Dynamic TTI Selection for Random Access Latency
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Solution Overview
Problem
In LTE systems, reducing transmission duration to minimize latency affects the operation of the random access (RA) procedure, as user equipment (UE) is unsure which transmission duration to use for the RA process, posing a challenge in handling the RA procedure effectively.
Innovation Solution
A communication device and base station that determine and execute different RA configurations based on specific conditions, using distinct transmission time intervals (TTI) lengths for RA procedures, allowing the UE to select or generate preambles accordingly and receive responses within the respective TTI lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the transmission duration is reduced to minimize latency, then the latency of transmission is improved, but the operation of the random access procedure becomes uncertain and difficult to handle
Solution Approach 1:
The patent implements dynamic TTI length selection for random access procedures. The system can adaptively choose between short TTI length (for low latency) and normal TTI length (for reliable operation) based on network configuration and channel conditions. This dynamic adjustment allows the system to optimize between latency reduction and procedural reliability, resolving the contradiction by making the transmission duration flexible rather than fixed.
Solution Approach 2:
The patent changes the TTI length parameter for random access procedures. By configuring different TTI lengths (short TTI vs. normal TTI) for different random access scenarios, the system can adjust the transmission duration parameter to balance latency requirements with procedural reliability. The base station can indicate which TTI length to use through RRC signaling or system information, enabling the UE to perform RA procedures with appropriate timing parameters.
2Loss of time
If a first RA procedure is performed according to a first RA configuration with shorter TTI length, then the transmission latency is reduced, but the device complexity increases due to multiple RA configurations
Solution Approach 1:
The patent creates a universal random access framework that supports multiple TTI lengths through a unified configuration mechanism. The same random access preamble format and procedure can be used with either short TTI or normal TTI length, depending on configuration. This multi-functionality allows the system to use a single RA procedure design that adapts to different timing requirements, reducing the need for separate specialized procedures for each TTI length and thereby managing complexity.
Solution Approach 2:
The patent performs preliminary configuration of TTI length for random access procedures before the actual RA process. The base station configures the appropriate TTI length through RRC signaling or system information blocks prior to when the UE needs to perform random access. This advance configuration allows the UE to prepare the correct timing parameters in advance, avoiding complex real-time decisions during the RA procedure itself and simplifying the operational complexity.
Data Source
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AI summary
A communication device for handling a random access (RA) procedure comprises a storage unit for storing instructions and a processing circuit coupled to the storage unit. The processing circuit is configured to execute the instructions stored in the storage unit. The instructions comprise performing a first RA procedure to a base station according to a first RA configuration, if the communication device determines that a first condition is satisfied; and performing a second RA procedure to the base station according to a second RA configuration, if the communication device determines that a second condition is satisfied; wherein the first RA configuration corresponds to a first transmission time interval (TTI) length, the second RA configuration corresponds to a second TTI length, and the first TTI length is shorter than the second TTI length.