EPDCCH Control Channel Search Space Mapping for LTE Efficiency
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Solution Overview
Problem
The PDCCH's association with a cell-specific reference signal limits the common search space to a single subframe, leading to inefficient control information notification and reduced transmission efficiency in LTE communication systems.
Innovation Solution
The proposed solution involves enhancing transmission efficiency by allowing the base station to map control channels with a CRC scrambled using a D-RNTI, enabling communication across a common search space, UE-specific search space, or a search space specific to a UE group, thereby improving the notification of control information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PDCCH is transmitted in association with the cell-specific reference signal, then the control channel can be reliably demodulated, but the common search space is limited to a single subframe, reducing transmission efficiency
Solution Approach 1:
The patent segments the control channel transmission by introducing a new control channel (EPDCCH) that is separately mapped to resource blocks, independent from the PDCCH structure. This allows the common search space to be distributed across multiple subframes while maintaining reliable demodulation through dedicated reference signals (DMRS) specific to the EPDCCH.
Solution Approach 2:
The patent introduces a new reference signal (DMRS) as an intermediary specifically for the EPDCCH demodulation. This DMRS is transmitted in association with the EPDCCH and provides the necessary channel estimation reference, enabling reliable demodulation without being constrained by the cell-specific reference signal limitations.
2Device complexity
If the common search space is limited to a single subframe, then the control channel structure remains simple, but the notification of control information becomes inefficient
Solution Approach 1:
The patent makes the control channel structure dynamic by allowing the EPDCCH to be flexibly mapped to different resource blocks and subframes based on traffic requirements. The common search space can dynamically span multiple subframes, enabling efficient control information notification while maintaining manageable complexity through standardized mapping procedures.
Solution Approach 2:
The patent extends the control channel search space from a single-subframe dimension to a multi-subframe dimension. The EPDCCH can be distributed across multiple subframes in the time domain, effectively adding a temporal dimension to the search space and improving notification efficiency without significantly increasing overall system complexity.
3Ease of manufacture
If the PDCCH uses cell-specific reference signal association, then implementation is straightforward, but transmission efficiency deteriorates significantly
Solution Approach 1:
The patent creates a universal control channel structure where the EPDCCH can serve multiple functions: it can be used for both common control information (in common search space) and UE-specific control information (in UE-specific search space). This multi-functional approach improves transmission efficiency while maintaining implementation simplicity through a unified resource allocation mechanism.
Solution Approach 2:
The patent changes key parameters of the control channel, including the reference signal type (from cell-specific CRS to dedicated DMRS), the resource mapping flexibility, and the search space distribution across subframes. These parameter changes significantly improve transmission efficiency while the standardized procedures maintain ease of implementation.
Data Source
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AI summary
A search space of a control channel which is monitored by a terminal is determined based on a first uplink-downlink configuration specific to a base station, a second uplink-downlink configuration specific to a terminal, and one or more EPDCCH subframe configuration, for each subframe. A scrambling sequence parameter which corresponds to the search space of the control channel and is used in scrambling of the control channel is switched. The terminal switches the scrambling sequence parameter, corresponding to the search space and a subframe configuration, and the terminal receives a DMRS and descrambles an EPDCCH by using the switched scrambling sequence parameter.