Uplink Data Transmission in LTE-U Unlicensed Bands
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Solution Overview
Problem
In LTE-U services, the hidden node problem and channel occupation in unlicensed bands pose challenges for efficient uplink data transmission, as user terminals need to share channels with heterogeneous systems without causing collisions, requiring effective clear channel assessment and scheduling methods.
Innovation Solution
The proposed method involves a base station notifying user terminals of downlink control information for multiple uplink subframes using a listen before talking (LBT) scheme, where user terminals perform clear channel assessment (CCA) and use a random back-off counter to schedule uplink data transmission, ensuring channel access parameters are shared for efficient uplink subframe transmission in unlicensed bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If user terminals perform independent clear channel assessment (CCA) in unlicensed bands, then channel access capability is improved, but hidden node interference and collision probability increase
Solution Approach 1:
The base station acts as an intermediary by performing CCA on behalf of multiple user terminals and providing unified channel access control. The base station's clear channel assessment results are shared with scheduled terminals, allowing them to transmit without performing independent CCA, thus resolving the hidden node problem while maintaining channel access efficiency
Solution Approach 2:
Multiple user terminals merge their channel access operations into a single base station-performed CCA. Instead of each terminal independently assessing the channel, the base station performs one assessment and controls access for all scheduled terminals, reducing redundant assessments and hidden node interference
2Productivity
If multiple user terminals are scheduled for uplink transmission in the same subframe, then uplink transmission efficiency is improved, but channel collision probability increases
Solution Approach 1:
The base station serves as an intermediary that coordinates uplink transmissions from multiple user terminals. By performing centralized CCA and providing unified scheduling decisions, the base station ensures that multiple terminals can transmit in the same subframe without colliding, as they all follow the same channel access control based on the base station's assessment
Solution Approach 2:
The base station performs clear channel assessment in advance before scheduling multiple user terminals for uplink transmission. This preliminary CCA ensures the channel is clear before multiple terminals begin transmission, preventing collisions while maintaining high uplink efficiency
3Adaptability or versatility
If each user terminal generates random back-off counter independently, then channel access randomness is improved, but synchronization and coordination between terminals deteriorate
Solution Approach 1:
The generation of back-off counter values is merged from individual terminal operations to a centralized base station operation. The base station generates and distributes back-off counter values to scheduled terminals, ensuring both randomness (for collision avoidance) and synchronization (for coordinated transmission timing)
Data Source
AI summary
The present invention relates to a method for transmitting uplink data in a spectrum sharing wireless communication system wherein, in order to enhance uplink transmission efficiency in an LTE-U service, clear channel assessment (CCA) is performed on a user terminal so as to consider the hidden node problem, and channel occupation based on an uplink signal of another terminal is considered, wherein applied are: a method for generating and transmitting a random backoff counter value at a base station so that all terminals can equally use a channel connection parameter needed for transmitting an uplink subframe in an unlicensed band; and a downlink controlling method for scheduling an uplink multi-subframe.