Dynamic DM-RS OCC Length Switching for 5G MU-MIMO
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Solution Overview
Problem
Current 5G NR systems face challenges in providing a large number of orthogonal DM-RS ports with minimal overhead, while ensuring good demodulation performance for massive SU/MU-MIMO transmissions.
Innovation Solution
The method involves configuring orthogonal cover codes (OCC) of lengths 4 and 2 for DM-RS communication between a gNB and UE, allowing for dynamic switching between these configurations based on signaling indications, such as RRC signaling, MAC control elements, or DCI messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a large number of orthogonal DM-RS ports are provided, then the number of data layers supported is increased, but the DM-RS overhead increases
Solution Approach 1:
The patent applies dynamics by enabling flexible switching between different OCC lengths (2 and 4) based on transmission requirements. The gNB can dynamically indicate which OCC length to use via signaling, allowing the system to adapt the number of DM-RS ports (4 ports for OCC length 2, or up to 8 ports for OCC length 4) according to the specific MU-MIMO transmission needs, thereby optimizing the balance between supporting more data layers and minimizing overhead.
Solution Approach 2:
The patent changes the parameter of OCC length from a fixed value to a variable parameter that can take different values (2 or 4). This parameter change allows the system to adjust the mapping between DM-RS ports and OCCs, enabling more ports to be supported with the same physical resources by changing the OCC length parameter rather than adding more physical elements.
2Quantity of substance
If OCC length 4 is used to increase DM-RS ports, then more data layers are supported, but the complexity of configuration and signaling increases
Solution Approach 1:
The patent applies universality by designing a system where the same set of DM-RS ports can serve multiple purposes depending on the OCC length configuration. The gNB can configure the system to use OCC length 2 for simpler transmissions or OCC length 4 for higher layer counts, and the UE can interpret the same physical ports differently based on the signaling. This multi-functionality reduces the need for separate physical configurations for different numbers of ports.
Solution Approach 2:
The patent applies preliminary action by pre-configuring both OCC length 2 and OCC length 4 modes in the system, with the gNB preparing the appropriate signaling information in advance. The UE is pre-configured with the capability to interpret different OCC length indications, so when the gNB signals a particular OCC length, the UE can immediately switch to the appropriate port mapping without complex real-time calculations or reconfiguration.
3Adaptability or versatility
If dynamic switching between OCC lengths is enabled, then adaptability to different transmission scenarios is improved, but the signaling overhead increases
Solution Approach 1:
The patent applies partial action by using a small, limited set of signaling bits to indicate the OCC length configuration rather than providing full detailed configuration information. Instead of signaling every possible parameter change, the system uses a simplified indication mechanism (such as a 1-bit indicator or pre-configured table lookup) to convey the essential OCC length information, achieving adaptability with minimal signaling overhead.
Data Source
AI summary
A user equipment (UE) may receive, from a base station, a configuration indicating a first orthogonal cover code (OCC) length that is 4 and a second OCC length that is 2 for demodulation reference signals (DM-RSs) communications between the base station and the UE. The UE may receive a signaling indicating the UE to communicate DM-RS(s) according to the first OCC length or the second OCC length. The UE may communicate, with the base station, a DM-RS according to the first OCC length or the second OCC length indicated by the signaling.