This section contains carefully selected MCQs and Previous Year Questions with explanations to help students understand concepts and prepare effectively for examinations, interviews, and competitive tests.
Q: 1Which of the following is not range of frequency band operate in Industrial Scientific and Medical (ISM)?
Option D
Industrial, Scientific, and Medical (ISM) bands are portions of the radio spectrum reserved internationally for non-commercial purposes like industrial heating, medical equipment, and scientific experimentation. Over time, they have also been widely used for unlicensed wireless communication, such as Wi-Fi and Bluetooth.
Q: 2Find the incorrect statement about Manchester encoding in computer networks
Option C
Manchester Encoding is a digital line‑coding scheme used at the physical layer to transmit data along with clock information. Each bit period is split into two phases, and there is always a transition in the middle of the bit, which provides self‑clocking and helps the receiver stay synchronized.
So, Manchester Encoding is used in the Physical Layer and provides signal synchronization through frequent transitions. It is called a Biphase Code because each bit has two phases, and its required transition occurs at the center of the bit, not necessarily at the bit boundary.
Q: 3The primary use of scramblers in Line Coding Schemes is to—
Option A
A scrambler is used in line coding schemes to modify the original data before transmission.
Q: 4Construction of a coaxial cable can be briefly given as
Option B
A coaxial cable consists of multiple layers designed to transmit signals efficiently with minimal interference. Its construction includes:
Q: 5During transmission digital data is more secure because of _____________.
Option D
Digital Data Transmission is considered more secure because the data can be encrypted before transmission. Encryption converts the original information into a coded form so that unauthorized users cannot easily understand or access the data.
In digital communication systems, techniques such as encryption, encoding, and authentication are commonly used to improve security during data transfer.
Q: 6In Ethernet 1000BASE-X, the encoding scheme used is ________ that encodes ________ bit data into ________ bit data groups.
Option C
Encoding schemes in Ethernet convert data bits into transmittable symbols over physical media (fiber/copper). They ensure clock recovery (frequent transitions), DC balance (equal 0s/1s), and error detection by adding overhead bits.
In Gigabit Ethernet (1000BASE-X), data transmission uses an encoding scheme to ensure reliable communication, proper synchronization, and error detection. The scheme used is 8B/10B encoding.
In this technique, 8 bits of actual data are converted into 10-bit code groups before transmission. This extra 2 bits help in:
Therefore, 1000BASE-X uses 8B/10B encoding, where 8-bit data is converted into 10-bit groups for reliable high-speed transmission.
Q: 7The frequency which is used for transmission of signal from the satellite to earth station receive is known as ___________.
Option D
In satellite communication, signals travel between the earth station and the satellite using different frequencies. There are two main communication links:
The frequency used for sending signals from the satellite to the earth station receiver is called the Downlink Frequency.
For example, a TV broadcast satellite sends signals to home dish antennas using downlink frequency.
Q: 8In digital modulation schemes using two carriers, a constellation diagram is particularly useful because it helps to
Option B
In digital communication, Modulation is the process of varying a carrier signal (sine wave) to transmit data. Digital modulation schemes often use two or more carriers, which can vary in amplitude, phase, or frequency to represent binary information.
A Constellation Diagram is a graphical representation of these modulated signals on a 2D plane, where the x-axis represents the in-phase component (I) and the y-axis represents the quadrature component (Q). Each point in the diagram corresponds to a unique amplitude and phase combination, allowing engineers to visualize the transmitted symbols and detect errors.
| TOOL | PURPOSE | OBSERVED PARAMETERS |
|---|---|---|
| Constellation Diagram | Visualization of digital modulation. | Amplitude and Phase. |
| Eye Diagram | Time-domain signal analysis. | Signal timing, Jitter, ISI. |
| Spectrum Analyzer | Frequency analysis. | Frequency, bandwidth, harmonics. |
Q: 9Which of the following uses simplex mode of data transfer?
Option A
In data communication, Simplex Mode is a type of transmission where data flows in only one direction with no possibility of data flowing back, like traffic on a one-way street. One device acts as the sender, and the other only receives.
