In NetSim 5G, the sender adapts the MCS based on the received SINR. NetSim assumes 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 spectral efficiency table is referenced to determine the MCS, as defined in section 5.2.1.1. Based on the MCS, the number of information bits is calculated using the Transport Block Size Determination method from standard 38.214, section 5.1.3.2.
Note that this process assumes a BLER of 0. Users can also set a target BLER (e.g., 0.1 or 10%), in which case the MCS selection would additionally depend on the outer loop link adaptation (OLLA) algorithm, detailed in the documentation
A example in NetSim
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 | 134.60 | 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) | SINR (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.
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: See the NetSim 5G manual in https://tetcos.com/netsim-documentation.html