ts can be encoded into each symbol in the case of baseband sys- tems (a) and (b) in Problem 4.15? How much higher is the data rate in case (b) in Problem 4.15 because of the wider bandwidth and how much higher is the bit rate because of the improved S/N compared with the channel in case (a) of Problem 4.15? Problem 4.17 Estimate how many symbol values (signals in the constellation diagram) there should be in the case of a 28.8-Kbps modem using QAM if the symbol rate is 3,200 bauds. Problem 4.18 Why do we perform line encoding before data are transmitted to the trans- mission channel? Introduction to Telecommunications Network Engineering Problem 4.19 Explain how binary values 1 and 0 are represented in the following codes: (a) NRZ, (b) RZ, (c) AMI, and (d) Manchester. Problem 4.20 Explain the operating principle of a regenerator (regenerative repeater). Problem 4.21 What are the main two multiplexing methods and how do they operate? Problem 4.22 Explain the structure of a 2-Mbps PCM frame. Problem 4.23 Explain the structure of a 1.5-Mbps PCM frame. Problem 4.24 Explain what is PDH? Problem 4.25 What is SDH and what advantages does it provide over PDH? Problem 4.26 The measured attenuation at 1 MHz of a 1-km copper cable pair is 18 dB. What is the approximate attenuation at (a) 250 kHz, (b) 500 kHz, (c) 2 MHz, and (d) 4 MHz? Problem 4.27 What are the advantages of (a) optical transmission, (b) microwave radio transmission, and (c) satellite transmission? Compare their characteristics. Problem 4.28 What do we mean by dispersion in optical fibers? Problem 4.29 What do we mean by dense wavelength-division multiplexing? Transmission Problem 4.30 Calculate the one-way delay and two-way delays of a transmitted signal from one Earth station to another Earth station via geostationary satellite. The dis- tance between a satellite and each Earth station is assumed to be 40,000 km. Problem 4.31 STM-1 contains 63 primary 2-Mbps data streams and each of them contains 30 time slots for speech. (a) How many simultaneous calls (6