Method and apparatus for providing downlink control information in an MIMO wireless communication system
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Solution Overview
Problem
Conventional 3GPP LTE systems face challenges in accurately receiving downlink signals due to control information limitations in new MIMO transmission methods, particularly with dual-layer beamforming and UE-specific reference signals, which restrict the number of layers and codewords that can be supported.
Innovation Solution
A method and apparatus for transmitting and receiving downlink control information in a wireless communication system that supports up to 8 layers, using UE-specific reference signals and codewords, allowing for accurate demodulation of downlink data by indicating the number of layers and codes for identifying these signals, enabling dual-layer beamforming and multi-user MIMO operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional DCI formats are used in new MIMO transmission schemes, then device complexity is reduced, but downlink signal reception accuracy deteriorates due to insufficient control information for dual-layer beamforming and UE-specific reference signals
Solution Approach 1:
The DCI format is segmented into multiple fields, each serving a specific function: layer indication field for specifying the number of layers (1-8), codeword-to-layer mapping field for defining mapping relationships, and UE-specific reference signal indication field for identifying reference signals. This segmentation allows comprehensive control information to be organized systematically, resolving the contradiction between providing complete control information and maintaining manageable format complexity.
Solution Approach 2:
The DCI format is designed to be dynamic and adaptable to different MIMO transmission schemes. The format can flexibly indicate various layer configurations (1-8 layers), different codeword-to-layer mapping relationships, and support multiple UE-specific reference signals. This dynamic structure enables the same DCI format to accommodate diverse transmission scenarios including dual-layer beamforming and multi-user MIMO, thereby improving reception accuracy without requiring separate formats for each scheme.
2Productivity
If the number of layers is increased to support higher rank transmissions, then system capacity is improved, but control information completeness deteriorates when using conventional DCI formats that only support up to 4 layers
Solution Approach 1:
The DCI format parameters are changed to support higher layer configurations. Specifically, the layer indication field is extended to indicate up to 8 layers (rank 8), and the codeword-to-layer mapping field is configured to support mapping relationships for up to 8 layers. This parameter expansion ensures that control information remains complete and accurate for high-rank transmissions, enabling increased system capacity without information loss.
3Adaptability or versatility
If dual-layer beamforming and multi-user MIMO are supported, then adaptability is improved, but control information accuracy deteriorates due to lack of UE-specific reference signal identification
Solution Approach 1:
An intermediary UE-specific reference signal indication field is introduced in the DCI format. This field explicitly identifies which UE-specific reference signals are associated with the downlink data, serving as a mediator between the transmitted data and the reference signals used for demodulation. This intermediary mechanism ensures that even when supporting multiple MIMO schemes simultaneously, the control information accurately specifies the correct reference signals, maintaining measurement precision and control information accuracy.
Data Source
AI summary
The present invention relates to a method in which a user equipment receives a downlink signal from a base station in a wireless communication system that supports downlink mimo transmission according to one embodiment of the present invention comprises: receiving downlink control information that includes information indicative of the number of layers (n, 1≦n≦8) where one or two enabled code words of the downlink mimo transmission are mapped; on the basis of the downlink control information, receiving downlink data transmitted over the respective n layers and a ue-specific reference signal for each of the n layers; and decoding the downlink data on the basis of the ue-specific reference signals, wherein the information indicative of the number of layers can further include information on a code for identifying the ue-specific reference signals.