Group MMSE-DFD with SINR Feedback for Cellular Downlink Interference
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Solution Overview
Problem
In wireless cellular systems, the downlink channel faces challenges in achieving sufficient signal-to-interference-plus-noise ratio (SINR) for users, especially at the cell edge, due to inter-cell interference and limited signal processing capabilities at mobile devices, which complicates the use of advanced multi-user detection techniques for interference cancellation.
Innovation Solution
A method that initializes with channel matrix estimates and inner codes from co-channel transmitter sources, iteratively selects and computes filters to maximize specific metrics, and determines the decoding order and rates for transmitter sources to improve interference suppression and cancellation, exploiting the structure of co-channel interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If advanced multi-user detection (MUD) techniques are employed for interference cancellation, then system performance is improved, but computational complexity at mobile devices increases beyond permissible limits
Solution Approach 1:
The patent segments the interference cancellation process into two distinct phases: a pre-processing phase where the base station computes interference covariance matrices and filter coefficients, and a execution phase where the mobile device applies these pre-computed filters to cancel interference. This segmentation offloads the computationally intensive matrix operations to the base station, enabling advanced MUD performance while keeping mobile device complexity within permissible limits
Solution Approach 2:
The base station performs preliminary computations of interference covariance matrices and optimal filter coefficients before transmitting data to mobile devices. These pre-computed parameters are then used by mobile devices to efficiently cancel interference without performing complex real-time matrix operations, thus achieving high system performance with limited mobile computational resources
2Object-affected harmful factors
If static frequency reuse planning is used to mitigate inter-cell interference, then interference is reduced, but spectral efficiency decreases
Solution Approach 1:
The patent implements feedback mechanisms where mobile devices measure and report interference covariance matrices back to their serving base stations. This feedback enables base stations to adaptively adjust frequency reuse patterns and compute optimal interference cancellation filters, allowing the system to dynamically balance interference mitigation and spectral efficiency rather than relying on static frequency planning
Solution Approach 2:
The system dynamically changes the parameter of frequency reuse factor based on measured interference conditions. Instead of using a fixed frequency reuse plan, base stations adjust their frequency allocation and compute interference cancellation parameters in real-time based on feedback from mobile devices, enabling flexible adaptation between interference reduction and spectral efficiency
3Object-affected harmful factors
If fractional frequency reuse is employed with different reuse factors for cell interior and cell-edge, then interference mitigation is improved, but system complexity increases
Solution Approach 1:
The patent implements a universal interference cancellation framework that works for all users regardless of their position in the cell. The base station computes interference covariance matrices and filters that are applicable to both cell-interior and cell-edge users, eliminating the need for separate frequency reuse planning and processing for different user groups, thus reducing system complexity while maintaining effective interference mitigation
Data Source
AI summary
The invention is a method directed to group MMSE-DFD with rate (SINR) feedback and without pre-determined decoding order for reception on a cellular downlink. The method includes initializing channel matrix estimates and inner codes of all co-channel transmitter sources in a wireless network. Each channel matrix estimate is converted into an effective channel matrix responsive to the inner code of the corresponding transmitter source; The channel estimates or the inner codes or the modulation and coding schemes are not known for some of the transmitter sources whose transmitted signals are consequently treated as interference and deemed un-decodable.