Short PUCCH HARQ Payload Mapping for Shared Unlicensed Uplink
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Solution Overview
Problem
In wireless communication systems with shared communication media, such as unlicensed frequency bands, there is a challenge in efficiently transmitting acknowledgments without causing cross-link interference and adhering to Listen-Before-Talk mechanisms, particularly for small cell LTE operations coexisting with Wi-Fi, where the fixed HARQ timelines and associations are not applicable.
Innovation Solution
The use of a short Physical Uplink Control Channel (PUCCH) for acknowledgments, which is designed to accommodate multiple downlink subframes and HARQ processes, employing subframe-based and HARQ-process-based payload mapping strategies to optimize transmission opportunities and reduce the need for Listen-Before-Talk, while supporting multiple-access systems like LTE and Wi-Fi.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If small cell LTE operations are extended into unlicensed frequency spectrum to increase spectral efficiency and capacity, then spectral efficiency and capacity are improved, but cross-link interference with other RATs (particularly Wi-Fi) occurs
Solution Approach 1:
The patent segments the acknowledgment transmission process by separating HARQ feedback for different downlink subframes into distinct uplink transmission opportunities. The access terminal transmits acknowledgments for first downlink subframes at a first time and acknowledgments for second downlink subframes at a second time, dividing the feedback burden across multiple time instances to avoid interference with other RATs while maintaining spectral efficiency
Solution Approach 2:
The patent implements preliminary action by having the access terminal transmit acknowledgments in advance of when the corresponding downlink data would be received, utilizing future uplink subframes to send feedback for past downlink subframes. This allows the system to maintain continuous operation on unlicensed spectrum while managing interference through temporal separation of critical feedback signals
2Reliability
If the access terminal transmits acknowledgments for multiple downlink subframes on the uplink channel, then HARQ reliability is improved, but the uplink transmission time and complexity increase
Solution Approach 1:
The patent segments the acknowledgment transmission across multiple uplink subframes rather than consolidating all feedback in a single transmission. The access terminal transmits acknowledgments for different sets of downlink subframes at different times, which maintains HARQ reliability through complete feedback coverage while reducing the time required for any single uplink transmission event
Solution Approach 2:
The patent employs periodic action by establishing a repeating pattern where the access terminal transmits acknowledgments for downlink subframes at regular intervals. The access terminal transmits acknowledgments for first downlink subframes at a first time and then transmits acknowledgments for second downlink subframes at a second time, creating a periodic feedback mechanism that maintains reliability without excessive time consumption
3Ease of operation
If the access terminal waits for downlink data reception before transmitting acknowledgments, then transmission timing is simplified, but the response time for HARQ feedback increases
Solution Approach 1:
The patent implements preliminary action by having the access terminal prepare and transmit acknowledgments in advance, utilizing future uplink subframes to send feedback for past downlink subframes before the downlink data is fully processed. This maintains simple timing operations while reducing HARQ feedback delay through proactive acknowledgment transmission
Solution Approach 2:
The patent applies dynamics by making the acknowledgment transmission timing flexible rather than fixed. The access terminal dynamically selects when to transmit acknowledgments for different downlink subframes, can transmit at the first time for some subframes and at the second time for others, adapting the timing to optimize both operational simplicity and feedback speed
Data Source
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AI summary
Techniques for transmitting acknowledgments on a shared communication medium are disclosed. In an aspect, an access terminal receives, from an access point, a plurality of downlink subframes on a downlink channel of the wireless communication medium, the plurality of downlink subframes carrying data for a plurality of processes. The access terminal transmits, to the access point, acknowledgments for the plurality of downlink subframes on an uplink subframe of an uplink channel of the wireless communication medium on one or more occasions, the uplink subframe including a plurality of bits, the plurality of bits corresponding to the plurality of downlink subframes or the plurality of processes.