SRNC Congestion Detection Control in HSDPA Systems
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Solution Overview
Problem
In wireless communication systems, particularly with HSDPA, timely detection of transport network layer congestion at the lub/lur interface is challenging due to inconsistencies in Frame Sequence Number (FSN) and Delay Reference Time (DRT) values during SRNC relocation or when the SRNC cannot access the RNC Frame Number Counter, leading to incorrect congestion detection and unnecessary reduction in downlink Transmission Credits, affecting Quality of Service (QoS).
Innovation Solution
A method to control the processing of FSN/DRT information elements at the Node B by sending a disabling command from the SRNC to the Node B, allowing for temporary suspension or reset of these measurements, enabling more accurate congestion management and flexibility in handling different priority flows without affecting high-priority data flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If congestion detection is based on FSN and DRT measurements at Node B, then congestion situations can be detected in advance and complete FP frame loss can be detected, but measurement inconsistencies during SRNC relocation or when SRNC cannot access RNC Frame Number Counter lead to incorrect congestion detection and unnecessary reduction in downlink Transmission Credits
Solution Approach 1:
A new information element called 'Congestion Detection Control' is introduced as an intermediary mechanism. This IE acts as a mediator between SRNC and Node B, allowing SRNC to control when Node B should perform congestion detection measurements. By introducing this control mechanism, the patent resolves the contradiction by enabling accurate congestion detection only when FSN/DRT values are consistent, thereby preventing incorrect detection during SRNC relocation while maintaining the ability to detect real congestion situations.
Solution Approach 2:
The patent implements a feedback mechanism where SRNC monitors the consistency of FSN and DRT values received from Node B. When inconsistencies are detected (indicating SRNC relocation or unavailable RNC Frame Number Counter), SRNC provides feedback by setting the Congestion Detection Control IE to disable measurements. This feedback loop ensures that congestion detection is performed only under reliable conditions, preventing false positives that would unnecessarily reduce downlink throughput.
2Loss of time
If FSN and DRT measurements are continuously performed at Node B, then timely congestion detection is achieved, but unnecessary measurements during SRNC relocation waste system resources and cause incorrect congestion management decisions
Solution Approach 1:
The patent applies preliminary action by having SRNC proactively set the Congestion Detection Control IE to 'measurements not allowed' before potential inconsistencies occur (e.g., during SRNC relocation). This preemptive disabling of measurements prevents wasted system resources on unnecessary measurements while ensuring that congestion detection is ready to operate immediately when conditions become favorable again, thus minimizing both detection delay and resource waste.
3Reliability
If congestion detection is disabled during SRNC relocation to prevent incorrect detection, then measurement consistency is maintained, but the ability to detect real congestion situations is reduced
Solution Approach 1:
The patent implements a dynamic approach where the Congestion Detection Control IE can switch between different states ('measurements allowed' and 'measurements not allowed') based on current system conditions. This dynamic control mechanism ensures that measurements are disabled only when necessary (during SRNC relocation or when RNC Frame Number Counter is unavailable) and enabled when conditions are favorable, thus maintaining measurement consistency while preserving congestion detection capability for real situations.
Data Source
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AI summary
There is disclosed method of controlling transport network layer congestion detection in HSDPA systems. The method comprises the steps of: detecting (10), at an SRNC, a condition requiring the disabling, at a Node B, of measurements performed on certain fields of a data frame for detecting congestion for certain packet flows; sending (11), from the SRNC to the Node B, a command for disabling said measurements for the concerned packet flows; and resetting (12), at the Node B, any measurement performed until reception of said command for disabling the congestion detection.