Terminal Interference Removal in Multihop Relay Networks

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Solution Overview

Problem

In multihop communication systems, terminals experience interference from relay apparatuses using the same frequency, leading to reduced signal quality and efficiency, especially when coverage areas of adjacent relay apparatuses overlap.

Innovation Solution

A terminal apparatus and method that selectively connects to an upstream relay apparatus and removes interference signals from downstream apparatuses by receiving and processing signals in specific subframe periods, allowing for interference cancellation and improved signal reception.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple relay apparatuses use the same frequency for communication, then frequency use efficiency is improved, but interference between relay apparatuses increases

Engineering Contradiction:

Improvefrequency use efficiencyVSAvoidinterference from relay apparatuses

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent segments the communication process into distinct time periods within subframes. Specifically, it divides communication between relay apparatuses and communication between relay apparatuses and terminals into separate time slots, allowing frequency reuse while preventing interference through temporal separation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements periodic time-division multiplexing where relay apparatuses alternate their communication roles in regular intervals. Upstream relays transmit to downstream relays in certain subframes while downstream relays transmit to terminals in other subframes, creating a periodic pattern that enables frequency reuse without interference.

Inventive Principle:

Principle #19Periodic action

2Reliability

If a terminal connects to an upstream relay apparatus, then signal quality from the intended relay is improved, but interference from downstream relay apparatuses persists

Engineering Contradiction:

Improvesignal qualityVSAvoidinterference from downstream relay apparatuses

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by having the terminal receive and store signals from downstream relay apparatuses in advance, before the actual communication phase. This allows the terminal to pre-acquire interference signals and use them for cancellation during the subsequent signal reception, improving signal quality through proactive interference mitigation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful interference from downstream relay apparatuses into a beneficial element by using the received interference signals for cancellation purposes. The terminal utilizes the downlink signals from downstream relays, which would otherwise be pure interference, to generate cancellation signals that eliminate the harmful effects, thereby turning harm into benefit.

Inventive Principle:

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

3Area of stationary object

If multihop communication is implemented to expand coverage, then coverage area is improved, but propagation loss increases

Engineering Contradiction:

Improvecoverage areaVSAvoidpropagation loss

Core Design Contradiction:

Area of stationary objectVSLoss of energy

Solution Approach 1:

The patent segments the long communication path into multiple shorter hops through the introduction of relay apparatuses. Instead of one long transmission from base station to terminal, the path is divided into base station to relay, relay to relay, and relay to terminal segments, reducing propagation loss in each individual hop while maintaining overall coverage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces relay apparatuses as intermediary nodes between the base station and distant terminals. These intermediaries receive signals from upstream nodes and retransmit them to downstream nodes, effectively bridging the gap and reducing the propagation distance each transmission must cover, thereby minimizing cumulative propagation loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8681686B2Terminal device and interference removal method

Publication Date: 2014.03.25 PANASONIC INTELLECTUAL PROPERTY CORP OF AMERICA

AI summary

When a terminal (200) is capable of connecting to two relay devices that are adjacent to the terminal, from among a plurality of relay devices, a receiving unit (208) receives signals in a first period and a second period for communication among the plurality of relay stations, which are transmitted from the higher order device to the lower order device toward other terminal devices. An interference removal unit (209) obtains a signal transmitted toward the terminal (200) from the higher order relay device by employing the signals toward the other terminal devices that are received in the first period and the second period and removing a signal toward other terminal devices that is transmitted in a third period for communication between the plurality of relay devices and the terminal device from the lower order device from a signal that is received in the third period.