Mixed FFT Size OFDM Frame for Legacy HEW Compatibility
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Solution Overview
Problem
Legacy devices are not compatible with high efficiency wireless local area network (HEW) systems, limiting their ability to communicate effectively in networks with both legacy and HEW compliant devices.
Innovation Solution
A method and system for transmitting frames with mixed OFDMA formats, featuring a preamble portion with a first FFT size modulated using BPSK and a data portion with a second FFT size modulated using QPSK, allowing both legacy and HEW devices to decode the frame, with auto-detection mechanisms and specific reference sequences for channel estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If HEW frame structure with different FFT sizes is used, then spectrum efficiency and system throughput are improved, but legacy device compatibility is lost
Solution Approach 1:
The frame structure is segmented into two distinct parts: a legacy portion with first FFT size and a HEW portion with second FFT size. This segmentation allows legacy devices to process the legacy portion while HEW-compliant devices can access both portions, thereby maintaining backward compatibility while enabling improved spectrum efficiency and throughput for modern devices.
Solution Approach 2:
Different parts of the frame are assigned different properties (FFT sizes and modulation schemes). The legacy portion uses BPSK modulation and first FFT size for legacy device compatibility, while the HEW portion uses QPSK modulation and second FFT size for enhanced performance. This local differentiation enables each device type to optimally process its designated frame portion.
2Adaptability or versatility
If unified frame format is used for both legacy and HEW devices, then device compatibility is maintained, but spectrum efficiency is reduced
Solution Approach 1:
Rather than forcing a unified frame format, the invention segments the frame into legacy and HEW portions with different FFT sizes and modulation schemes. This allows legacy devices to operate with traditional parameters while HEW devices utilize optimized parameters for higher spectrum efficiency, eliminating the need to compromise overall system performance for compatibility.
Solution Approach 2:
The frame structure is designed to serve multiple functions and device types simultaneously. The legacy portion ensures universal compatibility with legacy devices, while the HEW portion provides enhanced functionality for modern devices. This multi-functional design allows a single transmission to serve both legacy and HEW-compliant devices with appropriate performance levels.
3Adaptability or versatility
If different modulation schemes (BPSK and QPSK) are used in different frame portions, then backward compatibility and enhanced performance are achieved, but frame complexity increases
Solution Approach 1:
The frame is divided into distinct segments with different modulation schemes. Legacy devices only need to process the legacy portion with BPSK modulation, keeping their complexity low. HEW-compliant devices are equipped to handle both BPSK and QPSK modulation schemes, allowing them to process the entire frame with enhanced performance without imposing complexity requirements on legacy devices.
Data Source
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AI summary
System and method embodiments are provided for high efficiency wireless communications. In an embodiment, a method in a network component for transmitting a frame of two different fast Fourier transform (FFT) sizes includes generating a frame, wherein the frame comprises orthogonal frequency-division multiplexing (OFDM) symbols in two different FFT sizes, wherein the frame comprises a first portion and a second portion, wherein the first portion comprises a first FFT size and the second portion comprises a second FFT size; and transmitting the frame during a single transmission opportunity.