the received waveform is already in pulse

1.  As you may recall, in BB signaling, the received waveform is already in pulselike form.  Why then, is a demodulator needed to recover the pulse waveform?
2. Why is Eb/N0 is a natural figure of Merit for digital communication systems?  How is it different for an analog system?
3. In cable TV, modulation scheme of 256 QAM is commonly used.  Although this modulation scheme was in the 3GPP2 4G standard proposal, it was not implemented in LTE (4G) and instead the max modulation scheme was selected to be 64QAM.  Discuss the merits of the decision and explain why for a cable TV this is a common practice but for a wireless communication system it is a rarity.

Part 2

1. There are different source coding schemes in 3GPP (GSM, WCDMA, LTE) and 3GPP2 (CDMA. EVDO) systems. Discuss the issues with Having different source coding schemes and their impact on inter technology communication systems (GSM phone calling a CDMA phone)
2. Source coding reduces the BW requirements in a communication system.  Do you think it would be possible in a phone call, to convert a person’s voice into text, transmit the text and then have the receiver to convert the text to the person’s voice?  What are the challenges?  What about the time delay?  What is the potential BW savings?

Part 3

1.  As you may recall, in BB signaling, the received waveform is already in pulse like form.  Why then, is a demodulator needed to recover the pulse waveform?
2. Why is Eb/N0 is a natural figure of Merit for digital communication systems?  How is it different for an analog system?
3. In cable TV, modulation scheme of 256 QAM is commonly used.  Although this modulation scheme was in the 3GPP2 4G standard proposal, it was not implemented in LTE (4G) and instead the max modulation scheme was selected to be 64QAM.  Discuss the merits of the decision and explain why for a cable TV this is a common practice but for a wireless communication system it is a rarity.

Part 4

1.  Why do binary phase shift keyig (BPSK) and quaternary phase shift keying (QPSK) maintain the same bit error probability relationship?
2. In general digital modulation schemes fall into one of two classes, orthogonal signaling and phase/amplitude ignaling.What are the  advantages and disadvantages of each class?
3. Do a research on LTE and provide the modulation schemes used.  Argue why such modulation schemes were selected?
4. Discuss how enhancement in DSP and processing speed would impact future communication trends.

Part 5

1. Error correcting codes are very common in almost all types communication systems.  Discuss if it is always advantageous to do channel coding? Can you think of an example or conditions where you may not want to do coding?
2. In one of NASA’s space missions the high gain antenna did not deploy and the fear was that all the information collected by the satellite would be lost.  One of the engineers suggested to route the data to low gain antenna that was used for telemetry.  Discuss if this suggestion would work and its impact on the data rate, data recovery time and any other aspects of the communication system.
3. In real-time communication systems, added redundancy means faster signaling, less energy per channel symbol, and more errors out of the demodulator.  In the face of such degradation, explain how the coding gain is achieved.

Part 6

1. The travelling salesman problem (TSP)  is a classical problem that had been unsolved for centuries.  Would one be able to apply Viterbi decoding algorithm to solve this problem?  Do an internet search to find out if the problem had been solved?
2. Cyclic codes are primarily used for error detection in most communication system.  Can these codes be used for error correction?  If yes, why we prefer convolutional codes over them for error recovery?
3. Pseudo Random Noise (PN) codes are used in 2G and 3G systems for channelization and randomization of the data.  Describe how they are applied and the advantages of using them in spread spectrum technologies.

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