Sounding Reference Signal Permutation for MIMO Channel Diversity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In massive MIMO systems, the increased number of antennas leads to channel hardening, resulting in reduced fading diversity among user terminals, which complicates user scheduling and data transmission.
Innovation Solution
The method involves using sounding reference signal (SRS) information to artificially introduce channel variations by assigning SRS values to different antennas, thereby creating perceived changes in channel conditions that can be used for scheduling decisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large number of antennas is used in massive MIMO system, then throughput and reliability are increased, but channel fading diversity is reduced due to channel hardening
Solution Approach 1:
The system performs preliminary channel sounding using SRS signals to measure and characterize channel conditions before actual data transmission. This advance channel assessment enables the scheduler to make informed decisions about user allocation and resource distribution, compensating for the reduced natural fading diversity in massive MIMO systems.
Solution Approach 2:
The invention changes the parameter of channel condition perception by artificially introducing variations through SRS-based channel state information. Instead of relying on natural channel fading, the system uses SRS measurements to create perceived channel condition differences among users, enabling the scheduler to differentiate between users and make optimal scheduling decisions.
2Reliability
If a large number of antennas is used in massive MIMO system, then reliability is increased, but scheduling complexity increases due to reduced channel diversity
Solution Approach 1:
The system implements a feedback mechanism where user terminals transmit SRS signals that are measured by the base station to determine channel state information. This feedback loop provides the scheduler with real-time channel conditions, enabling it to make reliable scheduling decisions without requiring complex exploration of all possible user combinations. The SRS-based feedback replaces the need for complex scheduling algorithms by providing direct channel quality metrics.
3Measurement precision
If SRS values are assigned to corresponding antennas based on actual channel conditions, then transmission accuracy is improved, but channel diversity for scheduling is lost
Solution Approach 1:
The invention segments the use of SRS values into two distinct purposes: one set of SRS values is used for accurate channel measurement and beamforming control, while another set is artificially permuted and assigned to different antennas to create scheduling diversity. This segmentation allows the system to maintain measurement precision for transmission while simultaneously creating the channel diversity needed for flexible user scheduling.
Solution Approach 2:
The SRS-based channel state information acts as an intermediary that decouples the relationship between actual physical channel conditions and scheduling decisions. By using SRS measurements as an intermediate representation, the system can make scheduling decisions based on perceived channel conditions rather than actual physical fading, thereby maintaining scheduling flexibility without sacrificing transmission accuracy.
Data Source
AI summary
Methods and apparatus for increasing channel diversity in a MIMO system, e.g. a massive MIMO system, are described. Some selected sounding reference signal values are applied to control base station transmission for antennas, e.g., randomly or semi-randomly selected antennas, to which they do not actually correspond. The wireless terminal perceives this change as a change in channel conditions, which is subsequently reported in channel status information (CSI) to the base station. This results in increased channel diversity, which is beneficial to the base station scheduler.