3) a) 64 QAM modulation if there are 4 symbols S=[-1-3j,7-7j,-3+5j,5+1j] what is

Question

3) a) 64 QAM modulation if there are 4 symbols S=[-1-3j,7-7j,-3+5j,5+1j] what is original bit stream it tries to deliver? If the I channel and Q channel swaps at the receiever due to malfucnction. What is the bit stream demodulated at receiever> If a malfunction occurs what operation can be applied to recover the original demodulated one?

b)for 64QAM mod, calculate the probabilities of inner symbols, edge symbols and corner symbols drifitng to neighboring ones when nosie power is sigma equals -10dB.

c)Use first symbol as an examplel explain why Gray code is used?

d) For 4/16/64QAM schemes, when SNR=18 (liner value) calculate corresponding BERs and explain the advantage and disadvantage of adopting 64QAM? do all BER-SNR curves merg together when nosie goes infinite or zero?

alelity-le-mdrukoed iry [where·kile-lasarelerv e ter win Chanler torveher elseZi gaiks-gimm infitete 4e trtist what at? The til-run by arek yvear ainwrs to 1-2 se.teryees )

Explanation / Answer

QAM, Quadrature amplitude modulation is widely used in many digital data radio communications and data communications applications. A variety of forms of QAM are available and some of the more common forms include 16 QAM, 32 QAM, 64 QAM, 128 QAM, and 256 QAM. Here the figures refer to the number of points on the constellation, i.e. the number of distinct states that can exist.

The various flavours of QAM may be used when data-rates beyond those offered by 8-PSK are required by a radio communications system. This is because QAM achieves a greater distance between adjacent points in the I-Q plane by distributing the points more evenly. And in this way the points on the constellation are more distinct and data errors are reduced. While it is possible to transmit more bits per symbol, if the energy of the constellation is to remain the same, the points on the constellation must be closer together and the transmission becomes more susceptible to noise. This results in a higher bit error rate than for the lower order QAM variants. In this way there is a balance between obtaining the higher data rates and maintaining an acceptable bit error rate for any radio communications syste

Related Questions

Navigate

• Browse (All)
• Browse 3
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.