Measuring LTE Modulation Quality Over-The-Air With A Handheld Instrument

By Anritsu Company

Introduction

Most major mobile carriers in the United States and many worldwide carriers are in the process of converting their networks to Long Term Evolution (LTE), the next generation of radio technologies designed to increase the capacity and speed of mobile networks. LTE utilizes multi-antenna techniques such as spatial multiplexing, beamforming, and transmit diversity to support higher data rates and improve coverage. These same multi-antenna techniques, however, create challenges for base station engineers and technicians in performing basic measurements such as modulation quality. These challenges can be circumvented by connecting the instrument directly to the transmitter, but this method has problems of its own such requiring considerable additional time and possibly having to take the transmitter off the air.

At the same time, wireless operators are being pressured to reduce costs, yet improve network quality. By making Over-the-Air (OTA) modulation quality measurements, along with Pass/Fail, Scanner, and throughput tests, LTE eNodeB performance can be quickly verified and trouble spots easily detected.

This application note presents a simpler and faster method of measuring modulation quality—making the measurement over-the-air with a handheld instrument. This method is based on the fact that control channels do not use spatial multiplexing or beamforming because they have to operate over the entire cell, including at the cell edges. Over-the-air measurements of LTE modulation quality are not intended to replace direct-connect measurements because direct-connect measurements are more accurate and comprehensive. However, over-the-air measurements are much faster and more convenient so they provide a valuable tool to help meet the challenge of delivering seamless LTE service.