OFDM Frame Structure for Mixed TDMA FDMA Access

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Solution Overview

Problem

Current frame structures for OFDM-based signaling over noisy communication channels, such as powerlines, lack efficiency in enabling a mix of TDMA and FDMA point-to-point and broadband access, and require improved methods for data transmission.

Innovation Solution

A frame structure for filtered OFDM signaling is introduced, where a central controller broadcasts redundant data over all frequencies for a short time, allowing for a mix of TDMA and FDMA point-to-point and broadband access, and includes traffic channels using scheduled operations, with each device capable of acting as a central coordinator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If OFDM is used for high data rate transmission over noisy channels, then data rate and noise resistance are improved, but frame structure efficiency and access method flexibility deteriorate

Engineering Contradiction:

Improvenoise resistanceVSAvoidaccess method flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The frame structure is segmented into multiple subframes, each containing multiple slots, which can be independently allocated for different access methods (TDMA or FDMA). This segmentation allows the system to flexibly combine different access methods within a single frame while maintaining OFDM's noise resistance benefits.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The frame structure is designed to be dynamic, allowing the central controller to adaptively allocate time slots and frequency channels based on real-time network conditions. This enables the system to switch between TDMA and FDMA access methods as needed, improving flexibility while maintaining reliability.

Inventive Principle:

Principle #15Dynamics

2Stability of the object's composition

If a centralized frame structure is used for OFDM signaling, then synchronization and orthogonality are improved, but system complexity and coordination overhead increase

Engineering Contradiction:

ImproveorthogonalityVSAvoidcoordination overhead

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The frame structure merges TDMA and FDMA access methods into a unified OFDM-based framework, where the central controller coordinates both time and frequency allocations simultaneously. This merging maintains orthogonality by ensuring proper timing and frequency alignment while reducing the need for separate coordination mechanisms.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The frame structure incorporates feedback mechanisms where devices report their status and requirements to the central controller, which then adjusts the frame allocation accordingly. This feedback loop simplifies coordination by allowing dynamic adaptation based on actual network conditions rather than requiring complex predetermined coordination.

Inventive Principle:

Principle #23Feedback

3Reliability

If redundant broadcast data is transmitted over all frequencies, then reliability and noise resistance are improved, but transmission time and bandwidth consumption increase

Engineering Contradiction:

Improvedata transmission reliabilityVSAvoidtransmission time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Redundant broadcast data is transmitted periodically rather than continuously, with the central controller scheduling these broadcasts at optimal intervals. This periodic transmission maintains reliability by ensuring data is retransmitted if lost, while minimizing time consumption by avoiding unnecessary continuous retransmission.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The frame structure allows dynamic adjustment of transmission parameters such as broadcast frequency, redundancy level, and bandwidth allocation based on channel conditions. When channels are noisy, more redundancy and broader frequency usage are employed; when channels are good, less redundancy and narrower bandwidth are used, optimizing the trade-off between reliability and time.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7830907B1Frame structure for OFDM signaling, including beacons and traffic

Publication Date: 2010.11.09 SIGMA DESIGNS ISRAEL S D I

AI summary

Provided is a frame structure for filtered OFDM signaling, wherein once every frame a central controller passes redundant broadcast data for a short time (e.g. 16 symbol times) over all frequencies in use. This broadcast, called a beacon, may carry control information, frame structure information, and other data. The rest of the frame is divided into other assignments, including broadband redundantly coded channels for broadcast, ALOHA contention access, or point-to-point transmissions, and including traffic channels that may use only some of the assigned frequencies intended primarily for point-to-point access. This allows a mix of TDMA and FDMA point-to-point and broadband access. This system may be controlled by a central coordinator, which issues reservations. This system allows devices on a frequency-selective channel to communicate with scheduled operations.