Distributed MIMO Precoding for Phase-Coherent Transmission
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Solution Overview
Problem
Current technologies face challenges in achieving phase coherent transmission over large distances, especially in high frequency bands, and do not adequately address issues of radio blocking and macro diversity in distributed massive MIMO systems.
Innovation Solution
The method involves APUs determining a first pre-coding configuration and transmitting a DL reference signal, receiving phase adjustment parameters from the UE, and adjusting the pre-coding configuration based on these parameters to achieve phase coherent data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If distributed massive MIMO systems use non-co-located APU groups for coverage extension, then the coverage area is increased, but phase coherence between different APU groups deteriorates
Solution Approach 1:
The patent applies preliminary action by having the UE measure DL reference signals from multiple APU groups and determine phase adjustment parameters before actual data transmission. The UE feeds back these parameters to the APUs in advance, allowing the APUs to pre-adjust their pre-coding configurations to achieve phase coherence before transmitting data signals.
Solution Approach 2:
The patent implements feedback by having the UE measure the phase differences of DL reference signals from different APU groups and feed back phase adjustment parameters to the APUs. This feedback loop enables the APUs to adjust their transmission phases based on actual channel conditions, achieving phase coherence across distributed non-co-located APU groups.
2Manufacturing precision
If phase adjustment parameters are fed back from UE to APU, then phase coherence is achieved, but uplink control signaling overhead increases
Solution Approach 1:
The patent changes parameters by representing phase adjustment information in a compressed format. Instead of feeding back complete channel state information or raw phase measurements, the UE determines phase adjustment parameters that indicate the relative phase differences between APU groups, reducing the amount of uplink control signaling required.
3Reliability
If DL reference signals are transmitted from multiple non-co-located APU groups, then macro diversity is improved, but radio blocking effects worsen
Solution Approach 1:
The patent applies local quality by enabling each APU group to independently transmit DL reference signals with locally optimized pre-coding configurations. Each APU group adapts its transmission based on local channel conditions, allowing UEs to select and combine signals from multiple APU groups, thereby achieving macro diversity while mitigating radio blocking effects through spatial redundancy.
Data Source
AI summary
The embodiments herein relate to a method performed by an APU (103) for handling data transmissions in a distributed massive MIMO communication system (100). The APU (103) is comprised in one of at least two non-co-located groups of APUs (103) in the system (100). The APU (103) determines a first pre-coding configuration and a DL reference signal. The APU (103) transmits, to a UE (125), the DL reference signal pre-coded with the first pre-coding configuration. The APU (103) receives information indicating at least one phase adjustment parameter from the UE (125), and determines a second pre-coding configuration based on the first pre-coding configuration adjusted with the phase adjustment parameter. The APU (103) transmits DL data pre-coded with the second pre-coding configuration to the UE (125).