MIMO Precoded Uplink Pilot Signals for Spectral Efficiency
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Solution Overview
Problem
Massive MIMO systems face limitations in spectral efficiency due to the scarcity and overhead of pilot signals, which are required to be orthogonal in time and/or frequency domains, especially when multiple terminal devices share the same resources.
Innovation Solution
The method involves determining uplink precodings for terminal devices in cellular wireless MIMO systems, allowing precoded uplink pilot signals to be transmitted simultaneously without interfering with each other, enabling more frequent adjustments of receive and transmit parameters at the base station, thereby maintaining coherency and MIMO gain without significantly increasing pilot signal transmission capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pilot signals are transmitted orthogonally in time and/or frequency domains, then interference between multiple terminal devices is avoided, but spectral efficiency deteriorates due to pilot signal scarcity and overhead
Solution Approach 1:
The patent introduces a new dimension for pilot signal transmission by allowing non-orthogonal spatial multiplexing in addition to traditional time and frequency domain orthogonality. Multiple terminal devices transmit pilot signals simultaneously using different spatial precoding vectors, transforming the problem from 2D (time-frequency) to 3D (spatial) resource allocation, thereby improving spectral efficiency while maintaining reliable channel estimation
Solution Approach 2:
The patent changes the parameters of pilot signal transmission by introducing precoding vectors that modify the spatial characteristics of transmitted signals. By adjusting precoding parameters across multiple antenna elements, the system enables simultaneous pilot transmissions from multiple terminal devices with different spatial signatures, resolving the contradiction between orthogonality requirements and spectral efficiency
2Productivity
If multiple terminal devices share the same resources, then resource utilization improves, but pilot signal interference increases
Solution Approach 1:
The patent applies local quality by assigning different precoding vectors to different terminal devices, creating unique spatial signatures for each device. This localized differentiation in the spatial domain allows multiple devices to share the same time-frequency resources without interference, as each device's pilot signal has a distinct spatial characteristic that can be separately identified at the base station
Solution Approach 2:
The patent resolves resource sharing conflicts by adding the spatial dimension to resource allocation. Instead of allocating resources only in time and frequency domains, the system utilizes spatial precoding to create additional separation dimensions, enabling multiple terminal devices to simultaneously share the same resources with differentiated spatial characteristics
3Measurement precision
If pilot signal transmission capacity is increased, then channel estimation accuracy improves, but system overhead increases
Solution Approach 1:
The patent uses precoding vectors as virtual copies or representations of channel characteristics. Instead of increasing the quantity of actual pilot signals, the system creates multiple spatial copies of the pilot transmission through precoding, allowing the base station to estimate multiple channels simultaneously using the same physical pilot signal resources, thereby improving estimation accuracy without increasing overhead
Data Source
AI summary
The present application relates to methods for operating a terminal device and a base station of a cellular wireless multiple-input and multiple-output, MIMO, system. An uplink precoding for transmitting uplink signals from a plurality of antenna elements of the terminal device to the base station is determined. An uplink pilot signal using the uplink precoding and a radio resource of a transmission frame of the MIMO system is transmitted from the plurality of antenna elements. At the base station, a downlink precoding and uplink receive parameters are adjusted based on a receive property of the precoded uplink pilot signal from the terminal device.