QAM and Modulation

Abbreviations Galore and Column Legend
MCS - Modulation and Coding Scheme
QAM - Quadrature Amplitude Modulation
BPSK - Binary Phase Shift Keying
GI - Guard Interval 
HT - High Throughput
VHT - Very HT
RSSI - Received Signal Strength Indicator

BPSK – Change the Phase by 180 degrees
1 becomes 0

2 Bit Modulation Symbol – QPSK – Change the Phase by 90 degrees

00 becomes 01 or 11 or 10

16 QAM  using 4 zeros

16 QAM constellation diagram

25% amplitude , 225 degree phase – 1100
75% amplitude,  135 degree phase – 1001

We have to use MCS Index in order to correlate the different modulation schemes, techniques and bandwidth.

MCS INDEX

Spatial Streams – More SS More Throughput, theoretically 8 possible but currently on 4 supported.
Modulation – BPSK, QAM, 16 to 256 bit
Coding Rate : 5/6 – 83.3% data stream used to deliver data
Channel Bandwidth – 20MHz – 160Mhz (Most product support upto 80MHz)
Guard Intervals – 400/800 – Longer guard index will give more reliable wireless.

 

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