Cabling from eNB radio to a Huawei E3372 USB stick

Introduction

The OAI documents do not provide any basic guidance in getting the link from eNB to a basic UE working if you do  not want to radiate.

When done link back to Adventures In Open Source 4G/5G

Overview

  • The E3372 has a pair of micro co-ax connectors and some antenna diversity.
  • “Simply” cable the TX and RX of your software defined radio, each via (say) 60db of attenuation, to each of the micro co-ax connectors (does not matter which way around).

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Details

In more detail (URL are for UK suppliers)

  • Go buy an E3372.
  • Buy a pair of CRC9 to SMA cables to connect to USB stick
    • https://www.amazon.co.uk/gp/product/B00EZ6H4O0/
    • Please only buy one or two of these cables at a time. There are many micro co-ax connectors. I found these by trial and error, and returned a number of other cables by mail order (I originally guessed the connector was TS9 not CRC9). I can not guarantee your USB stick will not have the same connectors. See the Specialist Antennas Blog article for a great summary of the different co-ax connectors.
    • Attach these connectors with cable ties to the USB stick and attach the cables together as stress relief.
      • In the next version we will strap USB stick and cables onto a drilled plastic sheet for even better mechanical robustness.
  • Add a USB male to female extender cable
    • The white cable in the above picture. More on this later. Note you will be plugging and unplugging the USB stick frequently to reset it.
  • Add 60dB attenuation inline to each cable.
    • I used 3 x 20db attenuators connected in series.
    • E.g. RS Stock No. 285-9567 (http://uk.rs-online.com)
    • Do check you have attenuators that work up to 2GHz or 5GHz.
      • Some cheap attenuators are below 1GHz only.
  • Add some SMA cables to connect each attenuator block to the TX and RX of the SDR used for the eNB.
    • Remember, depending on the SMA cables, you may need some gender converters.
    • To avoid parasitic coupling and other RF problems recommend attenuators in middle of at least 1 metre cable run between SDR and USB stick.

When All Done

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When all done I suggest you put the USB stick inside a metal box to prevent parasitic transmission (and reception) from the USB stick internal antenna (therefore needing the USB extension cable mentioned earlier, not shown in above photo).

Finally note that the above picture is for illustration – I always had al least a metre or two cable and physical distance between eNB and UE, and the USB stick in a metal box.

Thats All!

For copying and attribution see Adventures In Open Source 4G/5G

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