In cellular networks, when a mobile moves from cell to cell and performs cell selection/reselection and handover, it has to measure the signal strength/quality of the neighbor cells. In LTE network, a UE measures two parameters on reference signal: RSRP (Reference Signal Received Power) and RSRQ (Reference Signal Received Quality).

In LTE network, a UE measures:

  • RSSI – Received Signal Strength Indicator: The carrier RSSI (Receive Strength Signal Indicator) measures the average total received power observed only in OFDM symbols containing reference symbols for antenna port 0 (i.e., OFDM symbol 0 & 4 in a slot) in the measurement bandwidth over N resource blocks.
    The total received power of the carrier RSSI includes the power from co-channel serving & non-serving cells, adjacent channel interference, thermal noise, etc. Total measured over 12-subcarriers including RS from Serving Cell, Traffic in the Serving Cell
  • RSRP – Reference Signal Received Power: RSRP is a RSSI type of measurement, as follows there are some definition of it and some details as well.

It is the power of the LTE Reference Signals spread over the full bandwidth (RSSI) and narrow-band (RSRP).
A minimum of -20 dB SINR (of the S-Synch channel) is needed to detect RSRP/RSRQ

  • RSRQ – Reference Signal Received Quality: Quality considering also RSSI and the number of used Resource Blocks (N) RSRQ = (N * RSRP) / RSSI measured over the same bandwidth. RSRQ is a C/I type of measurement and it indicates the quality of the received reference signal.
    The RSRQ measurement provides additional information when RSRP is not sufficient to make a reliable handover or cell re-selection decision. 

In the procedure of handover, the LTE specification provides the flexibility of using RSRP, RSRQ, or both.

Of course, it must to be measured over the same bandwidth:

  • Narrow-band N = 62 Sub Carriers (6 Resource Blocks)
  • Wide-band N = full bandwidth (up to 100 Resource Blocks / 20 MHz)

RSRP 3GPP Definition

Reference Signal Received Power (RSRP), is defined as the linear average over the power contributions (in [W]) of the resource elements (REs) that carry cell-specific reference signals within the considered measurement frequency bandwidth. For RSRP determination the cell-specific reference signals R0 according TS 36.211 [3] shall be used. If the UE can reliably detect that R1 is available it may use R1 in addition to R0 to determine RSRP.

The reference point for the RSRP shall be the antenna connector of the UE.

If receiver diversity is in use by the UE, the reported value shall not be lower than the corresponding RSRP of any of the individual diversity branches.

RSRP measurement, normally expressed in dBm, is utilized mainly to make ranking among different candidate cells in accordance with their signal strength. Generally, the reference signals on the first antenna port are used to determine RSRP, however, the reference signals sent on the second port can also be used in addition to the RSs on the first port if UE can detect that they are being transmitted.

  • Applicable for: RRC_IDLE intra-frequency, RRC_IDLE inter-frequency, RRC_CONNECTED intra-frequency, RRC_CONNECTED inter-frequency
    • Note 1: The number of resource elements within the considered measurement frequency bandwidth and within the measurement period that are used by the UE to determine RSRP is left up to the UE implementation with the limitation that corresponding measurement accuracy requirements have to be fulfilled.
    • Note 2: The power per resource element is determined from the energy received during the useful part of the symbol, excluding the CP.

In other words RSRP (Reference Signal Receive Power) is the average power of Resource Elements (RE) that carry cell specific Reference Signals (RS) over the entire bandwidth, so RSRP is only measured in the symbols carrying RS.

  • RSRP is the average received power of a single RS resource element
    RSRP Table

    RSRP

  • UE measures the power of multiple resource elements used to transfer the reference signal but then takes an average of them rather than summing them.
  • The reporting range of RSRP is defined from -140 dBm to – 44 dBm with 1 dB resolution. The mapping of measured quantity is defined in the table – RSRP mapping 3GPP TS 36.133 V8.9.0 (2010-03) –
  • RSRP does a better job of measuring signal power from a specific sector while potentially excluding noise and interference from other sectors
  • RSRP levels for usable signal typically range from about -75 dBm close in to an LTE cell site to -120 dBm at the edge of LTE coverage.

Reference Signals recap: OFDMA Channel Estimation

In simple terms the Reference Signal (RS) is mapped to Resource Elements (RE). This mapping follows a specific pattern (see to below).

