Homework And Assignment Help

Get help for University-of-Maryland-University-College TLMN 645 Homework Help. Post your answers or comments on other students answers here. For your answer post a new Thread. 1- Modulation turns bits into waveforms or signals. Compare the power efficiency and spectrum efficiency of some of the various PSK and FSK modulation schemes. Use some numbers (ie, for bandwidth efficiency the number that represents bits/sec/Hz, for power efficiency the Eb/Nsub0 at some value of BER for the various modulations). 0) 1 bps/Hz whereas QPSK provides 2 bps/Hz, why? 2- AMPS cellular channels work over 30 KHz bandwidths, and work at SNR’s of 18 dB. What is the maximum capacity possible, according to Shannon? Those channels have typically not been used for data, but only voice. Still, some use of those channels for data (like signaling) have typically only provided at most ten to twenty kilobits per second. Speculate (or explain) why that is so much lower than the Shannon capacity?

Note: this question requires you to figure out the Shannon capacity fo a certain channel, given by its bandwidth and the SNR it is working at. It involves plugging some numbers into a simple equation (Shannon’s), but with logarithms. For those of you too far away from any math use or course the logarithms can be a little daunting. B’s are in Stallings in App. I will not grade you on the numerical computation answers in the Conference, just give it a try. Then try to explain why AMPS always does less. If you can compute the Shannon capacity of a channel you can take credit for this course forever. And it’s so easy. 3- Compare BPSK to QPSK, and 8-PSK to QPSK. 5- 64 QAM has a higher BER at given values of Eb/Nsub0 than 16 QAM. And explain which has a higher spectral efficiency. 6- GMSK is a modulation used in GSM. 7. Explain how OFDM is different than FDMA, and why that is useful? Please post answers and comment on the instructor’s questions here. Post the answer to this question and show your work.

It’s numerical but I want to have you show how you get to the answer from the stuff in the lecture notes or textbooks. Do not use an online calculator to do it. Do not just provide an answer without showing how. Do not copy and paste anything, this needs to be your own work and words. 2 calls/hour with 3 minutes call duration for each per user (on the average), how many users can be supported with 10 available channels, given a blocking probability of 0.5%? The first cellular systems were introduced in the early 1980’s. Why architect the systems as cells, rather than a single central tower for the whole city, like big TV or radio broadcast stations? Traffic channels in AMPS take up 30 KHz bandwidth. US TDMA (also called IS-136) which is a TDMA technology inserts 6 time slots in a frame within that bandwidth. How much bandwidth does one slot take up and why?

This is an example of a short answer required. Note the question is about bandwidth, not data rates. Cellular architectures including 3G are circuit switched, with packet switching being provided in 2.5G/3G on top of the circuit switched channels. Some control channels, the ones from the phone to the basestation, are packet switched (and random access). In 3G, some circuit switched channels used for data and Internet access are combined and then used in a packet switched way. WLAN’s on the other hand are all packet switched. Discuss why this has evolved this way. Be short and to the point as much as possible. What is more important in wireless cellular services, power or bandwidth efficiency, and why? What about for mobile communication services offering both voice and high speed data? Also here, please be short and to the point. Describe briefly what are the traffic and the control channels in a cellular system, and what’s important about each?