Co-phasing Distributed Antenna System Transmissions
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In Coordinated MultiPoint (CoMP) processing for 4G broadband wireless cellular networks, the lack of co-phasing of signals from multiple infrastructure nodes leads to increased channel frequency selectivity and performance degradation due to large phase differences caused by varying propagation delays and channel transfer functions.
Innovation Solution
Implementing a co-phasing procedure at Distributed Antenna System (DAS) nodes to align transmissions by measuring and adjusting phase differences between signals from different infrastructure nodes, using methods such as linear phase adjustments per subcarrier across sub-bands, to synchronize signals and maximize signal strength at mobile stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If signals are transmitted from multiple infrastructure nodes without co-phasing, then the system complexity is reduced, but the network performance degrades due to destructive signal addition and increased frequency selectivity
Solution Approach 1:
The patent applies preliminary action by performing co-phasing adjustments before signal transmission. The network determines phase adjustments for multiple infrastructure nodes based on mobile station feedback, and these adjustments are applied in advance to ensure coherent signal combination at the mobile station, preventing destructive interference and improving network performance
Solution Approach 2:
The patent implements feedback mechanisms where mobile stations measure reference signals from multiple infrastructure nodes and provide feedback information about channel conditions and phase differences. The network uses this feedback to determine appropriate co-phasing adjustments, creating a closed-loop system that optimizes signal combination while managing complexity
2Reliability
If co-phasing adjustments are applied per subcarrier across all sub-bands, then signal coherence is maximized, but the processing complexity and overhead increase significantly
Solution Approach 1:
The patent applies segmentation by dividing the frequency spectrum into multiple sub-bands and determining co-phasing adjustments separately for each sub-band rather than uniformly across all frequencies. This allows the system to manage complexity by processing smaller frequency segments independently while maintaining signal coherence within each segment
Solution Approach 2:
The patent implements local quality by applying different co-phasing adjustments to different sub-bands based on local channel conditions. Each sub-band receives customized phase adjustments tailored to its specific frequency characteristics and propagation conditions, optimizing signal coherence locally rather than applying a uniform global adjustment
Data Source
AI summary
Briefly, in accordance with one or more embodiments, mobile station or user equipment receives pilot signals from two or more infrastructure nodes in a distributed antenna system, and calculates phase or timing information, or combinations thereof, from the pilot signals. The mobile station feeds back the phase or timing information, or combinations thereof, to the infrastructure nodes, and then receives one or more subsequent transmissions from the infrastructure nodes with phase shift or timing adjustments, or combinations thereof, calculated by the infrastructure nodes and applied to the spatial streams transmitted by the infrastructure nodes.