Non-orthogonal Multiple Access Receiver Interference Cancellation

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Solution Overview

Problem

In non-orthogonal multiple access systems, mobile stations face high processing loads and increased costs due to the need for complex signal processing to remove interference from signals with larger path losses, leading to processing delays.

Innovation Solution

Implementing a hybrid orthogonal/non-orthogonal multiple access system that uses a receiver with a radio signal reception unit, interference cancellation unit, and reference signal reception unit to demodulate and cancel non-orthogonal signals, with a transmitter that multiplexes reference signals within the same radio resource block as non-orthogonal signals for efficient interference cancellation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If non-orthogonal multiple access is implemented with signal separation through non-linear signal processing, then system capacity is increased, but processing load and cost in mobile stations increase significantly

Engineering Contradiction:

Improvesystem capacityVSAvoidprocessing load in mobile station

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The received signal is segmented into multiple non-orthogonal signals corresponding to different mobile stations. Each signal component is separately processed through demodulation and interference cancellation, allowing the mobile station to extract its intended signal while removing interference from others, thus reducing overall processing complexity compared to processing the entire mixed signal non-linearly

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Reference signals are transmitted in advance along with the non-orthogonal signals. These reference signals enable mobile stations to perform channel estimation and prepare for demodulation before the actual data signals arrive, reducing the real-time processing burden during signal reception and demodulation

Inventive Principle:

Principle #10Preliminary action

2Quantity of substance

If non-orthogonal signals are used for multiple access, then more users can be served concurrently, but processing delay increases due to complex signal processing

Engineering Contradiction:

Improvenumber of concurrent usersVSAvoidprocessing delay

Core Design Contradiction:

Quantity of substanceVSLoss of time

Solution Approach 1:

The composite signal from multiple users is segmented into individual signal components through linear demodulation based on reference signals. This segmentation allows each user's signal to be processed independently and efficiently, reducing the overall processing time compared to iterative non-linear separation methods

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Reference signals serve as intermediaries that carry channel information necessary for demodulation. By using these intermediary reference signals, mobile stations can perform efficient linear demodulation and interference cancellation without requiring complex non-linear processing, thus reducing processing delay

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If hybrid orthogonal/non-orthogonal multiple access is introduced, then processing load is reduced to some degree, but mobile stations cannot recognize conditions of multiplexed mobile stations

Engineering Contradiction:

Improveprocessing loadVSAvoidrecognition of multiplexed station conditions

Core Design Contradiction:

Device complexityVSLoss of information

Solution Approach 1:

The reference signal serves multiple functions: it enables channel estimation for demodulation, provides information about the presence of non-orthogonal multiplexing, and allows mobile stations to identify the conditions of other multiplexed stations. This multi-functionality ensures that processing is simplified while necessary information is preserved

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9843406B2Receiver, transmitter and radio communication method

Publication Date: 2017.12.12 NTT DOCOMO INC

AI summary

Provided are a receiver, a transmitter and a radio communication method capable of using non-orthogonal multiple access while suppressing cost increase and processing delay. A mobile station 200A receives non-orthogonal signals, also receives a reference signal to be used for interference cancellation, and extracts the non-orthogonal signal addressed to the mobile station 200A from the received non-orthogonal signals by demodulating and cancelling the radio signal addressed to another mobile station. In addition, the mobile station 200A demodulates the extracted non-orthogonal signal addressed to the mobile station 200A on the basis of the reference signal. The reference signal is multiplexed in the same radio resource block as a resource block allocated to the non-orthogonal signals, and is multiplexed in the radio resource block only when at least one signal is scheduled in the radio resource block.