Wireless Networks Viva Questions with Answers - Part 1

Q1) What is Wireless Network ?

Answer:

Wireless network :
• The computer networks where the nodes connected without using wires/cable called as wireless networks.
• Advantage: Mobility , increased reliability, easy installation ,lower cost.
• Disadvantage: Security, health hazards.

Q2) What are the components you require to establish a network infrastructure mode ?

Answer: We will require switches, routers, firewalls, and access points (APs), wireless device and wired device to establish a network in infrastructure mode.

Q3) What are types of wireless networks ?

Answer:

Classifications of wireless networks:
• Wireless body area networks ( WBAN )
• Wireless personal area networks ( WPAN )
• Wireless local area networks ( WLAN )
• Wireless metropolitan area networks (WMAN )
• Wireless wide area networks ( WWAN )

Q4) What are the advantages and disadvantages of wireless networks ?

Answer:

Advantages of wireless networks:
• Wireless network is easy to setup.
• Wireless network is more flexible and adaptable compared to wired network.
• Wireless network is easy to carry and re-install in another place.

Disadvantages of wireless networks:
• The bandwidth may not be optimally utilized in a wireless network.
• File transfers and resource sharing over a wireless network may not be as fast when compared to wired networks.
• Signal strength decreases when the user gets farther away from the range of wireless network sources.

Q5) Explain wireless body area networks ( WBAN ) ?

Answer:

Wireless body area networks ( WBAN ) :
• WBAN networks have minimum signal range of 2m. WBAN is network of tiny wireless sensors that are wearable. The wireless sensors transmit data from human body to home base station.
• It is used in movement sensors, blood pressure sensor for monitoring blood pressure.

Q6) Which standard is used for WBAN ?

Answer:

Wireless Body Area Network uses IEEE 802.15.6 standard.
• Data rate: upto about 2 Mbps
• Range: upto 2 meters
• WBAN uses Frequency bands: 2.4GHz, 800MHz,900MHz,400MHz

Q7) What are the advantages and disadvantage of WBAN ?

Answer:

Advantages of WBAN:
• Emergency services can be get fromthe doctor.
• Patient has not required to physical available to the doctor.
• Used in military for security purposes.
• Assists the communication between individual and machine

Disadvantages:
• Battery Life
• Interference of the multi devices that can share the channel.
• WBAN required to be more secure.

Applications of WBAN:
• Remote Patient Monitoring – Telemedicine and remote patient monitoring are the main applications of WBAN. Telemedicine means diagnosis and treatment of patients located at a remote location using information technology. Daily-life activities of patients can be monitored to collect vital parameters from the human body.
• A WBAN network placed ona patient can inform hospital even before patient gets a Heart attack
• WBAN on diabetic patient could auto-inject insulin through a pump as soon insulin level falls
• Other application include sports, military or security.

Q8) What is major disadvantage of WBAN ?

Answer: The major constrained faced by wireless body area network is Battery Life.

Q9) What is wireless sensor network ?

Answer: Wireless sensor network are spatially distributed autonomous sensors to monitor physical and environmental conditions,such as temperature, sound and pressure.

Q10) Which are the components used in WSN ?

Answer:

• Sensors in WSN are used to capture the environmental variables and which is used for data acquisition. Sensor signals are converted into electrical signals.
• Radio Nodes are used to receive the data produced by the Sensors and sends it to the WLAN access point. It consists of a microcontroller, transceiver, external memory, and power source.
• WLAN Access Point: It receives the data which is sent by the Radio nodes wirelessly, generally through the internet.
• Evaluation Software: is used for presenting the report to the users for further processing of the data which can be used for processing, analysis, storage, and mining of the data.

Q11) Which frequencies are used in WSN ?

Answer: Currently, frequencies used for wireless sensor systems include 315 MHz, 433 MHz, 868 MHz (Europe), 915 MHz (North America), and the 2.45 GHz Industrial-Scientific-Medical (ISM) band.

Q12) What are the applications and challenges with WSN ?

Answer:

Applications of WSN:
• Internet of Things (IOT)
• Surveillance and Monitoring for security, threat detection
• Noise Level of the surrounding
• Environmental temperature, humidity, and air pressure
• Medical applications like patient monitoring

Challenges of WSN:
• Quality of Service(QoS)
• Security Issue
• Energy Efficiency
• Scalability to large scale of deployment
• Coverage Problem

Q13) What is ISM band ?

Answer:ISM band is stands for Industrial, Scientific and Medical band. It is a part of the radio spectrum that can be used for any purpose without a license in most countries.The 902-928 MHz, 2.4 GHz and 5.7-5.8 GHz bands were initially used for machines that emitted radio frequencies, such as RF welders, industrial heaters and microwave ovens, but not for radio communications.

Q14) Features of Bluetooth.

Answer: Bluetooth is a standard that provides an Adhoc way of connecting device in range of 10m. It operates in 2.4GHz band and uses frequency hoping TDD method for each radio channel. Blutooth operates in unlicensed ISM band. Data rate of bluetooth ranges from 1Mbps to 3Mbps.

Q15) What is ZigBee and its features ?

