802.11ac TECHNOLOGY INTRODUCTION

802.11ac Modulation Coding Scheme(MCS)
Data Field for Single User

Lisa Ward
March 2012

802.11ac will use the 802.11n modulation, interleaving and coding architecture. However, there are a few differences to the 11n specification. 11ac and 11n requires device support for BPSK, QPSK, 16QAM and 64QAM modulation, but 11ac adds an optional 256 QAM. The second difference is in the number of defined MCS Indices. 10 single user MCS are defined in 11ac as shown in Table 1. Note that this is significantly lower than the 77 MCS indices specified in 11n. 11n required 77 because 11n supported "unequal" modulations, e.g. a single user might get BPSK on one stream and 16QAM on another. (See tables 20-38 to 20-43 of [10]). For 11ac, the decision to onlyallowequal modulations makes sense because in practice no 11n devices supported unequal modulations and given the additional options in .11ac (e.g. 256QAM, 160MHz bandwidth), the number of possibilities would be impractical.

Table 1. 11ac SingleUser MCSIndices

Link : 802.11ac Technology Introduction File