Difference between revisions of "Aufgaben:Exercise 1.1Z: ISDN Connection"
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| − | {{quiz-Header|Buchseite= | + | {{quiz-Header|Buchseite=Signal_Representation/Principles_of_communication}} |
[[File:EN_Sig_Z_1_1.png|right|frame|A telephone connection scenario]] | [[File:EN_Sig_Z_1_1.png|right|frame|A telephone connection scenario]] | ||
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<quiz display=simple> | <quiz display=simple> | ||
| − | {Which of the statements are true regarding source and | + | {Which of the statements are true regarding source and transmitter? |
|type="[]"} | |type="[]"} | ||
| − | + The | + | + The message source is the caller. The source signal ${q(t)}$ is the acoustic wave of her speech signal. |
| − | + The unit labelled "transmitter" contains, among other things, a signal converter and a modulator. | + | + The unit labelled "transmitter" contains, among other things, a signal converter and a modulator. |
- The transmitted signal $s(t)$ is analog. | - The transmitted signal $s(t)$ is analog. | ||
| − | {Which of the statements are true regarding | + | {Which of the statements are true regarding receiver and sink? |
|type="[]"} | |type="[]"} | ||
- The received signal $r(t)$ is digital. | - The received signal $r(t)$ is digital. | ||
| − | - The | + | - The message sink is the telephone set in Hamburg. |
| − | + The | + | + The message sink is the answering machine. |
| − | + The following applies $v(t) = \alpha \cdot q(t - \tau ) + {n(t)}$. | + | + The following applies: $v(t) = \alpha \cdot q(t - \tau ) + {n(t)}$. |
- There is an ideal transmission system. | - There is an ideal transmission system. | ||
| Line 58: | Line 58: | ||
*The message sink is the answering machine. | *The message sink is the answering machine. | ||
*In an ideal transmission system $v(t) = {q(t)}$ should apply. | *In an ideal transmission system $v(t) = {q(t)}$ should apply. | ||
| − | *However, due to the additive noise term ${n(t)}$, the attenuation $\alpha$ and the | + | *However, due to the additive noise term ${n(t)}$, the attenuation $\alpha$ and the delay time $\tau$ the following applies here: |
:$$v(t) = \alpha \cdot q ( t - \tau) + n(t).$$ | :$$v(t) = \alpha \cdot q ( t - \tau) + n(t).$$ | ||
*By our definitions, this is a distortion-free system. | *By our definitions, this is a distortion-free system. | ||
Latest revision as of 17:35, 23 January 2023
A telephone connection scenario
We consider the scenario shown in the picture:
A woman from Munich dials a number in Hamburg with her ISDN phone. However, she cannot reach the person she wants to talk to, so she leaves him a message on tape.
The distortion-free connection is fully described by
- an attenuation coefficient $\alpha$,
- a term $\tau$ and
- the current signal-to-noise ratio (SNR).
Notes: The task shall establish a relation between this real scenario and the functional units of a general communications system mentioned in the theory section .
Questions
Solution
(1) The first two statements are correct:
- The speech signal ${q(t)}$ must first be converted into an electrical signal and then prepared for transmission.
- For ISDN the transmitted signal ${s(t)}$ is digital.
(2) Correct are the solutions 3 and 4:
- The received signal ${r(t)}$ is always analog due to the unavoidable thermal noise.
- The message sink is the answering machine.
- In an ideal transmission system $v(t) = {q(t)}$ should apply.
- However, due to the additive noise term ${n(t)}$, the attenuation $\alpha$ and the delay time $\tau$ the following applies here:
- $$v(t) = \alpha \cdot q ( t - \tau) + n(t).$$
- By our definitions, this is a distortion-free system.
