Dynamic Call Admission Control Using Channel Busy Time Tracking

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Solution Overview

Problem

Existing call admission control (CAC) schemes in wireless networks fail to predictively manage call capacity, leading to network instability and quality of service degradation due to varying network conditions and interference, lacking dynamic and accurate metrics for admitting new calls without degrading voice quality.

Innovation Solution

A method and system that track channel busy time and transmission time of voice packets to calculate the number of admissible calls, using a dynamic CAC metric (Na) that adjusts to network conditions, ensuring stable admission decisions by approving new calls only if they do not exceed the network's capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional CAC schemes use metrics such as delay, jitter, and packet loss rate, then call admission decisions can be made, but these metrics do not provide predictive measurements and lead to network instability and QoS degradation

Engineering Contradiction:

Improvenetwork stabilityVSAvoidpredictive measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent calculates the number of additional admissible calls (Na) before actually admitting new calls, using predictive measurements of channel bandwidth requirement and voice packet queuing requirement. This preliminary calculation prevents network instability by ensuring admission decisions are made only when capacity exists, rather than reacting to degradation after admission.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors network conditions including channel busy time percentage and voice packet transmission times, using this feedback to dynamically recalculate Na. This closed-loop feedback mechanism ensures the CAC metric adapts to changing network conditions, maintaining reliability while providing accurate predictive measurements.

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If CAC metrics are predetermined by network simulations, then call capacity can be estimated, but network conditions are unlimited and change with time making simulations unrealistic for field deployments

Engineering Contradiction:

Improveadaptability to network conditionsVSAvoidCAC implementation complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The CAC metric Na is calculated autonomously by the system itself using real-time measurements of channel busy time and voice packet transmission times. The system serves its own need for capacity evaluation without requiring external simulation data, automatically adapting to any network condition it encounters in field deployments.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent changes the approach from using fixed simulation-based parameters to dynamically measuring actual network parameters (channel busy time percentage, voice packet transmission times). These parameters continuously change with network conditions, enabling the CAC metric to adapt to unlimited deployment scenarios without complex predetermined configurations.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the number of admissible calls is increased to maximize bandwidth use, then call capacity increases, but admitting even one more call than capacity causes significant degradation of voice quality

Engineering Contradiction:

Improvecall capacityVSAvoidvoice quality

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system performs preliminary anti-action by calculating Na to determine the maximum number of additional calls that can be admitted without degrading voice quality. This preventive calculation stops the system from admitting calls that would exceed capacity and cause instability, while still maximizing bandwidth utilization up to the calculated limit.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The patent uses partial action by admitting only the number of calls calculated as admissible (Na), rather than admitting calls up to theoretical maximum capacity. This partial admission strategy ensures voice quality is maintained while still utilizing available bandwidth effectively, avoiding the excessive action that would lead to degradation.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS7468951B2Method and system for evaluting number of additional admissible calls for use in call admission control

Publication Date: 2008.12.23 CISCO TECHNOLOGY INC

AI summary

A method for evaluating number of additional admissible calls for use in call admission control includes tracking a percentage of channel busy time and transmission time of downlink and uplink voice packets, receiving a call admission request, and calculating the number of admissible calls. The number of admissible calls is calculated based on a channel bandwidth requirement determined from the percentage of channel busy time and a voice packet queuing requirement determined from the transmission time of downlink and uplink voice packets. The call admission request is approved if the number of admissible calls is greater than one and rejected if the number of admissible calls is less than one.