EPDCCH Search Space Subband Hopping for LC-MTC
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Solution Overview
Problem
Low Complexity Machine Type Communication (MTC) User Equipment (UE) in LTE systems faces challenges with limited RF bandwidth, restricting its ability to efficiently receive control messages across varying subbands and subframes, as existing systems rely on static PRBs and lack frequency diversity benefits.
Innovation Solution
Implementing a User Equipment Specific Search Space (USS) that distributes PRBs across different subbands in multiple subframes, allowing for frequency diversity and enabling LC-MTC UE to operate with reduced bandwidth while maintaining compatibility with legacy systems, by dynamically shifting subbands and utilizing frequency hopping within subbands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If LC-MTC UE operates with limited RF bandwidth (1.4 MHz), then device complexity is reduced, but the ability to receive control messages across varying subbands is restricted
Solution Approach 1:
The patent implements dynamic frequency hopping for EPDCCH search spaces, where the frequency location of search space candidates changes across different subframes. This allows LC-MTC UE with limited RF bandwidth to access control messages distributed across different subbands over time, effectively achieving adaptability without requiring wide simultaneous bandwidth coverage
Solution Approach 2:
The patent transitions from spatial diversity (receiving control messages across multiple frequency subbands simultaneously) to temporal diversity (receiving control messages across multiple subframes at different frequency locations). By hopping frequency locations across subframes, the system compensates for limited RF bandwidth through time-domain distribution
2Device complexity
If static PRBs are used for control channel transmission, then system simplicity is maintained, but frequency diversity benefits are lost
Solution Approach 1:
The patent introduces dynamic frequency hopping patterns for EPDCCH search space candidates across subframes, transforming the static PRB allocation into a time-varying structure. This provides frequency diversity by distributing control channel transmissions across different frequency locations while maintaining relatively simple implementation through predefined hopping patterns
Solution Approach 2:
The patent changes the frequency parameter of search space candidates dynamically across subframes according to hopping patterns. This allows the system to achieve frequency diversity benefits by varying frequency location over time while keeping the overall system structure relatively simple through standardized hopping sequence definitions
3Reliability
If LC-MTC UE monitors multiple subbands across different subframes, then frequency diversity is enhanced, but power consumption increases
Solution Approach 1:
The patent divides the control channel monitoring task into segmented search space candidates distributed across different subframes and frequency locations. The UE only needs to monitor specific candidate locations in each subframe according to hopping patterns, rather than continuously monitoring all possible locations, thereby reducing overall power consumption while maintaining frequency diversity
Solution Approach 2:
The patent implements periodic frequency hopping patterns for search space candidates, where the frequency location follows a predetermined periodic sequence across subframes. This allows the UE to efficiently manage power consumption by knowing in advance when and where to monitor, avoiding continuous full-bandwidth monitoring while still achieving frequency diversity through periodic access to different subbands
Data Source
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AI summary
A method is provided for receiving, at a receiving device, a control information message from a transmitting device. The method includes monitoring a first plurality of reception resources contained in a first frequency range in a first subframe and a second plurality of reception resources contained in a second frequency range in a second subframe. The method also includes receiving a control information message in at least one of the monitored reception resources. The first frequency range is at least partly non-overlapping with the second frequency range.