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P-Series Power Meter/Sensor LTE Measurement

Technical Overviews

Using the industry’s latest development technology, the long term evolu­tion (LTE) standard from the 3rd Generation Partnership Project (3GPP) is deployed all around the world. The complexity of the LTE system requires comprehensive signal and modulation analysis as well as RF power measure­ment. The Keysight Technologies, Inc. P-Series power meter/sensor makes it possible to measure the sub-frame signal of time-division-duplex (LTE-TDD) and average burst power signal of frequency-division-duplex (LTE-FDD) with built-in LTE predefined measurement setup and statistical complementary cumulative distribution function (CCDF) measurement.

This document explains how to generate LTE-TDD and LTE-FDD signals using Keysight N7624B/N7625A Signal Studio software along with Keysight ESG Vector Signal Generator. A step-by-step guide demonstrates time-gated/average burst signal measurement as well as CCDF measurement for LTE-TDD and LTE-FDD signals using Keysight P-Series power meter and sensor.

Introduction

The combination of N1911A/12A P-Series power meters and N1921A/22A wideband power sensors can quickly and accurately measure peak, average, peak-to-average ratio power measurement, rise/fall time, pulse width, and complementary cumulative distribution function (CCDF) statistical data for wideband signals.

The 30 MHz video bandwidth and 100 x 106 samples per second sampling rate of the P-Series power meter make it possible to capture signals with high crest factor and fast transition times which is the characteristic of LTE signals. The diode-based P-Series power sensor offers a higher frequency range of up to 40 GHz and wider dynamic range of up to 55 dB for better sensitivity to enable reliable measurements of peak and average burst power.

Further simplifying measurement set up, the one-button predefined preset LTE setup of the P-Series power meter reduces the setup time required to capture the signal effectively. By following a few easy steps, you can use the P-Series power meter/sensor to obtain power versus time (PvT) measurement and statistical CCDF for LTE-TDD and LTE-FDD signals.

Power level transmission is an important LTE conformance specification. It is defined as the time-average power over the useful period of a downlink or uplink subframe burst. Peak-to-average power can also be obtained during this period. To make accurate and stable measurements, it is important that the power meter is able to capture the desired complete subframe consistently within the fixed timeframe. This can be achieved by applying a proper time-triggering mechanisms, such as trigger level, holdoff, and delay, which are available in the P-Series power meters.

The trigger level of a P-Series power meter is typically set at auto-level. Trigger holdoff ensures that the acquisition will not occur until the holdoff time has passed and a valid trigger is found. This is very useful for burst signals that have amplitude variations, because these variations can cause false triggering.

Trigger delay allows measurement of different signals. By just changing the delay setting of the power meter, you can make a power measurement of the next subframe.

Furthermore, the P-Series power meter is optimized to operate in the tracedisplay when measuring a burst signal. Downlink or uplink subframe burst signals can be captured via time-gated methodology by applying the markers (1 & 2) of the trace.

LTE is the next major step in mobile radio communications, and will be introduced in 3GPP Release 8.

The LTE specification provides a framework for increasing capacity, improving spectrum efficiency, improving coverage, and reducing latency compared with current high speed packet access (HSPA) implementations. In addition, transmission with multiple input and multiple output (MIMO) antennas will be supported for greater through­put, as well as enhanced capacity or range.

Key Attributes for LTE

  • Downlink capacity – Peak data rates up to 172.8 Mbps with 20 MHz bandwidth and 2x2 SU-MIMO
  • Uplink capacity – Peak data rates up to 86.4 Mbps with 20 MHz bandwidth and 64QAM
  • Spectrum flexibility – Scalable bandwidth up to 20 MHz
  • Spectral efficiency – Increased spectral efficiency over Release 6 HSPA by a factor of two to four
  • Latency – Sub-5 ms latency for small internet protocol (IP) packets
  • Mobility – Optimized for low mobile speed from 0 to 15 km/h; higher mobile speeds up to 120 km/h supported with high performance
  • Support for packet-switched domains only.

 

Demonstration Preparation

These demonstrations focuses on LTE measurements over a LAN connection.

The following instruments and software are used in this demo guide:

  • E4438C ESG vector signal generator1
  • N1911A/N1912A P-Series power meter
  • N1921A/1922A P-Series wideband power sensor
  • N7625A (for LTE-TDD) and N7624B (for LTE-FDD) Signal Studio software2

Keysight Signal Studio is a Windows-based utility software that simplifies creation of standard or customized LTE waveform. With the Signal Studio software, the desired LTE waveform profile can be configured and downloaded into a signal generator, and the signal generator will then gener­ate the waveform for testing.

Accurately measuring the sub-frame burst power of LTE-TDD and average burst power of LTE-FDD are very important for LTE conformance testing. The P-Series power meter/sensor are capable to measure downlink/uplink sub-frame signal of LTE-TDD and average burst power of LTE-FDD accurately. This document outlines the following key features of the P-Series power meter/sensor for LTE power measurement conformance testing:

  • One-button LTE predefined preset to simplify the measurement setup effectively
  • Auto-trigger with hold off
  • 30 MHZ video bandwidth capable to capture 20 MHz video bandwidth of LTE signal
  • 100 Msa/s
  • Measurement speed match burst rate: useful for high speed dynamic transmitter power calibration
  • Power statistical CCDF graphical and tabular format

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