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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