Network and Data Communications · Unit 2
Data Transmission and Encoding
Exam-focused notes for Data Transmission and Encoding (Network and Data Communications, BIT254): what the TU syllabus asks and how it has actually been tested, with 11 solved past questions from this unit.
What this unit covers
- Digital signal encoding NRZ-L
- Digital signal encoding NRZ-I
- Manchester encoding
- Differential Manchester encoding
- Binary Amplitude Shift Keying
- Binary Phase Shift Keying
- Attenuation distortion and noise
- Shannon capacity calculation
- Bandwidth and bit rate
Shannon capacity calculation
What are the services provided by Data Link Layer?A channel has a bandwidth of 5 MHz and a signal-to-noise ratio of 1000. Calculate the Shannon Capacity.[6+4]
--- The Data Link Layer (Layer 2 of the OSI model) provides reliable transit of data across a physical link. Its main services are: The bit stream received from the Network Layer is divided into manageable units called frames. A header and trailer are added...
Full solved answer →Write short notes on a.) Shannon Capacity Write short notes on b.) Connectionless service [2.5+2.5]
Shannon Capacity (also called Shannon's Channel Capacity theorem) defines the theoretical maximum data rate at which information can be transmitted over a noisy communication channel with arbitrarily low error probability. It was formulated by Claude Shanno...
Full solved answer →Digital signal encoding NRZ-L
Encode the bit stream 111001011 with: (i) Manchester (ii) NRZ-I and (iii) NRZ-L scheme. [5]
- Bit stream to encode: $1\ 1\ 1\ 0\ 0\ 1\ 0\ 1\ 1$ (9 bits) - Schemes required: (i) Manchester, (ii) NRZ-I, (iii) NRZ-L Note: These are standard line-coding schemes. I follow the conventions used in Forouzan (TU curriculum standard). Any consistent convent...
Full solved answer →Represent bit sequence 1100100111 by the following waveform: (a) NRZ-L (b) NRZ-I (c) Differential Manchester. [5]
- Bit sequence: 1 1 0 0 1 0 0 1 1 1 - Encoding schemes required: (a) NRZ-L, (b) NRZ-I, (c) Differential Manchester Convention used (Forouzan standard): - NRZ-L: bit 0 = High, bit 1 = Low (the level directly represents the bit; here I use the common Forouzan...
Full solved answer →Represent bit sequence 100111001 by the following wave forms: NRZ-L, NRZ-I [5]
- Bit sequence: $1\ 0\ 0\ 1\ 1\ 1\ 0\ 0\ 1$ (9 bits) - Encoding schemes required: NRZ-L, NRZ-I --- Rule (Forouzan convention): - Bit 1 → Low voltage level - Bit 0 → High voltage level The level is set purely by the current bit value (absolute level, no refe...
Full solved answer →Attenuation distortion and noise
What are the major differences between noise, distortion and attenuation? [5]
--- Feature Noise Distortion Attenuation ------------ Definition Unwanted random signals added to the original signal during transmission Change in the shape/form of the signal due to different propagation speeds of signal components Gradual loss of signal ...
Full solved answer →Differentiate between noise and attenuation. A pure ALOHA network transmits 200 bit frames using a shared channel with a 50 kbps bandwidth. What is the requirement to make this frame collision free?[10]
Parameter Value ------ Frame size (L) 200 bits Channel bandwidth (B) 50 kbps = 50,000 bps Protocol Pure ALOHA All required data is present. No missing values. --- Feature Noise Attenuation --------- Definition Unwanted electrical/electromagnetic energy adde...
Full solved answer →What are the major differences between noise, distortion and attenuation? [5]
--- Feature Noise Distortion Attenuation ------------ Definition Unwanted random signals added to the original signal during transmission Alteration in the shape/form of the signal due to different propagation speeds of signal components Reduction in the st...
Full solved answer →Write short notes on Attenuation and SNMP [5]
--- Attenuation is the loss of signal strength (energy) as it travels through a transmission medium over a distance. As a signal propagates along a cable or through the air, it gradually weakens due to resistance, absorption, and scattering effects of the m...
Full solved answer →Binary Amplitude Shift Keying
Explain the concept of Binary Amplitude Shift Keying. Represent bit sequence 11001010 by the following waveform a.) Manchester b.) Differential Manchester[10]
--- Binary Amplitude Shift Keying (BASK) is a form of digital modulation in which the amplitude of a carrier signal is varied to represent binary data (0s and 1s), while the frequency and phase remain constant. The BASK signal can be expressed as: $$s(t) = ...
Full solved answer →Binary Phase Shift Keying
Explain the concept of Binary Phase Shift Keying. Represent bit sequence 111000110 by the following waveform a.) NRZ-I, b) Differential Manchester[10]
- Bit sequence: 1 1 1 0 0 0 1 1 0 - Required encodings: (a) NRZ-I, (b) Differential Manchester - Assumed initial reference level: LOW (stated explicitly since the question does not specify) --- Definition: BPSK is a digital modulation technique in which the...
Full solved answer →Make Unit 2 stick
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