OFDM Transmitter Interference Cancellation for Capacity

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Solution Overview

Problem

Current OFDM/OFDMA-based communication systems face challenges in maximizing system capacity due to noise and interference, particularly in non-ideal channels, where existing techniques struggle to effectively utilize interference for improving performance.

Innovation Solution

The approach involves generating 2N' samples from N first sub-carriers, performing transformations on subsets of these samples, and combining them to minimize mean-squared error, thereby enhancing signal processing and interference utilization, which includes using Discrete Fourier Transforms and Fast Fourier Transforms to process both desired and interference signals coherently.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional OFDM/OFDMA techniques are used to transmit signals, then system implementation is straightforward, but system capacity is limited due to noise and interference in non-ideal channels

Engineering Contradiction:

Improvesystem capacityVSAvoidnoise and interference

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies interference cancellation techniques where received signals containing interference from multiple transmitters are processed to extract and cancel the interference components. By identifying and removing the harmful interference signals, the system converts the previously harmful multi-user interference into a benefit, enabling reliable detection of desired signals and thereby increasing system capacity in non-ideal channel conditions

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If matched filter principles are used to maximize signal acquisition, then desired signal strength is maximized, but noise rejection capability is compromised in complex interference environments

Engineering Contradiction:

Improvesignal acquisitionVSAvoidnoise

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent segments the received signal processing into distinct stages: initial signal reception, interference identification, interference cancellation, and desired signal detection. By dividing the processing into separate functional blocks, the system can apply specialized techniques at each stage, improving both signal acquisition reliability and noise rejection compared to a single matched filter approach

Inventive Principle:

Principle #1Segmentation

3Measurement precision

If equalization techniques are used to combat ISI and ACI, then signal quality improves, but system complexity increases

Engineering Contradiction:

Improvesignal qualityVSAvoidequalization complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent performs preliminary interference cancellation before the equalization stage. By removing the dominant interference components in advance, the subsequent equalization process operates on a cleaner signal with reduced interference, thereby achieving the same signal quality improvement with lower equalization complexity

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS8462860B2Increased capacity communications systems, methods and/or devices

Publication Date: 2013.06.11 ODYSSEY WIRELESS

AI summary

Communications architectures, systems, devices and/or methods are disclosed that can increase capacity of conventional OFDM/OFDMA systems, devices, methods and/or protocols by as much as 100%. Conventional OFDM/OFDMA transmitter/receiver architectures, methods, systems and/or devices are improved upon via additional signal processing to provide the increased capacity and reduce non-linear distortion effects on higher-order modulation alphabets such as, for example, 256-QAM.