PUCCH Interlaced Format for Unlicensed Spectrum
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Solution Overview
Problem
In the context of LTE-U and LAA, there is a challenge in designing an uplink control channel (PUCCH) that can operate effectively in unlicensed spectrum, where there is no guaranteed channel access and regulatory requirements must be met.
Innovation Solution
The proposed solution involves the development of two PUCCH formats, short PUCCH and long PUCCH, which can be used for UCI transmission in unlicensed spectrum. These formats utilize interlaced UL resources and support multiplexing with other PUCCH/PUSCH UEs, allowing for efficient transmission of control information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LTE operates in unlicensed spectrum using traditional PUCCH formats, then control information can be transmitted, but channel access is not guaranteed and Wi-Fi performance degrades due to lack of coexistence mechanisms
Solution Approach 1:
The PUCCH format is made dynamic by introducing a guard period at the beginning of the subframe, allowing the actual PUCCH transmission to start at a flexible time position. This dynamic structure enables the system to adapt to varying channel access conditions and LBT outcomes, resolving the contradiction between reliable control transmission and spectrum sharing capability.
Solution Approach 2:
The invention changes the temporal parameters of PUCCH transmission by introducing variable guard periods and flexible starting positions within the subframe. This parameter flexibility allows the system to adjust to different unlicensed spectrum conditions while maintaining control information transmission reliability, thereby resolving the contradiction with Wi-Fi coexistence requirements.
2Loss of information
If PUCCH transmission occupies the entire subframe, then control information can be transmitted with sufficient resources, but latency increases and responsiveness to channel conditions decreases
Solution Approach 1:
The PUCCH transmission is segmented into a guard period and an actual transmission period. This segmentation allows the control information to be transmitted in a compressed time window, reducing overall latency while ensuring complete control information delivery. The guard period handles channel access uncertainty, while the transmission period delivers the control data efficiently.
Solution Approach 2:
The guard period acts as a preliminary action that prepares the system for PUCCH transmission by handling LBT and channel access procedures in advance. This preliminary timing adjustment ensures that the actual control information transmission can occur with minimal delay, resolving the contradiction between complete information transmission and reduced latency.
3Ease of manufacture
If PUCCH uses fixed resource allocation, then resource management is simple, but flexibility to adapt to LBT outcomes and varying channel conditions is reduced
Solution Approach 1:
The resource allocation for PUCCH is made dynamic through the introduction of a configurable guard period and flexible starting position within the subframe. While the basic resource structure remains simple, the timing parameters can be adjusted based on LBT outcomes and channel conditions, resolving the contradiction between allocation simplicity and channel adaptability.
Data Source
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AI summary
A physical uplink control channel (PUCCH) format for transmission of uplink control information (UCI) in unlicensed spectrum is either short PUCCH or long PUCCH. The short PUCCH occupies less than 1 subframe in the time domain and spans an entire system bandwidth in the frequency domain with interlacing on a resource block level. The long PUCCH occupies one subframe in the time domain and spans the entire system bandwidth in the frequency domain with interlacing on a resource block level.