Modified 802.11a Preamble for MIMO Legacy Coexistence

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Solution Overview

Problem

The IEEE 802.11a standard limits data rates to 54 Mbps, and existing devices struggle to coexist and interoperate with extended devices using higher data rates or MIMO technology without interfering with legacy systems.

Innovation Solution

A modified preamble structure is introduced for extended devices that supports higher data rates and MIMO operations, allowing for coexistence and interoperability with legacy devices by using multiple antennas and channels, and incorporating modified training symbols and signal fields that can be detected by both legacy and extended receivers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If extended devices use higher data rates and MIMO technology, then data transmission rate is improved, but compatibility with legacy devices deteriorates

Engineering Contradiction:

Improvedata transmission rateVSAvoidcompatibility with legacy devices

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The preamble is segmented into multiple parts: a legacy-compatible portion (short training symbols and long training symbols) that ensures compatibility with legacy devices, and an extended portion (additional long training symbols or modified signal fields) that enables extended functionality. This segmentation allows different device types to process appropriate portions independently.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The modified preamble structure serves multiple functions simultaneously: it maintains backward compatibility with legacy 802.11a devices while also enabling extended functionality for higher data rates and MIMO operations. The same preamble structure is universally processed by both legacy and extended receivers, with extended receivers utilizing additional fields for advanced features.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If extended devices transmit using modified preamble structures, then extended functionality is enabled, but interference with legacy communications increases

Engineering Contradiction:

Improveextended functionalityVSAvoidinterference with legacy communications

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The extended functionality is localized to specific portions of the preamble (such as additional long training symbols or modified signal fields) without affecting the core legacy-compatible portions. This allows extended devices to transmit with modified preambles while legacy devices only process the compatible portions, minimizing interference.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The modified preamble acts as an intermediary structure that bridges legacy and extended systems. It contains elements that legacy devices can process normally while also embedding information that extended devices can utilize for advanced operations, thereby mediating between the two system types without causing harmful interference.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If legacy devices process modified preambles, then interoperability is maintained, but processing complexity increases

Engineering Contradiction:

ImproveinteroperabilityVSAvoidprocessing complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Legacy devices perform partial processing of the modified preamble, focusing only on the essential legacy-compatible portions (short and long training symbols) required for basic interoperability. They ignore or skip the extended portions, thereby maintaining interoperability without incurring the full processing complexity of the extended functionality.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

Instead of requiring legacy devices to fully process and understand the entire modified preamble structure, the approach is inverted: legacy devices process only what they need (the compatible portion), while extended devices handle the additional complexity. This reduces the processing burden on legacy devices while maintaining interoperability.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS7599332B2Modified preamble structure for IEEE 802.11a extensions to allow for coexistence and interoperability between 802.11a devices and higher data rate, MIMO or otherwise extended devices

Publication Date: 2009.10.06 QUALCOMM INC

AI summary

A modified preamble is used by extended devices that operate at higher rates, MIMO or other extensions relative to strict 802.11a-compliant devices. The extended devices might use multiple antenna techniques (MIMO), where multiple data streams are multiplexed spatially and/or multi-channel techniques, where an extended transmitter transmits using more than one 802.11a channel at a time. Such extensions to IEEE 802.11a can exist in extended devices. The modified preamble is usable for signaling, to legacy devices as well as extended devices, to indicate capabilities and to cause legacy devices or extended devices to defer to other devices such that the common communication channel is not subject to unnecessary interference. The modified preamble is also usable for obtaining MIMO channel estimates and/or multi-channel estimates. The modified preamble preferably includes properties that facilitate detection of conventional and/or extended modes (“mode detection”) and provides some level of coexistence with legacy IEEE 802.11a devices.