# Wireless Communication MCQ || Wireless Communication Questions and Answers

1. In LTE network architecture, the interface between the internet and PDN gateway is:

1. Um
2. SS7
3. S5
4. SGi

Explanation

In LTE network architecture, the interface between the internet and PDN gateway is SGi.

1. The SGi interface connects the PGW to an external network (PDN), and the Gi interface connects the GGSN to an external network (PDN).

2. The interface is based on the IP packet (user data/payload/data plane), possibly also enabling the exchange of signaling (ex. OSPF, BGP, etc.). The interface can connect to the Radius server if Remote Access Dial-In User Service (Radius) is used.

3. The functions of the SGi interface include access to the Internet, Intranet, or an ISP (Internet service provider) and involve functions such as IPv4 address allocation, IPv6 address autoconfiguration, and may also involve specific functions such as authentication, authorization, and secure tunneling to the intranet/ISP.

4. The implementation Gi, SGi Interface in a real topology network. All IP various packets combine in one routing table (virtual-router or routing-instance).

2. What is Mobile communication?

1. Allows to communicate from different locations without the use of physical medium
2. Allows to communicate from different locations with the use of physical medium
3. Allows to communicate from same locations without the use of physical medium
4. Allows to communicate from same locations with the use of physical medium

Answer.1. Allows to communicate from different locations without the use of the physical medium

Explanation

Mobile communication is talking, texting, or sending data or image files over a wireless network. Mobile Communication is the use of technology that allows us to communicate with others in different locations without the use of any physical connection (wires or cables). A mobile phone (also called a mobile cellular network, cell phone, or handphone) is an example of mobile communication (wireless communication).

3. Which of the following is not a service offered by SS7?

1. Alternate billing services
2. Touchstar
3. 400 services
4. 800 services

Explanation

Signaling System 7 (SS7) is a set of protocols allowing phone networks to exchange the information needed for passing calls and text messages between each other and to ensure correct billing. It also allows users on one network to roam on another, such as when traveling in a foreign country.

There are three main types of services offered by the SS7 network. They are the Touchstar, 800 services, and alternate billing services.

4. On which of the following frequencies does a Wi-Fi network work?

1. 2.4 MHz
2. 5 MHz
3. 10 GHz
4. 5 GHz

Explanation

• Wi-Fi is the wireless network system most commonly used in homes to connect multiple electronic devices through the internet. An instrument called a router is needed to connect several instruments through the internet.
• WiFi uses radio frequencies to send signals between devices.  WiFi works at a frequency of 2.4 GHz and 5 GHz.

5. If the voice activity interference reduction factor is 2.5, antenna sectorization gain factor is 2.5, and interference increase factor is 1.6, then the performance improvement factor in CDMA digital cellular system is

1. 1.2
2. 2.5
3. 3.1
4. 3.9

Explanation

Given voice interference reduction factor and antenna resize factor is 2.5 and 2.5 respectively.

The interference factor is 1.6

Performance Improvement Factor = GV.GA/P

Where

GV: Voice interference reduction factor

GA: Antenna sectoring factor

P: Interference increase factor

= 2.5 × 2.5/1.6 = 3.9625

Performance improvement factor = 3.9

6. Global positioning system (GPS) uses:

1. CDMA
2. SDMA
3. TDMA
4. FDMA

Explanation

The global positioning system (GPS) is a network of satellites and receiving devices used to determine the location of something on Earth. Some GPS receivers are so accurate they can establish their location within 1 centimeter (0.4 inches). GPS receivers provide location in latitude, longitude, and altitude.

Global positioning system (GPS) uses CDMA.

• CDMA (Code Division Multiple Access) uses a digital modulation technique called Direct Sequence spread spectrum which spreads voice data over a very wide spectrum using user or cell-specific pseudo-random codes.

7. What is wireless communication?

1. Sending data from one location to with the use of a physical medium
2. Sending data from one location to another without the use of a physical medium
3. Sending data from one location to another without the use of virtual medium
4. None of the mentioned

Answer.2. Sending data from one location to another without the use of the physical medium

Explanation

Wireless Communication is a method of transmitting information from one point to other, without using any connection like wires, cables, or any physical medium. Generally, in a communication system, information is transmitted from transmitter to receiver that is placed over a limited distance.

8. Which of the following is true for first-generation wireless systems?

1. Low rate
2. Efficient
3. High data rate
4. Digital technology

Explanation

1G or (1-G) refers to the first generation of wireless telephone technology (mobile telecommunications). These are the analog telecommunication standards that were introduced in 1979 and the early to mid-1980s and continued until being replaced by 2G digital telecommunications.

First-generation wireless systems provide analog speech and inefficient, low rate, data transmission between the base station and mobile user.

• First-time calling was introduced in mobile systems.
• It used analog signals.
• It used an FDD scheme and typically allocated bandwidth of 25 Mhz.
• The coverage area was small.
• No roaming support between various operators.
• Low sound quality.
• Speed :- 24 kbps.

9. If a total of 33 MHz of bandwidth is allocated to a particular FDD cellular telephone system that uses two 25 kHz simplex channels to provide full-duplex voice and control channels, compute the number of channels available per cell if a system uses 4-cell reuse

1. 55
2. 660
3. 95
4. 165

Explanation

Given,

Cluster size (N) = 4

Total bandwidth = 33 MHz

Channel bandwidth = 25 kHz × 2 simplex channel

Channel bandwidth = 50 kHz/duplex channel

Total available channels = (33,000 × 103)/(50 × 103)

Total available channels = 660 channels

Total number of available channels per cell = (Total available channels)/N

Total number of available channels per cell = 660/4

Total number of available channels per cell = 165

10. If a cellular system has p number of co-channel interfering cells, S is the desired signal power from the serving base station and IP is interference power from pth interfering co-channel cell base station, then what is the signal to interference ratio for a mobile receiver in the functioning cell?

1. $\dfrac{S}{\sum_{i = 1}^P I_P}$
2. $\dfrac{2\times S}{\sum_{i = 1}^P I_P}$
3. $\dfrac{\sum_{i = 1}^P I_P}{S}$
4. $\dfrac{S}{I_P}$

Answer.1. $\dfrac{S}{\sum_{i = 1}^P I_P}$

Explanation

The signal to interference ratio for a mobile receiver in the functioning cell is given by:

$\dfrac{S}{\sum_{i = 1}^P I_P}$

S = Desired signal power from the desired base station

Ii = Interference power caused by the ith interfering co-channel cell base station

i0 = Number of co-channel interfering cells

The average received signal strength at any point decays as a power law of the distance of separation between a transmitter and receiver (Propagation measurements).

The average received power (Pr) at a distance ( => R from the transmitting antenna is approximated by:

$P_r=P_0(\frac{d}{d_0})^{-n}$

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