Code Domain Multiplexing for Multi-Packet HARQ Spectral Efficiency
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Solution Overview
Problem
Current Hybrid Automated Repeat reQuest (HARQ) processes in mobile communications face inefficiencies in spectral usage and latency due to the separate handling of new data and retransmission data in the bit domain, leading to excessive data transfer and delay in successful decoding.
Innovation Solution
Implementing code domain multiplexing to combine new data and retransmission data in Multi-Packet HARQ (MP-HARQ) systems, where data and Incremental Redundancy (IR) bits are multiplexed together in layers, allowing for improved spectral efficiency and reduced latency through iterative decoding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If separate handling of new data and retransmission data in bit domain is used, then HARQ process is simple to implement, but spectral efficiency is poor and latency is high
Solution Approach 1:
The patent combines new data and retransmission data into a single codeword in the code domain, merging previously separate handling processes. This allows the receiver to decode the combined codeword and separate the data components, achieving better spectral efficiency while maintaining implementation feasibility through unified processing.
Solution Approach 2:
The patent transitions from bit-domain multiplexing to code-domain multiplexing, changing the dimension in which data is combined. By operating in the code domain rather than the bit domain, the system achieves improved spectral efficiency and enables multi-packet HARQ operations with reduced latency.
2Ease of operation
If separate handling of new data and retransmission data is used, then processing is straightforward, but data transfer volume is excessive
Solution Approach 1:
The patent merges new data and retransmission data into a single combined codeword, reducing the total data transfer volume. The receiver decodes the combined codeword and extracts both new and retransmitted data components, eliminating the need to separately transmit and process separate data streams.
3Reliability
If HARQ process stops until original data is successfully decoded, then decoding reliability is ensured, but latency increases
Solution Approach 1:
The patent enables continuous HARQ operations by allowing the system to proceed with combined codeword decoding without stopping to wait for individual packet acknowledgment. The receiver continuously processes combined codewords containing both new and retransmitted data, maintaining uninterrupted data flow and reducing latency while ensuring reliability through iterative decoding.
4Productivity
If code domain multiplexing is used to combine new data and retransmission data, then spectral efficiency is improved, but processing complexity increases
Solution Approach 1:
The patent employs code-domain multiplexing instead of bit-domain multiplexing, operating in a different domain to achieve better spectral efficiency. The processing complexity is managed through unified codeword encoding and decoding operations that leverage the mathematical properties of code-domain representations.
Data Source
AI summary
There is provided methods and apparatus to improve spectral efficiency in Hybrid Automated Repeat reQuest (HARQ) communications. New data and retransmission data is combined in packets using code domain multiplexing, where data layers carry data and retransmission layers carry retransmission data. This technique is leveraged to introduce Multi-Packet HARQ. The HARQ layers contain Incremental Redundancy (IR) bits to assist in the decoding of a subset of previously undecoded layers. Multiple packets are jointly decoded at the receiver. Using the properties of code multiplexing, and in particular Sparse Code Multiple Access (SCMA), the correct decoding of a subset of previously undecoded layers assists in the decoding of all previously undecoded layers. HARQ feedback for multiple packets is jointly interpreted by the receiver and the transmitter using state tables. These techniques are further leveraged to allow for Multiple-User SCMA.