Flexible TTI Length for Wireless System Information Acquisition
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Solution Overview
Problem
Current LTE specifications are limited to a single transmission time interval (TTI) of 1 millisecond for system information acquisition, which can lead to performance degradation when shorter TTIs are used, as the requirements for SI acquisition delay and ACK/NACK transmission are not adequately defined for shorter TTI durations.
Innovation Solution
The method involves determining a minimum number of uplink feedback signals based on the TTI duration used in wireless communication, allowing for flexible TTI lengths in both uplink and downlink, and adjusting the number of measurement gaps or acquisition time to maintain or enhance SI acquisition performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single TTI of 1 millisecond is used for system information acquisition, then the SI acquisition process is simple and well-defined, but the packet data latency and system responsiveness are degraded
Solution Approach 1:
The patent applies dynamics by making the TTI duration flexible rather than fixed. The system can dynamically select between different TTI lengths (e.g., 1ms, 0.5ms, 0.25ms) based on network conditions and service requirements. This allows the system to optimize for speed when needed while maintaining simplicity when conditions permit, resolving the contradiction between responsiveness and process complexity.
Solution Approach 2:
The patent changes the parameter of TTI duration from a fixed value (1ms) to a variable parameter that can be adjusted. By allowing TTI length to be modified based on network conditions, the system can improve responsiveness by using shorter TTIs when low latency is required, while avoiding complexity by using longer TTIs when conditions allow, thus resolving the contradiction.
2Loss of time
If shorter TTI durations are used to improve responsiveness, then packet data latency is reduced, but the requirements for SI acquisition delay and ACK/NACK transmission are not adequately defined leading to performance degradation
Solution Approach 1:
The patent changes the TTI duration parameter to be variable rather than fixed. By allowing the system to select appropriate TTI lengths (shorter for low latency, longer for reliability), it can reduce packet data latency when needed while maintaining adequate SI acquisition performance by selecting longer TTIs when appropriate, thus resolving the contradiction between time loss and reliability.
Solution Approach 2:
The patent introduces dynamic TTI selection that adapts to network conditions. The system can dynamically adjust TTI duration based on whether SI acquisition is正在进行 or whether reliability requirements are high, allowing it to optimize for low latency when conditions permit while maintaining reliability when needed, resolving the contradiction between reducing time loss and maintaining reliability.
3Productivity
If flexible TTI lengths are used in uplink and downlink, then scheduling performance is enhanced, but the complexity of managing different TTI durations increases
Solution Approach 1:
The patent enables the TTI duration parameter to be changed independently for uplink and downlink directions. This allows the system to optimize scheduling performance by using different TTI lengths suited to each direction's requirements (e.g., shorter TTI for downlink data transmission, longer TTI for uplink control signaling) while managing complexity through standardized procedures for TTI selection and configuration.
Data Source
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AI summary
According to some embodiments, a method for use in a wireless device of acquiring system information (SI) of a second cell, the first cell operable to use two or more transmission time intervals (TTIs), comprises: obtaining a request to acquire SI of the second cell; obtaining the SI of the second cell during a time period (T0); and determining a TTI length used in the first cell. In response to receiving downlink data from the first cell during time T0: when the determined TTI length equals a first TTI value (TTI1), the method further comprises transmitting a first minimum number (N1) of uplink feedback signals in the uplink of the first cell during T0; and when the determined TTI length equals a second TTI value (TTI2), the method further comprises transmitting a second minimum number (N2) of uplink feedback signals in the uplink of the first cell during T0.