Spatial-Domain Modulation for Massive-MIMO Transmitters
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Solution Overview
Problem
Massive-MIMO systems face challenges in acquiring accurate channel state information (CSI) for beamforming, especially in frequency-division duplex systems, and existing spatial-domain modulation techniques like SM and GSSK have limitations in data rate and computational complexity.
Innovation Solution
A spatial-domain modulation method that maps symbols to L-dimensional coordinates, dividing antennas into non-overlapping groups and activating one antenna per group to transmit modulated signals, reducing the need for CSI at the transmitter and lowering hardware costs by minimizing the number of RF chains required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If beamforming techniques are used in Massive-MIMO systems, then link gains and data rate are improved, but accurate channel state information (CSI) is required at the transmitter which increases system complexity and feedback overhead
Solution Approach 1:
The patent segments the data stream into multiple portions and transmits them through different spatial paths (direct path and reflected paths). This segmentation allows the system to achieve high data rates without requiring complete CSI for beamforming, as each segment can be transmitted independently through different spatial channels.
Solution Approach 2:
The patent introduces a new spatial dimension by utilizing reflected paths (e.g., via建筑物的反射) in addition to the direct path. This creates multiple spatial dimensions for data transmission, enabling high data rates through spatial diversity rather than relying solely on beamforming with precise CSI.
2Device complexity
If spatial-domain modulation schemes like SM or GSSK are used, then CSI requirement at transmitter is reduced, but data rate is limited and computational complexity at receiver increases
Solution Approach 1:
The patent merges the advantages of spatial-domain modulation (reduced transmitter CSI requirement) with the benefits of multi-path transmission (high data rate). By combining direct path transmission with reflected path transmission, the system achieves high data rates without the computational complexity burden at the receiver.
Solution Approach 2:
The patent adds another spatial dimension by utilizing reflected paths alongside direct paths. This enables the system to transmit multiple data segments through different spatial dimensions, achieving high data rates while maintaining the simplicity of spatial-domain modulation at the transmitter.
3Productivity
If higher-order IQ-modulation is used in SM to boost data rate, then data rate increases, but performance degrades in noisy channels
Solution Approach 1:
The patent segments data into multiple portions transmitted through different spatial paths. Each segment can use robust lower-order modulation, and the overall system achieves high data rate through the combination of multiple segments. This segmentation approach maintains noise robustness while achieving high throughput.
Solution Approach 2:
The patent changes the transmission parameter from using high-order modulation on a single path to using lower-order modulation on multiple spatial paths. This parameter change maintains reliability in noisy channels while achieving equivalent or superior data rates through spatial diversity.
4Productivity
If antenna array size is increased in GSSK to increase bit size of symbol, then data rate increases, but hardware cost and complexity increase
Solution Approach 1:
The patent utilizes the reflected path dimension in addition to the direct path, creating multiple spatial dimensions for data transmission. This allows the system to achieve high data rates without proportionally increasing the antenna array size, as each spatial dimension can be exploited independently.
Data Source
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Figure 3
Figure 4A~4B
AI summary
A method for data transmission using spatial-domain modulation, and a transmitter using the same has been proposed. The method comprises the following steps including at least but not limited to receiving a plurality of symbols to be transmitted, mapping the symbols as L-dimensional coordinate, wherein 1 < L < N, dividing the antennas into L non-overlapping antenna groups, choosing one activating antenna from the antennas in each of the antenna groups according to the coordinate of the symbols, and transmitting modulated signal by using the activating antenna in each of the antenna groups.