EPDCCH Resource Element Determination via ZP CSI-RS Reference
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Solution Overview
Problem
In the context of LTE-A, UEs face challenges in determining available transmission resources for EPDCCHs due to the absence of legacy PDCCH and the introduction of ZP/NZP CSI-RS, leading to resource wastage and increased overhead, as they cannot accurately map REs for EPDCCH transmission without knowing the configuration of ZP/NZP CSI-RS in the current sub-frame.
Innovation Solution
A method where a UE determines and indicates transmission resources by identifying REs occupied by ZP/NZP CSI-RS in a reference sub-frame as non-transmittable, and obtains configuration information for other sub-frames to determine available REs for EPDCCH transmission, thereby increasing the number of usable REs and reducing system overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE reserves all REs that may be configured for ZP/NZP CSI-RS to avoid mapping EPDCCH onto these REs, then the problem of unknown ZP/NZP CSI-RS configuration is addressed, but there is considerable overhead because some reserved REs are not actually configured for ZP/NZP CSI-RS
Solution Approach 1:
The network pre-configures ZP/NZP CSI-RS resource patterns and informs UEs about these configurations through system information or RRC signaling. This preliminary action allows UEs to know in advance which REs will be occupied by ZP/NZP CSI-RS in future sub-frames, eliminating the need to reserve all potentially occupied REs and reducing overhead while maintaining reliable EPDCCH transmission.
Solution Approach 2:
The network provides feedback to UEs about ZP/NZP CSI-RS configurations through system information blocks (SIB) or dedicated RRC signaling. This feedback mechanism ensures that UEs have accurate knowledge of which REs are occupied by ZP/NZP CSI-RS in current and future sub-frames, allowing precise rate matching without excessive resource reservation.
2Loss of substance
If the UE does not reserve REs for potential ZP/NZP CSI-RS configuration, then RE overhead is reduced, but the UE cannot determine which REs are available for EPDCCH transmission when ZP/NZP CSI-RS configuration is unknown
Solution Approach 1:
The network performs preliminary configuration of ZP/NZP CSI-RS resources and communicates these configurations to UEs before EPDCCH transmission occurs. This allows UEs to have complete information about which REs are occupied by ZP/NZP CSI-RS in advance, enabling precise determination of available REs for EPDCCH without excessive reservation.
Solution Approach 2:
The network acts as an intermediary that provides configuration information about ZP/NZP CSI-RS resources to UEs through system information or RRC signaling. This intermediary mechanism bridges the information gap, allowing UEs to accurately determine EPDCCH resource availability without needing to reserve excessive REs.
3Measurement precision
If separate configuration information is notified to each UE, then each UE has accurate ZP/NZP CSI-RS configuration information, but system overhead increases
Solution Approach 1:
The patent merges ZP/NZP CSI-RS configuration information into common system information blocks (SIBs) that are broadcast to all UEs in the cell. This combining approach allows all UEs to obtain the same configuration information through a single broadcast message, eliminating the need for separate dedicated signaling to each UE and significantly reducing system overhead while maintaining configuration accuracy.
Solution Approach 2:
The configuration information is designed to be universal and applicable to all UEs in the cell rather than being UE-specific. This multi-functional configuration serves all UEs simultaneously, allowing the same ZP/NZP CSI-RS resource patterns to be used across multiple UEs and reducing the total signaling overhead required to inform all UEs about resource allocations.
Data Source
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Figure 2(a)~2(b)
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AI summary
Disclosed are a method for determining and indicating a transmission resource, and a terminal and a base station. The method comprises: a base station and a UE agreeing that at least one subframe of a set number of wireless frames is used as a reference subframe, and considering that all REs in the reference subframe which are probably occupied by a ZP/NZP CSI-RS are REs unable to be used for EPDCCH transmission; and the base station sending to a UE configuration information about REs in other subframes which are occupied by the ZP/NZP CSI-RS in the reference subframe, so that the UE can determine REs in other subframes, which are probably occupied by the ZP/NZP CSI-RS but are in fact not occupied by the ZP/NZP CSI-RS as REs used for the EPDCCH transmission, thereby increasing the number of REs used for EPDCCH transmission, and reducing the system overheads.