Antenna Calibration Cable Delay Compensation

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Solution Overview

Problem

Existing wireless communication systems face challenges in antenna calibration due to mechanical and electrical variations, leading to amplitude, time, and phase deviations among antenna elements, which limits the deployment of distributed RRU systems, especially in LTE-TDD systems where calibration duration must be within strict time constraints.

Innovation Solution

A method and arrangement for antenna calibration in a communication system that involves calculating and compensating for cable delays between baseband units (BBUs) and radio remote units (RRUs) to adapt the antenna calibration chain, allowing for simultaneous calibration of distributed RRUs and extending calibration duration beyond the limitations of traditional methods.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If antenna calibration is performed in distributed RRU systems with strict time constraints, then calibration duration is reduced, but the cable distance between BBU and RRU is limited to less than 3 km

Engineering Contradiction:

Improvecalibration durationVSAvoidcable distance

Core Design Contradiction:

Loss of timeVSLength of stationary object

Solution Approach 1:

The patent applies preliminary action by calculating cable delay compensation values before the actual calibration process. The BBU calculates the cable delay based on pre-configured cable length information and computes compensation values that are stored and applied during calibration, eliminating the need for lengthy real-time measurements and extending the effective calibration window.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameter approach by introducing cable delay compensation as a new calibration parameter. Instead of merely measuring the actual delay, the system uses calculated compensation values based on cable length specifications, transforming the calibration process from pure measurement to parameter-based adjustment, thereby reducing the required calibration time window.

Inventive Principle:

Principle #35Parameter changes

2Length of stationary object

If cable distance between BBU and RRU is increased beyond 3 km, then deployment flexibility is improved, but calibration duration exceeds the required time window

Engineering Contradiction:

Improvecable distanceVSAvoidcalibration duration

Core Design Contradiction:

Length of stationary objectVSLoss of time

Solution Approach 1:

The system performs preliminary calculation of cable delay compensation values before calibration based on pre-configured cable length information. This advance preparation allows the calibration process to proceed with extended cable distances without exceeding the time window, as the compensation values are already computed and ready for application.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent substitutes the mechanical measurement approach (physically measuring actual cable delay during calibration) with a computational approach (calculating delay compensation based on cable length specifications). This substitution enables accurate calibration for longer cable distances without requiring extended real-time measurement windows.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If conventional antenna calibration methods are used, then calibration process is simple, but amplitude, time and phase deviations cannot be accurately compensated

Engineering Contradiction:

Improvecalibration process complexityVSAvoidcalibration accuracy

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent enhances calibration accuracy by introducing cable delay compensation as an additional parameter. The system calculates compensation values based on cable length specifications and applies these as correction parameters during calibration, enabling accurate compensation of amplitude, time, and phase deviations without significantly increasing process complexity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system implements feedback by using the calculated cable delay compensation values to adjust the calibration process. The compensation values are applied to correct the measured deviations, creating a feedback loop that improves calibration accuracy by continuously refining the compensation based on the calculated cable characteristics.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8965433B2Method and arrangement in a communication system

Publication Date: 2015.02.24 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

The present invention relates to the area of communication, and especially to a method and an arrangement for antenna calibration in a communication system comprising a baseband unit (BBU) and distributed radio remote units (RRUs). The present invention aims to limit antenna calibration duration in the antenna calibration chain. A cable delay based on the length of the cable connecting the BBU and the RRU is obtained. A delay compensation is calculated based upon the cable delay. Thereupon the antenna calibration chain utilized by the BBU and the RRU is adapted based upon the delay compensation.