Wireless Device Search Space Adaptation for Low Latency Retransmission
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Solution Overview
Problem
Current wireless communications networks face challenges in reducing latency for re-transmissions, particularly in LTE systems, where the HARQ Round-Trip Time (RTT) is too long to meet critical latency requirements such as 1 ms or 0.5 ms, due to difficulties in decoding HARQ-ACK and scheduling within the limited time frame.
Innovation Solution
A method where a wireless device and network node determine a search space for re-transmissions in subsequent subframes based on information about expected re-transmissions, allowing for a re-transmission assignment in a secondary search space, which can be located in a different OFDM symbol than the regular search space, enabling faster re-transmission processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If re-transmission scheduling follows conventional HARQ RTT timing in LTE, then system compatibility is maintained, but latency cannot be reduced below 10 ms round-trip time
Solution Approach 1:
The patent applies dynamics by making the search space location adaptive rather than fixed. The network node and wireless device dynamically determine the search space in the second subframe based on whether a re-transmission is expected, allowing the system to flexibly adjust scheduling timing between 1-10 ms rather than being constrained to fixed HARQ RTT timing, thereby reducing latency while maintaining compatibility
Solution Approach 2:
The patent changes the parameter of search space location from a fixed conventional position to a dynamically determined position in a second subframe. By obtaining information about expected re-transmissions and determining the search space based on this information, the system can adjust scheduling parameters to achieve latency as low as 1 ms or 0.5 ms while maintaining system compatibility
2Loss of time
If search space for re-transmission assignment is in the same OFDM symbol as regular search space, then resource allocation is simplified, but decoding and scheduling time is insufficient to meet 1 ms or 0.5 ms latency requirements
Solution Approach 1:
The patent segments the search space into different locations within the second subframe based on re-transmission expectations. By obtaining information about expected re-transmissions and determining the search space location accordingly, the system separates re-transmission handling from regular scheduling, providing sufficient time for decoding and scheduling while managing complexity through structured search space determination
3Productivity
If re-transmission assignment is placed in a secondary search space in a different OFDM symbol, then latency is reduced to meet critical requirements, but the complexity of determining and monitoring search spaces increases
Solution Approach 1:
The patent applies preliminary action by obtaining information about expected re-transmissions before determining the search space location in the second subframe. This advance knowledge allows the wireless device and network node to prepare the appropriate search space configuration, enabling faster re-transmission processing while managing complexity through structured determination based on pre-obtained information
Data Source
AI summary
Embodiments herein relate to a method performed by a wireless device for handling transmissions in a wireless communications network, wherein a first transmission is communicated to or from the wireless device in a first subframe (n) from or to a network node in the wireless communications network. The wireless device obtains information indicating that a re-transmission of the first transmission is expected in a second subframe (n+1) consecutive to the first subframe (n). Also, the wireless device determines a search space in the second subframe (n+1) based on the obtained information. Further, wireless device receives a transmission assignment for a retransmission of the first transmission in the second subframe (n+1) based on the determined search space. Embodiments herein also relate to a wireless device, and a network node and a method therein for handling transmissions in a wireless communications network.