Dedicated Reference Signal Generation for LTE-A MU-MIMO
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Solution Overview
Problem
In LTE-A systems, the existing methods for generating Dedicated Reference Signals (DRS) lead to unbalanced transmission power and interference between cells, limiting the performance of Multi-User Multiple-Input Multiple-Output (MU-MIMO) transmission and Coordinated Multi-Point (CoMP) transmission.
Innovation Solution
A new method for generating and mapping DRS, which involves generating RS sequences for each antenna port using initialization parameters that include port ID, cell ID, and UE ID, spreading the sequences with Walsh codes, and scrambling them with predefined codes to ensure independence and orthogonality, thereby balancing power and reducing interference between cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional DRS generation methods are used with random sequences and scrambling codes, then the basic reference signal transmission is achieved, but the transmission power becomes unbalanced and interference between cells increases
Solution Approach 1:
The patent changes the parameters used for sequence generation from random initialization to deterministic parameters including cell ID, port ID, and orthogonal cover code index. This parameter change ensures that DRS sequences from different cells are more distinguishable, reducing inter-cell interference while maintaining reliable channel evaluation through improved sequence orthogonality and power balance.
2Productivity
If DRS sequences are generated using conventional methods, then the overhead is reduced compared to CRS, but the MU-MIMO performance is limited due to inability to learn other UEs' DRS information
Solution Approach 1:
The patent enables a UE to copy or derive the DRS sequence of another UE by using the same generation parameters (cell ID, port ID, orthogonal cover code index) that are publicly known or can be inferred. This copying capability allows the receiving UE to reconstruct the interfering DRS sequence from other UEs, enabling interference cancellation and improving MU-MIMO performance while maintaining low overhead.
3Reliability
If multiple nodes transmit data to one UE using coordinated multi-point joint transmission, then the signal-to-noise ratio increases, but the interference control becomes complex requiring coordinated scheduling
Solution Approach 1:
The patent enables UEs to autonomously generate and identify DRS sequences using standardized parameters (cell ID, port ID, orthogonal cover code index) without requiring complex coordinated scheduling. Each UE can independently determine the DRS sequences from multiple transmitting nodes by knowing their respective parameters, simplifying the system while maintaining high signal-to-noise ratio through multi-point transmission.
Data Source
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AI summary
A method for generating a Dedicated Reference Signal (DRS) is provided, which includes generating a Reference Signal (RS) sequence of each antenna port, spreading each RS sequence and obtaining an spread RS sequence, multiplying each spread RS sequence by a predefined scrambling code and obtaining a desired DRS sequence. An apparatus for generating a DRS is also provided. The problem of the imbalance of the power of OFDM symbols is cured, and DRS interference between different cells can be randomized.