Random Access Feedback Mechanism for Downlink Efficiency
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Solution Overview
Problem
In 3GPP WCDMA networks, UEs without Enhanced Uplink for CELL-FACH feature cannot provide ACK/NACK feedback for downlink HS-DSCH transmission, leading to inefficient utilization of downlink resources and reduced throughput due to blind retransmissions.
Innovation Solution
A method and apparatus for random access that enables UEs to quickly complete uplink access and provide feedback by receiving access control information from a base station, acquiring an access time slot and preamble signature, and initiating an uplink random access procedure with preamble power ramping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If blind retransmission is used for downlink HS-DSCH transmission to UEs without Enhanced Uplink feature, then compatibility with legacy UEs is maintained, but downlink resource utilization efficiency deteriorates and throughput is reduced
Solution Approach 1:
The patent introduces a feedback mechanism where UEs in CELL-FACH state send ACK/NACK feedback on the HS-DPCCH channel to indicate successful reception of downlink data. This feedback enables the Node B to perform adaptive retransmission based on actual UE reception status, transforming the blind retransmission approach into a feedback-driven approach that improves downlink resource utilization while maintaining compatibility with legacy UEs through gradual feature introduction.
Solution Approach 2:
The patent performs preliminary configuration by pre-configuring UEs with uplink E-DCH resources and associated parameters before downlink data transmission. This preliminary setup includes allocating uplink grant resources, configuring transport formats, and establishing the feedback channel, enabling UEs to immediately participate in feedback-based retransmission without requiring full random access procedures, thus improving efficiency while maintaining legacy compatibility.
2Productivity
If UE completes uplink access to obtain E-DCH resources, then feedback capability is enabled and downlink transmission efficiency is improved, but access time and procedure complexity increase
Solution Approach 1:
The patent performs preliminary configuration by pre-allocating uplink E-DCH resources and configuring feedback channel parameters to the UE before actual downlink data transmission begins. This preliminary setup includes assigning uplink grant resources, configuring transport format combinations, and establishing the HS-DPCCH feedback channel, so that when downlink data needs to be transmitted, the UE is already equipped with the necessary uplink resources to provide immediate feedback, avoiding the need for time-consuming random access procedures.
Solution Approach 2:
The patent creates a universal feedback mechanism that works for both legacy UEs (through blind retransmission as default) and enhanced UEs (through ACK/NACK feedback). The system maintains backward compatibility by allowing UEs without Enhanced Uplink capability to continue using blind retransmission, while simultaneously enabling UEs with the capability to use the more efficient feedback-based approach, thus achieving multi-functionality that serves different UE types appropriately.
3Device complexity
If blind retransmission is used in downlink HS-DSCH transmission, then implementation complexity is reduced, but throughput and resource utilization efficiency deteriorate
Solution Approach 1:
The patent introduces a feedback mechanism where UEs send ACK/NACK signals on the HS-DPCCH channel to indicate successful reception or need for retransmission of downlink data. The Node B monitors this feedback and performs adaptive retransmission only when necessary, transforming the simple but inefficient blind retransmission approach into a more complex but throughput-optimized feedback-driven approach. The feedback processing complexity is managed through standardized ACK/NACK signal formats and efficient channel coding.
Solution Approach 2:
The patent implements dynamic adaptation where the Node B adjusts its downlink transmission strategy based on real-time feedback from UEs. The system dynamically determines whether to perform retransmission based on received ACK/NACK signals, dynamically adjusts transport format combinations based on channel conditions and UE capabilities, and dynamically manages uplink E-DCH resource allocation. This dynamic behavior enables the system to optimize throughput under varying conditions while managing implementation complexity through standardized procedures.
Data Source
AI summary
Method and apparatus for random access are provided. A base station sends access control information to a UE. The access control information includes an identifier of the UE and an access control command. The UE obtains an access time slot and a preamble signature according to the access control information received from the bases station. Then the UE initiate, according to the access time slot and the preamble signature, a random access procedure with a preamble power ramping. With the embodiments of the present invention, time delay in random access procedures may be decreased so as to enable the UE to complete the uplink access as quickly as possible and provide a feedback for a downlink transmission. Therefore efficiencies of the downlink transmission are enhanced.