  • So at any point in time the UE will measure all the REs that carry the RS and average the measurements to obtain an RSRP reading.
  • Channel estimation in LTE is based on reference signals (like CPICH functionality in WCDMA)
  • Reference signals position in time domain is fixed (0 and 4 for Type 1 Frame) whereas in frequency domain it depends on the Cell ID
  • In case more than one antenna is used (e.g. MIMO) the Resource elements allocated to reference signals on one antenna are DTX on the other antennas
  • Reference signals are modulated to identify the cell to which they belong
More Info about OFDMA
RSRP
OFDM Channel RSRP

RSSI (Received Signal Strength Indicator) is a parameter which provides information about total received wide-band power (measure in all symbols) including all interference and thermal noise. RSSI is not reported to e-NodeB by UE. It can simply be computed from RSRQ and RSRP that are, instead, reported by UE.

RSSI = wideband power = noise + serving cell power + interference power

So, without noise and interference, we have that 100% DL PRB activity: RSSI=12*N*RSRP

Where:

  • RSRP is the received power of 1 RE (3GPP definition) average of power levels received across all Reference Signal symbols within the considered measurement frequency bandwidth
  • RSSI is measured over the entire bandwidth
  • N, number of RBs across the RSSI, is measured and depends on the BW

Based on the above, under full load and high SNR:

RSRP (dBm) = RSSI (dBm) – 10*log (12*N)

 

Scaling Table

RSRQ 3GPP Definition

Reference Signal Received Quality (RSRQ) is defined as the ratio N×RSRP/(E-UTRA carrier RSSI), where N is the number of RB’s of the E-UTRA carrier RSSI measurement bandwidth. The measurements in the numerator and denominator shall be made over the same set of resource blocks.

In formula:

Scaling Table

Where:

  • N is the number of Physical Resource Blocks (PRBs) over which the RSSI RSRQ reporting rangeis measured, typically equal to system bandwidth
  • RSSI is pure wide band power measurement, including intracell power, interference and noise (noise + serving cell power + interference power during RS symbol)
  • The reporting range of RSRQ is defined from -3…-19.5dB

So we have that RSRQ depends on serving cell power and the number of Tx antennas

E-UTRA – RSSI (Carrier Received Signal Strength Indicator), comprises the linear average of the total received power (in [W]) observed only in OFDM symbols containing reference symbols for antenna port, in the measurement bandwidth, over N number of resource blocks by the UE from all sources, including co-channel serving and non-serving cells, adjacent channel interference, thermal noise etc.

The reference point for the RSRQ shall be the antenna connector of the UE. If receiver diversity is in use by the UE, the reported value shall not be lower than the corresponding RSRQ of any of the individual diversity branches.

  • Applicable for: RRC_CONNECTED intra-frequency, RRC_CONNECTED inter-frequency

e.g. – Impact of serving cell power to RSRQ:

Example for noise limited case (no interference): If all resource elements are active and are transmitted with equal power, then

  • RSRQ = N / 12N = -10.8 dB for 1Tx
  • RSRQ = N / 20N = -13 dB for 2Tx taking DTX into account

(because RSRP is measured over 1 resource element and RSSI per resource block is measured over 12 resource elements).

Remember that RSSI is only measured at those symbol times during which RS REs are transmitted – We do not have to take into the count DTx!!!

So, when there is no traffic, and assuming only the reference symbols are transmitted (there are 2 of them within the same symbol of a resource block) from a single Tx antenna then the RSSI is generated by only the 2 reference symbols so the result becomes

  • RSRQ = N / 2N = -3 dB for 1Tx
  • RSRQ = -6dB for 2Tx

SINR Definition

SINR is the reference value used in the system simulation and can be defined:

  1. Wide band SINR
  2. SINR for a specific sub-carriers (or for a specific resource elements)

SINR Total DefinitionAll measured over the same bandwidth!

SNR vs. RSRP

RSRP is measured for a single subcarrier, noisepower for 15KHz= -125.2dBm SNR to RSRP

  1. Noise figure = 7 dB
  2. Temperature = 290 K

Assumption: RSRP doesn’t contain noise power

SINR Limit

Update May 2016

Power Calculation Example

Lets try to calculate RSRP, RSSI and RSRQ for one very simple case of one resource block with 12 sub carriers and 0.5 ms in time domain. Let’s assume the power of reference symbols (shown by red square) and power of other symbols carrying other data channels (shown by blue square) is same i.e. 0.021 watt (take care anyway that also the Path Losses impacts on received power, not included in this RSRP calculation).

