Phase-Rotated Reference Signals for Multi-Antenna Overhead Reduction
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Solution Overview
Problem
In wireless communication systems with multiple antennas, transmitting reference signals at different resource elements increases overhead, reducing data transmission rates, while existing methods do not efficiently utilize phase-rotated reference signals to separate channel coefficients in the frequency domain.
Innovation Solution
Transmitting phase-rotated reference signals using the same resource elements allows receivers to separate channel impulse responses in the time domain, utilizing filtering or windowing techniques, and orthogonal cover codes to reduce overhead and enhance data transmission efficiency in OFDM systems like LTE and LTE-Advanced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference signals are transmitted at different resource elements for multiple antennas, then channel measurement accuracy is improved, but reference signal overhead increases reducing data transmission rate
Solution Approach 1:
The patent merges reference signal transmissions from multiple antennas into the same resource elements by applying different phase rotations to each antenna's reference signal. This combining approach allows simultaneous transmission of multiple reference signals without requiring separate resource elements, thereby reducing overhead while maintaining measurement capability through phase differentiation
Solution Approach 2:
The patent changes the phase parameter of reference signals transmitted from different antennas. By applying distinct phase rotations (e.g., 0, π/2, π, 3π/2) to reference signals from different antennas, the system enables separation of channel responses through phase domain processing, achieving accurate channel measurement without increasing resource element usage
2Measurement precision
If reference signals are transmitted at different resource elements for multiple antennas, then channel separation is improved, but resource overhead increases
Solution Approach 1:
The patent combines multiple antenna reference signals into identical resource elements by modulating each with unique phase rotations. This merging eliminates the need for separate resource elements per antenna, reducing reference signal overhead from 4 separate elements to 1 shared element while maintaining channel separation through phase domain differentiation
Solution Approach 2:
The patent transitions from separating reference signals in the resource element domain (time-frequency) to separating them in the phase domain. By moving the separation dimension from spatial/resource allocation to phase modulation, the system achieves channel separation without increasing resource consumption
Data Source
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AI summary
Systems, methods, and apparatuses for phase-rotated reference signals are provided. In accordance with one implementation, phase-rotated reference signals are transmitted from multiple transmit antennas on the same reference signal (RS) resource elements. The receiver may determine channel coefficients for links corresponding to the multiple antennas, based on the received signals at the RS resource elements. Time-domain filtering or frequency-domain orthogonal codes may be used to determine the channel coefficients for links corresponding to the multiple antennas. The phase-rotation information may be broadcasted in a system information block (SIB) message or signaled in a radio resource control (RRC) message.