LTE Uplink Link Adaptation Using Virtual SINR for Turbo SIC
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Solution Overview
Problem
Current link adaptation techniques for LTE/LTE-A uplink with turbo SIC receivers are inefficient due to the lack of explicit effective SINR expression, leading to conservative rate adaptation and high complexity, which limits the potential gains from advanced receivers.
Innovation Solution
A low complexity closed-loop link adaptation scheme that determines precoding matrix index (PMI) and rank index (RI) selection, decoding order, and modulation and coding scheme (MCS) assignment based on hard decision successive interference cancellation (SIC) rules, specifically using MMSE-SINR and single-user SINR for turbo SIC receivers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If linear MMSE SINR is used for MCS assignment in turbo SIC receivers, then the implementation is simple, but the performance gain from advanced receivers is insufficient
Solution Approach 1:
The patent changes the SINR calculation parameters by introducing virtual SINR values that account for the non-linear turbo SIC receiver characteristics. Instead of using standard linear MMSE SINR, the system computes virtual SINR values that reflect the actual performance of turbo SIC receivers, enabling accurate MCS selection while maintaining implementation feasibility through lookup tables.
2Measurement precision
If Gaussian approximation method is used to predict iterative turbo MMSE-SIC performance, then performance prediction is attempted, but the complexity is high and flexibility is low
Solution Approach 1:
The patent segments the rate assignment process by decoupling MCS selection for different codewords. Instead of treating all codewords together with high-complexity Gaussian approximation, the system divides them into groups based on decoding order and applies simplified virtual SINR-based MCS selection to each group independently, reducing overall complexity while maintaining accuracy.
Solution Approach 2:
The patent uses lookup tables that store pre-computed virtual SINR values and corresponding MCS selections. Instead of performing complex Gaussian approximation calculations in real-time, the system copies pre-determined MCS assignments from lookup tables based on channel conditions and decoding order, significantly reducing computational complexity.
3Measurement precision
If Gaussian approximation method is used for rate adaptation, then performance prediction is achieved, but the flexibility is low due to coupled MCS assignments
Solution Approach 1:
The patent segments the MCS assignment by determining decoding order first, then assigning MCS to codewords in sequence based on their decoded status. This segmentation allows each codeword's MCS to be selected independently based on virtual SINR and current decoding state, providing flexibility that was absent in the coupled Gaussian approximation method.
4Adaptability or versatility
If no explicit effective SINR expression is used for turbo SIC output, then the receiver design is flexible, but the link adaptation becomes non-trivial
Solution Approach 1:
The patent introduces virtual SINR as an intermediary parameter that bridges the gap between the flexible turbo SIC receiver design and the need for explicit SINR expressions in link adaptation. The virtual SINR acts as a mediator that captures the essential performance characteristics of turbo SIC without requiring a complex explicit expression, enabling simplified MCS selection while preserving receiver design flexibility.
Data Source
AI summary
An inventive method for link adaptation for an LTE/LTE-A uplink with a turbo SIC receiver includes the steps of determining a precoding matrix index PMI and rank index RI selection for an LTE/LTE-A uplink when precoding of the uplink is enabled, responsive to channel state information of a subcarrier in the uplink; determining a decoding order for codewords in the uplink i) when the precoding of the uplink is not enabled and ii) if needed when the precoding of the uplink is enabled; performing modulation and coding scheme MCS assignment for the uplink based on a hard decision successive interference cancellation SIC rule (without intra-CW cancellation) or a partial hard decision successive interference cancellation SIC rule (with intra-CW cancellation), responsive to the determined PMI and RI selection; and influencing data transmission in the uplink responsive to the MCS assignment for detection by a turbo SIC receiver.