Concatenated Reference Signal Design for 5G MIMO
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Solution Overview
Problem
Conventional methods for designing reference signals in wireless communication networks, particularly in 5G systems with massive MIMO and multi-user MIMO, face challenges in supporting partially overlapping users while maintaining good cubic metric properties, leading to severe pilot contamination or hard scheduling restrictions due to the requirement of orthogonality between different MIMO layers.
Innovation Solution
A transmission-point-specific function is used to determine concatenated reference signals by assigning a base sequence index and phase shift, allowing all users at a transmission point to use a common cyclic shift-hopping pattern and base sequence, while enabling different segments to use the same or different Zadoff-Chu sequences, thereby relaxing orthogonality conditions to limit correlation between reference signals from different users.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods use same base sequences for code division multiplexing to achieve orthogonality, then orthogonality between reference signals is improved, but cross-layer interference is introduced when data transmissions on different MIMO layers partly overlap
Solution Approach 1:
The reference signal is divided into multiple segments in the frequency domain, where each segment can be independently configured with different base sequences. This segmentation allows partial overlap between different MIMO layers while maintaining orthogonality in non-overlapping portions, thereby reducing cross-layer interference.
Solution Approach 2:
Different segments of the reference signal are assigned different base sequence configurations locally. Specifically, segments corresponding to non-overlapping frequency resources use different base sequences to ensure orthogonality, while segments with partial overlap can use the same base sequence, optimizing performance in each local region.
2Productivity
If conventional methods design reference signals for massive MIMO and multi-user MIMO, then system capacity is improved, but severe pilot contamination or hard scheduling restrictions occur
Solution Approach 1:
The frequency spectrum is segmented into multiple reference signal segments, each with independent base sequence configuration. This allows different user equipment to be assigned different base sequences in overlapping frequency regions, enabling partial overlap of data transmissions while maintaining distinguishable reference signals, thus supporting more users without severe pilot contamination.
Solution Approach 2:
The base sequence parameters (such as root indices and cyclic shifts) are dynamically changed across different segments and users. By varying these parameters, the system can accommodate more simultaneous users in massive MIMO and multi-user MIMO scenarios while maintaining orthogonality where needed and allowing controlled overlap where beneficial.
3Reliability
If conventional methods enforce orthogonality between base sequences mapped to different frequency sets, then orthogonality is improved, but flexibility in system design is reduced
Solution Approach 1:
The reference signal bandwidth is segmented into multiple frequency segments, with orthogonality enforced only within each segment rather than across the entire bandwidth. This segmented approach maintains sufficient orthogonality for channel estimation while providing flexibility in resource allocation and user scheduling across different frequency regions.
Solution Approach 2:
Orthogonality requirements are applied locally to each frequency segment rather than globally across all frequencies. This allows the system to enforce orthogonality where it is most beneficial (in segments with significant overlap) while relaxing constraints in other segments, thereby improving overall system flexibility and adaptability.
Data Source
AI summary
Method and devices determine parameters governing a concatenated reference signal design based on Zadoff-Chu sequences and having a limited correlation with other reference signals arriving at a same transmission point, wherein the concatenated reference signal has a controlled cubic metric. The cubic metric control is achieved by selecting base sequence root indices, phase shifts and/or block configurations in view of information related to the other reference signals.