PDCCH Search Space Mapping for Frequency Diversity
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Solution Overview
Problem
In LTE systems, the physical downlink control channel (PDCCH) lacks the ability to achieve beamforming gain similar to the physical downlink shared channel (PDSCH), limiting its performance and spectrum efficiency, especially for cell-edge user equipment (UE), due to its limited support for transmission diversity and lack of cell split gain.
Innovation Solution
A mapping method for the PDCCH search space is introduced, where candidates are mapped onto discrete time-frequency resources using a predefined interval, allowing for frequency selective scheduling or frequency diversity gains, thereby improving PDCCH performance by avoiding subcarriers within the same subband and optimizing resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PDCCH uses conventional CRS-based transmission with limited antennas, then spatial diversity is supported, but beamforming gain and spectrum efficiency are limited
Solution Approach 1:
The patent changes the transmission parameters of PDCCH by introducing DM-RS-based transmission with precoding and beamforming capabilities, allowing up to 8 transmission antennas compared to the conventional 4 antennas with CRS-based transmission. This parameter change enables both beamforming gain for improved spectrum efficiency and maintains reliability through diverse transmission schemes.
2Productivity
If PDCCH search space uses continuous resource allocation, then resource utilization is high, but frequency selective scheduling and frequency diversity gains are reduced
Solution Approach 1:
The patent segments the PDCCH search space into multiple discrete candidates distributed across different frequency resources. Instead of continuous allocation, each candidate is mapped to specific resource elements with predefined intervals, enabling both frequency selective scheduling (by selecting specific frequency locations) and frequency diversity gains (by distributing candidates across multiple frequencies).
3Productivity
If PDCCH is expanded to PDSCH region with DM-RS, then beamforming gain is achieved, but blind detection complexity increases
Solution Approach 1:
The patent applies local quality by providing UE-specific search space configurations that are tailored to individual user equipment requirements. The base station can configure specific search space parameters (such as frequency location, resource allocation) for each UE based on channel conditions, reducing the number of blind detection attempts needed while maintaining beamforming gain through DM-RS-based transmission.
Data Source
AI summary
Embodiments of the present invention provide a mapping method and apparatus for a search space of a physical downlink control channel. The method includes: determining a search space allocated to the PDCCH according to a resource allocation scheme; and mapping each of candidates of the PDCCH to a logic time frequency resource of the search space according to a predefined interval. With the method and apparatus of the embodiments of the present invention, a frequency selective scheduling gain is obtained by mapping different candidates onto discrete time frequency resources, or a frequency diversity gain is obtained by mapping one candidate onto discrete time frequency resources, thereby improving the performance of the PDCCH.