Cluster-Specific CSI Calibration for Cloud Radio Interference Mitigation
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Solution Overview
Problem
In cloud radio networks, inter-cluster interference and the need for accurate channel state information (CSI) feedback pose challenges for achieving interference-free communication and high network capacity, particularly due to differences in downlink and uplink CSI measurements caused by differing RF filters.
Innovation Solution
A method for cluster-specific CSI feedback and calibration, where calibration coefficients are derived for each antenna port using measured downlink and estimated uplink CSI, allowing for linear or non-linear precoding to mitigate interference, and enabling interference-free communication by calibrating uplink CSI using per-UE coefficients and applying these for precoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If uplink CSI measurements are used to obtain downlink CSI in TDD mode, then frequency resources are efficiently utilized, but measurement accuracy deteriorates due to different RF filters in downlink and uplink transmission paths
Solution Approach 1:
The patent introduces RF filter compensation coefficients as an intermediary element that mediates between uplink CSI measurements and downlink CSI requirements. These coefficients, derived from reference signal measurements, act as a correction factor that bridges the gap caused by different RF filters, enabling accurate downlink CSI estimation from uplink measurements while maintaining frequency resource efficiency
Solution Approach 2:
The patent changes the parameters of the CSI by applying RF filter compensation coefficients to adjust the measured uplink CSI. This parameter transformation converts inaccurate raw measurements into corrected CSI values that accurately reflect downlink channel conditions, resolving the accuracy issue while maintaining the resource-efficient TDD approach
2Object-affected harmful factors
If centralized precoding is applied to eliminate intra-cluster interference, then interference mitigation is achieved, but system complexity increases due to the need for CSI of all BSs/ATPs/RRHs in the cluster
Solution Approach 1:
The patent segments the interference mitigation approach by distinguishing between intra-cluster and inter-cluster interference. For intra-cluster interference, centralized precoding is applied using CSI from cluster members. For inter-cluster interference, the system selectively obtains CSI only from neighboring BSs that cause dominant interference, rather than all neighboring cluster members, thereby reducing complexity while maintaining effectiveness
Solution Approach 2:
The patent applies local quality by making CSI acquisition selective rather than universal. Instead of obtaining CSI from all neighboring clusters uniformly, the system identifies and acquires CSI only from specific neighboring BSs that cause dominant interference to specific UEs. This localized approach reduces overall system complexity while effectively mitigating the most significant interference sources
3Productivity
If high density deployment of RRHs is implemented, then network capacity increases and transmit power can be reduced, but handover frequency increases
Solution Approach 1:
The patent merges multiple RRHs into clusters that are jointly processed by a centralized cloud platform. This clustering approach allows coordinated transmission and reception across multiple RRHs, creating a unified service area that reduces the frequency of handovers while maintaining the high density deployment benefits for network capacity and power efficiency
Data Source
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AI summary
Embodiments herein provide a method implemented in a cloud radio access network (C-RAN). The method includes transmitting channel state information (CSI) reference signals to plurality of user equipments (UEs). The method includes receiving a measured downlink (DL) CSI from each UE among the plurality of UEs. The DL CSI corresponds to a plurality of antenna ports associated with a set of remote radio heads (RRHs) in cluster. Further, the method includes estimating an uplink (UL) CSI for each UE antenna port. The UL CSI is estimated using a pre-defined pilot structure received from each UE. The DL CSI or UL CSI is defined with respect to BS and UE antenna port pair. Furthermore, the method includes deriving a calibration coefficient for each antenna port based on measured DL CSI and estimated UL CSI. The calibrated DL CSI is used to precoder the data using a linear or non-linear precoder.