Applicable VersionsNetSim StandardNetSim Pro


Applicable Releases
v13.3
v14.0


In NetSim 5G, the sender adapts the MCS based on the received SINR. It is assumed that the sender knows the received SINR accurately and instantaneously; this dynamic adjustment is often referred to as inner loop link adaptation


From SINR, NetSim computes Eb/N0 by converting the logarithmic decibel scale SINR to a linear power scale and then normalizing it. Then NetSim calculates spectral efficiency, SE as 


SE = alpha*log2(1 + Eb/N0)


where alpha is the Shannon attenuation factor and is a user input.


Once the SE is obtained the 3GPP standards spectral efficiency table is looked up to get the MCS.  These are the tables defined in 5.2.1.1. And then based on MCS, the number of information bits is got from the Transport Block Size Determination calculations in standard 38.214 - 5.1.3.2. 


Note that the above explanation is for the case when the BLER is set to 0. Users can also set a target BLER (e.g..: 0.1 or 10%) , in which case the MCS selection would depend on additionally on the outer loop link adaptation (OLLA) algorithm, which is explained in the documentation.


A example in NetSim v13.3 / v14.0


Users can see example "4.3. Effect of UE distance on throughput in FR1 and FR2" to get an idea of how MCS adapts to the received SINR.

 


FR1 - Variation of path loss, SNR, Efficiency, CQI, Modulation, code rates, and throughput as the distance of the UE from the gNB is increased:


Distance(m)

Pathloss (dB)

SINR (dB)

CQI Index

Modulation

Code Rate R*[1024]

(MCS)

Throughput (Mbps)

100

97.34

37.46

15

64QAM

772

507.58

200

109.05

25.74

15

64QAM

772

507.58

300

115.93

18.86

15

64QAM

772

507.58

400

120.80

13.98

15

64QAM

772

448.13

500

124.59

10.20

13

64QAM

567

289.32

600

127.68

7.11

11

16QAM

616

183.52

700

130.30

4.49

10

16QAM

490

129.69

800

132.56

2.22

8

QPSK

602

79.59

900

134.6

0.22

7

QPSK

449

51.36

1000

136.35

-1.55

6

QPSK

308

36.20


FR 2 - Variation of path loss, SNR, Efficiency, CQI, Modulation, code rates, and throughput as the distance of the UE from the gNB is increased:


Distance(m)

Pathloss (dB)

SNR (dB)

CQI Index

Modulation

Code Rate R*[1024]

(MCS)

Throughput (Mbps)

50

108.43

16.36

11

64QAM

873

2690.37

100

120.01

4.77

5

16QAM

490

1013.12

150

126.86

-2.06

2

QPSK

193

186.41

200

131.73

-6.94

1

QPSK

78

106.52


These are single cell scenarios with no interfering gNBs; hence the SINR is equal to SNR


Related Articles

1. Obtaining Radio measurements: how-can-i-log-snr-cqi-mcs-into-a-file-in-netsim-5g-lte-


Useful links

1. Overview of NetSim 5G library: https://tetcos.com/5g.html

2. NetSim 5G documentation (v14): https://tetcos.com/downloads/v14/5G-NR.pdf