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I'm trying to understand QAM transmission and I'm struggling to understand this sentence, 'The advantage of using QAM is that it is a higher order form of modulation and as a result it is able to carry more bits of information per symbol. By selecting a higher order format of QAM, the data rate of a link can be increased. Article here'

Could someone explain what the term 'higher order form of modulation' means. Does it mean that the carrier frequency is higher?

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Higher order modulation means with each use of the channel, you transmit more bits. For example, in $8-$ary QAM, 3 bits are transmitted in each channel use. In other words, each 3 bits are mapped to one of the 8 available waveforms to be transmitted over the channel. If you use $16-$ary QAM, then 4 bits are transmitted with each channel use. In general, for $M-$ary QAM, $\log_2(M)$ bits are transmitted with channel use. The larger $M$, the more bits are transmitted per channel use. However, as $M$ increases, the distance between the constellation points decreases, and this means that the probability of error increases. So, there should be a trade-off between the constellation size, and the probability of error.

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