MIMO Receiver EVM Calculation for Single-Layer Power Distribution
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Solution Overview
Problem
Existing EVM definitions for single layer transmissions using MIMO receivers do not account for the power distribution between transmit antennas, leading to unrealistic noise floor dependencies and inconsistent EVM expressions.
Innovation Solution
A closed-form expression for EVM is proposed, based on a zero-forcing MIMO receiver, considering the EVM values for each antenna, transmitter noise correlation, and power distribution, allowing for accurate EVM calculation for single layer transmissions and transmit diversity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If unbiased linear MMSE receiver is used to define EVM, then EVM is independent of channel between transmitter and receiver, but EVM becomes independent of power distribution between transmit antennas leading to unrealistic noise floor dependencies
Solution Approach 1:
The patent changes the mathematical parameters of the EVM definition by introducing a new formula that incorporates power distribution weights (w1, w2) and transmitter noise correlation (ρTX). This transforms the EVM calculation from a simple minimum-based approach to a weighted combination that reflects actual power distribution, thereby maintaining measurement independence while improving realism regarding noise floor dependencies.
Solution Approach 2:
The patent introduces an intermediary weighted combination mechanism that mediates between the individual antenna EVM values and the overall port EVM. Instead of directly taking the minimum EVM value, the system uses power distribution weights as intermediaries to combine the EVM values, creating a more realistic representation that accounts for both channel independence and power distribution effects.
2Device complexity
If EVM definition is based on minimum EVM of all transmit antennas, then calculation is simplified, but UE vendors are encouraged to transmit small power on one antenna creating unrealistic scenarios
Solution Approach 1:
The patent modifies the EVM calculation parameters by replacing the minimum function with a weighted arithmetic combination. The new formula uses power distribution weights (w1, w2) and transmitter noise correlation (ρTX) as additional parameters, transforming the calculation from a simple minimum-based approach to a more realistic weighted combination that prevents unrealistic power distribution scenarios while remaining computationally manageable.
3Adaptability or versatility
If existing EVM definition is used for transmit diversity, then single layer transmission can be evaluated, but the definition does not account for power distribution between antennas leading to inconsistent EVM expressions
Solution Approach 1:
The patent introduces new parameters into the EVM definition including power distribution weights (w1, w2) and transmitter noise correlation (ρTX). These parameter changes create a more consistent EVM expression that properly accounts for power distribution between antennas in transmit diversity scenarios, while maintaining adaptability for single layer transmission evaluation through the generalizable formula structure.
Data Source
AI summary
Apparatuses, methods, and systems are disclosed for calculating an error vector magnitude (“EVM”) of a transmitter. An apparatus includes a transceiver that receives, using an unbiased linear multiple-input multiple-output (“MIMO”) receiver, a single layer transmission signal transmitted via a propagation channel, the signal generated and transmitted using an antenna port at a transmitter, the antenna port comprising a plurality of antennas and an antenna connector for each of the plurality of antennas and a processor that determines an EVM for the single layer transmission from the transmitter based on an output of the unbiased linear MIMO receiver, the EVM defined as 100 times a square root of a mean-square error at the output of the unbiased linear MIMO receiver.