Soft Handoff Load Control in UMTS E-DCH Networks
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Solution Overview
Problem
In UMTS wireless communication networks, there is no mechanism to control the sharing of available E-DCH resources between in-cell and soft handoff E-DCH users, leading to potential overloading and reduced cell throughput.
Innovation Solution
Implementing a method to control the load from non-served soft handoff users by using a soft handoff loading metric, which involves comparing this metric to a threshold and adjusting transmission rates to prioritize served users and reduce the load of non-served soft handoff users when necessary, ensuring that the estimated use of uplink resources does not exceed available amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If rate scheduling is performed for in-cell and soft handoff users without load control mechanism, then scheduling decisions can be made at each Node-B, but available E-DCH resources cannot be properly shared between in-cell and SHO users leading to potential overloading
Solution Approach 1:
The patent segments the user population into in-cell users and soft handoff users, and further segments the scheduling process into two distinct control mechanisms: one for in-cell users (Node-B based scheduling) and one for SHO users (RNC based rate control). This segmentation allows each user type to be managed by the most appropriate controller while ensuring proper resource sharing through the loading metric feedback mechanism.
Solution Approach 2:
The patent introduces an intermediary loading metric mechanism that bridges the gap between Node-B scheduling decisions and RNC resource management. The loading metric acts as a feedback signal from Node-B to RNC, enabling the RNC to make informed rate control decisions for SHO users based on actual cell loading conditions, thus mediating the resource allocation between the two network entities.
2Productivity
If transmission rates are increased to improve data service quality, then high-speed scheduled data service can be provided, but uplink resource usage may exceed available amounts causing overload
Solution Approach 1:
The patent implements dynamic rate control where the RNC adjusts transmission rates for SHO users based on real-time loading metric feedback from the Node-B. The rate control is not static but adapts continuously to changing cell conditions, increasing rates when resources are available and reducing them when the cell approaches capacity, thus dynamically balancing productivity and reliability.
Solution Approach 2:
The patent establishes a feedback loop where the Node-B calculates and reports the loading metric to the RNC, which then uses this feedback to adjust rate control decisions for SHO users. This closed-loop feedback mechanism ensures that transmission rates are continuously optimized based on actual uplink resource availability, preventing overload while maximizing data service quality.
3Reliability
If soft handoff loading metric is used to control non-served SHO users, then load from SHO users can be controlled, but served users may be deprioritized without proper priority-based rate control
Solution Approach 1:
The patent applies different quality of service treatments to different user categories: in-cell users receive priority-based rate control ensuring their throughput requirements are met, while SHO users receive load-controlled rate adjustments. This local quality differentiation ensures that each user type is managed according to their specific needs and priority level, preventing SHO user load control from negatively impacting served user productivity.
Solution Approach 2:
The patent implements preliminary priority-based rate control for in-cell users before applying load control to SHO users. The RNC first determines rates for in-cell users based on their priority and service requirements, then uses the remaining capacity and loading metric to control SHO user rates. This preliminary action ensures served users are always prioritized before SHO user load control is enforced.
Data Source
AI summary
In the method, rate control for at least one soft handoff user is selectively performed based on a soft handoff loading metric indicative of loading from soft handoff users on the channel.