MIMO Spatial Mapping Rotation to Mitigate Antenna Attenuation
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Solution Overview
Problem
Conventional spatial mapping techniques in MIMO systems, such as IEEE 802.11n, face challenges where attenuated streams from one antenna lead to packet loss, requiring complex and costly receiver adjustments to compute multiple equalizers for each permutation of subcarriers, increasing computational burden.
Innovation Solution
Applying a rotation matrix in the frequency domain to space-time streams, allowing them to be mapped variably across subcarriers, thereby enabling successful reception from other antennas without necessitating new equalizers at the receiver, thus maintaining receiver complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional spatial mapping techniques are used in MIMO systems, then signal transmission is performed, but attenuated streams from one antenna lead to packet loss requiring complex receiver adjustments
Solution Approach 1:
The patent applies spatial rotation matrices to the space-time streams before transmission, pre-distributing signal energy across multiple antennas in a rotated configuration. This preliminary action ensures that if one antenna's stream is attenuated, the rotated components from other antennas can still be successfully received and combined, eliminating the need for complex receiver adjustments while maintaining packet reception reliability
Solution Approach 2:
The patent introduces dynamic spatial rotation where the mapping of space-time streams to antennas is not fixed but rotated according to rotation matrices. This dynamic approach allows the system to adaptively distribute signal energy across different antenna configurations, improving reliability against attenuation without requiring the receiver to compute multiple equalizers for each permutation
2Reliability
If multiple equalizers are computed for each permutation of subcarriers, then packet loss from attenuated streams is recovered, but computational burden increases
Solution Approach 1:
The transmitter performs preliminary spatial rotation of space-time streams using rotation matrices before transmission. This pre-processing distributes signal energy across multiple antennas in a rotated configuration, ensuring that attenuation of one stream does not result in packet loss. The receiver simply applies the corresponding inverse rotation to recover the original streams, avoiding the need to compute multiple equalizers and significantly reducing computational energy consumption
Data Source
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AI summary
A method is provided for transmitting a digital signal. The method includes generating a plurality of spatial streams from a digital signal and transforming the spatial streams into a plurality of space-time streams. Each of the space-time streams are cycled in the frequency domain among each of a plurality of transmit antennas. The space-time streams are wirelessly transmitted from the plurality of transmit antennas.