In Computer to Printer communication, data flows only from the computer to the printer. The printer does not send data back to the computer. This is a perfect example of simplex communication.
| Term | Explanation |
|---|---|
| Internet Browsing | Uses two-way (full-duplex) communication (request and response). |
| Telephone Communication | Uses full-duplex communication because both users speak and listen simultaneously. |
Q: 10In a Walkie—Dalkie which data communication method is used?
Option B
A Walkie-Talkie uses the Half-Duplex communication method. In half-duplex communication, data can travel in both directions, but not at the same time.
In a walkie-talkie:
Q: 11In digital transmission the error performance is quantified in terms of ___________.
Option C
In digital communication, the quality or error performance of transmission is measured using BER (Bit Error Rate).
BER represents the number of bits received incorrectly compared to the total number of bits transmitted.
For example, if 1000 bits are transmitted and 10 bits are received incorrectly, then:
BER = 10/1000 = 0.01
A lower BER means better transmission quality.
| Term | Description | Example |
|---|---|---|
| Baud Rate | Number of signal changes (symbols) transmitted per second in a communication channel. One baud may carry one or more bits. | If a modem changes its signal 2400 times in one second, then baud rate is 2400 baud. |
| Symbol Rate | Number of symbols transmitted per second. It is another name for Baud Rate in digital communication. | If 5000 symbols are transmitted each second, Symbol Rate is 5000 baud. |
| Bit Rate | Total number of bits transmitted per second, including data and control bits. | If 1,000,000 bits are transmitted in one second, Bit Rate = 1 Mbps. |
| Data Rate | Amount of actual useful data transferred per second. It may be less than bit rate because of extra control/error bits. | Out of 1200 transmitted bits, if only 1000 bits are actual data, then data rate is 1000 bps. |
| BER (Bit Error Rate) | Measurement of errors in digital transmission. It shows how many bits are received incorrectly. | If 10 bits are wrong out of 10,000 transmitted bits, BER = 10/10000 = 0.001. |
| Bandwidth | Range of frequencies used for communication or maximum data carrying capacity of a channel. | A channel with 20 MHz bandwidth can carry more data than a 5 MHz channel. |
| Throughput | Actual amount of data successfully delivered over a network in real conditions. | A 100 Mbps network may provide only 80 Mbps throughput because of traffic and delays. |
| Latency | Time taken by data to travel from sender to receiver. | In online gaming, lower latency gives faster response. |
Q: 12Identify the diagram and write the type of conversion the system is performing.
Option B
Q: 13Which of the following statement(s) is/are true regarding Data Communication?
I. Half duplex communication is multidirectional communication.
II. Full duplex communication is bidirectional communication.
Option B
Data communication is the process of transferring data between two or more devices through communication channels such as cables, optical fibers, or wireless networks.
Communication modes define the direction of data flow between sender and receiver. The three main communication modes are:
In Simplex Communication, data flows only in one direction. One device only sends data and the other device only receives data.
In Half Duplex Communication, data can flow in both directions, but not at the same time. Only one device can transmit data at a particular moment. Therefore, half duplex communication is bidirectional, not multidirectional.
In Full Duplex Communication, data can flow in both directions simultaneously. Both devices can send and receive data at the same time. Therefore, full duplex communication is bidirectional communication.
Q: 14If the channel band is limited to 6 kHz and signal to noise ratio is 16, what would be the capacity of the channel?
Option B
Q: 15Which type of channel does not represent any correlation between input and output symbols?
Option C
A Useless Channel is a communication channel where there is no correlation between input and output symbols. This means the output is completely independent of the input, the received symbol gives no information about what was sent. In this, the channel capacity is zero because the output does not carry any meaningful information about the input.
A noiseless channel, output is exactly the same as input, so there is a perfect correlation between input and output.
A lossless channel, input can be uniquely determined from the output, so correlation still exists.
A deterministic channel, each input symbol corresponds to exactly one output symbol, hence strong correlation.
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