Pilot Signal Frequency Division for Interference Reduction

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Solution Overview

Problem

In radio communications systems, the mixed use of subframe formats with different guard interval lengths complicates cell search processing, leading to incorrect FFT timing and interference between unicast and multicast/broadcast pilot signals, which deteriorates cell search ability and increases error detection rates.

Innovation Solution

A radio communications method where pilot signals for unicast and multicast/broadcast services are transmitted using distinct bands within the transmission band, with the unicast pilot in a central band and multicast/broadcast pilot in other bands, allowing accurate detection and reducing interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If subframe formats with different guard interval lengths are mixed for unicast and multicast/broadcast services, then system adaptability to different propagation conditions is improved, but pilot signal interference increases and cell search ability deteriorates

Engineering Contradiction:

Improveadaptability to propagation conditionsVSAvoidcell search ability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The transmission band is segmented into a central band and other bands. Unicast pilot signals are transmitted only in the central band, while multicast/broadcast pilot signals are transmitted in other bands. This frequency-domain segmentation prevents pilot signal interference and enables reliable cell search processing while maintaining support for multiple subframe formats with different guard interval lengths.

Inventive Principle:

Principle #1Segmentation

2Productivity

If multiple pilot signals are transmitted in the same band, then spectrum efficiency is improved, but pilot signal interference increases leading to higher error detection rates

Engineering Contradiction:

Improvespectrum efficiencyVSAvoiderror detection rate

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Instead of separating pilot signals in the time domain or code domain where interference occurs, the invention separates them in the frequency domain by allocating different frequency bands. Unicast pilots occupy the central band while multicast/broadcast pilots occupy other bands, eliminating interference and enabling accurate detection of both pilot types simultaneously.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS8150347B2Radio communications method, transmitter, and receiver

Publication Date: 2012.04.03 1FINITY INC

AI summary

The transmitter transmits at least any one of the multiple kinds of generated pilot signals corresponding to the multiple types of communications services by use of a predetermined band set in a part of a transmission band beforehand, and transmits the other kinds of pilot signals using parts of the transmission band other than the predetermined band. The receiver detects a signal in a band containing at least the predetermined band, out of reception signals from the transmitter, and detects the pilot signal from the detected signal. With this construction, even if other pilot signals are frequency-division multiplexed to the same time domain, the receiver is capable of detecting a pilot signal accurately while avoiding the effect of interference due to the other pilot signals.