OFDM Search Space Monitoring for Low-Latency Control Decoding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing mechanisms for monitoring search spaces in communications networks result in high latency, as decoding of control regions cannot start until the end of the entire subframe is received, especially in evolved communications systems with beamformed control messaging and unknown system bandwidths.
Innovation Solution
Implementing a method and wireless device that monitor both device-specific and common search spaces within the same OFDM symbol, allowing for immediate decoding of control messages, using device-specific and non-device-specific reference signals, and enabling efficient monitoring of control regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wireless device monitors the entire subframe including ePDCCH control region before decoding data, then complete control information is obtained, but latency increases significantly
Solution Approach 1:
The control region is segmented into two types: common control region (L1/L2 control region) containing common search space, and ePDCCH control region containing device-specific search space. The patent allows decoding to proceed after receiving only the common control region and first data symbols, while the ePDCCH control region is monitored separately. This segmentation enables partial decoding without waiting for the entire subframe, reducing latency while maintaining reliability through selective monitoring.
Solution Approach 2:
The common control region and first data symbols are received and processed in advance before the entire subframe is received. The wireless device performs preliminary decoding operations on available data using reference signals from the common control region, rather than waiting for complete subframe reception. This preliminary action reduces the waiting time and enables earlier data processing.
2Productivity
If device-specific beamforming is implemented for device-specific PDCCHs, then communication efficiency improves, but device-specific reference signals cannot be used for channel estimation
Solution Approach 1:
Common reference signals (CRS) serve as an intermediary for channel estimation in the common control region, while device-specific reference signals (DMRS) are introduced specifically for the ePDCCH control region. The CRS provides a non-device-specific channel estimate that works for common control channels, while DMRS provides device-specific channel estimates for beamformed device-specific PDCCHs. This intermediary approach allows device-specific beamforming to improve efficiency while maintaining reliable channel estimation through the appropriate reference signal type for each control region.
Data Source
AI summary
There are provided mechanisms for monitoring search spaces. A first method performed by a wireless device comprises receiving an Orthogonal Frequency-Division Multiplexing (OFDM) symbol in a downlink slot. At least part of the OFDM symbol is included in a device-specific search space and in a common search space. The first method comprises monitoring the device-specific search space for at least one device-specific reference signal (RS) and monitoring the common search space for at least one non-device-specific RS. In a second method, a radio access network node transmits an OFDM symbol included in a device-specific search space and in a common search space. The device-specific search space contains a device-specific RS, or the non-device specific search space contains a non-device-specific RS, or both of these apply.