Adapting DM-RS Power for High-Order MIMO Channel Estimation
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Solution Overview
Problem
In LTE-Advanced systems, the existing power utilization scheme for demodulation reference signals (DM-RS) is not efficient for high-order MIMO transmissions, leading to inaccuracies in channel estimation and low power efficiency, as it assumes the same transmit power for both data and reference elements without proper power normalization.
Innovation Solution
A method and arrangement in a radio network node that adapt the transmission power of DM-RS to match the average transmission power of data elements, adjusting it by a factor of 2 independently of the MIMO transmission rank from three to eight, ensuring equal average transmission power over consecutive subcarriers, thereby filling power gaps and improving power utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same transmit power is used for both data resource elements and demodulation reference signal resource elements in high-order MIMO transmissions, then the system maintains simplicity in power allocation, but power utilization efficiency deteriorates and channel estimation accuracy decreases
Solution Approach 1:
The patent applies local quality by differentiating power allocation between different resource element types. Specifically, demodulation reference signal resource elements are allocated different transmit power levels compared to data resource elements, with power differentiation based on the transmission rank. This allows optimized power utilization for channel estimation purposes while maintaining simple overall power management through rank-based power indication.
2Loss of information
If the same transmit power is assumed for data and reference elements, then control signaling overhead is reduced, but channel estimation accuracy deteriorates due to power gaps
Solution Approach 1:
The patent changes the power parameter for demodulation reference signal resource elements based on transmission rank. By adjusting the transmit power of reference elements according to rank (with specific power offsets for different rank values), the system maintains accurate channel estimation without requiring extensive control signaling. The power indication is derived from existing rank information, avoiding additional overhead.
3Ease of operation
If power normalization is not applied to demodulation reference signals, then the system operates with simpler power processing, but power gaps between reference and data elements increase causing estimation inaccuracies
Solution Approach 1:
The patent introduces dynamic power adjustment for demodulation reference signal resource elements based on transmission rank. The power level is not fixed but adapts according to the rank value, with predefined power offsets applied for different rank scenarios. This dynamic approach maintains estimation precision while keeping power processing manageable through standardized rank-based power relationships.
Data Source
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AI summary
A method and an arrangement (800) in a radio network node (120) for adapting transmission power of resource elements for demodulation reference signals, referred to as "reference elements" are provided. The radio network node (120) is configured for multiple-input multiple-output transmission, referred to as "MIMO transmission", to a user equipment (110). The MIMO transmission comprises at least three layers. Two consecutive subcarriers of a resource block carry at least three reference elements. A first subcarrier of the resource block carries data elements. The radio network node (120) adapts transmission power of said at least three reference elements such that an average transmission power, over said two consecutive subcarriers, of said at least three reference elements is equal to a transmission power, for the first subcarrier, of the data elements for said at least three layers. The radio network node (120) uses the adapted transmission power to transmit, to the user equipment (110), said at least three reference elements.