Virtual Flexible Framing for TDMA Packet Jitter Reduction

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Solution Overview

Problem

TDMA systems, particularly MF-TDMA, experience significant packet jitter and latency due to variable time slot allocations and queuing delays, which degrade service quality, especially in voice applications like VOIP.

Innovation Solution

The implementation of Virtual Flexible Framing (VFF) allows for dynamic assignment of time slots based on a virtual frame structure that matches the periodicity of incoming data packets, independent of the physical TDMA frame timing, thereby reducing jitter and latency by optimizing slot allocation and transmission timing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional jitter buffers are used to remove packet jitter by retaining packets for regular interval output, then packet jitter is reduced, but packet latency increases significantly

Engineering Contradiction:

Improvepacket jitter removalVSAvoidpacket latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements dynamic slot allocation where time slots are assigned based on actual packet arrival patterns rather than fixed periodic intervals. The system adjusts slot timing dynamically to match packet generation rates, eliminating the need for fixed jitter buffer retention periods and thereby reducing latency while maintaining jitter removal.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system performs preliminary packet scheduling by pre-allocating time slots based on predicted packet arrival patterns. This allows packets to be transmitted immediately upon arrival without waiting for buffer retention periods to elapse, reducing latency while maintaining regular output intervals through proactive slot assignment.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If TDMA time slot allocations are used for packet transmission, then bandwidth sharing is achieved, but variable temporal gaps between packet arrival and transmission cause packet jitter

Engineering Contradiction:

Improvebandwidth sharing efficiencyVSAvoidpacket timing regularity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the timing parameters of TDMA slots dynamically to match packet arrival patterns. Instead of using fixed periodic slot allocations, the system adjusts slot intervals and positions based on actual traffic characteristics, maintaining both bandwidth sharing efficiency and packet timing regularity by adapting parameters to real-time conditions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system transitions from static TDMA slot allocation to dynamic slot assignment where timing parameters are adjusted continuously based on packet arrival rates. This dynamic adaptation allows the system to maintain regular packet transmission intervals even when packet arrivals are variable, thereby reducing jitter while preserving bandwidth sharing capabilities.

Inventive Principle:

Principle #15Dynamics

3Stability of the object's composition

If packets are queued in buffers for delayed transmission to match TDMA slot timing, then transmission synchronization is improved, but additional packet latency is introduced

Engineering Contradiction:

Improvetransmission synchronizationVSAvoidpacket latency

Core Design Contradiction:

Stability of the object's compositionVSLoss of time

Solution Approach 1:

The patent merges the packet queuing function with the slot allocation mechanism by assigning packets to slots based on their arrival time and predicted transmission window. This integration eliminates separate buffer retention periods, as packets are scheduled for transmission in near-real-time while maintaining synchronization through coordinated slot assignment rather than delayed buffer release.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS9203505B2Virtual data framing for data packet transmission over channels of a communications network

Publication Date: 2015.12.01 HUGHES NETWORK SYST

AI summary

An approach for transmission of data packets, based on virtual frame timing, over a communications channel is provided. A remote terminal receives a first stream of data packets at periodic time intervals. The terminal receives an allocation of time slots within a sequence of TDMA transmission frames, for transmission of the data packets over the channel. The timing structure of the allocated time slots is based on a virtual frame size relative to the interval timing of the first data packet stream, and independent of the frame size/timing of the TDMA transmission frames. The remote terminal may receive a second stream of data packets at periodic time intervals that differ from the time intervals of the first stream. In a multi-stream scenario, the virtual frame size for the time slot allocation is based on the greatest common denominator of the interval timings of the first and second data streams.