Understanding LTE Signal Strength

Understanding LTE Signal Strength Values

Jesse Rothschild

Understanding LTE Signal Strength

Understanding LTE signal strength can be confusing. We crafted the simple chart below to make it a little easier. The graphic below shows what approximate values may considered good and bad signal quality scores for various communication wave lengths.

Signal Type Definitions

Below are explanations of the LTE signal strength values (and also RSSI in relation to LTE):

  • SINR/SNR – The signal-to-noise ratio of the given signal.
  • RSRP – The average power received from a single Reference signal, and Its typical range is around -44dbm (good) to -140dbm(bad).
  • RSRQ – Indicates quality of the received signal, and its range is typically -19.5dB(bad) to -3dB (good).
  • RSSI – Represents the entire received power including the wanted power from the serving cell as well as all co-channel power and other sources of noise and it is related to the above parameters through the following formula:
    • RSRQ=N*(RSRP/RSSI) - Where N is the number of Resource Blocks of the E-UTRA carrier RSSI measurement bandwidth.

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Determining Factors of Signal Values

There are many different factors that influence signal strength and quality; these factors include, but are not limited, to the following:

  • Proximity to the cellular tower
  • Tower load
  • Physical barriers (mountains, buildings, trains, etc.)
  • Competing signal
  • Weather Signal going through a cellular repeater

Signal Strength and Signal Quality numbers do not incorporate all of the relevant factors. Keep in mind that measurements of Signal Strength and Signal Quality for a specific moment do not reflect on the STABILITY of a connection, as these values will vary as conditions change.

Interpreting Signal Values

Additional Disclaimers: There is no black and white answer to what constitutes a successful connection. It is possible to disconnect with green values – or connect with red values – for several reasons, including:

  • Modems may vary
  • We support hundreds of modems, and not all of them have the same ranges of acceptable values.
  • For example: in our experience the Pantech UML290 and Novatel 551L require minimum RSSI values of −64 for acceptable connections.
  • You must factor in BOTH Signal Strength and Signal Quality
    • It is possible to have excellent RSSI but disconnect because of poor quality (and vice versa).
  • Signal Strength and Signal Quality values do not hold constant
  • The variance of a signal is a significant factor in the success of a connection.
  • A particular reading represents one moment, but these values may vary dramatically over time. A stable connection requires consistency. This is a sample graph of RSSI values that shows how much the values jump (from https://cradlepointecm.com): Sample RSSI and SINR graph

Sample RSSO and SINR Graph

  • Environmental Factors can affect all of the above values.
  • Everything from other network hardware, to heavy machinery, to the weather can have any affect on RSSI, SINR, Ec/Io, RSRP, and RSRQ.
  • Other factors: tower load, signal going through a repeater/booster, etc.
    • Some factors that don't show up in Signal Strength/Signal Quality values can greatly impact a connection.

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