Considerando o protocolo 802.11n qual o valor da modulação ...

Redes Wi-Fi: O Padrão IEEE 802.11n

Estes objetivos exigiram alterações significativas nas 2 camadas de rede (PHY e MAC), permitindo a este padrão chegar até os 600 Mbps, quando operando com 4 antenas no transmissor e no receptor, e utilizando a modulação 64-QAM (Quadrature Amplitude Modulation).

http://www.teleco.com.br/tutoriais/tutorialwifiiee/pagina_4.asp

Conforme a tabela "MCS Coding Rates" [1]:

Modulation and Coding Scheme | Spatial Streams | Modulation Type | Coding Rate

MCS 15 | 2 | 64-QAM | 5/6

[1] https://community.cambiumnetworks.com/t5/ePMP-Configuration-Management/Understanding-MCS-Values/td-p/76621

d-

In the 802.11n protocol, MCS (Modulation and Coding Scheme) 15 uses 64-QAM (Quadrature Amplitude Modulation) modulation. This modulation scheme allows for higher data rates compared to lower MCS values which use simpler modulation schemes like BPSK (Binary Phase Shift Keying) or QPSK (Quadrature Phase Shift Keying).

Lembrando que o padrão wireless 802.11n utiliza a tecnologia MIMO − Multiple-Input and Multiple-Output, incorporada no Mobile Broadband Standard.

Multiple-Input Multiple-Output (MIMO) is a wireless technology that uses multiple transmitters and receivers to transfer more data at the same time. All wireless products with 802.11n support MIMO. The technology helps allow 802.11n to reach higher speeds than products without 802.11n.

https://en.wikipedia.org/wiki/IEEE_802.11n-2009

No padrão IEEE 802.11n, a largura de canal pode ser de 20 MHz ou de 40 MHz.