Since RSRP is linear average of downlink reference signal for given channel bandwidth therefore

RSRP = 10*log (0.021*1000) = 13.2 dBm

While RSSI is total received wide-band power. Therefore we have to add power of all 12 carriers in the given resource block

RSSI = 10*log(0.021*1000)+10*log(12) = 24 dBm

RSRQ is now simple ratio of RSRP to RSSI with N=1

RSRQ = 10*log(0.021/(12*0.021)) = -10.79 dB

Power Calculation Example

dBm vs dB

dB is ratio between two power values while dBm is used to express an absolute value of power. So when we mention RSRP and RSSI we shall always use dBm since we are talking about absolute power values but we need to use dB with RSRQ since it is the ratio of RSRP to RSSI

Join the discussion 48 Comments

  • […] You can find more info about RSRP and RSRQ in our HOT article: RSRP and RSRQ Measurement in LTE […]

  • Chaithanya says:

    Great Explanation !

    Suppose, RSRP and RSRQ values are same for two different signals at an instance. Then, Can I know, How it will be handled ?

     

    • Maurizio La Rocca says:

      Hi Chaithanya, what do you mean about how they will be handled? By mobile or by Network? To decide what?

      Please be more specifics.

  • Sohail Ahmad says:

    I want to convert this

    Signal strength:       1.7253e-10            into dBm

    can anyone know the formula to convert

  • J.Beretti says:

    How does RSRQ = 10*log(0.021/(12*0.021))   equals  -10.79 dB as 10 * log(1/12) = -24.8… ?

    • Maurizio La Rocca says:

      Hi John, please explain more. I didn’t get your point!

    • Basim says:

      Power calculation example.

      Please, can you update this example and mention that the Path Losses impacts on received one not included in this RSRP calculation.

      Regards.

      • Valerio Luciani Valerio Luciani says:

        Hi Basim,
        we have updated the article and now the fact that the path losses have not been taken into account is mentioned.
        Thank you for your useful observation!!

  • nouh says:

    Hi guys
    please i want to know if the SINR can be > 30 ? there’s a limite value for it ? what’s the MAX value for it?

    Thank you a lot

  • Oladele says:

    Hi, please i will need to know specifically the difference between RSRP, SINR, RSSI and the transmission power of a base station. I am working on increasing the coverage of picocell using cell range expansion which involves adding a positive bias value to RSRP (i.e RSRP + bias). I was heavily queried by my research group in a presentation that RSRP seen or measured by a user is just the same as the transmission power of the cell and therefore I have literally increased the transmission power which will ultimately increase interference to other cells and users. How do I explain this to my professors. I know for sure that (RSRP + bias) is not the same thing as increasing the transmission power. Thanks

    • Maurizio La Rocca says:

      Hello Oladele, your are asking about a Coverage Optimization based on RSRP.
      First of all let’s precise that RSRP received by UE is the transmitted RSRP – Path Loss.
      Furthermore, I confirm you that RSRP+bias is not the same thing as increasing the transmission power but I would like you will be more precise about RSRP+bias…
      Could you explain more about it? What do you exactly do? Do you have a block diagram of it?

  • hacper says:

    In order to constant power consumption in eNB, shall eNB transmit RE with power P per antenna port in the case of 1 antenna port and transmit RE with power P/2 per antenna port in the case of 2 antenna ports?
    If so, the following equation is not true: “RSRQ = N / 20N = -13 dB for 2Tx taking DTX into account”

    • Michele Roselli says:

      Hi hacper, the answer to your first question is yes. Anyway, the equation “RSRQ = N / 20N = -13 dB” is still valid because P/2 is a common factor in both numerator and denominator, then you simplify the equation.

  • Joe says:

    Hi, a practical question: can you explain why the RSRQ of the UE has a different value of e.g. -6dB with no traffic and -10dB with traffic?

    • Michele Roselli says:

      Hello Joe, -10.8 dB corresponds to the case 1 with TX and with Traffic (all active RE with equal power), and therefore the formula is RSRQ = N / 12N.
      If you want to switch to case with no-traffic & 2 TX with DTX, the number of active RE becomes 4 (#RE with RS) instead of 12 and, therefore, RSRQ = N / 4N = -6 dB.

