Multi-Channel FFT Pipeline Using Commutators for MIMO OFDM

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Solution Overview

Problem

Implementing Fast Fourier Transform (FFT) in multi-input multi-output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems doubles the gate count of FFT logic, increasing complexity.

Innovation Solution

A system comprising a Fast Fourier Transform (FFT) pipeline with radix-2 butterfly components and commutators, allowing continuous activation of radix-2 butterflies and multipliers to process samples from multiple channels efficiently, reducing complexity through pipelined decimation-in-frequency and decimation-in-time architectures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If separate FFT components are used for each input/output channel in MIMO OFDM systems, then each channel can be processed independently, but the gate count of FFT logic doubles, increasing device complexity

Engineering Contradiction:

Improvemulti-channel processing capabilityVSAvoidgate count of FFT logic

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges multiple FFT processing channels into a single shared FFT pipeline. Instead of having separate FFT components for each input/output channel, the system uses one FFT pipeline that processes multiple channels sequentially through time-division multiplexing, thereby reducing the gate count while maintaining multi-channel processing capability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The single FFT pipeline is designed to serve multiple functions by processing different channels at different time slots. The pipeline is configured to accept inputs from multiple channels and produce outputs for multiple channels through controlled switching, making it a universal processor that eliminates the need for duplicate hardware

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Device complexity

If a single FFT pipeline is used to process multiple channels sequentially, then device complexity is reduced, but the processing time for each channel increases

Engineering Contradiction:

Improvegate count of FFT logicVSAvoidprocessing time per channel

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The FFT pipeline is designed to remain continuously active by switching between processing different channels. Instead of idle time between channel processing, the pipeline continuously transforms samples from different channels in sequence, eliminating downtime and optimizing throughput. The commutator ensures seamless transitions between channels maintain continuous useful computation

Inventive Principle:

Principle #20Continuity of useful action

3Productivity

If radix-2 butterflies are activated continuously across multiple channels, then component utilization increases, but control complexity increases

Engineering Contradiction:

Improvecomponent utilizationVSAvoidcontrol logic complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

A commutator is introduced as an intermediary control element that manages the routing of signals between channels and the FFT pipeline. The commutator simplifies control by using a single control signal to switch between channels, thereby managing the complexity of multi-channel coordination while maximizing butterfly component utilization

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS7827225B2Methods and systems for a multi-channel Fast Fourier Transform (FFT)

Publication Date: 2010.11.02 TEXAS INSTRUMENTS INC

AI summary

In at least some embodiments, a method is provided. The method includes receiving samples from a first input channel and a second input channel. The method further includes controlling commutators to selectively switch samples between the first and second input channels for input to a radix-2 butterfly. The method further includes continuously activating the radix-2 butterfly while processing samples received from the first input channel followed by samples received from the second input channel.