UE-RS Sequence Mapping Orthogonality in MU-MIMO Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional wireless communication systems, such as LTE Release 8, are limited in their ability to efficiently map reference signals in multi-user multiple-input, multiple-output (MU-MIMO) systems, leading to non-orthogonal pseudo-random sequences for user equipment reference signals (UE-RS) across paired users and cells, which results in interference and reduced system performance.
Innovation Solution
The proposed solution involves initializing the pseudo-random sequence for UE-RS using a UE-independent method, removing the UE-ID dependency and using a common cell ID for sequence initialization, ensuring orthogonality across different cells and users, and mapping the sequence to resource elements based on antenna port indices and transmission rank, allowing for code division multiplexing and frequency division multiplexing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional UE-RS sequence initialization methods are used with UE-ID dependency, then each user can have unique reference signals, but orthogonality is lost across paired users and cells causing interference
Solution Approach 1:
The patent changes the initialization parameters of the pseudo-random sequence from UE-ID dependent to UE-independent, using only cell ID, slot number, and symbol number. This parameter change ensures that paired users in the same cell use identical sequences, maintaining orthogonality across different cells while enabling proper MU-MIMO operation.
Solution Approach 2:
The patent creates equipotential conditions by making all paired users use the same pseudo-random sequence initialization parameters within a cell. This ensures that all users experience equal treatment in terms of reference signal generation, eliminating the potential for inter-user interference and maintaining orthogonality across the network.
2Reliability
If UE-independent sequence initialization is used, then orthogonality is maintained across cells, but the ability to differentiate user-specific sequences is reduced
Solution Approach 1:
The patent moves the differentiation dimension from sequence content to resource element mapping. While the pseudo-random sequence itself becomes user-independent, the mapping of these sequences to specific resource elements remains user-specific through antenna port indices and layer associations, preserving user identification capability without sacrificing orthogonality.
Solution Approach 2:
The patent introduces the resource element mapping as an intermediary between the user and the reference signal. The UE-independent sequence serves as a common foundation, while the user-specific mapping parameters (antenna port, layer, resource block) act as intermediaries that restore user differentiation without compromising the orthogonality provided by the common sequence initialization.
3Productivity
If reference signal framework is extended to support MU-MIMO with multiple layers, then system capacity increases, but complexity of sequence mapping and resource allocation increases
Solution Approach 1:
The patent segments the reference signal framework into distinct components: UE-independent sequence initialization, user-specific resource element mapping, and antenna port association. This segmentation allows each component to be optimized independently, managing complexity while supporting multiple layers and users in MU-MIMO systems.
Solution Approach 2:
The patent creates a universal sequence initialization method that serves all users in a cell regardless of their specific allocation. This universal approach simplifies the base complexity while allowing flexible, user-specific mapping parameters to handle the diversity of MU-MIMO configurations, achieving multi-functionality without proportional complexity increase.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A wireless communication method implemented in a multi-user, multi-input multi-output MU-MIMO system is disclosed which includes forming one or more antenna port sets, wherein an antenna port set comprises two or more antenna ports and allocating transmission resources to a user equipment reference signal UE-RS, the allocating being based at least in part on an antenna port set index.