      I hope that now all is clear. 🙂

  • Luis Augusto says:

    Hi, thanks for your explanation. It was really very useful.
    But I still have a question.
    I am modeling in MATLAB a scenario (1Km x 1Km) with 2 macrocells, 200 femtocells and 50 random users.
    I am using Euclidean distance to get the values of measurements.
    I have already obtained the values of RSRP but I am having difficulties to calculate the RSSI and consequently the RSRQ (since this depends on that).
    Well, I understood that to get the RSSI I should consider:

    RSSI = wideband power = noise + serving cell power + interference power

    My question is:
    How do I get the values for “interference power?
    What should I consider to calculate the interference?
    Thanks in advance for any help.

    • Maurizio La Rocca says:

      Hi Luis, my personal suggestion is to have a different approach to perform your simulation.
      You could use the table of RSRQ measured by a mobile phone and use all values in a parametric view.
      What do you think? could this work in your case?
      Otherwise you should consider many other variables… e.g. you should consider also the RB used…

  • Ali Raza says:

    Hi Maurizio,

    How we can calculate the RSRQ for 4*2 MIMO?

    Regards
    Ali Raza

  • waseem uddin says:

    what is the threshold value for RSRP /RSRQ to keep the call alive without any HO message. Do we have any table for their combination please

  • Ahmed says:

    hi Maurizio, thanks for your explanation

    i have a question, what’s the difference between RxLev and RSRP

    • Maurizio La Rocca says:

      Hi Ahmed, we’re glad that you liked it!
      The difference between the two radio parameters is that RxLev refers to GSM technology while RSRP to LTE (as the RSCP refers to UMTS):

      • RSRP is the average power of RE that carry cell specific RS over the entire bandwidth, so RSRP is only measured in the symbols carrying RS
      • RxLev is evalueted by measuring the received level of the BCCH (Broadcast Control Channel) carrier which is continuously transmitted by the BS on all time slot of the B frames and without variations of the RF level. A MS measures the received signal level from the serving cell and from the BSs in all adjacent cells by tuning and listening to their BCCH carriers. The root mean square level of the received signal is measured over a dinamic range from -103 to -41 dBm for intervals of one SACCH (Slow Associated Control Channel) multiframe (480 ms). The received signal level is averaged over at least 32 SACCH frames (about 15 s) and mapped to give RxLev values between 0 and 63 to cover the range from -103 to -41 dBm in steps of 1 dB. The RxLev parameters are then coded into 6-bit words for transmission to the serving BS via the SACCH.
      • RSCP (Received Signal Code Power) is the received power on one code measured on the pilot bits of the P-CPICH (Primary Common Pilot Channel). See also https://www.laroccasolutions.com/141-rscp-rssi/

      Thanks and Share it!!!

  • Sohel says:

    HI Maurizo,

    Can you please tell me what is the value of good LTE signal RSRP and what is the value for Bad LTE signal RSRP in db .

  • Dziugas says:

    Hello. Thank you for the article, much useful information.

    I am working on a sort of a manual for mobile signal strength recommendations for my company. I was wondering, could I use some information from your article or would that be a copyright issue?

    • Valerio Luciani Valerio Luciani says:

      Hi Dziugas, no problem!! Of course, we expect to have a reference to our website and see the final work! Could you be interested to publish as well into our website? Thank you!!

  • Ravi says:

    Can you please clarify one doubt: Why is the range of rsrp increased in later releases of lte from its prior releases, like what is causing this change. In release 14, rsrp range -156 to -44 whereas in release 10 its range is -140 to -44.

    • Valerio Luciani Valerio Luciani says:

      LTE later releases introduce support for intra-frequency RSRP measurements and complete mobility support in connected mode in the form of intrafrequency RSRQ measurements.
      These improvements are welcome for the more mobile and real-time use cases for LTE-M devices, such as wearables and VoLTE [1].

      [1] O. Liberg, M. Sundberg, E. Wang, J. Bergman, J. Sachs – Cellular Internet of Things: Technologies, Standards, and Performance

  • wileyson says:

    Hi there, here r some figures, i want to know whether its good signal quality or bad, kindly guide me
    the router is Huawei B310s-927 lte. and 4g is Band 3 (1800z Mhz)
    PCI: 306
    RSRQ: -10dB
    RSRP: -88dB
    RSSI: -61dB
    SINR: 4db
    regards.

    • Francesco Cassenti Francesco Cassenti says:

      Hi,
      I know very well this device!! I examined your parameters and I find that the signal is quite good!!

