CSI Feedback Overhead Control via Subcarrier Subset Allocation
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Solution Overview
Problem
Conventional methods for reporting channel state information in wireless networks result in a linear increase in feedback overhead as the number of users increases, leading to reduced uplink channel resources available for data transmission, especially in CoMP and uncoordinated cellular systems.
Innovation Solution
Implementing a method where each mobile station reports channel state information on a dynamically allocated subset of subcarriers, with adjustable reporting interval and size, to maintain a constant total overhead, by modifying the subset, interval, or reporting size based on the number of mobile stations, using FDMA scheduling to optimize resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If each mobile station reports channel state information on all subcarriers using conventional methods, then the network obtains complete channel state information for coherent CoMP transmission, but the total feedback overhead increases linearly with the number of users
Solution Approach 1:
The patent divides the set of all subcarriers into multiple subsets and assigns each mobile station to report channel state information only on a specific subset rather than all subcarriers. This segmentation reduces the feedback overhead from O(W*N) to O(W*N/K) where K is the number of subsets, while still providing the network with sufficient channel state information through coordinated reporting from different mobile stations.
Solution Approach 2:
The patent implements a universal reporting framework where the same subset allocation mechanism applies to all mobile stations in the cell. Each mobile station follows the same protocol of reporting on its assigned subset, making the system scalable and manageable regardless of the number of users. The network universally applies the subset allocation strategy across all users to maintain constant total overhead.
2Adaptability or versatility
If the number of mobile stations reporting channel state information increases, then more users are serviced by the base station, but the uplink resources consumed for reporting channel state information increases
Solution Approach 1:
The patent dynamically adjusts the subset allocation for each mobile station based on the current number of active users in the cell. When the number of users increases, the system reassigns subsets to ensure that the total feedback overhead remains constant. This dynamic reallocation allows the system to adapt to varying user loads without proportionally increasing uplink resource consumption for CSI reporting.
Solution Approach 2:
The patent changes the reporting parameters (subset size, reporting interval, compression level) as a function of the number of mobile stations. Specifically, as the number of users N increases, the subset size W/N is reduced to maintain constant total overhead RT. This parameter adjustment ensures that uplink resources for CSI reporting remain stable even as user capacity scales.
3Measurement precision
If conventional CSI reporting methods are used, then complete channel state information is available for each user, but less uplink channel resources are available for transmission of user data
Solution Approach 1:
The patent extracts only the essential channel state information needed for coherent CoMP transmission by having mobile stations report on subsets of subcarriers rather than all subcarriers. The network reconstructs the complete channel state picture by combining reports from multiple mobile stations, each covering different subsets. This extraction approach reduces uplink overhead while preserving the necessary information for effective CoMP operation.
Solution Approach 2:
The patent employs partial reporting where each mobile station reports on a partial set of subcarriers (its assigned subset) rather than the complete set. This partial action from multiple mobile stations collectively provides the network with sufficient channel state information, reducing individual and total reporting overhead while maintaining system performance.
Data Source
AI summary
An amount of total overhead allocated by a wireless system for transmitting channel state information by a plurality of mobile stations serviced by the wireless system can be controlled by allocating a reporting interval, reporting size and subset of subcarriers to each of the mobile stations for use by the mobile stations in reporting channel state information on the subcarriers included in the subset allocated to the respective mobile stations. At least one of the reporting interval, reporting size and subset of subcarriers allocated to one or more of the mobile stations is modified as a function of the number of mobile stations reporting channel state information so that the total overhead allocated for transmitting the channel state information on all of the subcarriers remains generally constant regardless of the number of mobile stations reporting channel state information.