Applicable Versions | NetSim Standard | NetSim 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