DM-RS Port Grouping and OCC Mapping for MIMO Channel Estimation
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Solution Overview
Problem
Current wireless communication systems, such as LTE, face challenges in efficiently managing reference signals with multiple antennas, particularly in supporting increased spatial resources and layer demodulation, which limits the ability to enhance MIMO transmission beyond four layers due to restrictions in the number of antenna ports and CRS-based LD CDD schemes.
Innovation Solution
The method involves grouping DM-RS ports into antenna port groups and applying an orthogonal cover code (OCC) of length 2 to map DM-RS sequences across symbol resources, allowing for efficient transmission and channel estimation by using the same precoder across resource blocks, thereby increasing the number of supported antenna ports and improving channel estimation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of antenna ports is increased to support more spatial resources and MIMO layers, then the system capacity and transmission performance are improved, but the overhead of reference signals (DM-RS) increases significantly
Solution Approach 1:
The patent divides DM-RS ports into multiple groups (first group and second group) with different port numbers. Each group uses distinct time-frequency resources and orthogonal cover codes, allowing the system to support a larger total number of antenna ports while distributing the reference signal overhead across different resource sets, thereby reducing the overhead burden on any single resource allocation.
Solution Approach 2:
The patent extends the orthogonal cover code (OCC) length from traditional values to length-4 codes spanning multiple slots and symbol resources. By utilizing additional time and frequency dimensions (across slots 0 and 1, and multiple OFDM symbols), the system can multiplex more antenna ports orthogonally without proportionally increasing the total DM-RS overhead, as the same physical resources carry reference signals for multiple ports through code division.
2Adaptability or versatility
If traditional CRS-based LD CDD schemes are used, then the system maintains compatibility with existing LTE standards, but the system cannot support MIMO transmission beyond four layers due to antenna port restrictions
Solution Approach 1:
The patent changes the fundamental parameters of DM-RS configuration by introducing length-4 orthogonal cover codes that span multiple slots and increasing the number of DM-RS ports beyond the traditional four. This parameter extension allows the system to support more than four MIMO layers, breaking the limitation of conventional CRS-based schemes while maintaining the same basic reference signal structure and processing principles.
Solution Approach 2:
The patent enables dynamic allocation and configuration of DM-RS ports across multiple slots and antenna groups. The system can flexibly assign different OCC patterns and resource allocations to different antenna port groups based on current transmission needs, allowing adaptive support for varying MIMO layer configurations without being constrained by fixed port assignments.
Data Source
AI summary
Disclosed is a method of mapping a demodulation-reference signal (DM-RS) transmitted to a terminal by a base station in a wireless communication system based on multiple antennas. Specifically, the method includes grouping a plurality of DM-RS ports into antenna port groups including a predefined number of DM-RS ports, mapping a DM-RS sequence to two symbol resources of a first slot and two symbol resources of a second slot on one subcarrier, and transmitting the mapped DM-RS sequence to the terminal through the plurality of DM-RS ports, wherein a DM-RS sequence transmitted through DM-RS ports included in the same antenna port group is mapped by applying an orthogonal cover code (OCC) having a length of 2 to the same symbol resource, and the two symbol resources of the first slot correspond to a first antenna port group and the two symbol resources of the second slot correspond to a second antenna port group on the one subcarrier.