Base Station Controller Handoff Control via Throughput Estimation
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Solution Overview
Problem
Conventional handoff control methods in CDMA radio communication systems prioritize radio wave strength over load status and throughput, leading to potential decreases in user throughput and imbalances among base transceiver subsystems, especially when handoff is performed without considering congestion.
Innovation Solution
Implement a handoff control method that estimates the throughput ratio of access terminals before and after handoff, suspending handoff if the ratio is lower than a threshold and prioritizing handoff to destinations with higher estimated throughput ratios, ensuring that access terminals are transferred only when an increase in throughput is expected, thereby balancing load among base transceiver subsystems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If handoff is performed based on pilot signal strength threshold alone, then access terminals can maintain communication in good radio environments, but user throughput decreases and load imbalance occurs among base transceiver subsystems
Solution Approach 1:
The patent changes the handoff decision parameter from only pilot signal strength (C/I threshold) to a composite parameter that includes estimated user throughput and load status. The base station controller calculates estimated throughput ratios comparing current and target base transceiver subsystems, and only executes handoff when the ratio exceeds a threshold, thereby optimizing both communication reliability and user throughput while preventing load imbalance
Solution Approach 2:
The patent implements a feedback mechanism where the base station controller continuously monitors pilot signal strengths from multiple base transceiver subsystems, estimates user throughput based on current load status and signal quality, and dynamically adjusts handoff decisions. This feedback loop ensures that handoff occurs only when it will improve or maintain user throughput while balancing load across the network
2Strength
If handoff is executed without considering destination load status, then access terminals can switch to stronger signal zones, but base transceiver subsystem congestion increases and throughput decreases
Solution Approach 1:
The patent introduces load status and estimated throughput as additional parameters to the handoff decision process. Before executing handoff, the base station controller estimates the user throughput at the target base transceiver subsystem based on its current load and signal conditions. The handoff is conditioned on the estimated throughput ratio exceeding a threshold, ensuring that terminals switch to zones with both strong signals and available capacity, thereby maintaining high data transmission rates
Solution Approach 2:
The patent performs preliminary estimation of user throughput and load status at the target base transceiver subsystem before executing handoff. This preliminary assessment allows the system to predict whether the handoff will result in improved throughput, and only proceed when conditions are favorable, preventing terminals from switching to congested zones even if signal strength is high
3Ease of operation
If conventional handoff control is used, then radio channel switching can be performed, but handoff iterations increase and communication efficiency decreases
Solution Approach 1:
The patent changes the handoff execution criterion from simple C/I threshold comparison to a more comprehensive evaluation including estimated throughput ratio. By requiring the throughput ratio to exceed a threshold before handoff execution, the system reduces unnecessary handoff iterations and stabilizes the handoff process, thereby decreasing the time lost to repeated handoff attempts and improving overall communication efficiency
Data Source
AI summary
When an access terminal is handed off, requested-data-rate information based on a data rate control signal from each access terminal, average throughput of each access terminal before handoff, and a handoff request count are obtained from a base transceiver subsystem. A throughput after handoff of each access terminal is estimated from a ratio of the data rate information of each access terminal to the number of connected access terminals, and an estimated throughput ratio representing the degree of change from the average throughput of each access terminal before handoff to the estimated throughput is calculated. If the estimated throughput ratio is lower than or equal to a given value, the corresponding access terminal is not handed off. If the estimated throughput ratio is higher than the given value, the access terminal having the highest estimated throughput among access terminals requesting handoff is handed off.