Adaptive Subcell Multiplexing for VoIP Jitter Reduction
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Solution Overview
Problem
Conventional Voice over Packet (VoP) network systems face challenges in managing jitter and average delay, particularly due to fixed timer-based sub-cell multiplexing in ATM Adaptation Layer 2 (AAL2) systems, which lead to inefficient bandwidth usage and increased jitter when the number of active voice calls changes.
Innovation Solution
Adaptive adjustment of the default timer value in the subcell multiplexing unit based on current voice traffic conditions, using a Connection Admission Controller to track packet length, rate, and VAD state changes, and classifying packet types for expedited processing, thereby optimizing delay and minimizing bandwidth wastage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fixed timer-based sub-cell multiplexing is used in AAL2 systems, then bandwidth savings are achieved, but jitter and average delay increase when the number of active voice calls changes
Solution Approach 1:
The patent applies dynamics by making the timer value adjustable rather than fixed. The sub-cell multiplexing unit dynamically modifies the timer value based on the number of active voice calls, transitioning from a static parameter to a dynamic one that adapts to changing traffic conditions, thereby resolving the contradiction between bandwidth efficiency and jitter performance
Solution Approach 2:
The patent changes the parameter of timer value from a fixed constant to a variable that depends on the number of active voice calls. By modifying this critical parameter dynamically, the system optimizes both bandwidth utilization and delay performance across different call load conditions
2Device complexity
If fixed timer value is used in sub-cell multiplexing, then device complexity is reduced, but adaptability to call load changes deteriorates
Solution Approach 1:
The system introduces dynamic adaptability by allowing the timer value to change based on call load conditions. This dynamic mechanism provides versatility across different traffic scenarios while maintaining relatively simple implementation through straightforward conditional logic in the multiplexing unit
3Loss of time
If timer value is increased to reduce delay, then average delay decreases, but bandwidth wastage increases when fewer calls are active
Solution Approach 1:
The patent applies parameter changes by adjusting the timer value based on the number of active voice calls. When fewer calls are active, the timer value is reduced to prevent bandwidth wastage, while when more calls are active, the timer value is increased to reduce delay, thereby optimizing both parameters dynamically
Data Source
AI summary
Some embodiments adaptively adjust to the current call load in a packet based virtual circuit to minimize the delay experienced by the first packets of any talk spurt for a particular active call. Some embodiments minimize the jitter introduced by multiplexing voice packets by smoothing out the waiting time experienced by each of the voice packets. Some embodiments effectively minimize jitter when the number of active calls on a virtual circuit drops off suddenly. Some embodiments are able to differentiate signaling packets indicating a telephony event from voice packets and give the signaling packets expedited processing with no delay contributed by the subcell multiplexing process. Other embodiments are described in the claims.