1. (20 points) Supply the missing information in each statement. (1) Twelve sequ

Question

1. (20 points) Supply the missing information in each statement. (1) Twelve sequential data of 256-byte blocks is transmitted. Average number of errors received in this transmission is 2. The system BER is (2) The process of emphasizing lower-level signals and de-emphasizing higher-level signals is called (3) In TDM, multiple signals share a channel by transmitting in differert (4) The multiple signals in an FDM system are used to modulate separate (5) The magnitude of a quantization interval is also called the (6) The minimum sampling rate for a signal with a 4-kHz bandwidth is_kHz. (7) The even parity bit for the ASCII character A (1000001) is (8) When multiplexing is used to transmit information, thena must be used at the receiving end of the communications link. modulating wave shifts the output between two predetermined frequencies bits that indicate the beginning and ending of the word. is a form of data transmission in which the (10) In asynchronous transmission each data word is accompanied by

Explanation / Answer

1). Bit Error Rate (BER) = No. of Errors / total bits transmitted = 2/ (256 x8) = 0.000977, BER is a unitless quantity so we can express this in percentage as well i.e, 0.0977%

2). Companding. It is an amalgamation of the two processes expansion and contraction of signals, which is done to reduce/remove the quantization error from the sampled signal.  

3). Time slots. TDM stands for Time Divison Multiplexing which is a scheme that allocates the full channel bandwidth to multiple users in several different time slots.

4). Carrier Signals. Which are generated by the oscillator at the source end.

5). Step Size or Quantum

6). The minimum sampling rate is governed by the Nyquist criterion according to which sampling rate should be at least 2fmax, or twice the highest frequency component present in the analog signal to be sampled.

So, the minimum sampling rate = 2x 4Khz = 8Khz.

7). ASCII Characters are 7-bit codes. For the given character 'A' i.e, 1000001 we have total two 1's, that makes the total no. of ones present to be even. And, to indicate that as a even parity we add a 1 at the prefix of the given character. So, here the even parity bit would be 1. If the total no of ones present would have been odd then we have added a '0' for even parity bit.

8). Demultiplexer. It receives the output signals of a multiplexer and converts them back to original form of data at the receiving end.

9). Frequency Shift Keying (FSK), And, the phase of the output signal observes no change.

10). Start and Stop bits. This is done so as to be able to synchronize the data characters being transmitted. This also helps in error control of data bits that were incorrectly sent.

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