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The Parameters of Signal Quality of LTE

The modems have LTE parameters LTE connection. To determine the quality of the signal, note the following fields:
— Signal strength
The following table shows the different values of these parameters,

which correspond to very poor (Cell Edge), 
bad (Mid Cell), 
good (good) and 
very good (Excellent) the signal quality of the LTE:

Next, briefly explain each parameter, which determines the quality of the LTE signal.

 The power of the signal

The signal power shows the level of the received modem signal LTE. 
These values correspond to the readings of RSSI (Received Signal Strength Indication) of the LTE connection. 
The value is measured in dBm (dBm).
Usually routers have indicators if it means burning the maximum -90 dBm or higher (tends to zero). 
If any indicator is not lit, then the signal level is insufficient for the connection to the LTE network.
 When the values of RSRP= -120 dBm and below, the LTE connection may be unstable or not installed.


RSRP (Reference Signal Received Power) is the average value of the power taken by the pilot signal (Reference Signal) or the level of the received signal from the Base Station(BS) 
The RSRP value is measured in dBm (dBm). 
The signal strength of the LTE modem can also be defined using the SIGNAL STRENGTH indicators on the top panel of the device. 
The maximum level correspond to three burning indicator. 
If any indicator is not lit, then the signal level is insufficient for the connection to the LTE network. 
When the values of RSRP= -120 dBm and below, the LTE connection may be unstable or not installed.


RSRQ (Reference Signal Received Quality) determines the quality of received pilot signals. 
The value of RSRQ is measured in dB (dB).


SINR (Signal to Interference + Noise Ratio), also known as CINR (Carrier to Interference + Noise Ratio) – the ratio of the level of useful signal to noise level (or signal/noise). 
The value of SINR is measured in dB (dB). It's simple: the higher the value, the better the signal quality. 
When the values of SINR below 0, the connection speed will be very low, because this means that the received signal noise more than the useful part, while the probability of loss of the LTE connection also exists.


CQI (Channel Quality Indicator)
For each subscriber station UE (User Equipment) and each frequency carrier block formed quality indicators channel CQI (Channel Quality Indicator). 
Depending on the required for UE speed data transmission the base station, the decision on the number of resource blocks allocated to a particular user, and what frequency blocks to allocate to the user depends on the indicator CQI. 
Users are allocated to those resource blocks that have the highest CQI, and therefore, the best ratio signal/noise. 
This parameter can take values from 0 to 15. 
The higher the value, the better (the higher the speed that can be allocated by the base station operator LTE).



The most important first column — the value of RSRP. 
For example, we got to the target BS, the average is about -90 dBi. 
When determining the direction on the BS used a Yagi antenna with gain (KU) 12 dBi. 
Antenna cable, length 5 m "eats" on the attenuation of about 1.5 dBi, add about the same number of losses at the connectors — a total of 3 dBi. 
Accordingly, the default level of the signal at this location:

-90 - 12 + 2x1. 5 = -99 dBi.

As a result of the installation of the new antenna, we need guaranteed to get at least the second row of the table, in the interval from -90 to -80. 
Ideally, more than -80, the first line. 
If we keep the same cable, you need a antenna with KU at least 18dBi, better 20dBi (don't forget about the weather and the natural "swimming" signal). 
The output will be if not the first row, then close to it: -99 + 20 — 2x1. 5 = -82 dBi. 
The result can be considered very good: provided that the indicators RSRQ and RSRP SINR vary in proportion to (and usually do), we "pull out" of the connectome at least 80% of what he can give.
 Assume that the maximum supported rate on the BS 30 Mbit/s. Received 30 * 0,8 = 24 Mbps.




We are interested in two parameters:

RSSI (Received Signal Strength Indication) level of the received modem signal. This is the main "honest" indicator of the level. Is measured on a logarithmic scale in dBm. Other parameters from tables such as RSCP, RSRQ, RSRP, CQI — are service. They usually correlate with RSSI, so they shouldn't be ignored.

The second, not less important parameter, especially in dense areas – the ratio signal/noise. Denoted for 3G: ECIO (Ec/Io) or Ec/No; 4G: SINR (Signal to Interference / Noise Ratio) or CINR (Carrier to Interference / Noise Ratio). Is measured on a logarithmic scale in dB.

Ec/Io is a measure of signal/noise, but very tricky. Compared to conventional SINR indicator (which is used in LTE) of Ec/Io deducted natural noise. Indicator Ec/Io = 0 dB is the level when in addition to natural thermal noise nothing. Any interference of artificial origin reduce Ec/Io. (from their own neighboring BS in the first place, this effect operators is called "cell respiration" - on the border between the cells preventing the signal level from another cell of the same operator becomes significant, and in spite of a strong total signal prevent set high speed) 

As Ec/Io, Eb/No, SINR, and so this is all adaptive indicators. Because the link can't work with poor Ec/Io (Eb/No), then the weak signal to improve Ec/Io of BS and the subscriber agree to lower the bandwidth: used less than RB (resource blocks) and a lower modulation scheme (QAM64 - QAM16 - QAM8 - QPSK - BPSK)

Therefore, by itself, the Ec/Io does not show good signal or bad (in pulsometro this figure is NOT used). It shows the contribution of artificial noise (reflection, alien sector, industrial noise)

Need to watch it paired with RSCP. RCSP of these 3 the most objective indicator is the amount of energy per 1 resource block (in LTE) or channel (in 3G) is the Received Signal Code Power (RSCP). RSCP that is used to parcometre. Also it is based on the RSCP telephone/modem decides which of the cells to connect.




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I am not sure where you’re getting your information, but great topic. I needs to spend some time learning much more or understanding more.
Thanks for great info I was looking for this information for my mission.

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