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LTE Decoder

The LTE Decoder block synchronizes to your LTE cell, decodes and displays the most relevant data. Results can be saved as CSV/XML/JSON and as a screenshot. The equalized signal from the physical channels is sent to the output and can be inspected with other blocks.

Left hand side input:

  • IQ: signal source, e.g. from Spectran V6, from LTE Scanner or from a file

Right hand side output:

  • Channel: the LTE channel with the currently decoded bandwidth
  • IQCons: outputs the equalized constellation of the selected measurement channel

Available settings:

  • Center Frequency: the frequency on which the decoder looks for a cell. (LTE uses channel spacing of 100kHz.)
  • Auto PID / Manual PID: a center frequency can contain multiple cells, which can be distinguished with the PID (see FAQ). "Auto PID" will automatically detect and pick the best one on the given center frequency. "Manual PID" will pin the decoder to the given PID.
  • PID: entry of PID value for the "Manual PID" mode.
  • Clear PID: For "Auto PID" mode, clears the currently selected PID and restarts selection of the best available.
  • Measurement Channel: selects which equalized LTE physical channel is sent to the "IQCons" output for further inspection. Options are: None, S-SS, PBCH, PCFICH, PDCCH, PDSCH. Note that decoding of these channels might be incomplete and might represent only a subset of actually sent data.
  • Warn on missing input: there is a help message for you, when the decoder does not receive valid input. If this distracts your work, you can disable it here.

When operating the LTE Decoder, you have to make sure your signal source contains the configured center frequency with enough span (up to 18 MHz). Either Auto PID is set, or a valid manual PID was configured. If decoding is successful you will see details comparable to this:

 

These are the three most typical missions:

  • With V6, Scanner-Driven:

    You obtain available cell info using the LTE Scanner block. You pause the scanner and click on a found cell. That will automatically configure the attached LTE Decoder block (Center Frequency and PID) and you can inspect the decoding details in the decoder block.
  • With V6, manual:

    You configure the tuning of V6 and the LTE Decoder manually. V6 output must contain decoder's Center Frequency with enough span (up to 18 MHz).
  • Decoding a recording:

    Recording must contain decoder's Center Frequency with enough span (up to 18 MHz).

How-To & FAQ

  • How to export MIB & SIB data
    • click on the block widget export button
    • select one of the supported formats: csv (comma), csv (semicolon), xml, json
    • Example exports: [decoder-exports.zip] added to this message
  • How to export a visual
    • click on the widget export button
    • select 'Picture' as file format
    • supported formats: png,jpg,bmp,jpeg,tif
    • Example export:
  • How to show the map
    • install "Cell Geo Database" from package shop
    • configure map provider in block settings (e.g. Open Street Map)
    • if location is found in database, map will show a triangle with range
  • What kind of cells can be decoded?
    Currently, LTE FDD cells are supported (frame structure type 1). If your strong cell signal does not decode, let us know.
  • What is the PID?
    The physical cell ID (PID) is used to distinguish multiple LTE cells sending on the same center frequency. Set a manual PID to pin the decoder to the cell you want to monitor. Valid entries are from 0 to 503.
  • When will TDD cells be supported?
    If enough people are requesting it, we will add that feature. Consider sending us a recording of your TDD cell.
  • Is decoding of the Uplink supported?
    No. Please send us your request if you need that feature.

LTE Abbreviations

CID Cell-ID
EARFCN E-UTRA Absolute Radio Frequency Channel Number
MCC Mobile Country Code
MIB Master Information Block
MNC Mobile Network code
P-SS Primary Synchronization Sequence
PBCH Physical Broadcast Channel
PCFICH Physical Control Format Indicator Channel
PDCCH Physical Downlink Control Channel
PDSCH Physical Downlink Shared Channel
PID Physical Cell ID
S-SS Secondary Synchronization Sequence
SIB1 System Information Block 1
TAC Tracking Area Code

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