Reference Signal Correlation for Channel Estimation in Wireless Networks

Solution Overview

Problem

In wireless communications networks, simultaneous transmissions using the same training sequence in the same time slot and frequency cause severe degradation in channel estimation performance, particularly in synchronized networks like GSM, due to overlapping signals, which is exacerbated by limited available training sequences and close proximity of neighboring base stations using the same reference signals.

Innovation Solution

A method and apparatus for correlating received signals with reference signals to determine their suitability for use on communications channels, allowing for the detection of simultaneous use and selection of alternative reference signals to maintain high channel estimation performance even in networks with short distances between neighboring base stations or limited reference signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the same training sequence is reused between neighboring base stations to increase frequency re-use, then spectral efficiency is improved, but channel estimation performance deteriorates due to simultaneous transmissions causing signal distortion and interference

Engineering Contradiction:

Improvespectral efficiencyVSAvoidchannel estimation performance

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The training sequence is segmented into multiple parts with different cyclic shifts. Instead of using a single training sequence, the system divides it into segments that can be transmitted simultaneously without complete overlap, reducing interference while maintaining spectral efficiency

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the temporal parameter of the training sequence by applying different cyclic shifts to different base stations or user equipment. This parameter modification allows multiple entities to use the same base training sequence at different time offsets, enabling frequency re-use while avoiding simultaneous transmission conflicts

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If the number of available training sequences is increased to avoid simultaneous transmissions, then channel estimation performance is improved, but the system complexity and resource requirements increase

Engineering Contradiction:

Improvechannel estimation performanceVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

A single training sequence serves multiple functions and multiple base stations through the application of cyclic shifts. The same base sequence is universally applicable across different cells and users, eliminating the need to maintain large separate sets of training sequences for each entity while still providing sufficient differentiation to avoid interference

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Productivity

If base stations are placed closer together to increase network density, then coverage capacity is improved, but interference from simultaneous transmissions increases due to limited frequency re-use distance

Engineering Contradiction:

Improvenetwork capacityVSAvoidinterference from simultaneous transmissions

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The training sequence is segmented into multiple parts with different cyclic shifts. Instead of using a single training sequence, the system divides it into segments that can be transmitted simultaneously without complete overlap, reducing interference while maintaining spectral efficiency

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the temporal parameter of the training sequence by applying different cyclic shifts to different base stations or user equipment. This parameter modification allows multiple entities to use the same base training sequence at different time offsets, enabling frequency re-use while avoiding simultaneous transmission conflicts

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables effective channel estimation and separation of simultaneous transmissions, maintaining performance by selecting suitable reference signals and avoiding interference, even in scenarios with limited available sequences and close proximity of base stations.

Implementation Method 1

correlating means configured to correlate the received signal with a first reference signal

Methodology Applied

Scientific EffectCorrelation:

Data Source

PatentUS9185571B2Employing reference signals in communications

Publication Date: 2015.11.10 NOKIA SOLUTIONS & NETWORKS OY

AI summary

A method, an apparatus, a computer program product, and other embodiments are provided, which involve receiving a signal on a communications channel, correlating the received signal and a reference signal, and determining, on the basis of a result of the correlation, whether the reference signal can be employed on the communications channel. Additional aspects may provide improvements so that a simultaneous use of reference signals on the same communications channel may be detected. Further aspects may enable the performance of channel estimations on the basis of reference signals to be kept high even in networks where the distance between neighboring base stations employing the same reference signal is short and/or if the number of available reference signals is limited.