Answer: ZigBee is wireless protocol used for wireless networking and connectivity. It is based on IEEE 802.15.4 statndard. ZigBee devices have low power consumption and can be easily implemented. Data rate of ZigBee is around 25Kbps and packet size is small than Bluetooth and WiFi.

Q16) What is IEEE standard for Bluetooth and ZigBee (that is WPAN) ?

Answer:

Bluetooth Standard: IEEE 802.15.1

ZigBee Standard: IEEE 802.15.4

Q17) What are the frequency range of ZigBee and their data rate ?

Answer: ZigBee operate at 2.4GHz frequency with the speed up to 250kbps

Q18) What is the data transmission rate of Bluetooth and How many channels present ?

Answer:Data rate is ranges from 1Mbps to 3Mbps and 79 RF channnels are used in Europe, USA and almost all countries exept France and Spain there is 23 channels.

Q19) Differentiate between Bluetooth and ZigBee.

Answer:

S.NO	Bluetooth	Zigbee
1.	The frequency range supported in Bluetooth vary from 2.4 GHz to 2.483 GHz.	While the frequency range supported in Zigbee mostly 2.4GHz worldwide.
2.	There are seventy nine RF channels in Bluetooth.	There are sixteen RF channels in zigbee.
3.	It uses GFSK modulation technique.	Whereas it also uses BPSK and QPSK modulation techniques like UWB.
4.	There is maximum of 8 cell nodes in Bluetooth.	While there is more than sixty five thousand (65000) cell nodes in zigbee.
5.	Bluetooth requires low bandwidth.	While zigbee also requires low bandwidth but greater than Bluetooth’s bandwidth most of time.
6.	The radio signal range of Bluetooth is ten meters.	While the radio signal range of zigbee is ten to hundred meters.
7.	Bluetooth was developed under IEEE 802.15.1.	Whereas it was developed under IEEE 802.15.4.

Q20) Define the following terms Piconet, Scatternet, MAC address and hold mode.

Answer:

Piconet: Collection of devices connected via Bluetooth technologyare called as Piconets. There may be upto 8 connected devices in piconet. While stabilizing piconet one device acts as Master and other 7 acts as Slave.

Scatternets: Scatternets are two or more independent and non-synchronized piconets that communicates with each other by making bridge nodes.

MAC address: MAC address is the physical address, which uniquely identifies each device on a given network.It stands for Media Access Control, and also known as Physical address, hardware address. In bluetooth, It is a 3 bit Medium Access Control address used to distinguish between units participating in the piconet.

Sniff Mode: This is a low power mode in which the listening activity of the slave is reduced. In the sniff mode, the slave listens for transmission onlyat fixed intervals.

Hold Mode: In bluetooth, In Hold mode ACL link between master and slave temporaily suspended. In case of Hold mode,Master can force a slave into hold mode and alternatively Slave can request for Slave to be put in hold mode.

Q21) How many number of devices are supported in piconet ? why so ?

Answer: The total number of devices supported in piconet in 8. This is because a 3 bit MAC address is used to distinguish between different devices in the network.

Hence applying the logic 2³ = 8

We have only 8 unique addresses for the devices.

Q22) What is hoping rate in bluetooth ?

Answer: 1600 hops per second.

Q23) What are the security modes in Bluetooth ?

Answer: The bluetooth contains 3 modes of security:

• Non Secure mode: In this mode , the bluetooth device does not initiat any security mechanism. IT used for public devices such as public printers.
• Service Level Security: The security level is present while providing service to the user. The user can only access the services that are allowed to it such as downloading, read/write. Not all services are available freely.
• Link Level security: The establishment of a connection of bluetooth device has a security present so that not everyone can connect to the bluetooth device.

Q24) How many link types are present in Bluetooth ? What are they and each used for what purpose ?

Answer:

There are two Bluetooth links types named Synchronous Connection Oriented(SCO) and Asynchrounous Connection Less(ACL).

SCO is used for voice and ACL is used for data and packet.

25) Explain the "Park" mode in bluetooth connection management.

Answer: Park mode is used for saving power. It is acheived by reducing duty cycle.
If a slave desire to remain inactive for sometimes , it enters into Park mode. In this mode slave device mainttain synchronization with the master, but does not take part in data traffic. The park mode has time greater than hold and sniff modes.

Q26) ZigBee uses which type of channel access ?

Answer: The ZigBee uses CDMA-CA type of channel access.

Q27) Difference between RFID and Barcodes.

Answer: RFID are seen as replacement of barcodes because of following disadvantages of barcodes:

It require line of sight reading which RFID eliminates.

Distance requires between reader is also very less which is improved by RFID.

Barcodes can be easily spoofed by laser printer.

Q28) What are the Applications of RFID ?

Answer:

Applications of RFID(Radio Frequency Identification):
• Location tracking
• Car Lock system
• Supply chain management
• Animal Tracking

Q29) What are the advantages of RFID ?

Answer:

Advantagess of RFID(Radio Frequency Identification):
• Low maintenance
• Provide secure and reliable data.
• Can handle large amount of data.
• Used for tracking assets.

Q30) What are the applications of WPAN ?

Answer:

Application of WPAN:
• Computer or Laptop can be connected universely to projector.
• Digital pictures can be transferred from digital camera without the need of cable.
• While it has been used for a military, UWB is now going through the necessary authorization and developments for public and commercial us.