Downlink Control Channel Structure for Low Latency Wireless Applications
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Solution Overview
Problem
Wireless communication systems face challenges in efficiently supporting low latency applications due to high control overhead and the need for efficient coexistence between low latency and non-low latency transmissions, particularly in systems using shortened transmission time intervals (TTIs).
Innovation Solution
The proposed solution involves a base station indicating time and frequency resources for a low latency physical downlink control channel (PDCCH) to user equipment (UE), where the control region of a first TTI overlaps with a second TTI, allowing for efficient resource allocation and decoding by frequency division multiplexing the data regions, and optimizing the placement of downlink and uplink grants within the control region to minimize processing time and latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If shortened TTI is used for low latency transmissions, then transmission latency is reduced, but control overhead increases
Solution Approach 1:
The patent combines control regions of different TTIs (normal TTI and shortened TTI) in the time domain, allowing a single control message to provide resource allocations for both transmission types. This merging reduces the total control overhead by eliminating redundant control messages while maintaining support for both low latency and non-low latency transmissions.
Solution Approach 2:
The control message structure is designed to be universal, capable of indicating resource allocations for both normal TTI and shortened TTI transmissions within the same message. This multi-functionality allows the control channel to serve multiple purposes without requiring separate control structures, thereby reducing overall control overhead.
2Adaptability or versatility
If control region size is increased to provide resource allocations, then resource allocation capability is improved, but resource availability for data channels decreases
Solution Approach 1:
The patent utilizes the time dimension by allowing control regions of different TTIs to overlap in time. This temporal dimensionality change enables the control message to cover a broader time span without increasing the frequency-domain resources dedicated to control, thus preserving data channel resources while enhancing allocation capability.
3Reliability
If separate control regions are used for normal TTI and shortened TTI, then transmission reliability is improved, but processing time increases
Solution Approach 1:
The patent performs preliminary action by providing resource allocations for both normal TTI and shortened TTI in advance through a single control message. This allows the UE to prepare for both transmission types simultaneously without requiring separate decoding processes, thereby reducing processing time while maintaining reliable resource allocation.
Data Source
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AI summary
Methods, systems, and devices for wireless communication are described. In one example, an indication in a first control message in a control region of a first transmission time interval (TTI) identifies a data region of the first TTI. A data region of the second TTI may be identified based on a grant of resources received in a second control message of a second TTI, where the data region of the first TTI and the control region of the second TTI are frequency division multiplexed with the data region of the second TTI. Other examples include a downlink grant at the beginning of a control region and uplink grants at the end of the control region. In other examples, a downlink grant for a user equipment (UE) may include an indication of resources allocated to the UE in that resource block and a second resource block.