  • Eziwan Ahmad says:

    Hi Sir, if want to calculate RSRP for each antenna for IBC system, can I apply the above formula? what is good value of RSRP at underneath indoor antenna?

    • Eziwan Ahmad says:

      Can I assume all EiRP for each indoor antenna as Resource Element power? Is it true all RE power is 0.021 Watts?

      • Francesco Cassenti Francesco Cassenti says:

        During a time slot, each antenna transmits on more subcarriers (e.g. more Resource Elements). This means that for every RE you have only a portion of the total available power (EIRP) of an antenna.
        Furthemore, the RE power of 0.021 W is only an hypothesis taken into account in this example. In general, this is not always true.
        I hope I was helpful!!

    • Valerio Luciani Valerio Luciani says:

      Hi Eziwan,
      this formula can be applied in every environment, included IBC systems.
      A good value of RSRP close to an LTE cell site would be about -75 dBm, as you can find in the 3GPP TS 36.211 recommendation.

  • Nasir says:

    Is there any video lecture for the above topics?

    • Francesco Cassenti Francesco Cassenti says:

      Hi Nasir,
      Apart from free videos that you can find on the web, we do not have other video lectures to suggest.

  • jeremi says:

    Hello,
    Are RSRP and RSRQ implicated in coverage in LTE ?
    Let me explain, we are in TDD network in 20meg bandwith and where we have fixed power from antenna 8T8R=> 8*16watt.

    We have done coverage exercice and decided that we need 50 enodebs for example to cover a site, knowing that we are in 20Mega bandwith.
    Once we want to go to 40mega bandwith, knowing that power is fixed always 8*16watt.
    We discover that we will lose coverage, we increase bandwith and we lose coverage, how this is possible ?
    Is it related somehow to formula: RSRP=RSSI-10log(12N) ? or may be it something else ? thanks for your help

    • Francesco Cassenti Francesco Cassenti says:

      Hi Jeremi,
      For fixed antenna power, improving the bandwidth results in spreading this power on more resource blocks transmitted at the same time. The formula RSRP=RSSI-10log(12N) takes into account this fact with the N factor.

  • Terry Martin says:

    So which parameters and assumptions in RSRP would vary with altitude, and what impact would it have on handover performance.

    • Valerio Luciani Valerio Luciani says:

      Signal strengths are generally stronger for UEs at any altitude than for ground UEs because the free space propagation conditions at altitude compensate for antenna gain reductions.
      Handover performance (success rate of handovers, and lower frequency of handover events) is superior for UEs at any altitude than for ground UEs. This is attributed to the increased stability of signals with free space propagation relative to those subjected to the multipath, shadowing, and clutter experienced on the ground. [1]

      Reference:
      [1] “LTE Unmanned Aircraft System Trial Report Phase 1” – Qualcomm

  • Fernando says:

    Hi,

    Thanks a lot for the tutorial! I have learnt a lot but I have a very fundamental question.
    In 3GPP standard, I have found that the maximum transmit power is 23 dBm. But is there any constraint on how this power is divided across the PRBs in time and frequency? For example, are these cases correct?

    Case 1: For a transmit power of 23 dBm spread over 10 PRBs in 1ms (5 PRBs per slot). Then, each PRBs is allocated 2.3 dBm of power?

    Case 2: For a transmit power of 23 dBm spread over 10 PRBs in 0.5 ms (1 slot). Then, each PRBs is allocated 2.3 dBm of power?

    Case 3: For a transmit power of 23 dBm spread over 10 PRBs in a 5 ms (5 subframes). Then, each PRBs is allocated 2.3 dBm of power?

    Are all these cases correct??

    • Valerio Luciani Valerio Luciani says:

      Hi Fernando,
      The only constraint for transmitted power is derived from the constraint on the number of used RB (that is the constraint on the available bandwidths of 1.4, 3, 5, 10, 15 and 20 MHz); the spread of this transmitted power can be uniform or arbitrary and it can go from a total of -40 dBm to 23 dBm.

  • MAIDUL says:

    why it is called referance RSRP or RSRQ

    • Press Office Press Office says:

      Hi Maidul,
      the “reference” term points out the fact that, when measuring these two parameters, only the resource elements that carry Reference Signals (RS) are considered.
      RS to be used must comply with [TS 36.211] and their mapping follows a specific pattern, in order to make channel estimation.

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