modulation and coding scheme (MCS)

The Modulation and Coding Scheme (MCS) is an indexing used in WLANs, in Enhanced Data Service for GSM Evolution( EDGE) and in Enhanced General Packet Radio Service( EGPRS) to determine the data rate.

1. In WLANs according to 802.11, the Modulation and Coding Scheme is a digit that describes the modulation and the forward error correction used in WLANs according to 802.11ac. In WLANs there are ten MCS indices with the designations MCS-0 to MCS-9, in which the different modulation schemesBPSK, QPSK and the quadrature amplitude modulation( QAM) with 16 and 64 bits (16QAM, 64QAM, 256QAM) and the code rates (R) of 1/2, 3/4, 2/3 and 5/6 are distinguished.
   

   MCS values for IEEE 802.11ac

   Furthermore, the channel width, the number of spatial streams( SS) for MIMO and the width of the guard intervals ( GI) are included in the data rate for 802.11ac. Depending on the channel width of 20 MHz, 40 MHz, 80 MHz and 160 MHz, for example, a channel width of 20 MHz results in a data rate of 6.5 Mbit/s (20 MHz, BPSK, R=1/2, GI = 800 ns) for MCS-0, and a channel width of 40 MHz results in a data rate of 13.5 Mbit/s.
2. In Enhanced Data Service for GSM Evolution (EDGE), the Modulation and Coding Scheme (MCS) determines how many bits per second are transmitted in a time slot. Which of the nine possible MCS variants can be used depends not least on the quality of the radio link. The Modulation and Coding Schemes (MCS) are designated MCS-1 to MCS-9 and distinguish between the GMSK and phase- shift keying (PSK8) modulation schemes with eight states. MCS-1 has the lowest data rate with 8.8 kbit/w/slot for GMSK modulation and MCS-9 the highest with 59.2 kbit/s and per slot. This means a data rate of 430 kbit/s for the eight channels together. If the quality of the radio link deteriorates, then the base station can switch back to a lower MSC variant.