Shared Uplink Pilot Signal for Massive MIMO Channel Estimation
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Solution Overview
Problem
In wireless communications systems with large antenna arrays, acquiring accurate Channel State Information (CSI) for coherent beam-forming is challenging due to the high number of required pilots, leading to increased signaling overhead and reduced data rate performance, especially in high mobility scenarios where resource blocks are small and limited by the number of symbols.
Innovation Solution
Assigning a shared uplink pilot signal to multiple wireless devices and estimating a combined channel to determine a beamforming vector, allowing for simultaneous data transmission with improved multiplexing efficiency and reduced pilot resource requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional pilot assignment methods are used in massive MIMO systems, then each wireless device can be served, but the signaling overhead increases and data rate performance decreases due to the large number of required pilots
Solution Approach 1:
The patent combines multiple device channels into a single combined channel estimate by having multiple wireless devices share the same uplink pilot signal. The radio network node estimates the combined channel representing the superposition of individual device channels, thereby reducing the number of pilots required from being proportional to the number of devices to being proportional to the number of active transmissions, significantly reducing signaling overhead while maintaining sufficient CSI accuracy for beamforming
Solution Approach 2:
The shared uplink pilot signal serves multiple functions simultaneously: it enables channel estimation for multiple wireless devices at once, reduces pilot resource requirements, and supports both uplink data transmission and downlink beamforming preparation. This multi-functional approach allows the same pilot resource to be reused across multiple devices without compromising channel estimation quality
2Measurement precision
If more pilots are assigned to acquire accurate CSI, then beamforming accuracy improves, but the available resources for data transmission decrease
Solution Approach 1:
By merging the channel estimation process for multiple devices into a single combined channel estimate using shared pilots, the patent reduces the fraction of resources dedicated to piloting. This increases the number of symbols available for data transmission while maintaining the accuracy needed for coherent beamforming, thereby improving overall data rate performance
Solution Approach 2:
The patent accepts that the combined channel estimate represents a superposition of multiple device channels rather than perfectly isolated individual channels. This partial action approach provides sufficiently accurate CSI for beamforming purposes without requiring complete separate channel estimation for each device, achieving an optimal balance between measurement precision and resource efficiency
3Measurement precision
If separate channel estimation is performed for each wireless device, then accurate individual CSI is obtained, but the complexity of pilot management and processing increases
Solution Approach 1:
The patent merges the channel estimation process by having multiple devices share the same pilot signal and by estimating a single combined channel at the radio network node. This eliminates the need for separate pilot management and processing for each device, significantly reducing system complexity while still enabling effective beamforming through the combined channel estimate
Solution Approach 2:
The shared pilot signal and combined channel estimate serve as a universal solution for multiple wireless devices simultaneously. Instead of implementing separate pilot assignment and estimation procedures for each device, the system uses a unified approach that simplifies pilot management and processing while maintaining the capability to serve multiple devices effectively
Data Source
AI summary
A Radio Network Node (RNN) 110 and a method therein for improving capacity in a wireless communications system 100. The RNN is configured to serve a first wireless device 120 and a second wireless device (WD) 130. The RNN assigns a shared uplink pilot signal to the first and second WDs. Further, the RNN transmits, to the first WD, an indication of how possible second data intended for the second WD will be comprised in a signal to be transmitted to the first WD. Furthermore, the RNN estimates a combined channel based on a received shared uplink pilot signal from the first WD and/or the second WD. Yet further, the RNN determines a beamforming vector for the estimated combined channel; and transmits the signal to the first WD, wherein the signal comprises first data and the possible second data, which first data is decodable only by the first WD.