Radio Network Controller Discard Indication for HSDPA Redundancy
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Solution Overview
Problem
In multi-point HSDPA scenarios, redundant data transmission occurs due to out-of-order data reception at the UE, leading to unnecessary RLC retransmissions and inefficient use of air interface resources, as existing solutions fail to effectively eliminate duplicate data copies.
Innovation Solution
A method involving a discard indication signal with a data frame sequence number is used to instruct radio base stations to discard redundant MAC-d PDUs, allowing for efficient reduction of duplicate data transmission over the Uu interface by identifying and discarding redundant data before transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If data is transmitted via multiple NodeBs in MP HSDPA operation, then data delivery capability is improved, but redundant data transmission occurs leading to inefficient air interface resource usage
Solution Approach 1:
The RNC performs preliminary actions by tracking which MAC-d PDUs have been transmitted to each NodeB and proactively sending discard indication signals before the UE requests retransmissions. This prevents NodeBs from buffering and transmitting redundant data, thereby improving air interface resource efficiency while maintaining multi-point data delivery capability
Solution Approach 2:
The system implements feedback mechanisms where the RNC monitors transmission status across multiple NodeBs and sends discard indication signals based on this feedback. This feedback loop enables the RNC to identify and eliminate redundant data copies in NodeB buffers, resolving the contradiction between maintaining data delivery redundancy and avoiding wasteful retransmissions
2Reliability
If RLC status reports trigger retransmissions for missing data, then data completeness is improved, but unnecessary retransmissions occur when data already exists in other NodeBs
Solution Approach 1:
The RNC takes preliminary action by proactively identifying which MAC-d PDUs are already transmitted to which NodeBs and sending discard indication signals before the UE generates RLC status reports. This prevents unnecessary retransmission cycles while ensuring data completeness is maintained through coordinated multi-point transmission
Solution Approach 2:
The RNC acts as an intermediary between the UE and multiple NodeBs, coordinating retransmission requests and managing data redundancy. It receives RLC status reports from the UE, determines which data is actually missing versus already available at other NodeBs, and sends discard indications to prevent wasteful retransmissions, thereby improving retransmission efficiency while maintaining data completeness
3Reliability
If NodeBs buffer data pending retransmission requests, then data delivery reliability is improved, but redundant data copies are maintained consuming buffer resources
Solution Approach 1:
The RNC implements feedback by tracking the transmission status of MAC-d PDUs across all NodeBs and sending discard indication signals when data redundancy is detected. This feedback mechanism enables NodeBs to clear redundant data from their buffers, optimizing buffer resource utilization while maintaining data delivery reliability through coordinated multi-point transmission
Solution Approach 2:
The system applies discarding and recovering by having the RNC send discard indication signals to NodeBs for redundant MAC-d PDUs. This allows NodeBs to discard unnecessary data copies from their buffers, recovering buffer resources for new data while maintaining reliability through the coordinated transmission framework that ensures at least one valid copy reaches the UE
Data Source
AI summary
Explicit discard indications are used that allows a radio network controller, when operating in a multi-point High Speed Downlink Packet Access, HSDPA, scenario, to send data to a user equipment via plural radio base stations while reducing the risk for unnecessary duplicate data to be sent over the Uu interface between the radio base stations and the user equipment.