HARQ Feedback Grouping for Multi-Carrier Wireless Systems
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Solution Overview
Problem
In multiple carrier wireless communication systems, existing technologies face challenges in efficiently providing hybrid automatic repeat request (HARQ) feedback, especially when Multiple Input Multiple Output (MIMO) is configured, leading to cumbersome HARQ-ACK feedback scenarios and a large number of hypotheses that overwhelm existing code books.
Innovation Solution
The approach involves grouping downlink carriers into subsets to utilize existing HARQ feedback symbol code books from conventional HSDPA or DC-HSDPA systems, using dual channelization codes or a single channelization code with a reduced spreading factor to encode HARQ feedback symbols for uplink transmission, allowing for efficient encoding and transmission of HARQ feedback across multiple carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If HARQ feedback is provided for each downlink carrier separately in multi-carrier systems, then feedback accuracy is improved, but feedback overhead and complexity increase significantly
Solution Approach 1:
The patent combines HARQ feedback for multiple downlink carriers into a single uplink transmission. Specifically, it merges ACK/NACK feedback bits from multiple carriers and encodes them together using channel coding (e.g., (20,10) code or repetition code) to generate a single feedback message that conveys status information for all carriers, thereby reducing feedback overhead while maintaining accuracy
Solution Approach 2:
The patent creates a universal feedback mechanism that can handle both single-carrier and multi-carrier scenarios using the same uplink resources. The feedback structure is designed to be carrier-agnostic, allowing the same feedback message format and transmission channel to serve multiple carriers simultaneously, thus reducing system complexity
2Adaptability or versatility
If the number of HARQ feedback hypotheses increases to cover all carrier combinations, then feedback completeness is improved, but code book size becomes unmanageably large
Solution Approach 1:
The patent changes the approach from exhaustive hypothesis enumeration to parameter-based feedback representation. Instead of creating code books for all possible carrier combinations (2^N hypotheses), it uses a parameter-efficient method where each carrier's feedback state (ACK/NACK/DTX) is represented by a small number of bits, and these bits are systematically combined and encoded, dramatically reducing the effective code book size while maintaining completeness
Solution Approach 2:
The patent segments the feedback information into individual carrier-specific components (each with its own ACK/NACK/DTX state) that are then systematically combined. This segmentation allows the system to handle each carrier independently in terms of state tracking while using efficient combinatorial encoding to represent the combined state, avoiding the need for a single large code book covering all possible combinations
3Productivity
If MIMO is configured on multiple carriers, then system capacity is improved, but HARQ feedback scenarios become more cumbersome
Solution Approach 1:
The patent designs a universal feedback mechanism that works regardless of MIMO configuration. The same feedback structure and transmission method are used whether carriers are configured with MIMO, single-antport, or other modes. The feedback bits represent transport block reception status at the transport block level, which is the common denominator across different MIMO configurations, thus maintaining simplicity while supporting high capacity
Data Source
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AI summary
A method and apparatus provide hybrid automatic repeat request (HARQ) feedback corresponding to the status of multiple downlink carriers, with or without MIMO being configured. Here, for at least some configurations, with respect to the selection of HARQ feedback symbols, the downlink carriers are grouped into groups of one or two carriers such that HARQ feedback symbol code books that were previously implemented in conventional HSDPA or DC-HSDPA systems may be utilized. That is, after encoding a data stream, HARQ feedback symbols selected from a plurality of code books configured for groups of one or two of the downlink carriers are utilized to modulate an uplink channel. The modulation or channelization may be accomplished with dual channelization codes or a single channelization code with a reduced spreading factor to insert two symbols into a single time slot.