MIMO HARQ Sub-Stream Puncturing for Low-Latency Decoding
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Solution Overview
Problem
Existing wireless communication systems using HARQ and MIMO face challenges in minimizing retransmission delays and adapting to changing channel conditions, leading to latency issues and inflexibility in data transmission.
Innovation Solution
A method that encodes information into a low rate code word and transmits multiple spatial sub-streams with different combinations of bits, allowing for simultaneous transmission and retransmission based on channel quality, enabling flexible adaptation to channel conditions and data traffic requirements, and reducing the need for retransmissions by providing additional coded bits for decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple spatial sub-streams are transmitted simultaneously using MIMO, then system capacity and throughput are improved, but the complexity of decoding and error handling increases
Solution Approach 1:
The code word is segmented into multiple spatial sub-streams that are transmitted simultaneously through different antennas. Each sub-stream contains a portion of the coded bits, allowing the receiver to decode by combining subsets of these sub-streams. This segmentation enables parallel transmission while managing decoding complexity through selective combination of sub-streams.
Solution Approach 2:
The patent introduces a new dimension to HARQ by transmitting multiple spatial sub-streams simultaneously in the spatial domain rather than sequentially in time. This dimensional change from time-division to space-division multiplexing increases system capacity while the receiver manages complexity by selectively combining sub-streams for decoding attempts.
2Reliability
If retransmissions are handled in higher layers with multiple NACK signals, then error correction reliability is improved, but transmission latency increases
Solution Approach 1:
Forward error correction codes are applied preliminarily to the data before transmission across multiple spatial sub-streams. This preliminary coding action enables the receiver to attempt decoding with combinations of received sub-streams before requesting retransmissions, thereby reducing the need for multiple NACK signals and associated latency.
Solution Approach 2:
The patent enables the receiver to skip the traditional sequential process of sending multiple NACK signals and waiting for retransmissions by attempting to decode using combinations of already-received spatial sub-streams. This rushing through the decoding process with available data reduces transmission latency while maintaining reliability.
3Productivity
If spatial multiplexing is used to transmit multiple data streams simultaneously, then data rate is improved, but adaptability to changing channel conditions decreases
Solution Approach 1:
The patent implements dynamic adaptability by allowing the receiver to selectively combine different subsets of spatial sub-streams based on received signal quality indicators. When channel conditions change, the receiver can dynamically adjust which sub-streams are combined for decoding, providing adaptability while maintaining high data rates through parallel spatial transmission.
Solution Approach 2:
The system changes the parameter of sub-stream combination at the receiver based on channel conditions. By adjusting which spatial sub-streams are combined and how they are processed, the system adapts to varying channel quality while maintaining the high data rate benefit of simultaneous multi-stream transmission.
4Reliability
If multiple retransmissions are performed to ensure packet delivery, then reliability is improved, but system efficiency decreases due to latency
Solution Approach 1:
Multiple spatial sub-streams containing coded bits are merged at the receiver to form combinations for decoding attempts. By combining received sub-streams in different configurations, the system achieves reliable packet delivery without requiring multiple separate retransmission cycles, thereby improving system efficiency by reducing latency.
Solution Approach 2:
The receiver continuously attempts decoding using different combinations of received spatial sub-streams without interrupting the transmission flow with multiple NACK signals. This continuous useful action of decoding attempts with available data maintains reliability while improving system efficiency by eliminating idle waiting time.
Data Source
AI summary
A method of operating a wireless communications system, comprises encoding (12) information into a low rate code word, providing (20) at least two spatial sub-streams comprising different combinations of bits remaining after puncturing of the low rate code word, simultaneously transmitting (22) each of the at least two spatial sub-streams by way of a respective radio channel, receiving (24) the at least two spatial sub-streams, applying (28) a decoding process to the received at least two spatial sub-streams, and, if the decoding process is unsuccessful, transmitting simultaneously further spatial sub-streams comprising different combinations of bits remaining after puncturing of the low rate code word, at least one of the further spatial sub-streams being a not previously transmitted combination of bits remaining after puncturing of the low rate code word, receiving the further spatial sub-streams and applying the decoding process to the originally received at least two spatial sub-streams and the further sub-streams.