E-DCH TTI Indicator for RNC Configuration
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Solution Overview
Problem
In UMTS systems, the radio network controller (RNC) cannot determine the transmission time interval (TTI) used by user equipment (UE) in idle or Cell-FACH states, which hinders appropriate TTI configuration when the UE transitions from Cell-FACH to Cell-DCH state, especially when multiple TTIs (2 ms and 10 ms) are dynamically selected based on location.
Innovation Solution
The base station receives uplink data from the UE, determines the TTI used, and sends this information in an enhanced dedicated channel (E-DCH) data frame to the RNC through a corresponding transmission bearer, allowing the RNC to identify and configure the appropriate TTI for the UE.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the UE dynamically selects between 2ms TTI and 10ms TTI based on location, then the uplink transmission flexibility and coverage are improved, but the RNC cannot acquire the TTI information needed for proper configuration when the UE transitions to Cell-DCH state
Solution Approach 1:
The base station feeds back the TTI information to the RNC by including a TTI indicator in the E-DCH data frame transmitted over the Iub interface. This feedback mechanism ensures the RNC receives accurate TTI information about the UE's current transmission mode, enabling proper configuration during state transitions while maintaining the UE's dynamic TTI selection capability.
Solution Approach 2:
The base station acts as an intermediary between the UE and the RNC. It receives uplink data from the UE, determines the TTI used, and transmits this information to the RNC through the E-DCH data frame. This intermediary role resolves the information asymmetry, allowing the RNC to make informed configuration decisions without directly observing the UE's TTI selection.
2Device complexity
If only one uplink TTI is configured per cell, then the system configuration is simple, but the uplink transmission rate and coverage cannot be optimized for different UE locations
Solution Approach 1:
The system transitions from a static configuration where each cell has only one TTI to a dynamic configuration where multiple TTIs (2ms and 10ms) can be concurrently deployed. The UE dynamically selects the appropriate TTI based on its location and channel conditions, enabling both optimization of transmission rate and coverage while maintaining manageable system complexity through standardized selection criteria.
Data Source
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AI summary
Embodiments of the present invention provide a method for determining a transmission time interval, a base station, and a radio network controller. The method for determining a transmission time interval includes: receiving, by a base station, uplink data sent by a user equipment in idle state or Cell-FACH state on an E-DCH; determining, by the base station, a TTI used by the user equipment for sending the uplink data; and carrying, by the base station, the uplink data in an E-DCH data frame, and sending the E-DCH data frame to a radio network controller, where the E-DCH data frame carries a TTI indicator, so as to notify the radio network controller of the TTI used by the user equipment for sending the uplink data. The embodiments of the present invention may implement that the radio network controller acquires the TTI used by the user equipment in idle state or Cell-FACH state when sending the uplink data, thereby ensuring that the radio network controller selects and configures an appropriate TTI for the user equipment when the user equipment transits from the Cell_FACH state to the Cell_DCH state.