Non-Uniform Sub-Carrier Selection for CSI Feedback Overhead Reduction
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Solution Overview
Problem
Modern wireless communication networks face challenges in efficiently transmitting direct channel state information (CSI) from user equipment (UE) to the network without excessive uplink overhead, which is crucial for coordinated multipoint calculations like joint processing, due to bandwidth limitations.
Innovation Solution
The UE selects a set of non-uniformly spaced sub-carriers synchronized with the network, estimates their frequency responses, and quantizes these to transmit via the uplink control channel, reducing the number of samples needed while maintaining accurate channel characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct channel state information is transmitted from user equipment to the network, then accurate channel information is available for coordinated multipoint calculations, but uplink overhead increases excessively
Solution Approach 1:
The patent segments the channel state information feedback by dividing the uplink bandwidth into multiple bands and selecting only specific sub-carriers for CSI reporting. Instead of transmitting CSI across the entire bandwidth, the UE reports channel information only for selected sub-carriers in different bandwidth parts, thereby reducing the quantity of feedback information while maintaining accurate channel characterization through strategic sampling of the frequency spectrum.
2Quantity of substance
If the number of CSI feedback samples is reduced to decrease uplink overhead, then uplink resources are conserved, but channel characterization accuracy may deteriorate
Solution Approach 1:
The patent applies local quality by making the CSI feedback density non-uniform across the bandwidth. Different bandwidth parts have different numbers of selected sub-carriers based on local channel conditions and requirements. Some frequency regions may have denser sampling while others have sparser sampling, allowing the system to concentrate feedback resources where they are most needed while reducing overhead in regions with more stable or less critical channel characteristics.
Data Source
AI summary
A UE in a wireless communication network transmits succinct, direct channel state information to the network, enabling coordinated multipoint calculations such as joint processing, without substantially increasing uplink overhead. The UE receives and processes reference symbols over a set of non-uniformly spaced sub-carriers, selected according to a scheme synchronized to the network. The frequency response for each selected sub-carrier is estimated conventionally, and the results quantized and transmitted to the network on an uplink control channel. The non-uniform sub-carrier selection may be synchronized to the network in a variety of ways.