Base Station Request Signal for LAA Uplink Timing
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Solution Overview
Problem
In Licensed Assisted Access (LAA) wireless communication systems, when the unlicensed band is busy, terminals may miss the reservation signal, leading to postponed data transmission opportunities, which decreases the throughput of uplink data transmission from terminals to base stations.
Innovation Solution
A base station generates and transmits a request signal specifying a second transmission timing offset for terminals, allowing them to perform data transmission at a later time if they do not receive the permission signal at the initial timing, thereby avoiding retransmission delays and improving throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base station uses LBT in the unlicensed band before terminal transmission, then the unlicensed band can be accessed fairly, but the terminal may miss the reservation signal when the band is busy, causing transmission delays
Solution Approach 1:
The base station performs LBT and transmits the reservation signal in advance before the terminal's data transmission timing. This preliminary action ensures the terminal can detect the reserved resource before needing to transmit, preventing missed opportunities and reducing delays.
Solution Approach 2:
The system introduces a time cushion between the reservation signal transmission and the terminal's data transmission timing. This cushion allows the terminal sufficient time to receive and process the reservation signal even when the unlicensed band is busy, preventing transmission delays.
2Productivity
If the terminal waits for the reservation signal at the scheduled transmission timing, then the transmission timing is optimized, but the throughput decreases when the unlicensed band is busy
Solution Approach 1:
The terminal monitors for the reservation signal and provides feedback by transmitting data at the scheduled timing if the signal is received, or using an alternative timing if not received. This feedback mechanism ensures the system adapts to channel conditions while maintaining high throughput and reliable transmission opportunities.
Solution Approach 2:
The system changes the transmission timing parameter based on whether the reservation signal is received. If the signal is received, transmission occurs at the scheduled timing; if not, transmission occurs at an alternative timing specified by the base station, thereby maintaining throughput while improving reliability.
3Reliability
If the terminal cancels transmission when missing the reservation signal, then the system avoids conflicts, but the transmission opportunity is postponed until the next UL grant
Solution Approach 1:
The base station performs LBT and transmits the reservation signal in advance, allowing the terminal to detect available resources before transmission. This preliminary action prevents conflicts while maintaining transmission opportunities, improving both reliability and throughput simultaneously.
Data Source
AI summary
A base station that performs wireless communication with a terminal using a first frequency band which does not need the license to use for the wireless communication, the base station includes: a controller configured to generate a request signal for requesting data transmission of the terminal in the first frequency band and specifying a first transmission timing of the terminal; and a transmitter configured to transmit to the terminal the request signal, wherein, the request signal includes information used for specifying a second transmission timing, which is a next transmission timing when the terminal does not perform data transmission at the first transmission timing and is specified by an offset from a reference timing.