method for scheduling users in a mobile or wireless radio communication system comprising a base station with a multiple antenna system and at least two users, said base station communicating with users using precoding weights at said multiple antenna system, an indication on precoding weights to be used for communication with a first user being sent by said first user on a feedback channel to said base station. According to the present invention, the method comprises the steps of: ● Expressing said precoding weights used at said multiple antenna system as a combination of two types of precoding weights, a first type of precoding weights relating to long term channel information and a second type of precoding weights relating to short term channel changes; ● Sending on said feedback channel from said first user an indication related to precoding weights of said first type which, if used at said multiple antenna system for communication with a second user, would cause interference below a threshold on said first user if both said first and second users were scheduled on identical resources.