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Fading Testing | Fading test and measurement equipments

This article covers fading testing and fading measurement. It mentions fading test and measurement equipments used in fading testing from popular fading test solution providers.

What is fading?

Introduction: • The time varying received signal strength due to various impairments over the path is known as fading. It depends on various factors including the number of paths between transmitter and receiver, path loss, operating frequency, time and position of transmitter and receiver etc.
• There are different types of fading viz. large scale fading and small scale fading. Further small scale fading is categorized into slow fading, fast fading, flat fading and frequency selective fading.
Refer Fading basics and types >> in wireless communication.

Fading test setup for fading measurement

Fading Measurement Test Setup

• The test setup for all types of fading is almost the same but the settings will vary.
• As shown Signal generator is used to generate ideal modulated RF signal as per device under test (DUT). If the DUT is wimax compliant, Signal generator is configured to generate wimax signal with appropriate frequency, power level and other baseband physical layer parameters.
• Channel simulator is used to configure fading parameters as per standard specific profile such as number of paths, attenuation in each path, doppler frequency etc.
• Based on the requirement of the testing either SISO or MIMO channel models are configured.
• The pass criteria for the fading testing is that receiver should be able to process fading RF signals with an acceptable BER or PER. Refer BER vs PER >> for more information.

Fading Test and Measurement Equipments

Following table mentions fading test and measurement equipments from popular vendors.

Fading Test Equipments Description
EB Propsim F8 Channel emulator • Company: Elektrobit

• It offers MIMO OTA (Over the Air) testing.
• It supports frequency from 220 MHz to 6 GHz with BW of about 125 MHz.
• It supports upto 16 fading channels and upto 24 fading paths per channel.
• OTA antenna configurations: From 3 to 48 antennas in single polarized mode and 6 to 96 antennas in dual polarized mode can be configured.
SR5500 Channel emulator • Company: Spirent Communications

• It supports LTE, GSM, GPRS, EDGE, WCDMA, HSPA, HSPA+, CDMA20001X, EV-DO, WiMax (802.16d, 16e) etc.
• It supports SISO, MIMO, SIMO, MISO and beamforming.
• It supports frequency in different ranges with BW of about 26 MHz.
• The RF input level can be changed from +5 dBm to -50 dBm. The RF output level can be changed from -20 to -110 dBm.
• It supports configurations of upto 24 paths per channel, with path delay from 0 to 2000 µS and path loss from 0 to 32 dB.
• It supports real time fading models with provision to configure fading velocity, type (rician, rayleigh, doppler) etc.
ACE 400WB Channel emulator • Company: Azimuth Systems

• Supports 32 channels with 20 taps per channel.
• Provide provision to configure doppler shift, delay spread, path delay, RF frequency, BW, attenuation etc.

There are other companies such as Keysight Technologies, Octoscope, NI, R&S who develops channel simulator or channel emulator equipments used for fading testing. Other than channel emulator, fading tests also require standard compliant signal generators as per DUT test requirements. Test and Measurement companies such as NI, Keysight, R&S, Anritsu, Litepoint and more develops VSG and VSA equipments used for vector signal generation and analysis.

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