Balancing Reference Signal Powers Across OFDM Symbols
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In LTE wireless communication systems, there is a power imbalance across OFDM symbols due to the multiplexing of dual-layer beamforming reference signals, which affects the consistent power radiation and channel estimation performance.
Innovation Solution
The solution involves applying different Walsh cover codes and scaling factors to the reference signals across subcarriers and OFDM symbols to balance power distribution, using techniques such as Walsh cover mapping and reference signal scaling, ensuring consistent power across all OFDM symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If dual-layer beamforming reference signals are multiplexed using the same Walsh cover code across all subcarriers, then device complexity is reduced, but power imbalance across OFDM symbols occurs
Solution Approach 1:
The patent applies different Walsh cover codes (W1, W2, W2') to different subcarriers based on local conditions. Specifically, W1 is applied to subcarriers where the first layer has reference signals, W2 is applied to subcarriers where the second layer has reference signals, and W2' (a variation of W2) is applied to specific subcarriers to balance power. This local differentiation resolves the power imbalance without requiring complex system-wide changes.
2Quantity of substance
If reference signals are allocated to the same resource elements for both layers, then resource utilization is improved, but power imbalance and channel estimation performance deteriorate
Solution Approach 1:
The patent changes the Walsh cover code parameter locally across different subcarriers to achieve power balancing. By applying W1, W2, and W2' to different subcarriers, the patent maintains efficient resource utilization (same resource elements for both layers) while correcting the power imbalance that would otherwise degrade channel estimation performance.
Data Source
AI summary
A base station includes a reference signal allocator that allocates a first layer of dedicated reference signals and a second layer of reference signals to the same resource elements in a first resource block. The reference signals are allocated to two adjacent resource elements corresponding to a first OFDM symbol and a second OFDM symbol on a first, second, and third subcarriers of the first resource block. The base station also includes a reference signal multiplexer that multiplexes the first layer with the second layer. A first cover code W1 is applied to the first layer. A second cover code W2, different from the first cover code, is applied to the second layer in a first and third subcarriers, and a variation of the second cover code W2′ is applied to the second layer in a second subcarrier.