Single-Subband UE CQI Reporting for MTC Bandwidth Reduction
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Solution Overview
Problem
Reducing UE bandwidth in LTE systems for Machine-Type Communication (MTC) limits the ability of user equipment (UE) to report pertinent channel state information (CSI) effectively, as conventional wideband CQI reporting modes are not usable by reduced bandwidth UEs.
Innovation Solution
Configuring user equipment to operate within a single subband during each subframe, with the network indicating the subband location, allowing for wideband CQI reporting across the full system bandwidth by calculating and reporting CQI values assuming transmission on the operating subband, and optionally varying the subband location periodically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If UE bandwidth is reduced for MTC devices, then UE cost and power consumption are reduced, but the ability to report channel state information effectively deteriorates
Solution Approach 1:
The system bandwidth is divided into multiple subbands, and the UE is configured to operate in only one subband at a time. This segmentation allows the UE to have reduced bandwidth operation while the network can still obtain wideband channel state information by configuring the UE to report CQI for the entire system bandwidth based on measurements from its operating subband.
Solution Approach 2:
The patent introduces an intermediary mechanism where the UE reports wideband CQI values that are calculated assuming transmission on its configured subband. This intermediary CQI reporting mechanism bridges the gap between the UE's limited subband operation and the network's need for wideband channel state information.
2Device complexity
If UE bandwidth is reduced to 1.4 MHz, then device complexity and cost are reduced, but conventional wideband CQI reporting modes become unusable
Solution Approach 1:
The patent changes the parameter of CQI reporting by redefining how wideband CQI is calculated for reduced bandwidth UEs. Instead of using conventional wideband CQI calculation methods that assume full system bandwidth operation, the UE calculates wideband CQI based on channel quality measurements from its configured subband, assuming transmission on that subband. This parameter change makes wideband CQI reporting compatible with reduced bandwidth operation.
3Use of energy by moving object
If UE operates in single subband only, then power consumption and device complexity are reduced, but coverage capability deteriorates
Solution Approach 1:
The system dynamically configures which subband the UE should operate in, allowing the network to adapt to changing channel conditions. The UE's operating subband can be changed through reconfiguration, enabling the system to maintain coverage capability by steering the UE to subbands with better channel conditions while the UE itself maintains low power consumption through single subband operation.
Data Source
AI summary
A radio network node is configured to operate within a system bandwidth comprising multiple subbands and to serve a user equipment limited to operating within only one subband during any given subframe. The radio network node is configured to generate configuration information and to send that configuration information to the user equipment. In some embodiments, the configuration information indicates a location within the system bandwidth of a single subband within which the user equipment is to be operated during a subframe. Alternatively or additionally, the configuration information indicates a mode according to which the user equipment is to feedback channel state information to the radio network node. According to the indicated mode, in a subframe where CQI is reported, the user equipment shall report one wideband CQI value which is calculated assuming transmission on the subband within which the user equipment is configured to operate in that subframe.