UE Control Channel Search Space Allocation via Channel Quality
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Solution Overview
Problem
In LTE-A systems, there is a lack of clear criteria for eNBs to choose between using PDCCH or E-PDCCH for scheduling user equipment, and the placement of E-PDCCH in frequency bands is not determined, leading to inefficiencies in resource allocation and increased power consumption for user equipment during blind decoding.
Innovation Solution
The eNB determines the search space for downlink control channels based on user equipment-specific channel quality reports, allowing for dynamic allocation between PDCCH and E-PDCCH, and optimizing the frequency bands for E-PDCCH placement, thereby reducing the search space and conserving battery power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE searches for PDCCH across the whole control channel region, then the UE can reliably find its control channel, but the search space is too large causing high power consumption
Solution Approach 1:
The patent applies local quality by transitioning from a uniform search across the entire control channel region to a localized search within a specific subset of resource elements. The eNB determines a dedicated search space for E-PDCCH based on UE-specific channel quality reports, allowing the UE to focus its decoding efforts only in the relevant frequency region where its control channel is likely located, thereby reducing power consumption while maintaining detection reliability.
2Productivity
If the eNB uses E-PDCCH with localized resources, then spectral efficiency improves, but the criteria for choosing between PDCCH and E-PDCCH is unclear
Solution Approach 1:
The patent employs feedback by utilizing UE-specific channel quality reports (CQI) as input for the eNB's search space determination. The eNB receives channel quality information from the UE and uses this feedback to dynamically determine the appropriate search space for E-PDCCH, thereby establishing clear criteria for choosing between PDCCH and E-PDCCH based on actual channel conditions while maintaining spectral efficiency.
3Use of energy by moving object
If the search space is reduced based on channel quality, then power consumption decreases, but the placement of E-PDCCH in frequency bands becomes uncertain
Solution Approach 1:
The patent applies dynamics by making the search space determination adaptive and flexible rather than fixed. The eNB dynamically determines the search space based on real-time channel quality reports from individual UEs, allowing the E-PDCCH to be placed in optimal frequency bands for each user while reducing their search space accordingly. This dynamic approach maintains frequency placement flexibility tailored to each UE's channel conditions.
Data Source
AI summary
A user equipment UE reports its UE-specific channel quality to the network. The network uses this to narrow a search space in which the UE looks for its downlink control signaling. In one embodiment the search space is defined by downlink signaling the network sends. The width of the search space may also select between types of downlink control signaling (for example, between PDCCH and E-PDCCH). In the specific examples described the poorest channel qualities result in the whole-bandwidth PDCCH being used while better channel qualities result in progressively narrower search spaces to look for an E-PDCCH.