UE Cooperation Using Partial LLR Forwarding for Bandwidth Limits
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Solution Overview
Problem
Current user equipment (UE) cooperation methods in wireless networks require extensive bandwidth for forwarding log-likelihood ratios (LLRs), which is inefficient due to the high bandwidth demand, especially when each cooperating UE transmits one LLR for each encoded bit.
Innovation Solution
The method involves selecting and forwarding only the most useful LLRs from cooperating UEs to a target UE, reducing the burden on D2D links by exploiting frequency selectivity and quantizing LLRs to minimize the number of bits required for reliable forwarding, using techniques like LLR combining and Lloyd-Max quantization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all LLRs are forwarded from cooperating UEs to target UE, then decoding reliability is improved, but bandwidth consumption increases significantly
Solution Approach 1:
The patent extracts and forwards only the most useful LLRs from the complete set of LLRs generated by cooperating UEs. Instead of transmitting all LLRs, the system identifies and selects a subset of LLRs that provide the most significant contribution to decoding reliability, thereby reducing bandwidth consumption while maintaining effective cooperation performance.
Solution Approach 2:
The patent changes the parameter of LLR transmission by applying quantization techniques (such as Lloyd-Max quantization) to reduce the precision and bit representation of LLRs. This parameter transformation allows the system to maintain sufficient decoding reliability while significantly reducing the bandwidth required for LLR forwarding.
2Quantity of substance
If LLRs are quantized to reduce bits, then bandwidth usage is reduced, but LLR information accuracy decreases
Solution Approach 1:
The patent applies optimized quantization schemes (including Lloyd-Max quantization) that change the LLR representation parameters to use fewer bits. These quantization methods are designed to minimize information loss by optimally mapping continuous LLR values to discrete quantization levels, thereby achieving bandwidth reduction while preserving essential LLR information accuracy.
Solution Approach 2:
The patent uses partial action by transmitting only a quantized subset of LLRs rather than all original LLRs. By carefully selecting which LLRs to forward and applying appropriate quantization, the system achieves sufficient decoding performance with reduced bandwidth, accepting minimal information loss in exchange for significant resource efficiency.
Data Source
AI summary
User equipment (UE) cooperation can be improved by relaying partial soft information to target UEs. More specifically, a cooperating UE may relay a subset of log-likelihood ratios (LLRs) to the target UE. The subset of LLRs may correspond to fewer than all resource blocks of the original transmission. This may allow UE cooperation to be effective when the cooperating UE was only able to decode a portion of the original transmission. This may also allow fewer network resources (e.g., bandwidth, etc.) to be used when the target UE does not need all of the soft information to decode the original transmission. Multiple cooperating UEs can provide different subsets of LLRs, and the subsets may or may not overlap with one another.