数据通信练习题1答案(外教).doc

ECTE 364 Tutorial 1 Exercises1. Assume a data stream is made of the binary sequence 0001100111. Draw the digital signals that result from using the following encoding schemes. Unipolar using positive voltages for 1s NRZ-L NRZ-I RZ Manchester Differential ManchesterAnswer:2. What is the data stream does the following digital signal represent assuming Manchester encoding, assuming negative-to-positive transitions represent 1?TimeAnswer : 111011103. Repeat question 2 assuming differential Manchester encoding, where transitions mean 0s.Answer: 100110014. Illustrate ASK encoding for the sequence 1011 using a sine wave and two amplitudes where 10 volts represents 1s and 5 volts represents 0s and using 3 cycles per bit interval.Answer5. Illustrate FSK encoding for the sequence 1011 using a sine wave and two frequencies where 0s are represented by a frequency that is approximately twice the frequency used to represent 1s. Assume also that 1s are represented by 3 cycles per bit interval.6. Illustrate PSK encoding for the sequence 1011 using a sine wave and phases where a phase of 0 degrees represents 1s and a phase of 180 degrees represents 0s and using 3 cycles per bit interval.7. Show how Phase Shift Keying (PSK) can be used to encode 2 bits per symbol.Answer:1110Phase reference signal0100SignalBitsAcos(2fct+45o)11Acos(2fct+135o)10Acos(2fct+225o)00Acos(2fct+315o)01Note, the magnitude of each arrow or vector is equal to A. It is possible to use other phase angles, e.g.,