Uplink MIMO Reference Signal Multiplexing via Cyclic Shift and Orthogonal Cover Code
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Solution Overview
Problem
Current MIMO systems face challenges in efficiently designing Demodulation Reference Signals (DMRS) for uplink MIMO transmission, particularly in maintaining channel estimation performance while supporting multi-antenna transmission and ensuring backward compatibility with existing LTE systems.
Innovation Solution
The method involves using multiple cyclic shift resources and an orthogonal cover code to multiplex reference signals, allowing for efficient DMRS transmission across multiple antennas, with the cyclic shift values allocated to maximize spacing and the orthogonal cover code used for multiplexing in multiuser MIMO scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple antennas are used for uplink transmission to improve transmission rate and reliability, then MIMO performance is improved, but channel estimation complexity and reference signal design difficulty increase
Solution Approach 1:
The patent combines multiple reference signals for different antennas into a single uplink subframe transmission, using cyclic shifts and orthogonal cover codes to multiplex the reference signals. This merging approach allows the receiver to estimate channels for multiple antennas simultaneously, reducing the overall complexity of channel estimation while maintaining MIMO transmission reliability
Solution Approach 2:
The reference signal design creates a universal structure that can be used across multiple antennas and multiple users. The cyclic shift and orthogonal cover code mechanisms allow the same reference signal template to serve multiple antenna ports and support both single-user and multi-user MIMO scenarios, simplifying the channel estimation process
2Productivity
If reference signals are multiplexed for multiple users in MU-MIMO, then system capacity is improved, but interference between users increases
Solution Approach 1:
The patent introduces orthogonal cover codes as intermediary elements that separate user signals in the code domain. Each user is assigned a unique orthogonal cover code, which acts as a mediator to distinguish between different users' reference signals even when they share the same time-frequency resources, thereby enabling multi-user capacity while controlling interference
Solution Approach 2:
The system changes the code domain parameters by applying different cyclic shifts and orthogonal cover codes to different users' reference signals. This parameter transformation allows multiple users to share the same physical resources while maintaining signal distinguishability, increasing system capacity without proportionally increasing interference
3Productivity
If LTE-A supports multi-antenna transmission, then transmission rate increases, but backward compatibility with LTE systems becomes more difficult to maintain
Solution Approach 1:
The reference signal design creates a universal structure that works for both single-antenna LTE and multi-antenna LTE-A systems. By using cyclic shifts and orthogonal cover codes that are compatible with existing LTE single-antenna reference signal formats, the system maintains backward compatibility while enabling enhanced multi-antenna transmission capabilities
Solution Approach 2:
The patent segments the reference signal resources in the code domain, allocating specific cyclic shifts and orthogonal cover codes to different antenna ports. This segmentation allows the system to maintain the familiar single-antenna reference signal structure for legacy devices while providing additional segmented resources for multi-antenna operation in LTE-A
Data Source
AI summary
The present invention relates to a wireless communication system, and more particularly, to a method and an apparatus for transmitting reference signals in uplink MIMO transmission. According to one embodiment of the present invention, the method for transmitting uplink signals through a terminal in the wireless communication system comprises the steps of: receiving control information including the information on a cyclic shift and/or an orthogonal cover code; allocating the multiplexed reference signals onto an uplink subframe; and transmitting the subframe through a multi-antenna. When the uplink MIMO transmission is multiuser MIMO transmission, the reference signals of the terminal and the reference signals of other terminals can be multiplexed by using the orthogonal cover code.