Interlaced DM-RS Configuration for MIMO Channel Estimation
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Solution Overview
Problem
In multi-input multi-output (MIMO) wireless communication systems, legacy reference signals transmitted in a single symbol of a transmit time interval (TTI) are insufficient for channel estimation and decoding by the base station, leading to inefficiencies in uplink data communication.
Innovation Solution
The allocation of specific uplink resources for User Equipments (UEs) to transmit demodulation reference signals (DM-RS) in a comb structure across multiple symbols within a TTI, ensuring orthogonality and effective channel estimation, involves assigning different cyclic shifts and orthogonal cover codes to preserve orthogonality between UEs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If legacy reference signals are transmitted in only one symbol of a TTI, then the transmission time interval is shortened, but channel estimation accuracy deteriorates
Solution Approach 1:
The reference signal transmission is segmented across multiple symbols within the TTI rather than concentrated in a single symbol. This segmentation allows the channel estimation to utilize channel characteristics from multiple time instances, improving estimation accuracy while maintaining the shortened TTI structure for low latency communication.
Solution Approach 2:
The patent transitions from a single-symbol reference signal approach to a multi-symbol approach by adding the time dimension. By distributing reference signals across multiple symbols in the time domain, the system enhances channel estimation capability without extending the overall TTI duration, effectively utilizing the time dimension to resolve the contradiction.
2Productivity
If DM-RS are transmitted by multiple UEs in the same slot, then resource utilization improves, but orthogonality between UEs deteriorates
Solution Approach 1:
The patent applies local quality by assigning different cyclic shift values and orthogonal cover code indices to different UEs transmitting DM-RS in the same slot. This differentiation creates locally unique reference signal characteristics for each UE, maintaining orthogonality at the UE-specific level while allowing multiple UEs to share the same time-frequency resources, thus improving resource utilization without sacrificing orthogonality.
Solution Approach 2:
The system changes parameters (cyclic shift values and orthogonal cover code indices) to maintain orthogonality between multiple UEs' DM-RS transmissions. By varying these parameters across different UEs, the patent enables multiple users to transmit reference signals simultaneously in the same slot while preserving the orthogonality required for accurate channel estimation at the base station.
Data Source
AI summary
The present methods and apparatus enable transmission of an interlaced reference signal for two UEs using a comb structure. In some aspects, the present methods and apparatus may allocate resources and indicate whether a first UE and a second UE are to transmit DM-RS with a comb structure in a single slot based on the allocation. Further, in some aspects, the present methods and apparatus may allocate resources and transmit information indicating whether a first UE is to transmit DM-RS in a first slot or in both a first slot and a second slot within a subframe.