Uplink SC-FDMA Symbol Reservation for LAA Channel Access
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Solution Overview
Problem
In licensed-assisted access (LAA) systems, the inability of multiple user equipments (UEs) to perform uplink multiplexing due to continuous channel occupation by other UEs, leading to reduced channel access success probability.
Innovation Solution
Reserving at least one SC-FDMA symbol in uplink transmission bursts for listen-before-talk (LBT) access, creating time gaps at start and/or end positions of subframes, allowing other UEs to access the channel, thereby improving channel access success probability through LBT mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If all symbols of uplink subframes are used to send data, then data transmission efficiency is improved, but channel access probability for other UEs deteriorates
Solution Approach 1:
The uplink subframe is segmented by reserving specific SC-FDMA symbols (e.g., first and/or last symbol) as gap symbols that do not transmit data. This segmentation creates time gaps within the subframe structure, allowing other UEs to access the channel through LBT while maintaining data transmission in non-reserved symbols.
Solution Approach 2:
The reservation of SC-FDMA symbols follows a periodic pattern where certain symbols at regular intervals (e.g., first symbol of each subframe, or alternating symbols) are designated as gap symbols. This periodic structure ensures consistent channel access opportunities for multiple UEs while maintaining overall transmission efficiency.
2Productivity
If continuous transmission is maintained, then spectral efficiency is improved, but uplink multiplexing capability deteriorates
Solution Approach 1:
By segmenting the continuous transmission timeline and inserting reserved SC-FDMA symbols as gaps, the system enables multiple UEs to perform LBT and access the channel at different time points within the same uplink subframe, thus achieving uplink multiplexing while maintaining high spectral efficiency in non-gap symbols.
Solution Approach 2:
The SC-FDMA symbols are reserved in advance as predetermined gap positions within the uplink subframe structure. This preliminary arrangement ensures that time gaps are always available for other UEs to perform LBT and access the channel, enabling uplink multiplexing without disrupting the overall transmission schedule.
Data Source
AI summary
An uplink transmission method based on a licensed-assisted access (LAA) system, and an apparatus, where the method includes reserving, for a transmission burst transmitted on an unlicensed carrier, at least one single-carrier frequency-division multiple access (SC-FDMA) symbol in a subframe of an uplink transmission burst corresponding to the transmission burst, where in the reserved at least one SC-FDMA symbol, user equipment (UE) accesses a channel using a listen-before-talk (LBT) access mechanism. Hence, a time gap for accessing the channel through LBT can be reserved for another UE in the uplink transmission burst. This improves a probability of successfully accessing the channel by another UE such that a plurality of UEs in an LAA communications system can perform uplink multiplexing.