Demodulation Reference Signal Sequence Grouping for Orthogonalization
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Solution Overview
Problem
In communication systems, particularly in LTE Release 8 and beyond, demodulation reference signals (DM RS) face challenges in achieving low cross-correlation between different sequences, leading to scheduling restrictions in coordinated multi-point scenarios, where cyclic shifts require identical bandwidth and frequency allocation across devices, limiting flexibility and efficiency.
Innovation Solution
Implementing two modes of DM RS communication: one based on adjusted sequence groups for orthogonalization and another based on non-adjusted transmission, using cyclic shifts, IFDMA, and block spreading to manage bandwidth and frequency allocation dynamically, allowing for nearly orthogonal DM RS sequences without strict scheduling constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cyclic shifts are used to separate demodulation reference signals in coordinated multi-point scenarios, then orthogonality between sequences is improved, but scheduling flexibility deteriorates due to identical bandwidth and frequency allocation requirements
Solution Approach 1:
The patent segments the sequence group into multiple subsets, where each subset contains sequences with specific correlation properties. This allows different subsets to be assigned to different communication devices, enabling orthogonality to be maintained while providing flexibility in sequence selection and allocation, thus resolving the contradiction between orthogonality and scheduling flexibility
Solution Approach 2:
The patent introduces dynamic selection of sequence groups and subsets based on communication conditions, device capabilities, and scheduling requirements. The system can adaptively choose which sequence group to use and how to allocate sequences within groups, transforming the static cyclic shift approach into a dynamic framework that balances orthogonality with scheduling flexibility
2Reliability
If sequence groups are used to manage demodulation reference signals, then cross-correlation between sequences is reduced, but device complexity increases due to multiple sequence groups and adjustment mechanisms
Solution Approach 1:
The patent applies local quality by assigning different sequence group configurations to different communication devices or different resource blocks based on local requirements. Each device or resource block can use sequence groups optimized for its specific conditions, reducing overall cross-correlation while allowing the system to manage complexity through localized rather than universal adjustments
3Reliability
If adjusted transmission of demodulation reference signals is implemented, then orthogonality is improved, but transmission overhead increases due to additional signaling for mode indication
Solution Approach 1:
The patent implements partial adjustment by applying sequence group adjustments only when necessary for maintaining orthogonality, rather than always using the most complex adjustment mode. The system can select from multiple modes of operation, using simpler modes when they suffice and more complex modes only when required, thus improving orthogonality where needed while minimizing transmission overhead
Data Source
AI summary
At least two modes of communicating demodulation reference signals in a system providing a multiple of communication points for communication devices are provided. In a first mode demodulation reference signals are communicated based on an sequence group and separation of sequences provided by adjustment of transmitted demodulation reference signals. In a second mode demodulation reference signals are communicated based on one or more sequence groups and non-adjusted transmission of demodulation reference signals.