Uplink Feedback Assignment for Carrier Aggregation
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Solution Overview
Problem
In next-generation mobile communication systems, carrier aggregation (CA) and coordinated multi-point (CoMP) transmission/reception between macro and small base stations face challenges in transmitting feedback signals effectively, especially when there is no uplink data transmission command, as conventional mechanisms struggle to allow user terminals to transmit feedback to multiple radio base stations separately.
Innovation Solution
A user terminal is equipped with a receiving section for downlink signals from multiple radio base stations, a generating section for feedback signals, and an assignment control section that assigns these feedback signals to uplink control or shared channels based on the presence of an uplink grant, enabling feedback transmission to each radio base station, even in the absence of an uplink data transmission command.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If feedback signals for multiple radio base stations are transmitted through a single uplink control channel on the PCell, then the device complexity is reduced, but the ability to provide separate feedback to each radio base station is lost
Solution Approach 1:
The feedback mechanism is segmented into two paths: feedback for the PCell is transmitted through the PUCCH on the PCell, while feedback for the SeNB is transmitted through the PUSCH on the SCell. This segmentation allows separate feedback transmission to multiple radio base stations, resolving the information loss problem while maintaining reasonable device complexity.
2Ease of operation
If feedback signals are assigned to PUCCH on PCell when no UL grant is present, then the feedback transmission is simplified, but separate feedback transmission to multiple base stations becomes difficult
Solution Approach 1:
The feedback transmission path is made dynamic based on the presence of UL grant and the target base station. For PCell feedback, the system uses PUCCH when no UL grant is present (simple path). For SeNB feedback, the system uses PUSCH on SCell regardless of UL grant presence (versatile path). This dynamic adaptation resolves both the simplicity and versatility requirements.
3Productivity
If carrier aggregation and CoMP are implemented between macro and small base stations, then the network coverage and capacity are improved, but the feedback transmission mechanism becomes insufficient
Solution Approach 1:
The SCell acts as an intermediary carrier for feedback transmission to the SeNB. By utilizing the PUSCH on the SCell as an intermediate transmission path, the system enables reliable feedback transmission to multiple base stations in CA/CoMP scenarios, resolving the reliability issue while maintaining the productivity benefits of network expansion.
Data Source
AI summary
The present invention is designed to enable adequate feedback on the uplink even when CA and CoMP are employed between a plurality of radio base stations (inter-eNB CoMP/CA). A receiving section that receives downlink signals from a first radio base station that forms a first cell and a second radio base station that forms a second cell, a generating section that generates a feedback signal in response to the downlink signal from each radio base station, and a control section that assigns the feedback signal in response to the downlink signal from the first radio base station to an uplink control channel and/or an uplink shared channel on the first cell depending on whether or not there is a UL grant, and assigns the feedback signal in response to the downlink signal from the second radio base station to the uplink shared channel on the first cell or the second cell regardless of whether or not there is the UL grant, are provided in a user terminal.